Holy Spirit University of Kaslik-Lebanon

Grand round Saturday 1/11/2014

Khairallah Aoucar M.D pgy3 Ent

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 neuroophtalmologist)”never write on nystagmus it will lead you no where!!

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)

Ophtalmic nystagmus won’t be discussed in this lecture

We will discuss :

Vestibular nystagmus: peripheral vs central

We assess hearing by an audiogram

Vision by visual acuity

What abt balance?

eye mouvements

Vor

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

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

saccadeonly the fovea of the retina sees in detail. Saccades redirect foveas to objects of interest.

Push pull Horizontal canals are paired together

Vertical are paired together:RALP and LARP

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.

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

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

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

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

Central Peripheral

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

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+counterclockwise=counterclockwise

Central vs peripheral :waveformcentral 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.

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.

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

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

Central vs peipheral:waveformcentral pure torsional

Vestibular end organ damage can never do a pure torsional nystagmus

Small amplitude=>medullar lesion

Large amplitude=>diencephalic(thalamic)

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 nystagmusin congenital blindness.

However, lesion of the cortico-pontine-cerebellar or olivocerebellar pathway pendular nystagmus

=>hypothesis is incomplete and pendular nystagmushas a wide range of causes

John S. Stahl et al. Acquired nystagmus. Arch Opthalmology (2000), 118, pg. 544-549.

Central vs peripheral:waveformcentral see saw

Lesion in puititary gland and optic chiasm

Gaze Evoked Nystagmusphysiologic end point Physiologic end point nystagmus :3 types

1-fatigue

2-unsustained

3-sustained

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

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

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

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 doesntexceed 3 degrees

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

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).

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.

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

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

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

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

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

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

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

Abnl SN in the absence of recent unilateral peripheral lesion is uncommon.

Most examiners regard it as a nonlocalizing sign of vestibular dysfunction

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

cupulolithiasis

Aschanclassification

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

Head impulse test

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

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)

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

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.

ENG test Abnormality Localization

Saccade DysmetriaSlowing

CerebellumCentral

Tracking SaccadicDisorganized

Central

Optokinetic Asymmetry central

Positional Nystagmus(eyes open,fixed direction)Nystagmus (eyes open,changingdirection)Nystagmus (eyes closed, fixeddirection)Nystagmus (eyes closed, changingdirection)

Usually central

Central

Peripheral

central

Hallpike Rotatory, upbeatingRotatory, downbeating-onset after canallatency, fatigable

Posterior canalscc

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

Positive Result(indicates Perilymphatic Fistula)

Negative Result(Normal)

when positive pressure is applied with the pneumatic otoscope

Onset ofNystagmus towards ipsilateral ear.

No changes

when negative pressure is applied with the pneumatic otoscope

Nystagmus also reverses & changes its direction towards contralateralear.

No changes

+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

Fistula testFalse 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’sdisease.(here in 25% cases of meniere’s ,fibrous bands form connecting to utricularmacule to stapes footplate)

Also seen when cholesteatoma covers the site of fistula & doesn’t allow pressure changes to be transmits to labyrinth.

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).

PEARLS

THANK YOU