DIZZINESS, VERTIGO, AND HEARING LOSS

C H A P T E R
18
DIZZINESS, VERTIGO, AND
HEARING LOSS
Kevin A. Kerber and Robert W. Baloh
General Considerations 237
Historical Background 237
Epidemiology of Vertigo, Dizziness, and Hearing Loss
Normal Anatomy And Physiology 238
Approach to the Patient with Dizziness 240
History of Present Illness 240
Physical Examination 241
General Medical Examination 241
General Neurological Examination 241
The Neurotological Examination 242
Dizziness and Vertigo 245
Specific Disorders Causing Vertigo 245
Peripheral Vestibular Disorders 245
Central Nervous System Disorders 246
Vertigo in Inherited Disorders 247
Common Causes of Nonspecific Dizziness 249
Common Presentations of Vertigo 249
Acute Severe Vertigo 249
Recurrent Attacks of Vertigo 249
Recurrent Positional Vertigo 249
Hearing Loss 250
Classification of Hearing Loss 250
Conductive Hearing Loss 250
Sensorineural Hearing Loss 250
Central Hearing Loss 250
238
Dizziness is a term patients use to describe a variety of symptoms including spinning or movement of the environment
(vertigo), lightheadedness, presyncope, or imbalance. Patients
also may use the term for other sensations such as visual distortion, internal spinning, nonspecific disorientation, and anxiety,
so the most important initial step is to clarify the symptom. For
the neurologist evaluating patients with dizziness, peripheral
vestibular disorders are important to recognize because they are
common and definable at the bedside and often are missed by
referring physicians.
Patients may experience dizziness in isolation or with other
symptoms. Neurological causes should be considered when
other neurological signs and symptoms are present and when
common peripheral vestibular disorders have been ruled out.
It is critical to ask the patient about associated symptoms
because they may be the key to the diagnosis. Vertigo, a sensation of spinning of the environment, indicates a lesion within
the vestibular pathways, either peripheral or central. Associated
ear symptoms such as hearing loss and tinnitus can suggest a
peripheral localization, to the inner ear or eighth nerve. Many
Specific Disorders Causing Hearing Loss 250
Ménière’s Disease 250
Cerebellopontine Angle Tumors 251
Superior Canal Dehiscence 251
Otosclerosis 251
Noise-Induced Hearing Loss 251
Genetic Disorders 251
Ototoxicity 251
Common Presentations of Hearing Loss 251
Asymmetrical Sensorineural Hearing Loss
Sudden Sensorineural Hearing Loss 251
Hearing Loss with Age 252
Tinnitus 252
Clinical Investigations 252
Dizziness and Vertigo 252
General Tests 252
Imaging 252
Vestibular Testing 252
Auditory Testing 253
Hearing Loss and Tinnitus 253
251
different types of hearing loss occur with or without dizziness,
and an understanding of common auditory disorders is important to the practicing neurologist. With an understanding of
the neurotological bedside examination, specific findings often
can be identified.
This chapter provides background information regarding
dizziness, vertigo, and hearing loss and the clinical information
necessary for making specific diagnoses. Further details on
testing and management of these patients are presented in
Chapter 40.
GENERAL CONSIDERATIONS
HISTORICAL BACKGROUND
Accounts of dizziness and vertigo can be found in the writings of ancient Egyptian and Greek physicians. Before the late
19th century, however, not much was known about the causes
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of dizziness or hearing loss; as a result, quackery was commonplace. Patients complaining of dizziness or vertigo usually were
grouped together with those who had experienced epileptic seizures or stroke, under the rubric of “apoplectiform cerebral congestion,” meaning too much blood to the brain. Accordingly,
common treatments included bleeding, leeching, cupping, and
purging. In 1861, Prosper Ménière was the first to recognize
the association of vertigo with hearing loss and thus to localize
the symptom to the inner ear (Baloh, 2001). Although not well
received initially, his discovery provided the basis for later studies on the physiology and pathology of the vestibular system.
Caloric testing, the most widely used test of the vestibuloocular reflex (VOR), was introduced by Robert Barany in
1906. He later was awarded the Nobel Prize for proposing
the mechanism of caloric stimulation. Barany also provided
the first clinical description of benign paroxysmal positional
vertigo (BPPV) in 1921. Endolymphatic hydrops was identified
in postmortem specimens of patients with Ménière’s disease in
1938. A method for measuring eye movements in response to
caloric and rotational stimuli (electronystagmography [ENG])
was introduced in the 1930s, but it was not until the 1970s
that digital computers were used to quantify eye movement
responses.
The advent of modern neuroimaging in the late 1970s and
1980s greatly expanded our understanding of causes of dizziness and vertigo. Before this time, stroke was considered an
exceedingly rare cause of recurrent vertigo. Although the role
of stroke in the pathogenesis of vertigo remains a controversial topic even today, infarctions within the cerebellum and
brainstem have been identified on imaging studies in patients
with isolated vertigo. Such studies continue to lead to new discoveries of causes of vertigo, as demonstrated by the recently
described disorder of superior canal dehiscence. Unfortunately,
the most common causes of vertigo, such as Ménière’s disease,
benign paroxysmal positional vertigo, and vestibular neuritis,
still have no identifiable imaging characteristics.
Over the past two decades, our understanding of the mechanisms for the common neurotological disorders has been
enhanced. BPPV can now be readily identified and cured at the
bedside with simple positional maneuvers (Aw et al., 2005; von
Brevern et al., 2006). The head-thrust test can be used at the
bedside to confirm a vestibular nerve lesion (Nuti et al., 2005).
This sign is analogous to the afferent pupillary defect, which is
the definitive diagnostic sign for localizing lesions to the optic
nerve. Controversies regarding Ménière’s disease have been
clarified, and medical and surgical treatments have improved
(Minor et al., 2004). We now know that patients with recurrent
episodes of vertigo without hearing loss, a condition once called
“vestibular Ménière’s disease,” do not have Ménière’s disease.
Migraine is now recognized as an important cause of dizziness,
even in patients without simultaneous headaches. In fact, benign
recurrent vertigo (recurrent episodes of vertigo without accompanying auditory symptoms or other neurological features) usually is a migraine equivalent (Oh et al., 2001a). The disorder
of superior canal dehiscence was only recently described and
provides important insight into the physiology of the vestibular system (Minor, 2005). A more detailed description of the
rotational vertebral artery syndrome has led to the appreciation of the high metabolic demands of the inner ear and its susceptibility to ischemia (Choi et al., 2005). Genetic research has
identified ion channel dysfunction in disorders such as episodic
Ch18-H7525.indd 238
ataxia and familial hemiplegic migraine, two disorders commonly associated with vertigo (Jen et al., 2004a). Identification
of specific genes causing vertigo syndromes should lead to a
better understanding of the mechanisms and also will create the
opportunity to develop specific treatments in the future.
EPIDEMIOLOGY OF VERTIGO,
DIZZINESS, AND HEARING LOSS
A recent population-based telephone survey in Germany showed
that nearly 30% of the population has experienced moderate to
severe dizziness (Neuhauser et al., 2005). Although most affected
persons reported nonspecific forms of dizziness, nearly a quarter had true vertigo. Dizziness is more common among females
and older people and has important health care utilization implications, because up to 80% of patients with dizziness seek medical
care at some point. In the United States, the National Centers
for Health Statistics reports 7.5 million annual ambulatory visits
to physician offices, hospital outpatient departments, and emergency departments for dizziness, making it one of the most
common principal complaints (Burt and Schappert, 2004). Prevalence rates for specific types of dizziness, however, are not available outside of tertiary referral centers or small studies.
Hearing loss is an important cause of disability and affects
approximately 16% of adults (older than 18 years of age) in the
United States (Lethbridge-Cejku et al., 2006). Men are more
commonly affected than women, and prevalence increases dramatically with age, so that by age 75, nearly 50% of the population report hearing loss. The most common type of hearing
loss is sensorineural, and both idiopathic presbycusis and noiseinduced forms are common etiologic disorders. Tinnitus is less
frequent in the U.S. population, with approximately 3% reporting it, although this rate increases to approximately 9% for persons older than 65 (Adams et al., 1999). Among persons with
hearing loss, nearly 75% also experience tinnitus. The most
common type of tinnitus is a high-pitched ringing in both ears.
NORMAL ANATOMY AND PHYSIOLOGY
The inner ear is composed of a fluid filled sac enclosed by a
bony capsule with an anterior cochlear part, a central chamber (the vestibule), and a posterior vestibular part (Fig. 18-1).
Endolymph fills up the fluid-filled sac and is separated by a
membrane from the perilymph. These fluids differ primarily
in their composition of potassium and sodium, with the endolymph resembling intracellular fluid, with a high potassium and
low sodium content, and the perilymph resembling extracellular fluids, with a low potassium and high sodium content. Perilymph communicates with the cerebrospinal fluid through the
cochlear aqueduct.
The cochlea senses sound waves after they travel through
the external auditory canal and are amplified by the tympanic
membrane and ossicles of the middle ear (Baloh and Honrubia,
2001). The stapes, the last of three ossicles in the middle ear,
contacts the oval window, which directs the forces associated
with sound waves along the basilar membrane of the cochlea.
These forces stimulate the hair cells, which in turn generate neural signals in the auditory nerve. The auditory nerve
enters the lateral brainstem at the pontomedullary junction and
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C H A P T E R 18
Dizziness, Vertigo, and Hearing Loss
239
Figure 18-1
Cerebrospinal fluid
K+ = 4 mEq/liter
Na+ = 152 mEq/liter
Protein = 20 – 50 mg/dL
Anatomy of the inner ear. CSF,
cerebrospinal fluid. (From Baloh,
R. W. 1998, Dizziness, Hearing
Loss, and Tinnitus, F. A. Davis,
Philadelphia, Figure 6, p. 16.)
