Central and Peripheral Vestibular Tests + Disorders

Smooth Pursuit for Visual Gaze Stability

Smooth tracking of the eye when tracking an object. Operates at speeds <30 deg/sec

When an object moves to quick, what occurs?

Saccades to "catch up"

Can't exercise a smooth pursuit without ?

Targets

Saccades

Normal Reaction when eye reaches end range and must find a new end range larget. Eye will perform a corrective saccade with a failed smooth pursuit

Saccades are extremely fast and accurate eye movements that shift your gaze from one point to another. T or F?

T

Disruption of smooth pursuits or saccades is indicative of?

Central pathology

Nystagmus

Can physiologic or pathologic. Indicative of central or peripheral dysfunction

Repetitive, uncontrolled eye movements

Central Nystagmus

Pure, single vector nystagmus (downbeating)

Peripheral Nystagmus

Two-vector nystagmus, right upsetting, horizontal torsional

Slow Phase of Nystagmus

Under direct control of the vestibular system and initiated by SCC VOR

Fast Phase of Nystagmus

Under control of ocular system, process of quick, snapping back/return of eyes in opposite direction of slow phase (saccade)

Nystagmus is named after the ?

Fast phase

Vertigo

Sensation of motion or self or environment

Oscillopsia

False visual illusion of movement of environment due to excessive retinal slip leading to impaired VOR

DD of Vertigo

BPPV Testing: Peripheral Mechanical

Oculomotor Exam: Peripheral or Central

Peripheral Mechanical Conditions

HC, PC, AC canalithiasis or cupulolithiasis

Peripheral Neural Conditions

Vestibular organs, CN Vlll: Neuritis, labyrinthitis, UVH, UVL, BVH, BVL

Central Neural Conditions

Brainstem, Cerebellum: CVA or cerebellum degeneration

Spontaneous Nystagmus Test

Examiner places a hand under the patient's chin to keep it steady and observes gaze for nystagmus. Note direction of vertical, horizontal or torsional

+Central: Pure torsional vertical upbeating or downbeating, horizontal with no change with fixation removed

+Peripheral: Horizontal with slight torsional component. Increases with fixation removed, increases gaze in direction of fast beat

Nystagmus beats to side to side due to?

Increased neural activity

Gaze Evoked Nystagmus

Examiner uses a point (tip of finger or hand) 30 egg to right and hold, then left and hold. Do not go to end range, observe for nystagmus. Examine eye movement up, hold and then down, hold. May need to hold eyelid up with downward gaze

+Central: Direction changing nystagmus

+Peripheral: Unidirectional does not change direction with changes in gaze. Nystagmus beats side to side of increased neural activity away from lesion side

Smooth Pursuit

"Visual Tracking". Examiner places a hand on top of the patients head to keep steady. Hold tip of finger 18 inches in front of patient. Move finger slowly right, left, up and down, diagonally (20 deg/sec). Examine for smooth, conjugate eye movement

+Central Sign: Note if saccade is present "catch up"

During smooth pursuit, vertical motion can slightly saccadic in ?

Older individuals. End point nystagmus is normal, small jump in eye movement as the eyes cross midline is okay

Saccades Test

Stand directly in front of the patient eye level. Examine places a finger 15 deg to the side of their nose. Instruct the patient to look quickly from nose, then finger and back to nose. Look for accuracy, hesitation, hypo/hypermetria. One small corrective saccade is normal

+Central: >2 corrective saccades (hypo/hyper)

Convergence/Divergence

Instruct the patient to watch the tip of the examiners finger as it moves from 18 inches toward the patients nose and back. Examine add/abd, have them stop when vision doubles

+Central: Double vision >4-6cm away = abn

VOR Cancellation

Fixate on examiners nose, either can tilt head 30 deg down, examiners move the patient's head from side to side (1hz) while PT moves side to side so patients eyes and head move together. OR have patient interlace fingers and overlap thumbs, hold out arms length away and have patient keep eyes on thumbs and rotate trunk

+Central: Abnormal if unable to suppress or cancel the VOR noting corrective saccades