NPH Normal Pressure Hydrocephalus From Diagnosis to Treatment

NPH
Normal Pressure
Hydrocephalus
From Diagnosis to Treatment
Adam S. Mednick, M.D., Ph.D.
Addicus Books
Omaha, Nebraska
An Addicus Nonfiction Book
Copyright 2013 by Adam S. Mednick, M.D., Ph.D. All
rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in
any form or by any means, electronic, mechanical, photocopied, recorded, or otherwise, without the prior written permission of the publisher. For information, write
Addicus Books, Inc., P.O. Box 45327, Omaha, Nebraska
68145.
ISBN 978-1-936374-96-0
Cover and interior design by Jack Kusler
This book is not intended to be a substitute for a physician,
nor do the authors intend to give advice contrary to that
of an attending physician.
Library of Congress Cataloging-in-Publication Data
Mednick, Adam, 1959Normal pressure hydrocephalus : from diagnosis to
treatment / Adam Mednick.
p. cm.
Includes bibliographical references and index.
ISBN 978-1-936374-96-0 (alk. paper)
1. Hydrocephalus--Diagnosis. 2. Hydrocephalus--Treatment.
I. Title. II. Title: Hydrocephalus.
RC391.M43 2013
616.85’8843--dc23
2012028044
Addicus Books, Inc.
P.O. Box 45327
Omaha, Nebraska 68145
www.AddicusBooks.com
Printed in the United States of America
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ii
1
Normal Pressure
Hydrocephalus: An Overview
I
f you’re like most people, you’ve probably never
heard of the brain disorder called normal pressure
hydrocephalus (NPH). This disease is more common than
most people realize, however. It is rarely mentioned by
the media, and few, if any, famous people have brought
attention to NPH like they have with other diseases such
as Parkinson’s disease and breast cancer. Consequently,
NPH is little known, and, because its symptoms mimic
those of other diseases, it is also often misdiagnosed and
can be mistaken for Parkinson’s disease, Alzheimer’s
disease, or other forms of dementia. Because the disease
usually affects older individuals, symptoms are sometimes
associated with “just getting older.”
Perhaps you’ve become interested in NPH because
you or a loved one has been diagnosed with it. If this is
the case, you may find some relief in learning about the
disease—its symptoms, causes, and treatment. In many
cases, the symptoms can be reversed with surgery.
What Is Normal Pressure Hydrocephalus?
NPH is a slowly developing condition in which too
much cerebrospinal fluid builds up in the brain. This clear
liquid circulates throughout the brain and the spine. The
term “hydrocephalus” is derived from the Greek word
1
Normal Pressure Hydrocephalus
Anatomy of the Brain
Choroid
plexus
(CFS production)
Skull
Scalp
Pia mater
Arachnoid
Lateral
ventricle
Dura mater
Foramen of
Monro
Third
ventricle
Subarachnoid
space
Fourth
ventricle
Subdural
space
“hydro,” which means “water,” and the word “cephalus,”
which means “head.” The term literally translates
to “water head.” In common terms it is sometimes
referred to as “water on the brain.” NPH is considered
a neurodegenerative disorder, which means that the
symptoms affecting the brain gradually worsen, usually
over the course of many months to years.
How NPH Develops
To better understand how NPH develops, let’s first
take a brief look at the processes that occur in the brain
that can lead to NPH. The human brain is bathed in a
clear fluid called cerebrospinal fluid (CSF). This fluid
provides nutrients to the brain and helps to cushion the
brain against movement inside the skull. Cerebrospinal
fluid circulates through four specialized chambers within
2
Normal Pressure Hydrocephalus: An Overview
Normal Ventricles
NPH
The four ventricles of the brain are a network of cavities that carry cerebrospinal
fluid. The illustration on the right indicates NPH—the ventricles are enlarged due
to the build-up of cerebrospinal fluid.
the brain called ventricles. A group of specialized cells
within the lining of these ventricles produces about one
pint of this fluid per day.