Endolymphatic
sac
CSF
Cochlear aqueduct
Dura mater
Endolymphatic duct
Anterior
canal
Scala vestibuli
Perilymph
K+ = 10 mEq/liter
Na+ = 140 mEq/liter
Protein = 20 0 – 400 mg/dL
Posterior
canal
Horizontal
canal
Cochlear duct
Scala tympani
Endolymph
K+ = 144 mEq/liter
Na+ = 5 mEq/liter
Protein = 126 mg/dL
Saccule
Utricle
Round
window
Ductus
reuniens
synapses in the cochlear nucleus. The trapezoid body is the
major decussation of the auditory pathway, but many fibers
do not cross to the contralateral side. Signals then travel to
the superior olivary complex. Some projections travel from the
superior olivary complex to the inferior colliculus through the
lateral lemnisci, and others terminate in one of the nuclei of
the lateral lemniscus. Next, the fibers travel to the ipsilateral medial geniculate body, and then auditory radiations pass
through the posterior limb of the internal capsule to reach the
auditory cortex of the temporal lobe.
The peripheral vestibular system is composed of three semicircular canals, the utricle and saccule, and the vestibular component of the eighth cranial nerve (Baloh and Honrubia, 2001).
Each semicircular canal has a sensory epithelium called the
crista; the sensory epithelium of the utricle and saccule is called
the macule. The semicircular canals sense angular movements,
whereas the utricle and saccule sense linear movements. Two of
the semicircular canals (anterior and posterior canals) are oriented in the vertical plane nearly orthogonal to each other; the
third canal is oriented in the horizontal plane (horizontal canal).
The crista of each canal is activated primarily by movement
occurring in the plane of that canal. When the hair cells of these
organs are stimulated, the signal is transferred to the vestibular nuclei via the vestibular portion of the eighth cranial nerve.
Signals originating from the horizontal semicircular canal then
pass via the medial longitudinal fasciculus along the floor of
the fourth ventricle to the abducens nuclei in the middle brainstem and the oculomotor complex in the rostral brainstem. The
Ch18-H7525.indd 239
anterior (also referred to as the superior) and posterior canal
impulses pass from the vestibular nuclei to the ocular motor
and trochlear nuclei, triggering eye movements roughly in the
plane of each canal. A key feature is that once vestibular signals
leave the vestibular nuclei, they divide into vertical, horizontal,
and torsional components. As a result, a lesion of central vestibular pathways can cause a pure vertical, pure torsional, or pure
horizontal nystagmus.
The primary vestibular afferent nerve fibers maintain a constant baseline firing rate of action potentials. When the baseline rate from each ear is symmetrical (or an asymmetry has
been centrally compensated), the eyes remain stationary. With
an uncompensated asymmetry in the firing rate, resulting from
either increased or decreased activity on one side, slow ocular deviation results. By turning the head to the right, the baseline firing rate of the horizontal canal is physiologically altered,
causing an increased firing rate on the right side and a decreased
firing rate on the left side (Fig. 18-2). The result is a slow deviation of the eyes to the left. In an alert person, this slow deviation is regularly interrupted by quick movements in the opposite
direction (nystagmus) so that the eyes do not become “pinned”
to one side. In a comatose patient, the eyes deviate to the side of
the slow component because the corrective fast phases are truncated or absent.
The plane in which the eyes deviate as a result of
vestibular stimulation depends on the combination of canals
that are stimulated (Table 18-1). If only the posterior semicircular canal on one side is stimulated (as occurs with benign
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Physiologic nystagmus
Spontaneous nystagmus
AC
PC
Utricle
HC
Ampulla
Figure 18-2
Primary
afferent nerve activity associated
with rotation-induced physiological
nystagmus and spontaneous
nystagmus resulting from a lesion
of one labyrinth. The thin straight
arrows indicate the direction of
slow components; the thick straight
arrows indicate the direction of fast
components; curved arrows show
the direction of endolymph flow in
the horizontal semicircular canals.
AC, anterior canal; HC, horizontal
canal; PC, posterior canal. (From
Baloh, R. W. 1998, Dizziness,
Hearing Loss, and Tinnitus, F. A.
Davis, Philadelphia, Figure 16, p. 36.)
Primary afferent
firing rate
100 msec
Table 18-1
Physiological Properties and Clinical Features of the Components of the Peripheral Vestibular System
LOCALIZATION
SEMICIRCULAR CANALS
Posterior canal
Anterior canal
Horizontal canal
VESTIBULAR NERVE
Superior division
Inferior division
Common trunk (cranial
nerve VIII)
LABYRINTH
COMPONENT(S)
TRIGGERED EYE
MOVEMENTS
COMMON CLINICAL
CONDITIONS
LOCALIZING FEATURES
PC
AC
HC
Vertical, torsional
Vertical, torsional
Horizontal >> torsional
BPPV-PC
BPPV-AC, SCD
BPPV-HC, fistula
Nystagmus
Nystagmus, fistula test
Nystagmus, fistula test
AC, HC, utricle
PC, saccule
AC, HC, PC,
utricle, saccule
Horizontal > torsional
Vertical, torsional
Horizontal > torsional
VN, ischemia
VN, ischemia
VN, VP, ischemia
Nystagmus, head thrust test
Nystagmus
Nystagmus, head thrust test,
auditory findings
AC, HC, PC, utricle,
saccule
Horizontal > torsional
EH, labyrinthitis
Nystagmus, auditory findings
AC, anterior canal; BPPV, benign paroxysmal positional vertigo; EH, endolymphatic hydrops; HC, horizontal canal; PC, posterior canal; SCD, superior canal dehiscence;
VN, vestibular neuritis; VP, vestibular paroxysmia.
paroxysmal positional vertigo), a vertical-torsional deviation of the eyes can be observed, which is followed by a fast
corrective response in the opposite direction. However, if the
horizontal canal is the source of stimulation (as occurs with
the horizontal canal variant of BPPV), a horizontal deviation with a slight torsional component (because this canal
is slightly off the horizontal plane) results. If the vestibular nerve is lesioned (as in vestibular neuritis) or stimulated
(as in vestibular paroxysmia), a horizontal greater than torsional nystagmus occurs, which is the vector sum of all three
canals, because the two vertical canals on one side cancel each
other out.
Over time, either an asymmetry in the baseline firing rates
resolves (the stimulation has been removed), or the central nervous system compensates for it. This explains why an
Ch18-H7525.indd 240
entire unilateral peripheral vestibular system can be surgically
destroyed and the patient experiences vertigo only for several
days to weeks. It also explains why patients with slow-growing
tumors affecting the vestibular nerve, such as an acoustic neuroma, generally do not experience vertigo or nystagmus.
APPROACH TO THE PATIENT WITH
DIZZINESS
HISTORY OF PRESENT ILLNESS
The history and physical examination provide the most important information in the evaluation of patients complaining of
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C H A P T E R 18
dizziness (Colledge et al., 1996; Lawson et al., 1999). Often,
patients have difficulty describing the exact symptom experienced, so the clinician must elicit the pertinent information. The
first step is to define the symptom. No clinician should ever
be satisfied to record the complaint simply as “dizziness.” If the
patient is unable to provide a more detailed description of the
symptom, the physician can ask the patient to place the symptom into one of the following categories: movement of the environment (vertigo), lightheadedness, or imbalance alone, without
an abnormal head sensation. The physician also should ask the
following questions: Is the symptom constant or episodic? Are
there accompanying symptoms? How did it begin (e.g., gradual
or sudden)? Were there aggravating or alleviating factors? With
episodic dizziness, what are the duration and frequency of
attacks? Are there identifiable triggers?
Table 18-2 displays the key distinguishing features of common causes of dizziness. One key point is that any type of dizziness may worsen with position changes, but that some
disorders such as BPPV occur only after position change.
Table 18-2
241
Dizziness, Vertigo, and Hearing Loss
PHYSICAL EXAMINATION
General Medical Examination
A brief general medical examination is important. Identifying
orthostatic blood pressure changes can be diagnostic in the correct
clinical setting; therefore, blood pressure should be checked for
this pattern in any patient with orthostatic symptoms. Orthostatic
hypotension probably is the most common general medical cause of
dizziness among patients referred to neurologists. Identifying an
irregular heart rhythm also may be pertinent. Other general examination measures to consider in individual patients include a visual
acuity assessment (adequate vision is important for balance) and
a musculoskeletal inspection (significant arthritis can impair gait).
General Neurological Examination
The general neurological examination is an essential component of the evaluation of patients complaining of dizziness,
Distinguishing Among Common Peripheral and Central Vertigo Syndromes
CAUSE
PERIPHERAL
Vestibular neuritis
HISTORY OF VERTIGO
DURATION OF
VERTIGO
ASSOCIATED
SYMPTOMS
Single prolonged episode
Days to weeks
Nausea, imbalance
Benign paroxysmal
positional vertigo
Ménière’s disease
Positionally triggered
episodes
May be triggered by
salty foods
<1 min
Nausea
Hours
Vestibular
paroxysmia
Perilymph fistula
Abrupt onset; spontaneous
or positionally triggered
Triggered by sound or
pressure changes
Unilateral ear fullness,
tinnitus, hearing loss,
nausea
Tinnitus, hearing loss
Seconds
PHYSICAL EXAMINATION
“Peripheral” nystagmus, positive
head thrust test, imbalance
Characteristic positionally
triggered burst of nystagmus
Unilateral low-frequency
hearing loss
Usually normal
Seconds
Hearing loss,
hyperacusis
Nystagmus triggered by loud sounds
or pressure changes
Spontaneous “central” nystagmus;
gaze-evoked nystagmus; usually focal
neurologic signs
“Central” types or rarely “peripheral”
types of spontaneous or positional
nystagmus; usually other focal
neurologic signs
“Central” types of spontaneous or
positional nystagmus; gaze-evoked
nystagmus; cerebellar, extrapyramidal
and frontal signs
Normal interictal exam.
Ictal examination may show
“peripheral” or “central” types of
spontaneous or positional nystagmus.
“Central” types of spontaneous
or positional nystagmus; ictal,
or even interictal, gaze-evoked
nystagmus; ataxia; gait disorders
CENTRAL
Stroke/TIA
Abrupt onset; spontaneous
Stroke, >24 hr; TIA,
usually minutes
Brain-stem, cerebellar
Multiple sclerosis
Subacute onset
Minutes–weeks
Neurodegenerative
disorders
May be spontaneous or
positionally triggered
Minutes–hours
Unilateral visual loss,
diplopia,
incoordination,
ataxia
Ataxia
Migraine
Onset usually associated
with typical migraine
triggers
Seconds–days
Headache, visual aura,
photo-/phonophobia
Familial ataxia
syndromes
Acute-subacute onset;
usually triggered by
stress, exercise, or
excitement
Hours
Ataxia
TIA, transient ischemic attack.
