Nystagmus Flashcards
what is the pathophysiology of nystagmus?
inability to maintain fixation, loss of normal inhibitory influences on eye movement control and loss of the normal symmetric input from vestibular pathways to ocular motor nuclei
what is nystagmus?
rhythmic to-and-from eye movements that incorporate a slow phase
what is jerk nystagmus?
a slow drift phase from visual target followed by a fast corrective phase (saccade) back to the target
what is pendular nystagmus?
back and forth slow phase movements that occur without a fast phase
why are saccadic intrusions or saccadic oscillations not considered nystagmus?
they do not have a slow phase - they only abnormal saccadic movements that affect visual fixation
what is oscillopsia?
a sensation of environmental movement - seen in acquired nystagmus not congential
how is oscillopsia different than vertigo?
vertigo - sensation that your head is spinning
oscillopsia - sensation that environment is spinning
what type of history may be associated with nystagmus?
history of oscillopsia, decreased VA, associated neurological symptoms, and family history of abnormal eye movements or strabismus
what is a null point?
the position of gaze where the nystagmus is at its minimum or absent
what is a neutral point?
the point where the nystagmus changes direction
how do you report the direction of jerk nystagmus?
report the direction of the fast phase - the pathology is indicated by the slow phase
what is dissociated nystagmus?
the amplitude of the oscillations differs between eyes
what is disconjugate nystagmus?
the direction of the oscillations differs between eyes
what type of movement is seen with vestibular nystagmus?
linear (velocity stays the same)
what type of movement is seen with congenital nystagmus?
increasing velocity exponential (velocity increases towards the end phase)
what type of movement is seen with gaze-evoked nystagmus?
decreasing velocity exponential (some abnormality in gaze centers)
what type of movement is seen with congenital or acquired nystagmus?
pendular
what are the 3 types of normal fixational movements?
microtremor, slow drift and microsaccade (assist retinal/visual function)
what is a microtremor?
small up and down movements
what is a slow drift?
the eyes drift off fixation
what is a microsaccade?
the re-direction of the eyes back to fixation
what are the 3 types of physiologic nystagmus?
vestibular, optokinetic, and eccentric gaze or end gaze nystagmus
when is end gaze nystagmus considered pathologic?
when it is persistent, asymmetric and accompanied by other features
what are the 4 types of early onset nystagmus?
infantile nystagmus syndrome (congenital nystagmus), fusional maldevelopment nystagmus syndrome (latent nystagmus), monocular nystagmus of childhood and spasmus nutans
what conditions is infantile nystagmus syndrome associated with?
ocular albinism, achromatopsia, leber congenital amaurosis and aniridia
what do patients with infantile nystagmus syndrome require for testing?
electropysiologic testing (ERG, VEP) and neuroimaging
what is the VA like in patients with infantile nystagmus syndrome?
not associated with afferent pathway disease - VA is proportional to the foveation period between the involuntary movements
the amplitude and frequency match the level of VA loss
what types of nystagmus are seen in infantile nystagmus syndrome?
almost always conjugate and horizontal, even in up and down gaze - can be continuous or intermittent
can be jerk or pendular
frequently has a null point
what happens to the nystagmus in infantile nystagmus syndrome when the patient uses visual attention or focus (especially at distance)?
the nystagmus worsens or amplifies
what happens to the nystagmus in infantile nystagmus syndrome when the patient convergences (especially at near)?
the nystagmus is dampened
what happens to the optokinetic pattern in infantile nystagmus syndrome?
there is a reversal of the pattern = the slow phase of the eye movements move in the direction opposite of the rotating drum
what is fusional maldevelopment nystagmus (latent nystagmus)?
early onset, horizontal, jerk nystagmus that begins or is accentuated by monocular viewing conditions
what is the direction of the fast phase in fusional maldevelopment nystagmus?
the fast phase beats towards the viewing eye and away from the occluded eye (the slow phase is towards the nose) - it reverses direction on alternating covering
what is fusional maldevelopment nystagmus associated with?
always associated with esotropia and frequently associated with dissociated vertical deviation (DVD)
how do you measure VA with fusional maldevelopment nystagmus?
a standard occluder with degrade VA - need to use a high plus lens or frosted occluder/filter
what is manifest latent nystagmus (MLN)?
latent nystagmus seen when both eyes are open - MLN is initiated spontaneously when the esotropic eye is physiologically suppressed
what does latent nystagmus look like when studied with eye movement recordings?