After traveling through the brain, the cerebrospinal
fluid circulates down through the center of the spinal
cord and circulates back up toward the brain where it
is reabsorbed back into the bloodstream. If the fluid is
not reabsorbed properly, however, it slowly builds up
within all of the ventricles, causing them to enlarge.
This enlargement distorts the surrounding brain tissue
and can cause permanent brain damage. It is this lack
of reabsorption of fluid that causes normal pressure
hydrocephalus.
It may seem confusing that the word “normal” is
part of the name of a serious brain disorder. What does
“normal” mean in this context? In this case, “normal”
refers to the level of pressure the cerebrospinal fluid is
3
Normal Pressure Hydrocephalus
Normal Brain
Front part
of lateral
ventricle
Third
ventricle
Back part
of lateral
ventricle
NPH Brain
Front part
of lateral
ventricle
Third
ventricle
Back part
of lateral
ventricle
The dark areas toward the center of the MRI scan show the ventricles. Notice the
ventricles in the NPH brain are enlarged.
putting on the brain. If doctors were to perform medical
tests on a person with NPH to measure the pressure of the
cerebrospinal fluid inside the brain, the pressure would
appear normal or only slightly elevated. This is because
NPH develops so slowly, over a period of months to
years, that the brain is able to gradually increase its
capacity to store the fluid within the ventricles. As a result,
4
Normal Pressure Hydrocephalus: An Overview
Types of Hydrocephalus
• Congenital hydrocephalus is present at birth and may
be caused by environmental influences during fetal
development or by genetic factors.
• Primary NPH can occur at any age, but is more
common in the elderly. If the NPH is primary, it
means the cause is unknown. The symptoms of
primary NPH usually develop slowly over the course
of months to years.
• Secondary NPH means the disease resulted from
previous injury such as hemorrhage, head trauma,
brain infection, tumor, or complications of radiation
therapy treatment for brain tumors. Symptoms in
secondary NPH may develop quickly.
• Hydrocephalus ex vacuo sometimes occurs in older
people, who have had considerable shrinkage of
their brains as part of the aging process. As a result of
this shrinkage, the ventricles, which contain cerebrospinal fluid, may appear larger in an MRI scan. This
enlargement is not caused by excess cerebrospinal
fluid and is not considered serious.
the pressure appears normal. The building pressure on
the brain, however, eventually leads to the development
of symptoms.
You may hear your neurologist refer to NPH as
“communicating hydrocephalus.” To understand what
“communicating” means in this context, you might think
of it in this way: because the fluid is circulating freely
through all the ventricles and the channels between them,
the fluid is communicating with all parts of the brain.
There are two types of NPH. The most common type is
called primary or idiopathic NPH, which means the cause
5
Normal Pressure Hydrocephalus
for the disease is not known. About 75 percent of all NPH
cases fall into this category. The other form, secondary
NPH, is the result of known causes such as previous brain
trauma, prior bleeding into the brain, infection, or as a
result of radiation therapy for the treatment of a brain
tumor. These conditions may leave scarring that interferes
with the way the cerebrospinal fluid drains from the brain.
This NPH that develops later in life is called “acquired
hydrocephalus.” There are other forms, including
that which is present at birth. It is called congenital
hydrocephalus. Another form, hydrocephalus ex vacuo,
is caused by shrinkage of brain tissue rather than an
excess of cerebrospinal fluid and does not cause the same
debilitating symptoms.
Symptoms of Normal Pressure Hydrocephalus
With NPH, not all the symptoms appear at the same
time, and some individuals may not develop all symptoms
even in advanced stages. Symptoms start to occur as the
build-up of cerebrospinal fluid gradually distorts brain
tissues around the ventricles, particularly in the nerve
fibers responsible for gait (one’s foot sequence or pattern
of walking), urinary continence, and cognition. As a
result, normal pressure hydrocephalus is characterized by
three primary symptoms: unsteadiness in gait, or trouble
walking; urinary incontinence; and cognitive difficulties,
which is often referred to as dementia.
