THE ENG BATTERY

Clinical Eye Movement Videos ENG & VNG Clinical Eye Movement Videos

Voltage/Infrared video feed Calibration Confirming relation between: Voltage/Infrared video feed and Eye position Fixed Targets/Sinusoidal Tracking

Gaze testing Gaze at visual targets. Eye movements are recorded Spontaneous nystagmus gaze evoked nystagmus other extraneous movments Pt. asked to close there eyes without shifting gaze. There are 47 named types of nystagmus. This can be a very challenging and difficult area of eye movement disorder to deal with clinically. However there are essentially only two divisions of nystagmus to worry about : pathological and non-pathological. The control and coordination of ocular movements depends on good connections between the eyes, the visual conducting system, the occipital cortex, the visual memory areas, the frontal lobe, the cerebellum, brainstem and finally the cranial nerves. It represents the biggest single functional unit in the Central Nervous System. Virtually anything which disorganises the inputs in the cerebellar, vestibular of or brain stem regions will result in nystagmus. Fortunately the most common form of nystagmus, congenital nystagmus, is non-pathological It is often familial and there will always be a past history of it. Also the amplitude of the beat will often be augmented by covering one eye (latent nystagmus). Most importantly, this nystagmus will always beat horizontally in up or down gaze. It is benign and often associated with congenital difficulties with sight. There is also no oscillopsia or sensation movement of the environment with it. Pathological nystagmus is usually associated with oscillopsia and is of usually associated with recent onset. It will tend to beat parallel to the direction of gaze. The distinction between beat and pendular nystagmus is useful for the ophthalmologist but can be difficult for someone not used to watching eye movements. The beat is applied to the direction of the fast phase and represents the correcting direction under the control of the frontal cortex. Thus if the level of consciousness is reduced this phase will be less prominent and may disappear. The most common form of acquired pathological nystagmus is vestibular, usually associated with a labyrinthitis. It may however be associated with demyelinatve disease or space-occupying lesions. Other forms of acquired nystagmus are: 1.Internuclear opthalmoplegia: the nystagmus appears in the ADDUCTING eye. This is due to a lesion in the Median Longtitudnal Fasciculus. 2.Retraction nystagmus: this appears when a patient with a sylvian aqueduct syndrome is asked to look up, the eyes converge and retract. Rara avis 3.Downbeat and Upbeat Nystagmus: Downbeat nystagmus is usually associated with disease in the region of the foramen magnum. Upbeat is usually associated with drug overdose (barbiturates, phenothiazines or Dilantin). In absence of drugs it is due to cerebellar disease. 4.Opsoclonus: characterised by congugate wild ocular pendular movements in all directions. This is dramatic and usually associated with inflammation thus the prognosis is relatively good.

Peripheral Gaze Nystagmus: strongest on gaze in direction of beating never vertical declines quickly (within days to a couple of weeks) Alexander's Law: 1st degree Nystagmus: present only on lat. gaze 2nd deg: both on center and lat. side of beat 3rd deg: on center, and both lateral gazes. Video Periph Gaze

Alexander's Law Alexander’s system of grading vestibular nystagmus.

Central Nervous System Lesions: Often bilateral beating Can have vertical beating declines slowly if at all

Some Central Gaze Nystagmi: Bilateral Horiz. Gaze (Brun's) Nystagmus: Rebound Nystagmus: Periodic Alternating Nystagmus: Vertical Nystagmus: Congenital Nystagmus: What is Going on here?:Voluntary Nystagmus

Bilateral Horiz. Gaze (Brun's) Nystagmus: in large CPA tumors. Gaze ipsi to lesion generates large slow nyst, with exp. decay in slow phase. Gaze contra to lesion generates small fast nyst, in opposite direction of ipsi resp. Video Bruns

Rebound Nystagmus: Cerebellar disease movement-generated, decays rapidly (10-20s) Beats in direction of movement Video Rebound

Midline cerebellum is atrophied.

Periodic Alternating Nystagmus: Medullary disease. Periodic Alternating Video cyclic, 90 s one direction, 10 s nothing or vertical, then 90s in other direction, 10 s down time, and back again. present w/ eyes open or closed. strongest in middle of phases>>visual impairment.

Vertical Nystagmus: Brainstem/Cerebellar or Inf. olivary disease Can be generated by alcohol, drugs, too. Upbeat Video Downbeat Video

Congenital Nystagmus: From fixed brain defect either genetic or developmental in origin. Pendular and/or jerk-type Disorder of slow eye movement sub-system. Null points or periods. Convergence inhibition Congenital Video

Saccade Testing Horizontal Vertical Regular pattern or random Through 20 to 30 degrees. 

Saccadic Disorders: Occular dysmetria: CBL lesion akin to dysdiadochokinesia overshoots/undershoots Saccadic Slowing: basal ganglia lesion normal saccade for 20 deg = 188/sec Internuclear Ophthalmoplegia: MLF lesion rounded tracings one eye lags, smoothing curve. separate eye recordings to confirm INO VIDEO

Watch out for: Superimposed nystagmi i) gaze nystagmus ii) congenital nystagmus Drug effects: usually dysmetria Patient problems: i) inattention ii) eye blinks iii) head movement: scalloped tracings

Tracking Tests: Following pendular movements Problems to look for saccadic pursuit-eyes snap repeatedly to keep up with movement = CNS lesion disorganized pursuit, wandering, slow, inaccurate tracking - CNS lesion, usually above the level of the occulomotor nuclei disconjugate pursuit, eyes don't stay together in tracking - CNS lesion

Things to look out for: Drug influences Inattention: multiple, rapid gaze deviations Head movement: depressed amplitude superimposed nystagmus gaze: R, L, or bil. >> jerks at extremes congenital: often overlies entire tracing

Optokinetic test Repeated tracking of moving target, producing nystagmatic motion. Disorders: Asymmetry: CNS lesion diff of > 30 degs, at more than one stim rate. Flat / declining resp. to faster rates. brainstem lesion, possible MS Inverted movement: Congenital nystagmus