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Timothy C. Hain, MD Page last modified: August 11, 2013
ENG and rotatory testing of patients with Congenital Nystagmus generally just shows that they have CN. On the other hand, tests that don't use eye movements such as evoked potentials (i.e. VEMP) and posturography, can potentially provide useful information about vestibular function.
Movie of this patient's Congenital nystagmus during fixation and then in dark (listen for click for dark, 53 meg).
Here the CN is brisker in the light than in the dark. It slower in the dark. This is typical of CN, and opposite of the pattern of vestibular nystagmus. Sometimes the ENG technician/audiologist will say that there is "poor fixation suppression". This is not just poor -- it is opposite. See the movie above that illustrates this again.
There is a CN nystagmus after saccades.
The eye is in constant motion. It does not show the usual "backup saccades" seen in a CN variant, LN.
This Dix-Hallpike test is dominated by CN. It would be very difficult to determine if this person has BPPV.
OKN follows the drum somewhat, but with oscillation superimposed.
Rotatory chair test results are distorted by the nystagmus.