Unsteadiness in Gait
Unsteadiness in gait, or trouble walking, is typically
the first symptom to develop in NPH, and it is also the
most common feature of this disease. Nearly everyone
with NPH develops unsteadiness. The unsteadiness
in NPH is typically described as “magnetic” because it
seems as if the feet are stuck to the floor. This symptom
is easily recognized by family and friends. Symptoms of
6
Normal Pressure Hydrocephalus: An Overview
unsteadiness range from mild to severe and may include:
• reduction in length of stride (short, shuffling
steps)
• reduction in step height
• difficulty taking steps, as if feet are stuck to the
floor
• forward-leaning posture
• a wide-based gait (walking with legs farther apart
than normal)
Because it can be difficult for individuals with NPH
to lift their feet, they typically have problems going up
stairs or curbs; they also have problems turning around
and may need to take multiple, short steps to do so. The
unsteadiness occurs when walking and is not associated
with weakness or numbness of the legs.
Urinary Incontinence
Urinary incontinence refers to the inability to control
one’s urine flow. With NPH, incontinence usually develops
gradually over the course of months to years. Symptoms
may include:
• urinating more frequently
• feeling an urgent need to urinate
• inability to hold urine
In severe cases, a person may become totally
incontinent and require the use of a diaper. In rare cases,
bowel incontinence may occur as well. Not all patients
with NPH will develop urinary incontinence and in those
who do, it usually begins after the onset of unsteadiness,
although either symptom may precede the other. There
are no characteristic features of urinary incontinence to
help distinguish NPH from other disorders.
7
Normal Pressure Hydrocephalus
Cognitive Difficulties
Cognition refers to the process of thinking and
knowing things. It includes awareness, reasoning,
remembering, perception, and problem solving. Cognitive
problems, or dementia, are typically the last of the three
primary features of NPH to develop; they usually begin
several months or years after the onset of unsteadiness
and urinary incontinence. By the time dementia settles
in, a person with NPH is usually in the more advanced
stages of this disease. Symptoms of cognitive difficulties
or dementia may include:
• forgetfulness
• loss of interest in daily activities
• short-term memory loss
• change in mood or behavior
• difficulty performing routine tasks
• difficulty in reasoning or making decisions
In the early stages of NPH, the dementia may be mild.
Symptoms may include such things as forgetting where
you left the car keys or forgetting someone’s name. Family
and friends may attribute these symptoms to a person’s
Normal pressure hydrocephalus was first described in the
New England Journal of Medicine in 1965 by Salomón Hakim,
M.D., a neurosurgeon. Dr. Hakim noted that many patients
whose symptoms included unsteadiness, urinary incontinence,
and dementia had unusually enlarged ventricles in the brain
without significant shrinkage of the surrounding brain seen in
people with Alzheimer’s dementia.
8
Normal Pressure Hydrocephalus: An Overview
William’s Story
I retired as an iron worker when I was sixty-five. About
three years later, I began having urgent needs to urinate; at
times, I would not make it to the bathroom and would wet my
pants. I blamed it on my prostate.
Then a year later, I developed a tremor in my right hand,
which made it difficult to write and to hold things. Also, my
walking had become slow like I was wading through water.
My doctor sent me to see a neurologist.
A neurologist said he didn’t see anything seriously wrong
with me so I didn’t have any tests. However, my symptoms
worsened. My doctor referred me to a second neurologist
who took one look at me and said I had Parkinson’s disease.
I started a medication called Sinemet, which did help my
walking and tremors a lot but it seemed the improvements
didn’t last long, usually a couple of months. So, the neurologist
increased the medication. But instead of improving, I started
worsening again.
My regular doctor then suggested I see a third neurologist
to figure out why I wasn’t improving. This neurologist took
a long time talking to me, and he watched me walk. He
performed a spinal tap to take off fluid that had collected in
my brain. Immediately, my walking improved for a few hours.
The neurologist told me I had a combination of Parkinson’s
disease and normal pressure hydrocephalus. He sent me to a
neurosurgeon, who recommended shunt surgery.
