Bilateral internal auditory canal enlargement without acoustic nerve tumor in von Recklinghausen neurofibromatosis.

The common (and definitive) intracranial tumors in patients with one form of neurofibromatosis (NF), bilateral acoustic NF (NF-2), are bilateral acoustic neuromas. In this study, we present 2 cases with what appears to be another form of NF, namely, NF-1, who showed bilateral enlargement of the internal auditory canals. Bilateral caloric responses were remarkably impaired in both cases; a unilateral sensorineural hearing loss was observed in 1. No tumor was demonstrated in the enlarged internal auditory canals in either case. Although the pathophysiology remains uncertain, some patients with NF-1 show abnormal cochleovestibular function in association with bilateral internal auditory canal enlargement without an acoustic tumor.