Nystagmus: clinical implications in otorhinolaryngology.one should understand anatomy and physiology of semicircular canals and vestibuloocular reflex in order to understand pathophysiology of nystagmus

1. Holy Spirit University of Kaslik-Lebanon
Grand round Saturday 1/11/2014
Khairallah Aoucar M.D pgy3 Ent

2.  In greek :”to nod in one’s sleep”
 Repetitive involuntary oscillatory mvt of the eyes
 The rythmic to and fro oscillation of the eyes has been
regarded as enigmatic
 Willbrand (distingueshed neuro
ophtalmologist)”never write on nystagmus it will lead
you no where!!

4.  Traditionaly divided into 2 types (upon clinical
impression of the waveform):
 1-pendular nystagmus :sinusoidal
 2-jerk nystagmus:
 slow phase away from the object of regard(strength of
nystagmus)
 by fast phase or saccadic(formed in the reticular
formation)toward the target(direction of nystagmus)

5.  Ophtalmic nystagmus won’t be discussed in this
lecture
 We will discuss :
 Vestibular nystagmus: peripheral vs central

6.  We assess hearing by an audiogram
 Vision by visual acuity
 What abt balance?
eye mouvements

7. Vor

8.  Stabilizes eye in space
 Necessary to see while head is in motion
 turn off(cancellation): flocculus.
 when we are following a moving target by moving our
head.
 If VOR stayed on the eyes would be driven off in the
wrong direction

9. The direct path, by itself, is not
enough. Why? Neural integrator

10. saccade only the fovea of the retina sees in detail. Saccades redirect
foveas to objects of interest.

12. Push pull
 Horizontal canals are paired together
 Vertical are paired together:RALP and LARP

14.  Ewald’s three laws:
 1. A stimulation of the semicircular canal causes a
movement of the eyes in the plane of the stimulated
canal
 2. In the horizontal semicircular canals, an
ampullopetal endolymph movement causes a greater
stimulation than an ampullofugal one.
 3. In the vertical semicircular canals, the reverse is
true.

15. Central vs peripheral:
central
 often pendular
 Usually do not have a fast-slow phase
 vertical in direction
 even though horizontal and jerk nystagmus can occur
with central lesions

16. Central vs peripheral:
peripheral
 typically present as a horizontal and jerk nystagmus.
 jerk nystagmus has its fast phase beating away from
the side of lesion while central lesion has its fast phase
beating towards the side of lesion
 Except in irritative forms like :bppv,acute attack of
meniere,acute phase of labyrinthitis

17. Central vs peripheral:
fast phase not so helpful
fixing gaze is helpful
 Why?because you do not know which side the lesion is
in the first place.
 A better way to do so is by fixing the gaze and see if
nystagmus is reduced or relieved
 In peripheral nystagmus, it is often relieved by gaze-fixation
while central nystagmus is not

18. Central vs peripheral:
sym and signs helpful
 cerebellar sign such as ataxia, dysdiadokinesia,
intention tremor, and scanning speech
 brainstem sign such as bulbar palsy, hemiplegia, or
unilateral sensory loss.
 But this may not be enough, central lesion can be
cerebellar, brainstem, posterior hemisphere and
cerebral hemisphere

19. Central Peripheral

20. Central vs peripheral:
waveform helpful
horizontal
 Peripheral: usually horizonto rotatory why? examples
 Lesion Rhscc:left horizontal nystagmus
 Lesion rpscc:downbeat and counterclockwise
 Lesion rscc:upbeat and counterclockwise

21. Central vs peripheral :peripheral
vertical and torsional
Maths!
 If lesion in all 3 canals in one side:
 horizontal+upbeat +counterclockwise
+downbeat+counterclockwise=horizonto-rotatory
 Extremely rare to get lesions to cause for pure vertical
or pure torsional=>
 To get pure vertical upbeat(eg): Rscc+lscc=>Upbeat
+conterclockwise+upbeat +clockwise=Upbeat
 To get Pure torsional(ipsi anterior canals )(eg)
:rscc+rpscc=>Upbeat+counterclockwise+downbeat+co
unterclockwise=counterclockwise

22. Central vs peripheral :waveform
central horizontal
 Horizontal nystagmus is a well-recognized finding in
patients with a unilateral disease of the cerebral
hemispheres, especially with large, posterior lesions. It
often is of low amplitude.
 Such patients show a constant velocity drift of the eyes
toward the intact hemisphere with fast saccade
directed toward the side of the lesion.