I had the surgery and it definitely gave me a better quality
of life. My walking improved a great deal, and I have had no
problem with the shunt. I still take medication for Parkinson’s,
but all in all, I’ve done pretty well.
William, age 77
9
Normal Pressure Hydrocephalus
Characteristics of NPH
• unsteadiness, urinary incontinence, and dementia
• too much cerebrospinal fluid in all four brain ventricles, due to impaired reabsorption of the fluid
• all of the ventricles in the brain are enlarged
• normal or mildly increased intracranial pressure
• condition is chronic
• cause may be unknown (primary/idiopathic
NPH) or known (secondary NPH)
• unsteadiness, incontinence, and dementia are
potentially reversible with surgical treatment.
getting older rather than a sign of a serious disease. The
dementia in NPH usually continues to worsen to the point
where a person requires help with all daily activities.
There are no characteristic features to distinguish
the dementia that comes with NPH from other forms of
dementia.
Order in Which Symptoms Appear
An important distinction between NPH and other
brain disorders is the order in which the symptoms appear.
It is extremely important to establish the timing of the
onset of the symptoms of NPH. The first symptom of NPH
is almost always unsteadiness, followed by incontinence
and then the gradual onset of memory problems, which
may not develop for years. In NPH, unsteadiness and
urinary incontinence, in either order, always occur before
the onset of dementia. If an individual’s symptoms do not
occur in this order, it is unlikely that he or she has NPH.
For example, one of the first symptoms of Alzheimer’s
disease is memory problems; then, as a person becomes
10
Normal Pressure Hydrocephalus: An Overview
progressively mentally incapacitated, he or she may
lose the ability to walk and control the bladder. With
Parkinson’s disease, unsteadiness is typically one of the
early symptoms, with incontinence developing later, but
incontinence is usually due to the difficulty in walking
to the bathroom. Furthermore, people with Parkinson’s
disease usually develop tremors and have diminished arm
swing when walking—neither of which is a symptom of
NPH. Dementia may occur late in the development of
Parkinson’s disease, usually long after the onset of other
symptoms such as tremors, stiffness, and shuffling the feet
when walking.
Risk Factors for NPH
The risks of developing NPH differ depending upon
whether you have primary or secondary NPH. Primary
NPH is a disease affecting individuals in their sixties and
beyond but is more common in those who are in their
seventies and eighties. Because secondary NPH occurs as
a result of an underlying cause, such as brain hemorrhage,
brain infection, head trauma, or radiation therapy to the
brain, this form of NPH may affect individuals of any age.
Primary and secondary normal pressure hydrocephalus
affect both men and women equally, regardless of race
or ethnicity.
How Common Is NPH?
There are no solid statistics on how many people
have NPH; however, various published studies, including
one from the Hydrocephalus Study Group, published in
the journal Neurosurgery in 2005, estimate that as many
as 350,000 Americans with dementia may have NPH.
Unfortunately, only about 11,000 are being treated for the
disease. The organization Alzheimer’s Disease International
estimates that worldwide, 36 million people have dementia
of whom 1.8 million (5 percent) may have NPH.
11
Normal Pressure Hydrocephalus
Treatment for NPH
There are currently no drugs to slow or reverse the
symptoms of normal pressure hydrocephalus. However,
some individuals with NPH may be candidates for surgery
that can often reverse the symptoms or at least slow
the progression of the disease. There are two forms of
surgery that can be performed. The first involves placing
a shunt in the brain, which is a tube that allows the
excess cerebrospinal fluid to drain away. The second
procedure involves creating a small hole in one of the
brain’s ventricles, which also allows the excess fluid to
drain away from the ventricles.
As a general rule, the longer the symptoms have
been present, the less likely it is that surgery will help.
This is why it is so important to get a diagnosis as early as
possible—the earlier the diagnosis, the better the chance
for reversing symptoms. Still, some people who have had
symptoms for years can also improve with surgery. The
surgical procedures for NPH are explained in chapter 4.
12