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because dizziness can be the earliest symptom of a neurodegenerative disorder (de Lau et al., 2006) and also can be an important symptom of stroke, tumor, demyelination, or other problems
of the nervous system. Mental status usually can be inferred
from the patient’s ability to provide a history.
The cranial nerves should be thoroughly inspected in
patients complaining of dizziness. The most important part of
the examination lies in the assessment of ocular motor function
(described in more detail in the neurotology examination section). The examiner should determine whether the patient has
full ocular movements. A posterior fossa mass can impair facial
sensation and the corneal reflex on one side. Assessing facial
strength and symmetry is important because of the close anatomical relationship between the seventh and the eighth cranial
nerves. The lower cranial nerves also should be assessed by
observing palatal elevation, tongue protrusion, and trapezius
and sternocleidomastoid strength.
Increased tone or cogwheel rigidity may be the main finding
in a patient with an early neurodegenerative disorder. The peripheral sensory examination is important because a peripheral neuropathy can cause a nonspecific dizziness or imbalance. Reflexes
should be tested for their presence and symmetry. Also to be taken
into consideration are the normal decrease in vibratory sensation
and the possibility of absence of ankle jerks in elderly patients.
Coordination is an important part of the neurological examination in patients with dizziness because disorders characterized
by ataxia can manifest with the principal symptom of dizziness.
The finger-nose-finger test, the heel-knee-shin test, and rapid
alternating movements assess extremity coordination.
The Neurotological Examination
The neurotological examination is a specialty examination
expanding on certain aspects of the general neurological examination and also includes an audiovestibular assessment.
Ocular Motor Function Testing
The first step in assessing ocular motor function is to search
for spontaneous involuntary movements of the eyes. The examiner asks the patient to look straight ahead while observing for
nystagmus or saccadic intrusions. Nystagmus is characterized
by a slow and fast phase component and is classified as spontaneous, gaze-evoked, or positional. The direction of nystagmus
is described conventionally by the direction of the fast phase.
Whether the nystagmus is vertical, horizontal, or torsional,
or a mixture of these, provides important localizing information. Spontaneous nystagmus can have either a peripheral or
a central pattern. As a general rule with only rare exception,
central lesions can mimic a “peripheral” pattern of nystagmus
(Lee and Cho, 2004), but peripheral lesions cannot cause “central” patterns of nystagmus. A peripheral pattern of spontaneous nystagmus is unidirectional; that is, the eyes beat only to
one side (shown in Video 18-1, available at www.nicp.com).
Peripheral spontaneous nystagmus never changes direction. It
usually has a horizontal greater than torsional pattern because
of the physiology of the asymmetry in firing rates within the
peripheral vestibular system whereby the vertical canals cancel each other out. The prominent horizontal component results
from the unopposed horizontal canal. Other characteristics of
peripheral spontaneous nystagmus are suppression with visual
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fixation, increase in amplitude with gaze in the direction of the
fast phase, and decrease with gaze in the direction opposite that
of the fast phase.
Some patients are able to suppress this nystagmus so well
at the bedside, or have partially recovered from the initiating
event, that spontaneous nystagmus may appear only by removing visual fixation. Several simple bedside techniques can be
used to remove the patient’s ability to fixate. Frenzel glasses
are designed to remove visual fixation by using +30-diopter
lenses. An ophthalmoscope can be used to block fixation. While
the fundus of one eye is being viewed, the patient is asked to
cover the other eye. Probably the simplest technique involves
holding a blank sheet of paper close up to the patient’s face
(so as to block visual fixation ability) and observing for spontaneous nystagmus from the side.
Saccadic intrusions are spontaneous, unwanted saccadic
movements of the eyes that do not have the rhythmic fast and
slow phases characteristic of nystagmus. Saccades (fast movements of the eyes normally under voluntary control) shift gaze
from one object to another. Square wave jerks and saccadic
oscillations are the most common types of saccadic intrusions.
Square wave jerks are small-amplitude, involuntary saccades
that take the eyes off a target, followed after a normal intersaccadic delay (around 200 ms) by a corrective saccade to bring
the eyes back to the target. Square wave jerks can be seen in
neurological disorders such as cerebellar ataxia, Huntington’s
disease, or progressive supranuclear palsy but also occur in normal persons (see Chapter 38).
Saccadic oscillations are back-to-back saccadic movements
and thus do not have the intersaccadic interval characteristic of
square wave jerks. The appearance is thus of an oscillation.
When a burst occurs only in the horizontal plane, the term
ocular flutter is used (as shown in Video 18-2, available at
www.nicp.com). When vertical or torsional components are
present, the term opsoclonus is used. The eyes make constant
random conjugate saccades of unequal amplitude in all directions. Ocular flutter and opsoclonus are pathological findings
typically encountered in several different types of central nervous system diseases involving brainstem-cerebellar pathways.
Paraneoplastic disorders should be considered in patients presenting with ocular flutter or opsoclonus.
Gaze Testing
The patient should be asked to look to the left, right, up, and
down; the examiner looks for gaze-evoked nystagmus in each
position (demonstrated in Video 18-3, available at www.nicp.
com). Occurrence of a few beats of nonsustained nystagmus
with gaze greater than 30 degrees is called end-gaze nystagmus
and is a variable finding in normal persons. Gaze-evoked downbeating nystagmus (shown in Video 18-4, available at www.
nicp.com), vertical nystagmus that increases on lateral gaze,
localizes to the craniocervical junction and midline cerebellum.
Gaze testing also may trigger saccadic oscillations.
Smooth Pursuit
Smooth pursuit refers to the voluntary movement of the eyes
used to track a target moving at a low velocity. It functions to
keep the moving object on the fovea to maximize vision.
Although characteristically a very smooth movement at low
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C H A P T E R 18
velocity testing, smooth pursuit capability inevitably breaks
down when tested at high velocities. Although smooth pursuit
traditionally was thought to be highly variable in elderly subjects, a recent study found no significant decline in smooth pursuit capability in a group of healthy elderly persons (older than
75 years) tested yearly for at least 9 years (Kerber et al., 2006).
Patients with impaired smooth pursuit require frequent small
saccades to keep up with the target; accordingly, the term saccadic pursuit is used to describe this finding (see Video 18-3).
Abnormalities of smooth pursuit occur as the result of disorders
throughout the central nervous system and with use of tranquilizing medicines or alcohol and with fatigue. Patients with
diffuse cortical disease, basal ganglia disease, or diffuse cerebellar disease consistently have bilaterally impaired smooth
pursuit. Patients with early or mild cerebellar degenerative disorders may have markedly impaired smooth pursuit with mild
or minimal truncal ataxia as the only findings.
Saccades
Saccades are fast eye movements (velocity of this eye movement can be as high as 600 degrees per second) used to quickly
bring the image of an object onto the fovea. Saccades are generated by the burst neurons of the pons (horizontal movements)
and the midbrain (vertical movements). Lesions or degeneration of these regions leads to slowing of saccades, which can
also occur with lesions of the oculomotor neurons or extra ocular muscles. Severe slowing can be readily appreciated at the
bedside by instructing the patient to look back and forth from
one object to another. The examiner observes both the velocity
of the saccade and the accuracy. Overshooting saccades—
missing the target and then needing to correct, termed ocular
dysmetria—indicates a lesion of the cerebellum (as seen in
Video 18-5, available at www.nicp.com). Undershooting saccades are less specific and often occur in normal persons.
Dizziness, Vertigo, and Hearing Loss
243
lated by rotation of the chair. Nystagmus will be observed
during the rotation movements in patients with impairment of
VOR suppression, which is analogous to impairment of smooth
pursuit.
Vestibular Nerve Examination
Although the vestibular nerve examination often is omitted as
part of the cranial nerve examination in general neurology texts,
important localizing information can be obtained about the
functioning of the vestibular nerve at the bedside. A unilateral
or bilateral vestibulopathy can be identified using the head
thrust test (as shown in Video 18-6, available at www.nicp.
com). To perform this test, the physician stands directly in front
of the patient seated on the examining table. With the patient’s
head held in the examiner’s hands, the patient is instructed to
focus on the examiner’s nose. The head is then quickly moved
about 5 to 10 degrees to one side. In patients with normal
vestibular function, the VOR results in movement of the eyes
in the direction opposite the head movement. Therefore, the
patient’s eyes remain fixated on the examiner’s nose after the
sudden movement. The test is repeated in the opposite direction.
If the examiner observes a corrective saccade bringing the
patient’s eyes back to the examiner’s nose after the head thrust,
impairment of the VOR in the direction of the head movement
is identified. Rotating the head slowly back and forth (the doll’s
eye maneuver) also induces compensatory eye movements, but
both the visual and vestibular systems are activated by this lowvelocity test, enabling a patient with vestibular function loss but
normal visual pursuit to have normal-appearing compensatory
eye movements. This slow rotation of the head, however,
is helpful in a comatose patient, who is not able to generate
voluntary visual tracking eye movements. Slowly rotating the
head also can be a helpful test in patients with impairment of the
smooth pursuit system because smooth movements of the eyes
with slow rotation of the head indicate an intact VOR.
Optokinetic Nystagmus and Fixation Suppression
of the Vestibulo-ocular Reflex
Positional Testing
Optokinetic nystagmus (OKN) and fixation suppression of
the vestibulo-ocular reflex (VOR suppression) also can be
tested at the bedside. OKN is a combination of fast (saccadic) and slow (smooth pursuit) movements of eyes and can be
observed in normal persons when they are watching a moving train, for example. OKN is maximally stimulated with both
foveal and parafoveal stimulation; thus, the proper laboratory
technique for measuring OKN utilizes a full-field stimulus by
having the patient sit stationary while a large rotating pattern
moves around the patient. This test can be approximated at
the bedside by moving a striped cloth in front of the patient,
although this technique stimulates only the fovea. Patients with
disorders causing severe slowing of saccades will not be able to
generate OKN, so their eyes will become “pinned” to one side.
