Rare Lesions of the Internal Auditory Canal.
BACKGROUND
Approximately 95% of tumors occurring within the internal auditory canal (IAC) are vestibular schwannomas. Many undergo stereotactic radiation without definitive tissue diagnosis. Rare IAC tumors are not all radiosensitive and are poorly described.


METHODS
Between 1992 and 2015, 289 consecutive patients with IAC lesions operated on were reviewed retrospectively.


RESULTS
Fifteen patients (5.2%) (16 operations) had unusual histologic findings, including nonvestibular schwannomas (2 facial schwannomas, 2 cochlear schwannomas, 2 intermedius schwannomas), 3 meningiomas, 3 cavernous hemangiomas, a mucosa-associated lymphoid tissue lymphoma, an arachnoid cyst, and a lipochoristoma. None of these rare tumors could be identified before surgery. Three operative approaches were used: the retrosigmoid approach, middle fossa subtemporal approach, or translabyrinthine approach. Few complications occurred, including facial nerve palsy, loss of hearing, and vestibular function. Five-year average follow-up revealed one patient with recurrence.


CONCLUSIONS
Clinical examination and imaging alone were insufficient to correctly identify these tumors. Definitive pathologicdiagnosis should be strongly considered to help tailor treatment.
['Watanabe|Kentaro|K|', 'Cobb|Mary In-Ping Huang|MIH|', 'Zomorodi|Ali R|AR|', 'Cunningham|Calhoun D|CD|', 'Nonaka|Yoichi|Y|', 'Satoh|Shunsuke|S|', 'Friedman|Allan H|AH|', 'Fukushima|Takanori|T|']
D000328:Adult D000368:Aged D003937:Diagnosis, Differential D004428:Ear Neoplasms D007758:Ear, Inner D005260:Female D006801:Humans D007759:Labyrinth Diseases D008297:Male D008875:Middle Aged D035583:Rare Diseases D016896:Treatment Outcome
Internal auditory canal Facial schwannoma Cochlear schwannoma Intermedius schwannoma Meningioma Cavernous hemangioma Arachnoid cyst Lipochoristoma Acoustic neuroma Mucosa-associated lymphoid tissue (MALT) lymphoma