23. Central vs peripheral:
central horizontal
 Periodic alternating nystagmus (PAN), presented as
horizontal (almost always) nystagmus, then stopped
and followed by reverses direction of the nystagmus;
this cycle is repeated usually every 2 minutes.
 The presumed mechanism is damage to the vestibulo-ocular
tract at the pontomedullary junction; usually a
cerebellar lesion or brainstem lesion. Hence, it is also
has a wide range of causes.

24. Central vs peripheral:
central vertical:upbeat
 Upbeat nystagmus is due to pontine lesion which
result from the damage of ventral tegmental tract
(VTT) originating from the superior vestibular
nucleus(SVN).
 This tract course through the ventral pons and
transmitting excitatory upward vestibular signals to
the 3rd (oculumotor) nerve nucleus.
 Thus any lesion that disturbed this pathway could
result in upbeat nystagmus
 similar nystagmus is produced from lesion of caudal
medulla
Pierrot-Dseilligny C. and Milea D. Vertical nystagmus: clinical facts and hypothese. Brain
(2005), 128, pg. 1237-1246

25. Central vs peripheral :
central vertical :downbeat
 Downbeat nystagmus is usually caused by lesion of
cerebellar flocculus, which in turn resulting in
disinhibition of SVN-VTT pathway, followed by
relative hyperactivity which drive the upward slow-phase.
 structural lesion of the cervicomedullary junction such
as Chiari-malformation.
 Other possible causes include any form of lesion to
cerebellar flocculus.
Pierrot-Dseilligny C. and Milea D. Vertical nystagmus: clinical facts and hypothese. Brain
(2005), 128, pg. 1237-1246

26. Central vs peipheral:waveform
central pure torsional
 Vestibular end organ damage can never do a pure
torsional nystagmus
 Small amplitude=>medullar lesion
 Large amplitude=>diencephalic(thalamic)

27. Central vs peripheral :
waveform
pendular nystagmus
 Nystagmus invariably occurred in total blindness.
 If this response mechanism is disrupted, as in the case
of lesion to the optic nerve (optic neuritis or multiple
sclerosis), there will be pendular nystagmus.
 This also explains the presence of pendular nystagmus
in congenital blindness.
 However, lesion of the cortico-pontine-cerebellar or
olivocerebellar pathway pendular nystagmus
 =>hypothesis is incomplete and pendular nystagmus
has a wide range of causes
John S. Stahl et al. Acquired nystagmus. Arch Opthalmology (2000), 118, pg. 544-549.

28. Central vs peripheral:waveform
central see saw
Lesion in puititary gland and optic
chiasm

30. Gaze Evoked Nystagmus
physiologic end point
 Physiologic end point nystagmus :3 types
 1-fatigue
 2-unsustained
 3-sustained

31. 1:fatigue nystagmus
 Begins during extended (30 sec) maintenance of an
extreme gaze position(when horizontal gaze is
maximally deviated.
 Occurs in up tp 60%of normals
 May become increasingly torsional with prolonged
deviation effort
 May be greater in the adducting eye

32. 2-Unsustained end point
nystagmus
 1:the most frequently encountered physiologic
nystagmus
 2:its characteristics have never been studied
quantitatively
 3:few beats of nystagmus are within normal at gaze
deviation of 30 degrees or more