VOR suppression can be tested at the bedside using a swivel
chair. The patient sits in the chair and extends his or her arm in
the “thumbs-up” position out in front. The patient is instructed
to focus on the thumb and to allow the extended arm to move
with the body so that the visual target of the thumb remains
directly in front of the patient. The chair is then rotated from
side to side. The patient’s eyes should remain locked on the
thumb, demonstrating the ability to suppress the VOR stimu-
Positional testing can help identify peripheral or central causes
of vertigo. The most common positional vertigo, BPPV, is
caused by free-floating calcium carbonate debris, usually in the
posterior semicircular canal but occasionally in the horizontal
canal or, rarely, the anterior canal. The characteristic burst of
upbeat, torsional nystagmus is triggered in patients with BPPV
by a rapid change from erect sitting to supine head-hanging
left or head-hanging right—the Dix-Hallpike test (as shown
in Video 18-7, available at www.nicp.com). When present, the
nystagmus usually is triggered in only one of these positions.
A burst of nystagmus in the opposite direction (downbeat
torsional) occurs when the patient resumes the sitting position. A
repositioning maneuver can be used to liberate the clot of debris
from the posterior canal. We use the modified Epley maneuver
(Fig. 18-3) (as shown in Video 18-8, available at www.nicp.
com), which is more than 80% effective in treating patients with
posterior canal BPPV, compared with 10% effectiveness of a
sham procedure (von Brevern et al., 2006). The key feature of
this maneuver is the roll-across in the plane of the posterior
canal so that the clot rotates around the posterior canal and out
into the utricle. Once the clot enters the utricle, it may reattach
to the membrane, dissolve, or even remain free-floating in the
Ch18-H7525.indd 243
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Approach to Common Neurological Problems
A
PSC
D
E
C
B
E
Utricle
D
A
C
utricle, but the debris no longer disrupts semicircular canal
function. Recurrences, however, are common.
If the debris is in the horizontal canal, positionally triggered
direction-changing horizontal nystagmus is seen. Patients are
tested for the horizontal canal variant of BPPV by turning the
head to each side while lying in the supine position. The nystagmus can be either paroxysmal geotropic (beating toward the
ground) or persistent apogeotropic (beating away from the
ground) nystagmus. The side with the stronger nystagmus is
the side with the debris in the horizontal canal. The debris can
be removed from the canal by rolling the patient (barbecue
fashion) toward the normal side.
Positional testing also can trigger central types of nystagmus
(usually persistent downbeating), which may be the most prominent examination finding in patients with disorders like the
Chiari malformation or cerebellar ataxia (Kattah and Gujrati,
2005; Kerber et al., 2005). Positional nystagmus also may be
prominent in patients with migraine-associated dizziness (von
Brevern et al., 2005).
Figure 18-3
Treatment maneuver for
benign paroxysmal positional vertigo affecting
the right ear. The procedure can be reversed for
treating the left ear. The drawing of the labyrinth
in the center shows the position of the debris as
it moves around the posterior semicircular canal
(PSC) and into the utricle (UT). A, The patient is
seated upright, with head facing the examiner,
who is standing on the right. B, The patient is
then rapidly moved to head-hanging right position
(Dix-Hallpike test). This position is maintained
until the nystagmus ceases. The examiner moves
to the head of the table, repositioning hands as
shown. C, The head is rotated quickly to the left
with right ear upward. This position is maintained
for 30 seconds. D, The patient rolls onto the left
side while the examiner rapidly rotates the head
leftward until the nose is directed toward the floor.
This position is then held for 30 seconds. E, The
patient is rapidly lifted into the sitting position,
now facing left. The entire sequence should be
repeated until no nystagmus can be elicited. After
the maneuver, the patient is instructed to avoid
head hanging positions to prevent the debris
from reentering the posterior canal. (From Rakel,
E. (Ed.). 1995, Conn’s Current Therapy,
WB Saunders, Philadelphia.)
canal) and observing the eyes for brief associated deviations.
Pneumatoscopy (introducing air into the external auditory canal
through an otoscope) or Valsalva maneuver performed against
pitched nostrils or closed glottis also can trigger associated eye
movements. The direction of the triggered nystagmus helps
identify the location of the fistula.
Gait Assessment
Casual gait is examined for initiation, heel strike, stride length,
and base width. Patients are then observed during tandem walking and while standing in the Romberg position (with eyes open
and then closed). Taken together, a decreased heel strike or
stride length, flexed posture, and decreased arm swing suggest
Parkinson’s disease. A wide-based gait with inability to tandem
walk is characteristic of truncal ataxia. Patients with acute vestibular loss will veer toward the side of the affected ear for several days after the event. Patients with peripheral neuropathy or
bilateral vestibulopathy may be unable to stand in the Romberg
position with eyes closed.
Fistula Testing
In patients reporting sound- or pressure-induced dizziness,
testing for a defect of the bony capsule of the labyrinth can
be performed by pressing and releasing the tragus (small
flap of cartilage that can be used to occlude the external ear
Ch18-H7525.indd 244
Auditory Examination
The bedside examination of the auditory system begins with otoscopy. The tympanic membrane normally is translucent; changes
in color indicate middle ear disease or tympanosclerosis, a
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C H A P T E R 18
semicircular crescent or horseshoe-shaped white plaque within
the tympanic membrane. Tympanosclerosis is rarely associated
with hearing loss but is an important clue to past infections. The
area just superior to the lateral process of the malleus should be
carefully inspected for evidence of a retraction pocket or cholesteatoma. Findings on otoscopy usually are not associated
with causes of dizziness, because the visualized abnormalities
typically do not involve the inner ear.
The bedside hearing examination is not very sensitive as a
screening tool for hearing loss but can provide important information in patients with auditory symptoms. When a patient has
auditory complaints or when an audiovestibular disorder is
strongly suspected, a standard audiogram should be performed
because it more accurately assesses the wide spectrum of the
auditory system. The whisper test has been shown to be the
most sensitive test in picking up hearing loss at the bedside
(Bagai et al., 2006). For this test, the examiner stands behind
the patient to prevent lip reading and occludes and masks the
non-test ear using a finger to rub and close the external auditory
canal. The examiner then whispers a set of three to six random
numbers and letters. Overall, the patient is considered to have
passed the screening test if he or she repeats at least 50% of the
letters and numbers correctly.
The Weber and Rinne tests are commonly used bedside tuning fork tests. To conduct the Weber test, the base of a 256-Hz
or 512-Hz vibrating tuning fork is placed on the vertex, bridge
of the nose, upper incisors, or forehead. The patient is asked if
the sound is heard, and whether it is heard in the middle of the
head or in both ears equally, toward the left, or toward the right.
In a patient with normal hearing, the tone is heard centrally.
In asymmetrical or a unilateral hearing impairment, the tone
lateralizes to one side. Lateralization indicates an element of
conductive impairment in the ear in which the sound localizes,
a sensorineural impairment in the contralateral ear, or both.
The Rinne test compares the patient’s hearing by air conduction with that by bone conduction. The fork is first held against
the mastoid process until the sound fades. It is then placed 1 inch
from the ear. Normal persons can hear the fork about twice as
long by air as by bone conduction. If bone conduction is greater
than air conduction, a conductive hearing loss is suggested.
DIZZINESS AND VERTIGO
SPECIFIC DISORDERS CAUSING VERTIGO
Peripheral Vestibular Disorders
Peripheral vestibular disorders are important to understand
because they are common and readily identified at the bedside
and often are missed by frontline physicians (see Table 18-2).
Vestibular Neuritis
A common clinical presentation seen in the emergency department or outpatient clinic is severe vertigo of rapid onset, with
nausea, vomiting, and imbalance. The symptoms gradually
resolve over several days, but some symptoms can persist for
months. The etiology of this disorder probably is viral because
the course generally is benign and self-limited and it occurs in
Ch18-H7525.indd 245
Dizziness, Vertigo, and Hearing Loss
245
young healthy persons, occasionally in epidemics. Histopathological studies provide evidence of a peripheral vestibular localization and support a viral cause. A viral etiology also is likely
in most cases of Bell’s palsy and sudden sensorineural hearing
loss. The key to the diagnosis of vestibular neuritis is in recognizing the peripheral vestibular pattern of nystagmus and identifying a positive result on the head thrust test, in the setting of
vertigo of rapid onset without other neurological symptoms.
MRI findings usually are normal in these patients (Strupp et al.,
1998a). The course of vestibular neuritis is self-limited, and the
mainstay of treatment is symptomatic. A recent study showed
improvement in peripheral vestibular function, as measured by
caloric testing at 1 year, in patients with vestibular neuritis after
receiving methylprednisolone within 3 days of onset, compared
with placebo (Strupp et al., 2004). A formal vestibular rehabilitation program can help some patients compensate for the vestibular lesion (Strupp et al., 1998b).
Benign Paroxysmal Positional Vertigo
BPPV may be the most common cause of vertigo in the general
population. Patients typically experience brief episodes of vertigo when getting into and out of bed, turning in bed, bending
down and straightening up, or extending the head back to look
up. The condition is caused when calcium carbonate debris, dislodged from the otoconial membrane, inadvertently enters a
semicircular canal. The debris can be free-floating within the
affected canal (canalithiasis) or stuck against the cupula (cupulolithiasis). Repositioning maneuvers are highly effective in
removing the debris from the canal, although recurrence is common (see Fig. 18-3) (von Brevern et al., 2006). Once the debris
is out of the canal, patients are instructed to avoid extreme
head positions to prevent the debris from reentering the canal.
Patients also can be taught to perform a repositioning maneuver
should they experience a recurrence of the positional vertigo.
Ménière’s Disease
Ménière’s disease is characterized by recurrent attacks of vertigo
associated with auditory symptoms (hearing loss, tinnitus, and
aural fullness) during attacks. Over time, progressive hearing loss
develops. Attacks are variable in duration, with most lasting longer than 20 minutes, and are associated with severe nausea and
vomiting. The course of the disorder is also highly variable. For
some patients, the attacks are infrequent and decrease over time
while for others they can become debilitating. Occasionally, auditory symptoms are not appreciated by the patient or identified on
interictal audiogram early in the disorder, but these features inevitably develop in all patients with Ménière’s disease, usually within
the first year. Thus, the term “vestibular Ménière’s disease,” previously used to describe the disorder in patients with recurrent
episodes of vertigo but no hearing loss, is no longer used.
Although usually a disorder involving only one ear, Ménière’s
disease becomes bilateral in approximately one third of patients.
