Can the nystagmus pattern in patients with a 'light cupula' be reproduced in hemi-labyrinthectomized subjects during...

A positional nystagmus pattern compatible with a condition of a light cupula in the lateral semicircular canal seen in clinical patients could be reproduced only partially in hemi-labyrinthectomized subjects during the stage of positional alcohol nystagmus 1 (PAN 1).

To mimic the condition of a light cupula in the lateral semicircular canal by using unilaterally deafferented subjects during the stage of PAN 1 and compare the results with those of patients with a light cupula.

Five hemi-labyrinthectomized subjects were studied during PAN 1 with videonystagmography when they kept their heads straight forward or turned sideways in the prone and supine positions, respectively. A zero zone, indicating a cupula dysfunction, in which the geotropic nystagmus changed direction during slow head turn in the supine position, was also looked for.

When the subjects were examined with their heads turned left or right in the supine or prone positions, the alcohol-induced nystagmus pattern was compatible with that of a light cupula. However, the nystagmus directions at the head straight forward in the prone and supine positions, as well as localization of the zero zones, deviated from the pattern seen in patients with a light cupula.