constant velocity slow phase vs. increasing exponential seen in congenital nystagmus
what is monocular nystagmus of childhood?
small amplitude, same eye, and vertical or elliptical movement (vertical is never good - always neuroimage these patients)
if APD and optic atrophy = may be glioma
what is Heimann-Bielschowsky phenomenon?
monocular nystagmus with long standing decreased vision - caused by optic atrophy or amblyopia
what is spasmus nutans?
develops in first year of life - intermittent, binocular, very small amplitude, high-frequency, horizontal, pendular nystagmus
what is spasmus nutans accompanied with?
head nodding (subtle), abnormal head posture or torticollis, strabismus and amblyopia
what is the triad seen in spasmus nutans?
low amplitude/high frequency, head nodding and eccentric fixation
what are the 3 types of vestibular nystagmus?
peripheral vestibular nystagmus, central vestibular imbalance nystagmus and central vestibular instability nystagmus (periodic alternating nystagmus)
what is peripheral vestibular nystagmus?
unilateral, typically sudden, dramatic onset of disequilibrium with vertigo, nausea/vomiting worsened by particular head movements or postures, oscillopsia, tinnitus and hearing loss
followed by a slow phase and gradually waning symptoms
what is the origin for peripheral vestibular nystagmus?
peripheral end-organ (semi-circular canals, otolithic structures, vestibular nerve)
disruption of normally symmetric vestibular afferent inputs to neural integrator
if there was a reduction in input from the left-sided vestibular lesion (in peripheral vestibular nystagmus) what does the nystagmus look like?
a leftward bias and requires a corrective saccade away from the side of the lesion - left slow phase and right jerk nystagmus
what is the typical direction for peripheral vestibular nystagmus?
vestibular neuropathy disrupts all 3 semicircular canals and the otolithic organs - mixed horizontal-torsional pattern is seen
can be vertical and changes depending on direction of gaze
what is Alexander’s law?
the nystagmus is more pronounced when gaze is directed towards the side of the fast-beating component
if the nystagmus is purely vertical or torsional what type of nystagmus is that?
central vestibular nystagmus
what is a way to dampen peripheral vestibular nystagmus?
focusing or visual fixation will dampen movement
what will amplify peripheral vestibular nystagmus?
vigorous head shaking, hyperventilation, mastoid vibration and valsalva maneuver
what are the 4 clinical patterns of peripheral vestibular nystagmus?
- acute, monophasic, secondary to (viral) vestibular neuronitis
- recurrent form of vestibular dysfunction - exemplified by Meniere disease
- BPPV (benign paroxysmal positional vertigo)
- toxic aminoglycosides (will be bilateral)
what is Bruns nystagmus?
combination of gaze-evoked and peripheral vestibular nystagmus
due to large cerebellopontine angle tumor
what is central vestibular nystagmus?
mixed horizontal-torsional nystagmus, associated neurological signs/symptoms and VA may be normal
acute onset of vertigo, nausea, dizziness, oscillopsia
what is CVS downbeat nystagmus?
the most common form of central vestibular nystagmus - results from lesions that produce defective vertical gaze (upward drift of eyes and corrective downward saccade)
what type of lesion can cause CVS downbeat nystagmus?
cervical-medullary junction (structural lesion)
what is the most common structural lesion for CVS downbeat nystagmus?
Arnold-Chiari type 1 malformation = developmental abnormality with posterior fossa crowding and cerebellar tonsillar protrusion into the foramen magnum
what are the differentials for CVS downbeat nystagmus?
arnold-chiari type 1 malformation, tumors at foramen magnum, demyelination (MS), paraneoplastic syndrome
what is the management for CVS downbeat nystagmus?
“off label” clonazepam, baclofen, gabapentin, BO prisms to induce convergence, memantine, 4-aminopyridine, and 3,4-diaminopyridine
what causes CVS upbeat nystagmus?
lesions in the posterior fossa = in the brainstem (often medulla), anterior cerebellar vermis
other common causes = demyelination, stroke, cerebellar degeneration, and tobacco smoking
what is CVS torsional nystagmus?
indicates a central lesion if purely torsional - associated with medullary lesion (syringobulbia, lateral medullary infarction)
what is periodic alternating nystagmus?
strictly horizontal nystagmus that oscillates predictably in direction, amplitude, and frequency
congenital or acquired
what does the acquired form of periodic alternating nystagmus look like?
oscillation cycle of 2-4 minutes
ex: a right beating nystagmus develops progressively larger amplitudes and higher frequencies up to a certain point, then wanes, eventually leading to a short period of downbeat or no nystagmus - then it reverses direction
what is periodic alternating nystagmus typically associated with?
dysfunction of the cerebellar nodulus and uvula
what are common causes of periodic alternating nystagmus?
