Clinical Correlate: Examination of Nystagmus Najwa Al-Bustani Neurology AHD July 20-2011

Objectives: Define Nystagmus. How to describe Nystagmus. Types. Physiological & Physilogical Nystagmus.

What is Nystagmus ? A repetitive rhythmic involuntary oscillation of the eyes that is usually conjugate. Biphasic ocular oscillation containing slow eye movement that are responsible for its genesis and continuation.

How to describe Nystagmus ?

Waveforms: Jerk (most common): slow drift ‘slow phase’ followed by quick reset ‘quick phase’. Slow phase waveforms can be: Increasing velocity exponential = congenital. Decreasing velocity exponential = gaze- evoked. Constant (linear) velocity = vestibular. 2. Pendular: sinusoidal oscillation ‘like pendulum’, phases have equal speed.

Waveforms:

Trajectory: Horizontal. Vertical. Torsional. Combination of all three.

Direction: Usually defined by its fast phase. Conjugacy: Conjugate: both eyes move in same direction. Disconjugate: eyes move in different direction >> disjunctive.

Alexander’s law: Null zone: Jerk nystagmus usually increases in intensity when looking in the direction of the fast phase. Null zone: The field of gaze where nystagmus intensity is minimal.

Grading of jerk Nystagmus: Grade 1: present only when looking in the direction of the quick component. Grade 2 : also present when looking straight ahead.     Grade 3 : present when looking in the direction of the quick component, when looking straight ahead and when looking in the direction of the slow component.

Not all Nystagmus is Pathological

Physiologic Nystagmus: End-position: few beats of horizontal nystagmus when the eyes are first moved to extreme horizontal positions in the orbit.

Vestibular Nystagmus: Caloric Nystagmus: Irrigation with worm water (in the head up supine position) causes endolymph in the horizontal canal to move toward the ampulla, exciting the hair cells & driving a slow phase eye movement away from the irrigated side. Cold water: inhibits the horizontal canal, produce slow phase toward the irrigated side.

Vestibular Nystagmus: Rotational Nystagmus (VOR): Prolonged head rotation produces a slow phase in the direction opposite to the head movement interrupted by quick phases in the same direction as head movement. This serves to stabilize retinal images as head moves.

Optokinetic Nystagmus: Driven by prolonged full-field visual motion. Supplements the VOR to stabilize vision.

Pathological Nystagmus

38 year old female, c/o vomiting X few hours. ? left earache and tinnitis. http://www.youtube.com/watch?v=yo-zA1CuKUI&feature=related

Peripheral Vestibular Nystagmus: Jerk nystagmus due to imbalance of vestibular inputs.

Unilateral Vestibular hypofunction: Acute lesion to one labyrinth or vestibular nerve >> spontaneous horizontal/torsional nystagmus. Because of the tonic input from the intact side is suddenly unopposed.

Unilateral Vestibular hypofunction: The eyes drift (slow phase) toward the lesioned side and quick phase beat toward the intact side. The intensity usually greatest when looking toward the intact side (Alexander’s law). Direction does not change with gaze, unlike gaze-evoked nystagmus.

Unilateral Vestibular hypofunction: May be partially or fully suppressed by vision and is best seen when fixation is removed: Frenzel goggles. When looking at one optic nerve with direct ophthalmoscope, cover the fellow eye.

Vestibular hypofunction: Bilateral vestibular lesions do not cause nystagmus because the lesion is symmetric and there is no imbalance.

Bruns Nystagmus Primary position Rt. Lt.

Bruns Nystagmus: May be seen in large tumors in the CP angle. 2 components: Horizontal nystagmus beating away from the lesion when looking away from the lesion (vestibular nystagmus-accentuated by Alexander’s law) due to vestibular nerve involvement.

Bruns’ Nystagmus: Horizontal nystagmus beating toward the lesion when looking toward the lesion (unilateral gaze-evoked nystagmus) due to compression of the adjacent brainstem and cerebellar flocculus.

Benign Paroxysmal Positional Nystagmus (BPPN): Brief (<1min) nystagmus provoked by changes in head position relative to gravity. Caused by free-moving otoconia that have become lodged in a semicircular canal. Usually affects the posterior canal: slow phase directed downward with a torsional component in which the upper pole of the eyes rotate away from the affected ear (upbeating-torsional nystagmus).

Benign Paroxysmal Positional Nystagmus (BPPN): Diagnosed by Dix-Hallpike maneuver. Treated by repositioning maneuvers (Epley) that move the otoconia out of the affected canal.

Dix-Hallpike maneuver: Rt. Ear.

Epley Maneuver

Congenital Nystagmus: May be present at birth, more commonly appears later in infancy. Sporadic or Genetic: AD (6p12), AR, X-linked recessive. Associated with oculocutaneous albinism. Commonly accentuated by attempted fixation or anxiety. Typically damped by eye closure, sleep & convergence.

Congenital Nystagmus: Does not cause oscillopsia. Distinct waveforms: Conjugate horizontal-torsional pendular and/or jerk nystagmus. Similar amplitude in both eye. Jerk nystagmus has increasing velocity slow phases.

