Is the cause of sensorineural hearing loss in patients with facial schwannomas multifactorial?

OBJECTIVES: Facial nerve schwannomas (FNSs) and vestibular nerve schwannomas (VNSs) may occupy similar locations in the internal auditory canal (IAC). Risk factors for hearing loss in patients with FNS are unknown. Similar to VNSs, we hypothesize that the size and location of FNSs do not correlate with hearing loss.

STUDY DESIGN: Retrospective cohort study and otopathology case review.

METHODS: A single institution retrospective review of all patients diagnosed with FNS was performed. Demographic data, tumor size and location, severity and type of hearing loss, and facial nerve function were analyzed. Otopathologic review of a case of FNS was also performed.

RESULTS: Thirty-three patients with FNS were identified. Mean age was 44 years, and 61% (n = 21) were female. Nine patients had tumors involving the IAC facial nerve, whereas 24 had distal tumors without IAC involvement. Eleven patients (33%) had hearing loss, and 55% of patients with sensorineural hearing loss (SNHL) had tympanic segment tumors without IAC involvement. The presence of SNHL was not associated with IAC tumor location (P = 0.21). Maximal dimensions of FNSs were 3 mm to 42 mm, without correlation between size and SNHL severity (r = -0.017, P = 0.926). Otopathologic review of an untreated 5-mm IAC FNS demonstrated disproportionate spiral ganglion and hair cell loss within the ipsilateral cochlea compared to the contralateral ear.

CONCLUSION: Tympanic segment FNS without IAC involvement may result in SNHL. Tumor size is not associated with the presence or severity of SNHL. Otopathologic review suggests degenerative cochlear changes in FNS. Mechanisms for SNHL in schwannomas are likely multifactorial and may be unrelated to cochlear nerve compression.

LEVEL OF EVIDENCE: 4. Laryngoscope, 127:1676-1682, 2017.