Individual semicircular canal function in superior and inferior vestibular neuritis.

OBJECTIVE

To examine the concept of selective superior and inferior vestibular nerve involvement in vestibular neuritis by studying the distribution of semicircular canal (SCC) involvement in such patients.

BACKGROUND

Vestibular neuritis was traditionally thought to involve the superior and inferior vestibular nerves. Recent work suggests that in some patients, only the superior nerve is involved. So far there are no reported cases of selective involvement of the inferior vestibular nerve.

METHODS

The authors measured the vestibuloocular reflex from individual SCC at natural head accelerations using the head impulse test. The authors studied 33 patients with acute unilateral peripheral vestibulopathy, including 29 with classic vestibular neuritis and 4 with simultaneous ipsilateral hearing loss, 18 healthy subjects and 15 surgical unilateral vestibular deafferented patients.

RESULTS

In patients with preserved hearing, eight had deficits in all three SCC, suggesting involvement of the superior and inferior vestibular nerves. Twenty-one had a lateral SCC deficit or a combined lateral and anterior SCC deficit consistent with selective involvement of the superior vestibular nerve. Two patients with ipsilateral hearing loss had normal caloric responses and an isolated posterior SCC deficit on impulsive testing. The authors propose that these two patients had a selective loss of inferior vestibular nerve function.

CONCLUSION

Vestibular neuritis can affect the superior and inferior vestibular nerves together or can selectively affect the superior vestibular nerve.