Congenital Nystagmus: Foveation periods: brief cessation of eye motion, often following quick phases, during which clear vision is possible (if there are no afferent visual abnormalities). There is often orbital position (null point) where nystagmus is minimal and vision is best.

Congenital Nystagmus: May be associated with other abnormalitis: Strabismus, latent nystagmus, head oscillations.

Spasmus Nutans

Spasmus Nutans: Triad of: head turn, head nodding and nystagmus. Typically develops during the first year of life. Resolves by age 10. Horizontal or vertical pendular nystagmus with low amplitude and high frequency.

Spasmus Nutans: May be monocular or of different amplitude and/or phase in each eye. Optic pathway glioma can cause acquired monocular nystagmus and should be ruled out by MRI.

Convergence-retraction nystagmus

Convergence-retraction nystagmus: Convergence and/or retraction of the eyes elicited by attempted upward saccades or quick phases. Best seen during stimulation with a downward-moving OKN stimulus.

Convergence-retraction nystagmus: Part of the dorsal midbrain syndrome: Impaired vertical gaze (particularly upwoard). Light-near dissociation of pupillary responses. Lid retraction (Collier’s sign). Convergence-retraction nystagmus. Spasm or paresis of convergence, accommodation. Skew deviation.

Convergence-retraction nystagmus: Due to lesion affecting the area of the posterior commissure: Tumors (pineal). Hydrocephalus (e.g aqueductal stenosis). Hemorrhage or infarction (midbrain, thalamus). Multiple sclerosis or inflammatory lesions.

Upbeat Nystagmus

Upbeat Nystagmus: Spontaneous nystagmus with downward slow phases in primary position. Etiologies: Focal lesions: (infarction, tumor, demyelinating) of the medulla or cerebellum. Cerebellar degeneration. Wenicke’s encephalopathy.

Downbeat Nystagmus:

Downbeat Nystagmus: Spontaneous upward drift of the eyes. Characteristic sign of a lesion of the vestibulocerebellum or its pathway or its pathway in the brainstem (cerebellar degeneration, MS, stroke). Other causes: drug toxicity ‘Li, AED’, Wernicke’s encephalopathy.

Downbeat Nystagmus: Often occurs in the context of a more general cerebellar syndrome but may present in isolation & be progressive. Slow phase waveform may have constant, decreasing, or increasing velocity. Commonly enhanced by down and lateral gaze.

Gaze-Evoked Nystagmus

Gaze-Evoked Nystagmus: Loss of eccentric gaze holding, eyes tend to drift back to the center of the orbit. Weak neural intergrator does not produce suffeciently strong tonic innervation to hold the eyes against elastic forces.

Gaze-Evoked Nystagmus: Direction of nystagmus depends on gaze direction. Typically horizontal. May also include upbeat nystagmus with upgaze. With sustained gaze >> nystagmus will often diminish.

Gaze-Evoked Nystagmus: Upon return to center position, there may be a brief oppositely directed nystagmus (rebound nystagmus). Gaze-evoked & downbeat nystagmus often occur together in patients with cerebellar degeneration.

Gaze-Evoked Nystagmus: Etiologies: Vestibulocerebellar lesions >> cerebellar degeneration. Functional neural integrator impairment due to drugs (sedatives, AED), metabolic derangements.

Pendular Nystagmus

Pendular Nystagmus: Sinusoidal oscillation (no quick phase). May have complex waveform that include horizontal, vertical, and torsional components. Elliptical nystagmus: horizontal & vertical components out of phase. Congenital or acquired.

Pendular Nystagmus: Etiologies: MS. Oculopalatal tremor syndrome. Whipple’s disease. Toulene toxicity. Severe visual loss. Pelizaeus-Merzbcher disease.

Seesaw Nystagmus

Seesaw Nystagmus: The interstitial nucleus of Cajal (INC), adjacent to the medial longitudinal fasciculus in the midbrain tegmentum, has been frequently implicated in the pathogenesis of SSN.

Seesaw Nystagmus: Disconjugate vertical-torsional nystagmus. Torsional component has the same direction in both eyes, vertical movement is in opposite direction. During each cycle, one eye moves upward and intorts and the other eye moves downward and extorts.

Seesaw Nystagmus: May be pendular (seesaw) or jerk (hemi- seesaw). Associated with: Midbrain stroke. Medial medullary stroke. MS. Chiari Malformation. Visual loss Parasellar masses. Congenital.

Periodic Alternating Nystagmus (PAN): Horizontal jerk nystagmus that changes direction every 2 minute. Present in the primary position, unlike gaze-evoked nystagmus. May be accompanied by periodic head deviations that reduce the nystagmus by moving the eyes into relative null position.

Periodic Alternating Nystagmus (PAN): Results from lesions to the vestibulocerebellum (nodulus/uvula) combined with either flocculus/paraflocculus lesions or visual loss. Baclofen abolishes nystagmus.

Periodic Alternating Nystagmus (PAN): In cases of visual loss >> improvement of vision (viterectomy, cataract extraction) may eliminate nystagmus. Congenital PAN is less regularly periodic than acquired, does not respond well to baclofen. In comatose patient with no quick phase, PAN may be seen as periodic alternating gaze deviation.

Latent Nystagmus

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