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Nystagmus definition, causes, diagnosis,types, investigations

Definition: Involuntary deviation of the eyes away from the direction of the gaze followed by return of the eyes to the central resting position.

Classification and types:
a. Physiologic (optokinetic): the rapid phase is towards the center.
b. Pathologic:
  • Occular: rotatory or pendular.
  • Vestibular: has a rapid phase and a slow phase.
  • Central: vertical.

Detection and diagnosis of Nystagmus

a. Direct observation by looking into the eyes.
b. Observation using Frenzel glasses to abolish the optic fixation.
c. Electronystagmography and videonystagmography.
A. Positional testing and search for any nystagmus (central or peripheral) in:
i. Static head and body position tests (supine - head right- head left - body right - body left).
ii. Dynamic (positioning tests) for diagnosis of BPPV:
  • Dix-Hallpike test
  • Roll test.
B. Sound stimuli, the Valsalva maneuver, and tragal compression to test Tullio phenomenon
C. The Vestibulo-Ocular Reflex testing (VOR)
  • Horizontal Head impulse test (hHIT)
  •  Dynamic visual acuity test (DVA)
D. Clinical oculography test: Saccades, smooth pursuit and optokinetic testing (rotating drum test).

Vestibular investigations to diagnose Nystagmus

1. Video-nystagmography (VNG): A video of the eye that could be recorded

Caloric test:

  • The caloric test is performed with the subject reclining, head inclined 30 degree up from horizontal so as to make the lateral canal horizontal.
  • Bi-thermal caloric test stimulates the left or right ear with warm and cool air or water causing a fluid density change in the lateral canal.
  • Water is introduced into the ear canal on one side, either 7 deg centigrade above or below assumed body temperature.
  • The flow rate is such that the ear rapidly equilibrates with the water. The water is stopped after 30 seconds, and nystagmus is observed, while the subject is distracted.
  • Eye movements are usually recorded, and by comparing the response of the left and right ear to warm and cool stimuli one can determine if there is a unilateral or bilateral weakness.

Positional testing

and search for any nystagmus and determine whether central or peripheral, as in clinical testing.

Occulographic tests:

  • Saccades testing: re-fixation on new targets
  • Smooth Pursuit: tacking slow objects with foveal vision
  • Optokinetic test: sensing objects with peripheral vision

Determining the presence or absence of spontaneous or Gaze evoked nystagmus

2. Computerized dynamic Posturography (CDP):

  • Postural sway has been used as an indicator of balance function.
  • It can be recorded by force platform Posturography that measures forces needed to maintain the balance and support the body weight while standing on the platform.

3. Rotatory chair testing:

  • The rotational chair has primarily been used for analyzing horizontal canal vestibulo-ocular reflex (VOR). 
  • Angular acceleration stimulus to test VOR. Both sides are stimulated simultaneously. 
  • It is the Gold-standard test for Bilateral vestibular loss  
  • Useful to validate caloric paresis.

Other investigations:

Audiologic: PTA, Speech audiometry, Tympanometry, ABR, and OAE.
Laboratory: CBC including Hb %., blood lipid profile, Blood glucose level, Thyroid function tests, and Syphilis serology.
Radiological: -CT scan Bain, brainstem and cerebellum -MRI Bain, brainstem and cerebellum.


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