Acoustic Neuroma Presenting as a Middle Ear Mass

Abstract

Acoustic neuromas (ANs) are schwannomas of the eighth cranial nerve that typically arise in the vicinity of the vestibular ganglion (Scarpa's) at the junction of peripheral and central myelin (Schwann-glial junetion).' This junction usually lies within the internal auditory canal (lAC). 2 ANs enlarge medially from the lAC to involve the cerebellopontine angle (CPA) cistern and eventually interface the brainstem.!" Lateral spread of the AN from the lAC, to involve the inner and middle ear space, is exceedingly rare.We report a case involving a patient with an AN that spread laterally from the lAC to involve the cochlea, semicircular canals, and middle ear space. The potential causes of schwannoma involvement in the middle and inner ear are reviewed and the mechanism by which an AN may invade the inner ear is explored.

Vestibular Schwannoma Presenting as a White Middle Ear Mass Behind an Intact Tympanic Membrane

“…However, because the bone of the otic capsule is very hard, an extension laterally is very uncommon, and authors postulate that these tumors may be of intralabyrinthine origin with extension both medially toward the CPA and laterally via the round window into the middle ear (4). Amoils et al (2) postulated a deficiency in the cribriform area at the lateral aspect of the internal auditory canal predisposing to direct tumor extension into the cochlea, vestibule, and middle ear. Storrs (3) describes a tumor that was confined to the cochlea with extension into the middle ear via the round window.…”

Intralabyrinthine schwannoma involving the cochlea, vestibule, and internal auditory canal: ‘canalolabyrinthine schwannoma’

“…Because this patient had experienced hearing loss before vertigo, the cochlear involvement may have preceded the vestibular involvement. This is supported by the fact that cochlear involvement is more frequent than vestibular involvement, which may be explained by the presence of the weakest part of the fundus, the cribriform area between the IAC and the cochlea [3]. However, if the tumor's origin was in the IAC, it is diYcult to understand why the tumor Wrst eroded the cribriform area before growing along the route of least resistance toward the porus.…”

“…These tumors develop from the perineural Schwann cells and are most commonly located at the Schwann cell-glial junction of vestibular nerves in the internal auditory canal (IAC) [1][2][3]. However, Schwann cells are also present in the modiolus close to the spiral ganglia; therefore, schwannomas theoretically may develop in the cochlea.…”

“…A schwannoma extending to a cochlea or semicircular canals is called as an 'intralabyrinthine schwannoma (ILS)' [4]. To date, about 70 cases of ILSs have been reported in the medical literatures [1][2][3][4][5], but most of the ILSs involved only cochleavestibule, IAC-cochlea, or IAC-vestibule areas [1][2][3][4][5]; however, there was no study reporting on schwannomas involving simultaneously the vestibule, cochlea, and IAC. Therefore, we report the Wrst experience of a schwannoma involving simultaneously the vestibule, cochlea, and IAC, with the discussion of its possible origin and propose one more new classiWcation, the 'canalolabyrinthine schwannoma', among the ILSs.…”

The CT and Magnetic Resonance Imaging Features of Transotic Schwannoma: A Case Report

“…Transotic schwannoma is extremely rare. Only five cases have been reported in the English literature (1)(2)(3)(4)(5), while none has appeared in the Korean radiological literature. We report a case of transotic schwannoma in a 38-year-old woman along with the CT, MRI, and pathologic findings.…”