33. 3-sustained nystagmus
 Begins immediately upon or within several sec of
reaching an eccentric lateral gaze position
 Occurs in >60% of normal subjects with horizontal
gaze maintenance >40 degrees
 Quantitative oculography reveals that physiologic
nystagmus can begin with only 20 degree deviation
and is almost universal at deviations 40 or more to 50
degrees

34. Sustained nystagmus cnt
 The slow phase is lienar except with an extreme 40 to
50 degree deviation which a decreasing velocity
exponential may develop
 The nystagmus may be different in the 2 eyes but is
symmetric
 The amplitude of physiologic nystagmus doesnt
exceed 3 degrees

35. Gaze evoked nystagmus
 Pathologic in case of any:
 1-asymmetry in the two directions
 2-amplitude of 4 degree or more
 3-exponential slow phase with a gaze angle of <40
degree

36. Gaze-evoked nystagmus
 eyes cannot be maintained at an eccentric orbital
position and are pulled back toward primary position
by the elastic forces of the orbital fascia.
 corrective saccade moves the eyes back toward the
eccentric position in the orbit.
 the neural integrator network:
 between the vestibulocerebellum, the medulla (region
of the nucleus prepositus hypoglossi and adjacent
medial vestibular nucleus [NPH/MVN]), and the
interstitial nucleus of Cajal (INC).

37. Spontaneous Nystagmus
 Misnomer
 Doesnt arise spontaneously but rather is caused by
asymmetry in the tonic activity of the vestibular
system
 Spontaneous nystagmus refers to nystagmus that is
present without visual or vestibular stimulation.

38.  Spontaneous nystagmus can be observed both at the
bedside and in the vestibular laboratory

39.  The most common type of spontaneous nystagmus,
that is, spontaneous vestibular nystagmus, occurs with
unilateral peripheral vestibular lesions

40.  Spontaneous vestibular nystagmus is always
unidirectional and increases when the patient gazes in
the direction of the quick component of the
nystagmus.
 This gaze dependent change in nystagmus intensity is
called Alexander's Law

41.  As noted previously, loss of visual fixation also
increases the magnitude of spontaneous vestibular
nystagmus
 Thus, judicious use of gaze direction and presence or
absence of visual fixation can aid the examiner both at
the bedside and in the laboratory in judging whether
or not a spontaneous nystagmus is a result of a
vestibular abnormality.
 Failure of fixation suppression is highly suggestive of a
central pathologic condition

42. Conditions for spontaneous
 1 : it is a horizontal rotatory nystagmus
 2:it is suppressed by visual fixation
 3:it obeys alexanders law
 4:is present when the patient is in the sitting position

43. Clinical significance of spontaneous
 1:any SN with visual fixation is abnl
 2:many normal individuals have weak SN with vision
denied =>its abnl if the intensity of nystagmus is at
least 6 to 7 deg/sec

44.  The most common cause :
 Sudden unilateral lesion of the labyrinth or the
vestibular nerve
 Vestibular compensation normally minimizes this
asym within a few days but often doesnt entirely
abolish the asym so SN with vision denied persist for
years following a peripheral vestibular lesion

45.  Abnl SN in the absence of recent unilateral peripheral
lesion is uncommon.
 Most examiners regard it as a nonlocalizing sign of
vestibular dysfunction

46. Positional nystagmus
 Refers to a nystagmus that appears only during certain
positions of the head or which is greatly influenced by
the position of the head

47. Aschan
classification
cupulolithiasis

48. Head shake test  pts head is positioned with chin inclined down 30
degrees
 Head is rotated rapidly to one side.
 Normal response includes no nystagmus / few beats of
nystagmus
 In unilateral labyrinthine dysfunction - nystagmus is
present with slow phase directed towards the direction
of dysfunctional labyrinth

49. Head impulse test

50. Head impulse test
 Does the absence of an overt saccade mean that the
canal is normal? No
 Covert saccade(hidden saccades during the head
rotation had concealed their inadequate VOR).
 can entirely obscure or conceal even a complete, total
loss of canal function.
 scleral search coils: “gold standard” or VHIT