Endolymphatic hydrops, or expansion of the endolymph relative to the perilymph, is regarded as the etiology though the
underlying cause is not clear. The characteristic histopathological changes of endolymphatic hydrops, however, have been
identified in temporal bone specimens from patients with no
clinical history of Ménière’s disease (Merchant et al., 2005).
Some patients with well-documented Ménière’s disease experi-
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ence abrupt episodes of falling to the ground without loss of
consciousness or associated neurological symptoms. They often
report the sensation of being pushed or thrown to the ground.
The falls are hard and often result in fractures or other injuries.
These episodes have been called “otolithic catastrophes of
Tumarkin” because of the suspicion that they represent acute
stimulation of the otoliths.
The bedside interictal examination of patients with Ménière’s
disease may identify asymmetrical hearing, but the results of
the head thrust test usually are normal. Treatment initially
involves an aggressive low-salt diet and diuretics, although the
evidence for benefit of these treatments is poor. Intratympanic
gentamicin injections can be effective and are minimally invasive. Sectioning of the vestibular nerve and destruction of the
labyrinth are other procedures for patients with intractable disease (Minor et al., 2004). Autoimmune inner ear disease manifests as a fulminant variant of Ménière’s disease. Another
variant is so-called delayed endolymphatic hydrops, characterized by recurrent episodes of severe vertigo, without auditory
symptoms, developing years after a severe unilateral hearing
loss caused by a viral or bacterial infection.
Vestibular Paroxysmia
Vestibular paroxysmia is characterized by brief (seconds in
duration) episodes of vertigo, occurring suddenly without any
apparent trigger. The disorder may be analogous to hemifacial
spasm and trigeminal neuralgia, which are thought to be caused
by spontaneous discharges from a partially damaged nerve. In
patients with vestibular paroxysmia, usually unilateral dysfunction can be identified on vestibular or auditory testing. Some
cases may be caused by compression of cranial nerve VIII by a
normal vessel, and surgical removal of the vessel from the nerve
may cure the condition in rare cases. Many asymptomatic persons, however, have a normal vessel lying on the eighth nerve
(usually the anterior inferior cerebellar artery), so the decision
to operate in this delicate region should not be made without
strongly weighing the potential benefits against potential complications. A trial of an antiepileptic drug such as carbamazepine is clearly indicated before surgery is undertaken (Moon
and Hain, 2005).
or increasing middle ear pressure (Valsalva maneuver performed against pinched nostrils or compression of the tragus)
trigger brief nystagmus in the plane of the affected canal. Surgical repair of the fistula may be effective treatment in some cases.
Patients with this disorder may have hypersensitivity to boneconducted sound and low bone conduction thresholds on the
audiogram, even though air conduction thresholds remain normal (Minor, 2005). Other vestibular fistulas can result from
trauma or erosion of a cholesteatoma into the horizontal semicircular canal.
Other Peripheral Disorders
Many other peripheral vestibular causes of vertigo have been
recognized, but most are uncommon. Vertigo often follows a
blow to the head, even without a corresponding temporal bone
fracture. This so-called labyrinthine concussion results from
the susceptibility of the delicate structures of the inner ear to
blunt trauma. Vestibular ototoxicity, usually from gentamicin,
can cause a vestibulopathy that usually is bilateral but rarely
can be unilateral (Waterston and Halmagyi, 1998). Although
the most prominent symptoms are oscillopsia and imbalance,
some nonspecific dizziness may occur as well. Acoustic neuromas (vestibular schwannomas) typically manifest with slowly
progressive unilateral hearing loss, but vertigo can occur only
rarely. Because the tumor growth is slow, the vestibulopathy is
compensated by the central nervous system. Finally, any disorder affecting the skull base, such as sarcoidosis, lymphoma,
bacterial and fungal infections, or carcinomatous meningitis,
can cause peripheral vestibular symptoms.
Central Nervous System Disorders
The key to the diagnosis of central nervous system disorders
in patients presenting with dizziness is the presence of other
focal neurological symptoms or identifying central ocular motor
abnormalities or ataxia. Because central disorders can mimic
peripheral vestibular disorders, the most effective approach
in patients with isolated dizziness is first to rule out common
peripheral causes.
Brainstem or Cerebellar Ischemia/Infarction
Vestibular Fistulas
Superior canal dehiscence was first described in 1998 (Minor et
al., 1998). As the name implies, dehiscence of the bone overlying the superior canal results in formation of a fistula between
the superior canal and the middle cranial fossa. Normally the
semicircular canals are enclosed by the rigid bony capsule and
are unaffected by sound pressure changes. The oval and round
windows direct the forces associated with sound waves into the
cochlea and along the spiral basilar membrane. A break in the
bony capsule of the semicircular canals can redirect some of the
sound or pressure to the semicircular canals causing vestibular
activation, a phenomenon known as Tulio’s phenomenon. Before
the recognition of superior canal dehiscence, fistulas were
known to occur with rupture of the oval or round window or
erosion into the horizontal semicircular canal from chronic
infection. Pressure changes generated by increasing intracranial
pressure (Valsalva maneuver performed against a closed glottis)
Ch18-H7525.indd 246
Ischemia affecting vestibular pathways within the brainstem or
cerebellum often causes vertigo. Brainstem ischemia normally
is accompanied by other neurological signs and symptoms,
because motor and sensory pathways are in close proximity to
vestibular pathways. Vertigo is the most common symptom
with Wallenberg’s syndrome, characterized by infarction in the
lateral medulla in the territory of the posterior inferior cerebellar artery (PICA), but other neurological symptoms and signs
(e.g., diplopia, facial numbness, Horner’s syndrome) invariably
are present (see Chapter 21). Ischemia of the cerebellum can
cause vertigo as the most prominent or only symptom, and a
common dilemma is whether the patient with acute-onset vertigo needs an MRI study to rule out cerebellar infarction. CT
scans of the posterior fossa are not sensitive for excluding ischemia (Wasay and Halmagyi, 2005). Abnormal ocular motor
findings in patients with brainstem or cerebellar strokes include
(1) spontaneous nystagmus that is purely vertical, horizontal, or
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C H A P T E R 18
torsional; (2) direction changing gaze-evoked nystagmus (the
patient looks to the left and has left-beating nystagmus, then
looks to the right and has right-beating nystagmus); (3) impairment of smooth pursuit; and (4) overshooting saccades. Rarely,
central causes of nystagmus can closely mimic the peripheral
vestibular pattern of spontaneous nystagmus (Lee and Cho, 2004).
Dizziness, Vertigo, and Hearing Loss
247
der (de Lau et al., 2006). Usually, however, dizziness in these
patients is better clarified as imbalance. Positional downbeat
nystagmus occurs in patients with spinocerebellar ataxia type
6 (SCA6) and other progressive ataxia disorders (Kattah and
Gujrati, 2005; Kerber et al., 2005).
Epilepsy
Multiple Sclerosis
Dizziness is a common symptom in patients with multiple sclerosis (MS), and vertigo is the initial symptom in approximately
5% of patients. A typical MS attack has a gradual onset, reaching its peak within a few days. Milder spontaneous episodes of
vertigo, not characteristic of a new attack, and positional vertigo lasting seconds also are common in MS patients. The key
to the diagnosis is to find lesions disseminated in time and
space within the nervous system. Nearly all varieties of central
spontaneous and positional nystagmus occur with MS, and
occasionally patients show typical peripheral vestibular nystagmus when the lesion affects the root entry zone of the vestibular nerve. MRI of the brain identifies white matter lesions
in approximately 95% of patients with MS, although similar
lesions sometimes are seen in patients without the clinical
criteria for the diagnosis of MS.
Posterior Fossa Structural Abnormalities
Any structural lesion of the posterior fossa can cause dizziness.
With the Chiari malformation, the brainstem and cerebellum
are elongated downward into the cervical canal, causing pressure on both the caudal midline cerebellum and the cervicomedullary junction. The most common neurological symptom is a
slowly progressive unsteadiness of gait, which patients often
describe as dizziness. Vertigo and hearing loss are uncommon,
occurring in approximately 10% of patients. Spontaneous or
positional downbeat nystagmus is particularly common with
Chiari malformations, but other forms of central nystagmus
also occur. Dysphagia, hoarseness, and dysarthria can result
from stretching of the lower cranial nerves, and obstructive
hydrocephalus can result from occlusion of the basilar cisterns.
MRI is the procedure of choice for identifying Chiari malformations; midline sagittal sections clearly show the level of the
cerebellar tonsils.
The most common central nervous system tumors in the posterior fossa are gliomas in adults and medulloblastoma in children. Ocular motor dysfunction (impaired smooth pursuit,
overshooting saccades), impaired coordination, or other central
nervous system abnormalities occur in these patients. An early
finding in patients with cerebellar tumors can be central positional nystagmus. Vascular malformations (arteriovenous malformations, cavernous hemangiomas) similarly can cause dizziness
but generally are asymptomatic until bleeding occurs, at which
time they can be life-threatening.
Neurodegenerative Disorders
It is not uncommon for a patient with the main complaint of dizziness to have, or later develop, typical features of Parkinson’s
disease, a parkinsonian syndrome (progressive supranuclear
palsy, multiple systems atrophy), or a progressive ataxia disor-
Ch18-H7525.indd 247
Vestibular symptoms are common with focal seizures, particularly those originating from the temporal and parietal lobes. The
key to differentiating vertigo with seizures from other causes of
vertigo is the almost invariable association of seizures with an
altered level of consciousness. Episodic vertigo as an isolated
manifestation of a focal seizure is a rarity, if it occurs at all.
Vertigo in Inherited Disorders
The clinical evaluation of patients presenting with dizziness
has traditionally hinged on the history of present illness and
examination. With the recent rapid advances in molecular
biology, however, many causes of vertigo have been found to
have a strong genetic component. Obtaining a complete family
history is therefore very important, particularly in patients
without a specific identifiable cause for their dizziness. Because
the symptoms of these familial disorders often are not debilitating and can be highly variable, simply asking the patient
about a family history at the time of the appointment may not
be adequate. The patient should be instructed to specifically
interview other family members regarding the occurrence of
these symptoms.
Migraine
Migraine is a heterogeneous genetic disorder characterized
by headaches in addition to many other neurological symptoms. Several rare monogenetic subtypes have been identified.
