Individual semicircular canal function in superior and inferior vestibularneuritis

Objective: To examine the concept of selective superior and inferior vestib ular nerve involvement in vestibular neuritis by studying the distribution of semicircular canal (SCC) involvement in such patients. Background: Vesti bular neuritis was traditionally thought to involve the superior and inferi or 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 measure d the vestibuloocular reflex from individual SCC at natural head accelerati ons 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 subj ects and 15 surgical unilateral vestibular deafferented patients. Results: In patients with preserved hearing, eight had deficits in all three SCC, su ggesting involvement of the superior and inferior vestibular nerves. Twenty -one had a lateral SCC deficit or a combined lateral and anterior SCC defic it 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 propos e that these two patients had a selective loss of inferior vestibular nerve function. Conclusion: Vestibular neuritis can affect the superior and infe rior vestibular nerves together or can selectively affect the superior vest ibular nerve.