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fixate on a stationary target in neutral gaze position - with & without frenzel glasses
- Peripheral lesions
- intense, direction-fixed horizontal-rotary nystagmus
- enhanced under Fresnel lenses
- intensifies when gazing in direction of fast phase (Alexander's law)
- irritative lesions - beating toward affected ear
- destructive lesions -beating toward unaffected ear
- Central lesions
- less intense, direction-changing horizontal, vertical, torsional, or pendular nystagmus
- diminished under Fresnel lenses.
gaze at a target placed 20 - 30 degrees to the left and right of centre for 20 seconds
- ability to maintain eccentric gaze is under control of the brain stem and midline cerebellum
- When these mechanisms fail to hold the eye in the eccentric position, the eye drifts toward the midline (exponentially decreasing velocity), followed by refixation saccades toward the target
- gaze-evoked nystagmus=central in origin
- beats in the direction of intended gaze
- In contrast, enhancement of peripheral spontaneous nystagmus (linear slow component velocity) occurs without direction change when gazing in the direction of the fast phase
- Causes=drug effect (sedatives, antiepileptics), alcohol, CNS tumors, cerebellar degenerative syndromes.
follow your finger as you slowly move it left and right, up and down
not exceed 60 degrees in total arc or 40 degrees per second
Cerebellar or brain stem disease can cause saccadic eye tracking in which the patient repeatedly loses the target and then catches up with a small saccade
look back and forth between two outstretched fingers held about 12 inches apart in the horizontal and vertical plane
- Delayed saccades - cortical and brain stem lesions
- Slow saccades - brain stem disease Inaccurate saccades(especially overshoots) - lesions of the cerebellar vermis and fastigial nuclei.
- Disconjugate eye movements with slowing of the adducting eye and overshoots of the abducting eye imply medial longitudinal fasciculus pathology frequently associated with multiple sclerosis
Halmagyi head thrust test
fixate on a target on the wall in front of the patient while the examiner moves the patient's head rapidly (>2000 deg/sec2) to each side
examiner looks for any movement of the pupil during the head thrust and a refixation saccade back to the target
- eye movement during maneuvre = decreased neural input from the ipsilateral ear to the vestibulo-ocular reflex because contralateral ear is in inhibitory "saturation" and cannot supply enough neural activity to stabilize gaze.
- In such instances, the eye travels with the head during the high-velocity movement, and a refixation saccade is necessary to refoveate the target.
- Bilateral refixation movements are seen frequently in cases of ototoxicity.
Dynamic Visual AcuityAction
Ask the patient to read the lowest (smallest) line possible on a Snellen eye chart with best corrected vision (glasses, contact lenses). Repeat the maneuver while passively shaking the patient's head at 2 Hz, and record the number of lines of acuity "lost" during the headshake.
- Excessive retinal slippage during head movement is a sign of vestibular dysfunction
- most frequent etiology is bilateral vestibular loss related to ototoxicity or aging
- Poorly compensated unilateral dysfunction can also cause loss of dynamic visual acuity but is harder to identify with this clinical test.
head 45 degrees to one side while seated and rapidly but carefully have the patient recline
Observe the eyes for nystagmus and, if present, note the following five characteristics: latency, direction, fatigue (decrease on repeated maneuvers), habituation (duration), and reversal upon sitting up.Interpretation.
- geotropic torsional direction
- brief latency (5 to 20 seconds)
- decline with repeated positioning
- 30 seconds or less duration
- reversal upon arising
Limb Coordination Tests
rapid alternating motion
oberve for dysmetria or dsrhythmia.
dysmetria or dysdiadochokinesia = cerebellar cortical disease, which may or may not accompany midline or vestibulocerebellar oculomotor dysfunction.
stand with feet close together and arms at the side
eyes open and then eyes closed
Observe for the relative amount of sway with vision present versus absent
- primarily a test of somatosensation and proprioception and not of vestibular input
- Patients with compensated bilateral vestibular loss stand normally in both eyes-open and eyes-closed Romberg position because of adequate proprioception from the stable support surface.
- 3-inch foam to make this test more sensitive to vestibular deficits
walk 50 feet in the hall, turn rapidly, and walk back without touching the walls
Observe for initiation of movement, stride length, arm swing, missteps and veering, and signs of muscle weakness or skeletal abnormality (kyphoscoliosis, limb asymmetry, limp)
- cute unilateral vestibular lossveer toward the side of the lesion
- variety of central brain stem and musculoskeletal lesions also produce lateral deviation during ambulation
- Difficulties with gait initiation and turns and decreased arm swing can be seen in extrapyramidal disease
- Gait ataxia implies cerebellar dysfunction and is distinctly different from gait deviation associated with uncompensated peripheral vestibular disease
- exaggerated hip sway, rhythmic deviations, and an excessive reliance on touching the wall during walking may constitute signs of a functional gait disorder.
With Fresnel lenses in place
observe for nystagmus or tonic eye deviations with symptoms of dizziness under four test conditions:
(1) steady tragal compression to increase pressure in the external auditory canal,
(2) positive and negative pressure applied with the pneumatic otoscope
(3) presentation of loud tones via tuning fork or impedance bridge
(4) increased pressure during breath holding against pinched nostrils or closed glottis.
- Consistent eye deviations or nystagmus during any of the preceding maneuvers implies abnormal coupling between either the outside atmosphere or the intracranial space and the inner ear.
- This can occur with abnormal connections between the labyrinth and the middle ear or middle fossa at the following sights:
- oval window (fistula, excessive footplate movement)
- round window
- lateral semicircular canal
- superior semicircular canal (dehiscence).
- In particular, eye elevation and intorsion with loud sounds or Valsalva maneuver against pinched nostrils is suggestive of superior canal dehiscence syndrome
In addition, cranial-cervical junction abnormalities (Arnold-Chiari malformation in particular) produce vertical downbeat nystagmus with any maneuver that increases intracranial pressure.
Fukuta Step Test
march in place with arms extended and eyes closed for 1 minute.
Note the degree of lateral rotation at the end of the maneuver.Interpretation.
Most normal subjects deviate less than 45 degrees in rotation to one side during the step test, whereas some patients with uncompensated unilateral dysfunction deviate more than 45 degrees toward the affected side. This finding alone, however, is not conclusive for otolith dysfunction.
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