Linkage analysis has identified a number of chromosomal loci
in common forms of migraine, but no specific genes have been
found. Benign recurrent vertigo usually is a migraine equivalent
because no other signs or symptoms develop over time, neurological examination findings remain normal, and a family or personal history of migraine headaches is common, as are typical
migraine triggers. Some patients with benign recurrent vertigo
(BRV) also report auditory symptoms similar to those described
by patients with Ménière’s disease, and a mild hearing loss also
may be evident on the audiogram (Battista, 2004). The key
factor distinguishing between migraine and Ménière’s disease
is the lack of progressive unilateral hearing loss in patients
with migraine. Positional vertigo also may occur in patients
with migraine (von Brevern et al., 2005). The cause of vertigo
in migraine patients is not known. Long-standing motion sensitivity including carsickness, sensitivities to other types of
stimuli, and a clear family history of migraine help support
the diagnosis. Although the diagnosis of migraine-associated
dizziness remains one of exclusion, little else can cause recurrent episodes without any other symptoms over a long period
of time.
In a genome-wide linkage scan in BRV patients (20 families),
linkage to chromosomal region 22q12 was found, but genetic
heterogeneity was evident (Lee et al., 2006). Testing linkage
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using a broader phenotype of BRV and migraine headaches
weakened the linkage signal. Thus, no evidence exists at this
time that migraine is allelic with BRV, even though migraine
has a high prevalence among BRV patients.
Familial Bilateral Vestibulopathy
In familial bilateral vestibulopathy (FBV), patients typically
have brief attacks of vertigo (seconds in duration), followed
by progressive loss of peripheral vestibular function leading
to imbalance and oscillopsia, usually with onset by the fifth
decade of life. Quantitative rotational testing shows gains
greater than 2 standard deviations below the normal mean for
both sinusoidal and step changes in angular velocity. Caloric
testing is insensitive for identifying bilateral vestibulopathy
because of the wide range of normal caloric responses. The
bedside head thrust test may show bilateral corrective saccades
when vestibulopathy is severe.
As the vestibulopathy becomes more severe, attacks of vertigo become less frequent and eventually cease. In contrast
with the genetic causes of hearing loss—for which 46 distinct
dominantly inherited genetic syndromes are recorded (Van
Camp and Smith, 2006)—only a few families afflicted with
FBV have been described (Brantberg, 2003; Jen et al., 2004b).
This disparity may be explained by the difficulty in identifying
such families; quantitative vestibular function testing is available only at major medical centers. Additionally, patients with
FBV may not present to doctors for evaluation if they have adequately compensated for the vestibular loss with other sensory
systems. Despite the profound vestibular loss, hearing remains normal. Linkage analysis performed in four families with
FBV maps to a chromosomal locus on 6q (Jen et al., 2004b).
This region does not overlap that for any known autosomal
dominant deafness or migraine syndromes.
gene was screened for mutations in idiopathic Ménière’s disease patients, but none were found. No studies report the use of
effective treatments for vertigo attacks, but as with FBV, these
attacks generally last only a few years and then become less
frequent, presumably as a result of loss of vestibular function.
Enlarged vestibular aqueduct syndrome (EVA), designated
DFNB4 (DFNB = deafness, familial, nonsyndromic, type B
[autosomal recessive inheritance]), is characterized by early-onset
hearing loss with enlargement of the vestibular aqueduct, best
seen on temporal bone computed tomography. The vestibular
aqueduct normally is less than 1.5 mm in diameter, but in EVA
it is much larger. The mechanism leading to hearing loss and
vertigo is not clear. The vestibular aqueduct contains the endolymphatic duct, which connects the medial wall of the vestibule
to the endolymphatic sac and is an important structure in the
exchange of endolymph. The enlargement may cause increased
transmission of intracranial pressures to the inner ear structures.
Nevertheless, the Valsalva maneuver, which increases intracranial pressure, does not trigger symptoms in patients with EVA.
Vertigo attacks last 15 minutes to 3 hours and are not associated with changes in hearing. Vertigo attacks may begin at the
onset of hearing loss (early childhood) or years later and can be
triggered by blows to the head or vigorous spinning (Oh et al.,
2001b). Quantitative vestibular testing may give normal results
in patients with EVA or may reveal mild to moderate loss of
vestibular function. Enlargement of the vestibular aqueduct
also has been observed in Pendred’s syndrome (PS), in branchiootorenal syndrome, with the CHARGE association (coloboma,
heart disease, atresia choanae, retardation of growth and
development and/or central nervous system anomalies, genital
hypoplasia, ear anomalies and/or deafness), in Waardenburg’s
syndrome, and in distal renal tubular acidosis with deafness.
EVA syndrome is allelic to PS, which is characterized by developmental abnormalities of the cochlea in combination with
thyroid dysfunction and goiter.
Familial Hearing Loss and Vertigo
Familial progressive vestibular-cochlear dysfunction was first
identified in 1988. Linkage to chromosomal locus 14q12-13
was later found, and the disorder was designated DFNA9
(DFNA = deafness, familial, nonsyndromic, type A [autosomal
dominant inheritance]) (Manolis et al., 1996). Using an organspecific approach, mutations within COCH were found to cause
DFNA9 (Robertson et al., 1998). This disorder of progressive
hearing loss is unique because no other genetic hearing loss
syndromes of autosomal dominant inheritance have vertigo as a
common symptom. Progressive hearing loss is the most prominent symptom of DFNA9, and vertigo occurs in approximately
50% of patients. When present, vertigo may be spontaneous or
positionally triggered (Lemaire et al., 2003). Age at onset is
variable, with symptoms developing in the second to third
decade of life in some patients and appearing later in others.
Vertigo attacks last minutes to hours and can be accompanied
by worsening of hearing, aural fullness, or tinnitus, thus closely
mimicking Ménière’s syndrome. Vertigo episodes can precede
or accompany onset of hearing loss. In addition to severe progressive hearing loss, eventually DFNA9 patients develop progressive loss of vestibular function and corresponding symptoms
of imbalance and oscillopsia. Because some patients have attacks
closely resembling those in Ménière’s syndrome, the COCH
Ch18-H7525.indd 248
Familial Ataxia Syndromes
Vestibular symptoms and signs are common with several of
the hereditary ataxia syndromes, including spinocerebellar
ataxia types 1, 2, 3, 6, and 7; Friedreich’s ataxia; Refsum’s
disease; and episodic ataxia (EA) types 2, 3, 4, and 5 (see
Chapter 76). In most of these disorders, the symptoms are
slowly progressive, with the cerebellar ataxia and incoordination overshadowing the vestibular symptoms. Head movement–
induced oscillopsia commonly occurs because the patient is
unable to suppress the VOR with fixation. Attacks of vertigo
may occur in up to half of patients with SCA6 (Takahashi et al.,
2004), many of which are positionally triggered (Jen et al.,
1998). Persistent down-beating nystagmus often is seen in
patients placed in the head-hanging position. The positional
vertigo and nystagmus can even be the initial symptom in these
patients. Most of the episodic ataxia syndromes have onset
before the age of 20 (Jen et al., 2004a). The attacks are characterized by extreme incoordination, leading to severe difficulty
in walking during attacks. Vertigo can occur as part of these
attacks, and migraine headaches are common. In fact, EA2,
SCA6, and familial hemiplegic migraine type 1 all are caused
by mutations within the same gene, CACNA1A. An additional
feature of EA2 and EA4 is the eventual development of interic-
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C H A P T E R 18
tal nystagmus and progressive ataxia. Patients with EA2 often
exhibit a dramatic response to treatment with acetazolamide.
COMMON CAUSES OF NONSPECIFIC
DIZZINESS
Patients with nonspecific dizziness probably are referred to
neurologists more frequently than patients with true vertigo.
These patients usually are bothered by lightheadedness (“wooziness”), presyncope, imbalance, motion sensitivity, or anxiety.
Side effects and toxicity from medications are common causes
of nonspecific dizziness. Bothersome lightheadedness can be
a direct effect of the medication itself or the result of lowering
of the patient’s blood pressure. Ataxia can be caused by antiepileptic medications and usually is reversible once the medication is decreased or stopped. Patients with peripheral neuropathy
causing dizziness report significant worsening of their balance
in poor lighting and also the sensation that they are walking
on cushions. Patients with panic attacks can present with nonspecific dizziness, but their spells invariably are accompanied
by other symptoms or signs such as sense of fear or doom, palpitations, sweating, shortness of breath, or paresthesias.
Other medical conditions such as cardiac arrhythmias or metabolic disturbances can cause nonspecific dizziness. In the
elderly, confluent white matter hyperintensities have a strong
association with dizziness and balance problems. Presumably
the result of small vessel arteriosclerosis, decreased cerebral
perfusion (Marstrand et al., 2002) has been identified in these
patients even when blood pressure taken at the arm is normal.
Patients with dizziness associated with white matter hyperintensities on MRI usually feel better sitting or lying down and
typically have impairment of tandem gait. Because many elderly
patients are taking blood pressure medications, at least a trial of
lowering or discontinuing these medications may be
warranted.
Dizziness, Vertigo, and Hearing Loss
249
most common diagnosis in older patients, but acute ischemia
of the vestibular nerve or vestibular labyrinth cannot be
excluded.
When the head thrust test gives a negative result (i.e., no
catch-up saccades are present), the possibility of a small
brainstem or cerebellar stroke that mimics vestibular neuritis should be considered (Lee and Cho, 2004; Norrving et al.,
1995; Thomke and Hopf, 1999). If hearing loss accompanies the episode, labyrinthitis is the most likely diagnosis,
but auditory involvement does not exclude a vascular cause,
because the anterior inferior cerebellar artery supplies both the
inner ear and brain. When hearing loss and facial weakness
accompany acute-onset vertigo, the examiner should closely
inspect the outer ear for vesicles characteristic of herpes zoster (Ramsay Hunt syndrome). An acoustic neuroma is a
slow-growing tumor and thus does not typically cause
acute-onset vertigo. Migraine can mimic vestibular neuritis,
although the diagnosis of migraine-associated vertigo hinges
on recurrent episodes and lack of progressive auditory
symptoms.
Recurrent Attacks of Vertigo
Patients present with symptoms, rather than with specific diagnosable disorders. The most common presentations of vertigo
are described next.