51. Head impulse :red flag
 Can be + in lateral pontine stroke(aica)
 using caloric test will help
 A normal HIT with acute vestibular syndrome :r/o
PICA stroke (pseudo neuritis)

52. Caloric test
 Unilateral weakness (UW) is used to evaluate
symmetry. In many clinics, a UW greater than 25% is
significant.
 %UW = [((RC + RW) – (LC + LW))/(RC + RW + LC +
LW)] X 100.
 A negative number => right unilateral weakness
 positive number=> left unilateral weakness.
 Unilateral weakness is indicative of a peripheral
vestibular lesion

53. Caloric test
 Bilateral weakness: Average caloric responses of 6° per
second or less are consistent with a bilateral weakness.
 Borderline bilateral weakness is noted when the
average responses are between 7-9° per second.
 Abnormally weak bilateral responses may be due to
bilateral peripheral vestibular pathology or central
interruption of the vestibuloocular reflex (VOR).
 When a borderline bilateral weakness or bilateral
weakness is observed, drug effects should be excluded.

54. ENG test Abnormality Localization
Saccade Dysmetria
Slowing
Cerebellum
Central
Tracking Saccadic
Disorganized
Central
Optokinetic Asymmetry central
Positional Nystagmus(eyes open,
fixed direction)
Nystagmus (eyes open,changing
direction)
Nystagmus (eyes closed, fixed
direction)
Nystagmus (eyes closed,
changing
direction)
Usually central
Central
Peripheral
central
Hallpike Rotatory, upbeating
Rotatory, downbeating
-onset after canal
latency, fatigable
Posterior canal
scc

55. Eye Movements Evoked by Sound or Changes in
Middle Ear Pressure:
Fistula test
 Performed by applying +ve &- ve
 Nystagmus can be visualized by the
examiner or recorded using ENG
machine
 Positive in the presence of fistula

56. Positive
Result(indicates
Perilymphatic Fistula)
Negative
Result(Normal)
when positive pressure
is applied with the
pneumatic otoscope
Onset of
Nystagmus towards
ipsilateral ear.
No changes
when negative pressure
is applied with the
pneumatic otoscope
Nystagmus also reverses
& changes its direction
towards contralateral
ear.
No changes

57. +ve fistula :perilymphatic fistula
 Oval Window –(most common site)
 Stapedectomy surgery (for otosclerosis)
 Head trauma or barotrauma (pressure injury)
 Acoustic trauma
 Round window -
 Barotrauma -- SCUBA diving, airplane pressurization
 Congenital malformations (such as Mondini dysplasia)
 Otic capsule—3rd window
 SCC Dehiscence syndrome (anterior SCC)
 Cholesteatoma
 Fenestration(stapedectomy)
 Temporal bone fracture
 Micro-fissure

58. Fistula test
False positive fistula test(Hennebert
sign)
False negative fistula test
Congenital syphilis
(here stapes footplate is hypermobile,
so even small pressure changes in ear,
cause excessive movement of stapes
footplate & excessive stimulation of
utricular macule)
In Dead ear ( inner ear is damaged),
there will be NO response even if a
Perilymphatic fistula exists.
25% cases of Meneire’s disease.
(here in 25% cases of meniere’s ,fibrous
bands form connecting to utricular
macule to stapes footplate)
Also seen when cholesteatoma covers
the site of fistula & doesn’t allow
pressure changes to be transmits to
labyrinth.

59. Eye Movements Evoked by Sound or
Changes in Middle Ear Pressure:
Tullio phenomenon
 Sound-induced vestibular symptoms such as vertigo,
nystagmus, oscillopsia, and postural imbalance .
 Tullio's phenomenon is seen mainly in:
 Superior canal dehiscence,
 Meniere's syndrome,
 vestibulofibrosis.
 other causes of perilymph fistula,
 post fenestration surgery(for otosclerosis).

60. PEARLS

61. THANK YOU