Facial nerve schwannoma in the inner auditory canal and geniculate ganglion

Abstract

Schwannoma of the vestibular nerve is the most common tumor found in the inner auditory canal. If a schwannoma of the facial nerve is found unexpectedly during surgery, the original surgical plan may have to be changed. In our series, we describe the symptoms, diagnostic procedures and therapy of this infrequent, benign tumor. In particular, we want to analyse the influence of diagnostic techniques, such as magnetic resonance tomography and electrophysiology, on the diagnosis of these tumors. Between 1975 and 2001, we diagnosed 17 cases of facial nerve schwannoma in the inner auditory canal or the geniculate ganglion. All patients were treated surgically. In 16 cases, we used the enlarged middle fossa approach and in the remaining patient the translabyrinthine approach was used. In 11 cases, the facial nerve could be saved but in six the nerve had to be rebuilt with a transplant. During the first years of our study, palsy of the facial nerve was a frequent finding. In the later years, a hearing impairment and tinnitus became the most frequent symptoms. Advances in magnetic resonance imaging have, in many cases, facilitated the differentiation between schwannomas of the facial nerve and the vestibular nerve over the last years. Signal enhancement at the geniculate ganglion is important for the diagnosis of facial nerve schwannoma. In individual cases, we found significant findings using electrophysiological procedures. In three cases, the temporal delay was elongated. Based on these findings, the therapeutic procedures can be discussed together with the patients.