In patients with recurrent attacks of vertigo, the key diagnostic
information lies in the details of the attacks. Ménière’s disease
is the likely cause in patients with recurrent vertigo lasting
longer than 20 minutes and associated with unilateral auditory
symptoms. If the Ménière’s-like attacks manifest in a fulminant
fashion, the diagnosis of autoimmune inner ear disease should
be considered. Transient ischemic attacks (TIAs) should be
suspected in patients who experience brief episodes (minutes
in duration) of vertigo, particularly when vascular risk factors
are present and other neurological symptoms are reported.
Case series of patients with rotational vertebral artery syndrome
demonstrate that the inner ear and possibly central vestibular
pathways have high energy requirements and are therefore susceptible to levels of ischemia tolerated by other parts of the
brain (Choi et al., 2005). The migraine equivalent, benign recurrent vertigo, is characterized by a history of similar symptoms,
normal findings on physical examination, family or personal
history of migraine headaches, and typical triggers. Attacks are
otherwise highly variable, lasting anywhere from seconds to
days. If the duration of attacks is consistently only seconds, the
diagnosis of vestibular paroxysmia should be considered.
Acute Severe Vertigo
Recurrent Positional Vertigo
The patient presenting with new-onset severe vertigo probably
has vestibular neuritis, but stroke also should be a concern. An
abrupt onset with accompanying focal neurological symptoms,
particularly those that can be related to the posterior circulation,
suggests an ischemic stroke. If no significant abnormalities are
noted on the general neurological examination, attention should
focus on the neurotological evaluation. If no spontaneous nystagmus is observed, a technique to block visual fixation should
be applied. The direction of the nystagmus should be noted and
the effect of gaze assessed. If a peripheral vestibular pattern of
nystagmus is identified, a positive result on head thrust testing
localizes the lesion to the vestibular nerve. In young patients,
the diagnosis is vestibular neuritis. This also is probably the
Positional vertigo is defined by the symptom being triggered,
not simply worsened, by certain position changes. In the patient
complaining of recurrent episodes of vertigo triggered by certain head movements, the likely diagnosis is BPPV, but this is
not the only possibility. BPPV can be identified and treated at
the bedside, so positional testing should be performed in any
patient with this complaint. Positional testing also can uncover
the other causes of positionally triggered dizziness (Bertholon et al., 2002). The history strongly suggests the diagnosis of
BPPV when the positional vertigo is brief (duration less than
1 minute), has typical triggers, and is unaccompanied by other
neurological symptoms. A burst of vertical torsional nystagmus
is specific for BPPV of the posterior canal (Aw et al., 2005).
COMMON PRESENTATIONS OF VERTIGO
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If the result of the Dix-Hallpike test is negative, the examiner should search for the horizontal canal variant of BPPV.
Central positional nystagmus occurs as the result of disorders affecting the posterior fossa including tumors, cerebellar
degeneration, Chiari malformation, and MS. The nystagmus
of these disorders typically is downbeating and persistent,
although a pure torsional nystagmus may occur as well. Following loss of one vertebral artery, vertigo or significant
dizziness after head turns to the direction opposite the intact
artery may develop, because the bony structures of the spinal column can pinch off the remaining vertebral artery (Choi
et al., 2005). Central types of nystagmus develop as a result,
and vertigo can be the most prominent symptom. Finally,
migraine also can closely mimic BPPV (von Brevern et al.,
2005). Patients with migraine as the cause typically report
a longer duration of symptoms once the positional vertigo is triggered, and the nystagmus may be of a central or
peripheral type.
Sensorineural Hearing Loss
Sensorineural hearing loss may be secondary to lesions of the
cochlea, the auditory division of the acoustic nerve, or both,
and results in inability to perceive both bone- and air-conducted
sound normally. The spiral cochlea mechanically analyzes the
frequency content of sound. For high-frequency tones, only sensory cells in the basilar turn are activated, but for low-frequency
tones, all sensory cells are activated. Therefore, with lesions of
the cochlea and its afferent nerve, the hearing levels for different frequencies usually are unequal, and the phase relationship
between different frequencies may be altered. Patients with sensorineural hearing loss often have difficulty hearing speech that
is mixed with background noise, and they may be annoyed by
loud speech. Distortion of sounds is common; a pure tone may
be heard as noisy, rough, or buzzing, or it may be distorted so
that it sounds like a complex mixture of tones.
Central Hearing Loss
HEARING LOSS
Neurologists generally do not encounter patients principally
bothered by auditory symptoms, such as hearing loss or tinnitus, as opposed to patients with dizziness, who frequently are
referred for evaluation. Nevertheless, an understanding of the
auditory system, certain disorders causing auditory symptoms,
and audiograms can enhance the diagnostic abilities of the
neurologist.
CLASSIFICATION OF HEARING LOSS
Hearing loss can be classified as conductive, sensorineural, or
central based on the anatomical site of the pathological process.
Central hearing loss results from lesions of the central auditory
pathways. These lesions involve the cochlear and dorsal olivary
nuclear complexes, inferior colliculi, medial geniculate bodies,
auditory cortex in the temporal lobes, and interconnecting afferent
and efferent fiber tracts. As a rule, patients with central lesions do
not have impaired hearing levels for pure tones, and they understand speech so long as it is clearly spoken in a quiet environment.
If the listener’s task is made more difficult with the introduction
of background or competing messages, performance deteriorates
more markedly in patients with central lesions than it does in normal persons. Lesions involving the eighth nerve root entry zone
or cochlear nucleus (demyelination or infarction in the lateral pontomedullary region), however, can cause unilateral hearing loss
for pure tones. Because approximately half of afferent nerve fibers
cross central to the cochlear nucleus, this is the most central
structure in which a lesion can result in a unilateral hearing loss.
Conductive Hearing Loss
Conductive hearing loss results from lesions involving the
external or the middle ear. The tympanic membrane and
ossicles act as a transformer, amplifying the airborne sound and
effectively transferring it to the inner ear fluid. If this normal
pathway is obstructed, transmission can occur across the skin
and through the bones of the skull (bone conduction) but at
the cost of significant energy loss. Patients with a conductive
hearing loss can hear speech in a noisy background better than
in a quiet background, because they can understand loud speech
as well as anyone. The most common cause of conductive
hearing loss is impacted cerumen in the external canal. The
most common serious cause of conductive hearing loss is otitis
media, which can result from accumulation of either infected
fluid (suppurative otitis) or noninfected fluid (serous otitis) in
the middle ear, where it impairs the conduction of air-borne
sound. With chronic otitis media, a cholesteatoma may erode the
ossicles. Otosclerosis produces progressive conductive hearing
loss by immobilizing the stapes with new bone growth. Other
common causes of conductive hearing loss are trauma, congenital malformations of the external and middle ear, and glomus
body tumors.
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SPECIFIC DISORDERS CAUSING
HEARING LOSS
Ménière’s Disease
Auditory symptoms in Ménière’s disease consist of a fluctuating
sense of fullness and pressure, along with tinnitus and decreased
hearing in one ear. In the early stages, the hearing loss is completely
reversible, but in later stages, a residual hearing loss remains. Tinnitus may persist between episodes but usually increases in intensity
immediately before or during the acute episode. It typically is
described as a “roaring” like the sound of the ocean or a hollow seashell. In the early stages, evidence of hearing loss in the low frequencies appears on the audiogram. As the disorder progresses, a more
complete hearing loss occurs. In approximately 30% of patients, the
disorder becomes bilateral. Eventually, severe permanent hearing
loss develops, and the episodic nature spontaneously disappears.
When the hearing loss, particularly when bilateral, is fulminant
and rapidly progressive, the diagnosis of autoimmune inner ear disease should be considered. (See also see earlier section on Ménière’s
disease under “Specific Disorders Causing Vertigo.”)
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C H A P T E R 18
Cerebellopontine Angle Tumors
Acoustic neuromas (vestibular schwannoma) account for about
5% of intracranial tumors and more than 90% of cerebellopontine angle tumors. These tumors usually begin in the internal
auditory canal, producing symptoms by compressing the nerve
in its narrow confines. As the tumor grows, it protrudes
through the internal auditory meatus with stretching of adjacent
nerves over the surface of the mass, and deforms the cerebellum
and brainstem. By far the most common symptoms associated
with the acoustic neuromas are slowly progressive unilateral
hearing loss and tinnitus from compression of the cochlear
nerve. Rarely, acute hearing loss occurs, apparently from compression of the labyrinthine vasculature. Vertigo occurs
infrequently, but approximately half of the patients with an
acoustic neuroma complain of mild imbalance or disequilibrium. An epidermoid tumor, meningioma, facial nerve
schwannoma, or metastatic disease also can cause mass lesions
within the cerebellopontine angle. The audiometric pattern is
variable, but patients with angle tumors causing hearing loss
usually have poor speech discrimination, acoustic reflex decay,
and pure tone decay, rather than a marked asymmetry of pure
tones.
Superior Canal Dehiscence
Patients with superior canal dehiscence may experience conductive hyperacusis (hearing their eye move or the impact of
their feet during walking or running) and autophony (hearing
their own breath and voice sounds) in the affected ear. An airbone gap often is identified on standard audiograms. The Weber
tuning fork test typically permits lateralization to the affected
ear, and the Rinne turning fork test may show bone conduction
greater than air conduction. (See also section under “Specific
Disorders Causing Vertigo.”)
Dizziness, Vertigo, and Hearing Loss
251
Examples of noise greater than 85 dB that are common sources
of exposure include motorcycles, firecrackers, factory machinery, and music concerts.
Genetic Disorders
Familial hearing loss syndromes with vertigo are discussed earlier under “Familial Hearing Loss and Vertigo.” Currently, 46
genetically defined autosomal dominant hearing loss disorders
have been identified, as well as an additional 54 autosomal
recessive disorders and 5 X-linked disorders (Van Camp and
Smith, 2006). These disorders typically start early in life and
cause profound hearing loss. Vestibular symptoms are not
common.
Ototoxicity
The most common medications causing hearing loss are
aminoglycoside antibiotics, loop diuretics, and cisplatin.
Impaired elimination of these drugs, such as occurs with
renal insufficiency, predisposes affected patients to ototoxicity. Patients receiving high-dose salicylate therapy frequently complain of hearing loss, tinnitus, and dizziness,
which are rapidly reversible after cessation of the salicylate
ingestion.
