Downbeat nystagmus

drift [ °/s]
Downbeat nystagmus
5
gaze -evoked
0
-5
bias
upward drift
-20
up
0
position [ °]
20
down
vertical
motoneurons!
-
-
y-group!
Ncl. vest. sup.!
-
-
cerebellar
flocculus!
-
no drift!
vertical
motoneurons!
-
-
y-group!
Ncl. vest. sup.!
-
-
cerebellar
flocculus!
-
downbeat!
Removal of flocculus / paraflocculus leads
to downbeat nystagmus
Zee et al. 1981
Flocculus
Nodulus
vertical
motoneurons!
-
-
y-group!
Ncl. vest. sup.!
-
-
cerebellar
flocculus!
-
no drift!
vertical
motoneurons!
-
-
y-group!
Ncl. vest. sup.!
-
-
cerebellar
flocculus!
-
upbeat!
vertical
motoneurons!
-
-
y-group!
Ncl. vest. sup.!
-
-
cerebellar
flocculus!
-
no drift!
vertical
motoneurons!
-
-
y-group!
Ncl. vest. sup.!
-
-
cerebellar
flocculus!
-
upbeat!
Push-pull semicircular canals
ampulla
Top View
anterior
horizontal
posterior
head
Right Horizontal –
Left Horizontal
(RHLH)
excitation
inhibition
Push-pull semicircular canals
ampulla
Right Anterior –
Left Posterior
(RALP)
head
Right Anterior –
Left Posterior
(RPLA)
excitation
inhibition
head
Ewald‘s 2nd law
Excitation drives the VOR better than inhibition (1892).
linear pathway
linear
•  excitation ! -inhibition
$
nonlinear
•  not cutoff (always > 0 Hz)
nonlinear pathway
•
h
•
h head velocity
•
e eye velocity
NI neural integrator
$
•  excitation only
NI
Eye
Plant
•
e
•  sensitive to high accelerations
nonlinear
$
linear
Lasker et al. 2000
(modified)
Normal head-impuls test*
*Halmagyi G.M., Curthoys I.S (1988)
Archives of Neurology
Normal
response
30
Position [°]
20
Head
10
0
-10
Eye
-20
-30
0
50
100
150 200 250
Time [ms]
300
350
Normal response
30
VOR latency ~ 5–10 ms
VOR relatively symmetric
in the horizontal plane
20
Head
Position [°]
10
0
-10
Eye
-20
-30
Aw et al. 1996
Collewijn and Smeets 2000
Tabak et al. 1997
Weber et al. 2008
0
50
100
150
200
Time [ms]
250
300
350
Head not moving
Head impulse to the right
linear
linear
90
150
0
non-linear
+80
non-linear
0
•
h=0
0
non-linear
0
20
•
h = 200 º/s
non-linear
140
0
0
43%
-60
90
linear
57 %
30
linear
Head impulse to the right
Head impulse to the right
linear
150
80
non-linear
20
•
h = 200 º/s
non-linear
140
0
•
h = 200 º/s
non-linear
60
0
-60
-60
30
linear
30
linear
Vestibular deficit 30
on the left
20
Position [°]
Eye
10
0
-10
Head
-20
-30
0
50
100
150
200
Time
Time[ms]
[ms]
250
300
350
Head impulse to the right
Head impulse to the left
•
h = 200 º/s
•
h = 200 º/s
60
non-linear
0
-80
non-linear
20
-60
+80
30
linear
150
linear
Gain reduction is greater during ipsilesional head acceleration.
Head impulse to the right
Head impulse to the left
•
h = 200 º/s
•
h = 200 º/s
60
non-linear
0
-80
non-linear
20
-60
+80
30
150
linear
linear
central enhancement of
contralesional nonlinear pathway
contralesional gain #
gain asymmetry #
Horizontal head impulse testing
Gain
ipsilateral
contralateral
1.2
1.2
1.0
1.0
0.8
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0
0
acute
acute: < 3 days
chronic: > 2 months
chronic
acute
chronic
Schmid-Priscoveanu et al. 2001
Leftsided vestibular deficit
correcting saccade
Vestibular catch-up saccades
" VOR gains
! VCUS Frequency
30
Position [°]
20
10
Eye
! VOR gains
" VCUS Frequency
0
-10
Head
-20
-30
0
50
100
150 200 250
300 350
Time [ms]
Tian et al. 2000
Vestibular catch-up saccades
Overt saccades
Covert saccades
Weber et al. 2008
DVA in unilateral vestibular
deafferentiation
**
**
*
difference between
* Significant
ipsi- and contralateral HIT
*
difference between
** Significant
patients and healthy subjects
Tian et al. 2001
Rotation
Translation
Motion simulator
Turntable
Linear vestibulo-ocular reflex
SWAY
HEAVE
SURGE
Otolith organs
acceleration
Tilt translation dilemma
Equivalence principle:
An accelerometer can
not distinguish between
gravity and linear
acceleration.
(1907)
or
acc
„tilt-translation
dilemma“
Horizontal translational VOR
20
Horizontal [º]
15
10
5
0
-5
0
0.2
Time [s]
0.4
static ocular
counterroll
(OCR)#
subjective visual vertical
(SVV)#
Static ocular counterroll
Eye torsion [°]
right eye intorts
left eye extorts
right eye
left eye
10
5
0
-5
-10
Chair roll with 2°/s
right ear
down
Hermann Rudolph Aubert (1826-1892)#
Georg Elias Müller
(1850-1938)#
A-effect!
undercompensation of SVV#
roll: 60-150°#
E-effect!
undercompensation of SVV#
roll: < 60° (Müller)#
> 150° (Kaptein & Van Giesbergen)#
SVV accuracy during
eccentric rotation#
eccentric rotation vs. tilt
normal
patient