MS, cerebellar degeneration, Arnold-chiari type 1 malformation, and stroke
anticonvulsant medication
what medication can you use for periodic alternating nystagmus?
baclofen for acquired
what type of vision loss is seen with periodic alternating nystagmus?
bilateral VA loss - if it is reversible then PAN may stop
what is acquired pendular nystagmus?
pendular, slow-phase eye movements in horizontal, vertical and torsional planes (vs. congenital which is more common and only horizontal)
what are some causes of acquired pendular nystagmus?
MS (asymmetric or monocular forms), blindness secondary to optic nerve disease
assuming reduced VA in both eyes the nystagmus is larger in the eye with poorer VA
what is oculopalatal myoclonus or tremor?
acquired pendular nystagmus + palatal myoclonus (an acquired oscillation of the palate)
eye movements are continuous and rhythmic (1 Hz) and associated with synchronous movements of the facial muscles, pharynx, tongue, larynx, diaphragm, trunk and extremities
what causes oculopalatal myoclonus or tremor?
arises after several months after a lesion occurs that involves the Guillain-Mollaret triangle
what is see-saw nystagmus?
form of disconjugate nystagmus in which 1 eye elevates/intorts and the other depresses/extorts
pendular, slow frequency and similar amplitudes
what causes see-saw nystagmus?
can be congenital (congenital achiasma is rare cause)
acquired = large tumors of the parasellar region that impinge the 3rd ventricle (crainopha-ryngioma)
what is see-saw nystagmus associated with?
retinitis pigmentosa, albinism, and optic nerve hypoplasia
what can cause dissociated nystagmus?
associated with lesions of the medial longitudinal fasciculus (MLF) which produce INO
nystagmus of the abducting eye when gaze is opposite the lesion
what are the 2 types of gaze-holding deficiency nystagmus?
eccentric gaze nystagmus and gaze instability (“run-away”) nystagmus
what causes eccentric gaze nystagmus?
develops due to inability to maintain fixation in eccentric gaze - eyes drift back to midline and a corrective saccade brings them back on eccentric target
dysfunction in the neural integrator
what happens in eccentric gaze nystagmus when the eyes move towards the fast phase?
the amplitude/frequency of the nystagmus increases (Alexander’s law)
what is the neural integrator for horizontal gaze?
nucleus prepositus hypoglossi and the medial vestibular nuclei
what is the neural integrator for vertical gaze?
interstitial nucleus of cajal
what is the job of the neural integrator?
ensures a level of neural activity adequate to maintain eyes against the elastic forces of the orbit - if it fails to function properly (leaky) eccentric eye position cannot be maintained
what are some causes of sustained gaze evoked nystagmus (no longer normal)?
ethanol, medications like anticonvulsants, sedatives, and hypnotics
what do you assume is present if the gaze-evoked nystagmus is asymmetric?
an ipsilateral lesion of the brainstem or cerebellum (typically stroke, demyelination or tumor is present)
what causes rebound nystagmus?
usually a manifestation of cerebellar disease
what is rebound nystagmus?
prolonged eccentric viewing - a jerk nystagmus in the opposite direction after an attempted return to primary gaze
what is gaze instability or run-away nystagmus?
oscillation slow phases are directed away from central position
associated with neurological signs/symptoms and vestibulo-cerebellar involvement
what causes gaze instability or run-away nystagmus?
MRI/CT scan of brain show underlying central nervous system pathology
prognosis depends on underlying disease
what type of nystagmus can you use Ofbaclofen (GABA agonist) for?
acquired form of PAN (periodic alternating nystagmus)
what type of nystagmus can you use Carbamazepine derivatives for?
superior oblique myokemia
what types of nystagmus can you use Clonazepam (GABA agonist) for?
downbeat and other central vestibular forms
what can you use Memenatine or Gabapentin for?
acquired forms of pendular nystagmus
what are some non-medical forms of nystagmus treatment?
amblyopia therapy, BO prisms, CL, botox injections, extraocular muscle therapy (congenital forms) or reattaching EOMs
what is convergence-retraction syndrome?
not a true nystagmus - lacks slow phase = all EOMs contract simultaneously on attempted up gaze and the eye retracts (similar to Duane) - it converges because MR is the boss muscle