COMMON PRESENTATIONS OF HEARING
LOSS
Asymmetrical Sensorineural Hearing Loss
Otosclerosis is a metabolic disease of the bony labyrinth that
usually manifests itself by immobilizing the stapes, thereby
producing a conductive hearing loss. A positive family history
for otosclerosis is reported in 50% to 70% of cases. Bilateral
involvement is usual, but approximately one fourth of cases are
unilateral. Conductive hearing loss is the hallmark of otosclerosis, but a combined conductive-sensorineural hearing loss pattern is frequent. Although otosclerosis is primarily a disorder
of the auditory system, vestibular symptoms and signs are more
common than is generally appreciated.
The evaluation of patients identified as having an asymmetrical sensorineural hearing loss is primarily the search for a tumor
in the area of the internal auditory canal or cerebellopontine
angle, or more rarely other lesions of the temporal bone
or brain. With an asymmetry of hearing defined as 15 dB or
greater in two or more frequencies, or a 15% or more asymmetry in speech discrimination scores, approximately 10%
of patients will have lesions identified on MRI (Cueva,
2004).
Acoustic neuromas are by far the most common abnormality
found. Other causative lesions may include glomus jugulare
tumors, ectatic basilar artery with brainstem compression, or
petrous apex cholesterol granuloma. Auditory brainstem response
testing shows sensitivity and specificity of approximately 70%,
with a false-positive rate of 77% but a false-negative rate of
29% (Cueva, 2004).
Noise-Induced Hearing Loss
Sudden Sensorineural Hearing Loss
Noise-induced hearing loss is extremely common in today’s
industrialized society. Approximately one third of people with
hearing loss can attribute at least part of the loss to noise exposure. The loss almost always begins at 4000 Hz, creating the
typical notched appearance on the audiogram, and does not
affect speech discrimination until late in the disease process.
Typically, levels of noise exposure greater than 85 dB are
required to cause the changes in the ear induced by loud noise.
The etiology of sudden sensorineural hearing loss is similar to
that in both Bell’s palsy and vestibular neuritis in that a viral
cause is presumed in a majority of cases, but proof of a viral
pathophysiology in a given case is difficult to obtain. The hearing loss can develop abruptly or evolve over several hours.
Acoustic neuromas may be found in approximately 5% of
patients with this presentation (Aarnisalo et al., 2004), but the
clinician also should be aware of the possibility of false-
Otosclerosis
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positive findings on MRI, particularly for lesions less than 6 mm
in diameter (Arriaga et al., 1995). Focal ischemia affecting the
cochlea, cochlear nerve, or the root entry zone also can cause an
abrupt loss of hearing over several minutes. In a patient at risk for
stroke, this cause should be considered early because it can be
the harbinger of basilar artery occlusion (Toyoda et al., 2002).
Sudden-onset bilateral hearing loss rarely can result from bilateral
lesions of the primary auditory cortex in the transverse temporal gyri of Heschl. Deficits can range from auditory agnosia
for speech or nonspeech sounds, with relatively normal hearing
thresholds, to rare cases of cortical deafness, characterized by
markedly elevated pure tone thresholds.
Hearing Loss with Age
The bilateral hearing loss commonly associated with advancing
age is called presbycusis. It is not a distinct entity but rather
represents multiple effects of aging on the auditory system. It
may include conductive and central dysfunction, but the most
consistent effect of aging is on the sensory cells and the neurons
of the cochlea. The typical audiogram appearance in patients
with presbycusis is that of symmetrical hearing loss, with the
tracing gradually sloping downward with increasing frequency.
The most consistent pathological condition associated with
presbycusis is a degeneration of sensory cells and nerve fibers
at the base of the cochlea.
TINNITUS
Tinnitus is a noise in the ear that usually is audible only to the
patient, although occasionally the sound can be heard by the
examining physician. It is a symptom that can be associated
with a variety of disorders that may affect the ear or the brain.
The most important piece of information is whether the patient
localizes it to one or both ears, or whether it is nonlocalizable.
As a general rule, tinnitus localized to one ear will have an
identifiable cause, but not when localized to both ears or nonlocalizable. The characteristics of the tinnitus can provide helpful
information. For example, the typical tinnitus associated with
Ménière’s disease is described as a roaring sound, like listening
to a seashell. The tinnitus associated with an acoustic neuroma
typically is a high-pitched ringing or resembles the sound of
steam blowing from a tea kettle. If the tinnitus is rhythmic, the
patient should be asked whether it is synchronous with the pulse
or with respiration. Recurrent rhythmic or even nonrhythmic
clicking sounds in one ear can indicate stapedial myoclonus.
The most common form of tinnitus is a bilateral high-pitched
sound that usually is worse at night when it is quiet, with less
background noise to mask it. It also may worsen when the
patient is under stress, or with the use of caffeine.
CLINICAL INVESTIGATIONS
DIZZINESS AND VERTIGO
The history and physical examination should determine what
diagnostic tests, if any, are necessary in patients presenting with
dizziness or vertigo. Studies have repeatedly shown that MRI,
Ch18-H7525.indd 252
audiogram, and vestibular tests are no different in unselected
patients complaining of dizziness when compared with agematched controls (Colledge et al., 1996, 2002; Hajioff et al.,
2002; Lawson et al., 1999; Yardley et al., 1998). Many disorders
causing dizziness can be diagnosed and even treated on the
initial encounter with no further diagnostic tests indicated.
General Tests
General tests such as blood chemistry panels, chest x-ray studies, or electrocardiograms are indicated only when the clinician
is searching for a specific abnormality. If a patient has otherwise unexplained nonspecific dizziness, ruling out metabolic
causes is indicated.
Imaging
Brain imaging commonly is ordered in patients complaining of
dizziness. Although a CT scan can rule out a large mass, smaller
lesions cannot be excluded, because of artifact and poor resolution in the posterior fossa (Wasay et al., 2005). MRI is the imaging modality of choice but is expensive. Determining which
patients should have an MRI can be difficult; an understanding
of the common peripheral vestibular disorders is important
for making this decision. Patients identified as having BPPV,
vestibular neuritis, or Ménière’s disease do not require an imaging study. In addition, patients with normal findings on neurological and neurotological examinations who report episodes
of dizziness dating back more than several months are unlikely
to have a significant abnormality on MRI. Although studies
show improved hearing preservation after surgery in patients
with acoustic neuromas when diagnosed early, this does
not mean every patient complaining of dizziness requires an
MRI to exclude this cause. Acoustic neuromas are rare, whereas
dizziness and vertigo are extremely common. In dizzy
patients with gradually progressive hearing loss, MRI may be
helpful.
Vestibular Testing
Vestibular testing consists of both ENG (or videonystagmography) and rotational chair testing (Fife et al., 2000; Furman
et al., 1996). A standard ENG test battery includes tests of
visual ocular control (saccades, smooth pursuit, and optokinetic
nystagmus), a search for pathological nystagmus with fixation
and with eyes open in darkness, and a bithermal caloric test
(Baloh and Honrubia, 2001). Standard rotational testing applies
multiple graded vestibular stimuli over short periods of time
and also can be used for tests of visual-vestibular interaction
(fixation suppression of the VOR). Vestibular testing can help
identify and quantify a unilateral or bilateral vestibular loss and
ocular motor abnormalities. The usefulness of vestibular testing
is highly dependent on both test administration and test interpretation. No agency in the United States monitors or credentials persons administering or interpreting vestibular tests.
Furthermore, artifacts are common, and patient cooperation
must be maintained throughout the test. With most subtests,
either ranges of normal are wide or standards have not been set.
These issues contribute to the large degree of variability in vestibular testing and thus to variable results from laboratory to
10/24/07 2:46:43 PM
C H A P T E R 18
laboratory. Despite these issues, reliable and clinically useful
results can be obtained from the numerous specialty centers
and community-based groups that have the requisite skills, ability, and knowledge.
Caloric testing is used mainly to identify a unilateral vestibulopathy. Rotational chair testing, used principally to identify a
bilateral vestibulopathy, is not readily available outside of academic centers. Abnormal findings on these tests must be put in
the context of the patient’s presentation and clinical findings.
Thus, even a decreased caloric response on one side does not
mean the patient’s symptoms are “peripheral” unless the clinical presentation fits. Most laboratories require a caloric asymmetry of 25% to 30% to indicate a significant reduced caloric
response on one side. Even with use of this criterion, finding a
caloric asymmetry is not uncommon in “normal” control subjects, particularly those with diabetes or migraine. Additionally,
impaired smooth pursuit or slow saccades should not be used
to make a “central” diagnosis if the patient did not understand
instructions or was overly tired or sedated.
Vestibular testing is particularly helpful in identifying the
affected side in patients with Ménière’s disease, although the
most localizing test is the audiogram. BPPV is a bedside diagnosis, and vestibular neuritis can be diagnosed at the bedside
as well. Vestibular testing does not add additional information
in patients with BPPV, in patients diagnosed with vestibular
neuritis who have a positive result on the head thrust test, or
in patients with bedside central nervous system findings unless
quantifying the abnormality is important. Although patients
with a bilateral vestibulopathy generally can be identified at the
bedside with bilateral catch-up saccades, rotational chair testing
can pick up more subtle impairment.
Auditory Testing
Because of well-established standards and formal certified
training programs, audiograms are a reliable and reproducible
test. Testing is not subject to the many artifacts and subjective
interpretations of vestibular testing. Because the hearing and
balance organs are close to one another and connected as part of
the labyrinth, share overlapping vascular supply, and have key
nervous system components in close proximity with a common
trunk entering the brain stem, a lesion of one system generally
affects the other. For patients complaining of vertigo, with or
without hearing loss, obtaining an audiogram may be helpful
in making a diagnosis or at least in establishing the patient’s
baseline hearing for later comparison. Although Ménière’s disease is characterized by hearing loss in addition to vertigo and
tinnitus, the auditory symptoms may not develop in the early
stages, or patients may not perceive the hearing loss.
HEARING LOSS AND TINNITUS
Virtually every patient with complaints of hearing loss or tinnitus should undergo a standard audiogram. Any patient with unilateral symptoms who may be a surgical candidate also should
have an MRI study with gadolinium to evaluate for a cerebellopontine angle mass. No study provides predictive information
regarding which patients with sudden sensorineural hearing loss
are most likely to have a causative lesion identified by MRI.
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253
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