Basilar membrane displacement related to endolymphatic sac volume

Objective: To demonstrate that the amount of basilar membrane displacement toward the scala tympani and its attachment to the bony wall of the scala tympani (i.e., interscalar septum) in hydropic temporal bones is related to the intraosseous endolymphatic sac volume. Study Design: A retrospective analysis of temporal bones from individuals with the histopathologic diagnosis of “endolymphatic hydrops.” Methods: Fifty-two temporal bones, from 38 patients, with the histopathologic findings of “endolymphatic hydrops” were analyzed microscopically. Data were obtained regarding the displacement of the basilar membrane, endolymphatic sac volume, hair cell loss, strial atrophy, ganglion cell loss, and last measured auditory thresholds. The relationships between these variables were examined statistically. Results: Nineteen of the 52 temporal bones (36.5%) with endolymphatic hydrops showed displacement of the basilar membrane toward the scala tympani in the apical and middle segments of the cochlea. A reduced volume of the endolymphatic sac was significantly related to increased severity of basilar membrane deformation (Rho = -.646; P less than or equal to .001). Multiple regression analysis showed that severity of basilar membrane deformation was the single best predictor of low frequency thresholds while loss of hair cells was the best predictor of pure-tone average threshold. Conclusions: The displacement of the basilar membrane in the apical and middle segments that may occur with endolymphatic hydrops, to the extent that it impinges on the interscalar septum, is related to a reduction in the intraosseous endolymphatic sac volume

What is the site of origin of cochleovestibular schwannomas

The belief that cochleovestibular schwannomas arise from the glial-Schwann cell junction has repeatedly been quoted in the literature, although there is no published evidence that supports this statement. A systematic evaluation of the nerve of origin and the precise location of cochleovestibular schwannomas using our respective archival temporal bone collections was conducted. Forty tumors were within the internal auditory canal (IAC), while 10 were intralabyrinthine neoplasms. Of the 40 IAC schwannomas, 4 arose from the cochlear nerve, and 36 from the vestibular nerve. Twenty-one tumors clearly arose lateral to the glial-Schwann cell junction, while 16 tumors filled at least two thirds of the IAC, with the epicenter of the neoplasm located in the mid part or the lateral part of the IAC. Only 3 schwannomas were located in the medial one third of the IAC in the area of the glial-Schwann cell junction. We concluded that cochleovestibular schwannomas may arise anywhere along the course of the axons of the eighth cranial nerve from the glial-Schwann sheath junction up until their terminations within the auditory and vestibular end organs

Primary lymphoma of the internal auditory canal - Case report and review of the literature

We report a rare case of a primary intracranial B cell lymphoma originating in the internal auditory canal. The clinical manifestations were indistinguishable from those of other, more common tumors of the same region. We achieved total gross tumor removal with preservation of the facial nerve. A detailed histologic examination and a systemic workup confirmed the primary nature of this tumor. To our knowledge, this is the second case reported in the literature of a primary malignant lymphoma originating in the internal auditory canal. This is the first instance that includes immunohistochemical and cytometric studies of fresh tissue. We discuss the management of primary lymphomas of the central nervous system, with special emphasis on their association with acquired immunodeficiency syndrome and other immune system diseases. Awareness of primary central nervous system lymphomas is important, since a greater occurrence of these rare tumors in the cerebellopontine angle is probable in the future