Cases reported "Neuroma, Acoustic"

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1/8. Is cochlear implantation possible after acoustic tumor removal?

    HYPOTHESIS: This study aimed to assess the possibility of hearing restoration after acoustic tumor removal. BACKGROUND: Hearing restoration surgery may be indicated after surgery of bilateral acoustic tumors or surgery of acoustic tumor in the only hearing ear. The choice is between cochlear implantation and brainstem implantation. methods: From the temporal bone collection at the House Ear Institute, los angeles, the author histologically examined eight temporal bones from seven patients who had undergone acoustic tumor removal during their lifetime. Special emphasis was put on examining the patency of the cochlear turns and on survival of the spiral ganglion cells and cochlear nerve. RESULTS: This study showed that after translabyrinthine acoustic tumor removal, there is progressive osteoneogenesis of the cochlea associated with almost complete degeneration of the spiral ganglion cells and cochlear nerve. Similar findings were noticed after middle fossa removal of acoustic tumor with unsuccessful hearing preservation. CONCLUSIONS: The histologic changes described in the cochlea and cochlear nerve represent the effects of ischemia resulting from inadvertent cutting of the blood supply during acoustic tumor removal. It is possible to do cochlear implantation after acoustic tumor removal provided that the result of promontory electrical stimulation test is positive (the cochlear nerve is intact) and that implantation is done at the time of acoustic tumor removal or shortly thereafter, before cochlear ossification is complete.
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keywords = ganglion
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2/8. temporal bone pathology of acoustic neurinoma (unilateral and bilateral) in relation to the internal auditory canal surgery.

    temporal bone pathology of 3 cases with large unilateral acoustic neurinoma (AN) and 2 cases with large bilateral AN (neurofibromatosis 2; NF2) were studied. One case with unilateral AN was diagnosed as neurofibromatosis 1 (NF1). Unilateral AN had distinct borderlines at the fundus in 5 of 12 examination points between tumor tissues and nerve fibers, but only 1 of 12 was distinct around the porus acousticus. Bilateral AN showed no distinct borderlines at the fundus and around the porus acousticus. These findings suggest that clear separation of the VIIth or VIIIth nerve from large tumors is very difficult, especially in cases of bilateral AN. geniculate ganglion cells of tumor origin on ears were fairly well preserved in 2 cases with unilateral AN and 1 case with bilateral AN. Well preserved geniculate ganglion cells could be dependent on blood supply not from the internal auditory artery.
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keywords = ganglion
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3/8. Cerebello-pontine angle paraganglioma simulating an acoustic neurinoma.

    An unusual case of paraganglioma arising from the internal auditory meatus and growing into the cerebello-pontine angle is reported. Clinical features, pre-operative radiological appearances and intra-operative findings were indistinguishable from those of an acoustic neurinoma. However, the paraganglionic nature of the tumour was confirmed by the electron microscopic evidence of neurosecretory features.
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4/8. Histological changes of vestibular nerves and ganglion cells in the acoustic tumor in relation to clinical functions.

    The superior vestibular nerves and vestibular ganglion cells were observed electron microscopically in acoustic tumors removed surgically from 15 patients. Furthermore, the sensory cells of the vestibular organs were examined. Histological changes of vestibular nerves and ganglion cells were compared with the caloric responses of the patients. In most cases, the degree of degeneration of myelinated nerve fibers was proportional to the reduced responses of vestibular nerves. The myelinated nerve fibers decreased in number and showed some features of demyelination. The alteration of vestibular ganglion cells was unremarkable in comparison with vestibular nerves. In some cases, the number of lipofuscin granules, vacuolar organelles and amorphous materials markedly increased in the ganglion cells. However, the sensory cells of the vestibular organs appeared normal.
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keywords = ganglion
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5/8. Surgery of the skull base.

    Tumors involving the base of the skull are often occult and may become quite large before detection is possible. Symptomology varies depending upon the nature of the tumor and its placement. These neoplasms have frequently been considered inoperable simply because of their location, but in recent years microsurgical technique and high speed air drills have allowed the modern temporal bone surgeon to gain improved access to the skull base. A wide variety of surgical approaches to tumors in this area have been described in the past 20 years: translabyrinthine, middle fossa, transcochlear, retrolabyrinthine, retrosigmoid, transpalatal-transclival, and through the jugular bulb. The purpose of this paper is to review the indications, complications, and results of each of these procedures in relation to specific tumors involving the skull base. case reports illustrate the diagnosis and surgical management of a variety of unusual neoplasms, including an extradural meningioma of the temporal bone and clivus, a low grade squamous cell carcinoma on the tegmen in a radical cavity, a large primary cholesteatoma, an osteoblastoma of the temporal and occipital bones, an XIth nerve neuroma in the jugular bulb area, and an osseous hemangioma involving the facial nerve at the geniculate ganglion.
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6/8. Human vestibular nerve morphology and labyrinthectomy.

    Surgical labyrinthectomy leads to extensive and degenerative changes in the membranous labyrinth and is often followed by fibrosis and ossification of the vestibule and neuroma formation. After labyrinthectomy the distal processes of the vestibular nerve degenerate, but the nerve trunk within the internal auditory canal, including Scarpa's ganglion, does not show an obvious loss of neurons. Electron microscopic examination of the cells of Scarpa's ganglion revealed many changes similar to those of chromatolysis, indicating increased cell metabolism and probable regenerative changes. Many nerve fibers appeared to be in the process of regeneration. Some ganglion cells were fibrotic and showed ultrastructural features similar to those of cells that had undergone atrophy but survived in a sublethal state.
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keywords = ganglion
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7/8. Rosenthal fibers and eosinophilic granular bodies in a classic acoustic schwannoma.

    We describe unique features seen in a case of classic acoustic schwannoma. In the central portion of the tumor, abundant Rosenthal fibers and occasional eosinophilic granular bodies were present. Rosenthal fibers are homogeneous eosinophilic structures commonly seen in central nervous system lesions, such as pilocytic astrocytoma, or in the gliotic tissues adjacent to slowly growing neoplasms and some congenital malformations. Eosinophilic granular bodies are also structural markers of slow-growing, well-differentiated neuroglial neoplasms, such as pleomorphic xanthoastrocytoma, ganglion cell tumors, and pilocytic astrocytoma. To the best of our knowledge, however, these two structures have never before been described in schwannomas.
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8/8. temporal bone pathology of acoustic neuroma correlating with presence of electrocochleography and absence of auditory brainstem response.

    The temporal bone pathology of a 74-year-old female affected by vestibular schwannoma was compared with findings of auditory brainstem response and electrocochleography. At age 71, she complained of hearing loss in the left ear in which pure tone audiometry revealed threshold elevation in the middle- and high-frequency range. temporal bone CT scanning revealed a medium-sized cerebellopontine angle tumour in the left ear. ABR showed no response in the left ear, but the electrocochleography showed clear compound action potentials. Three years later, at age 74, she died of metastatic lung cancer and sepsis. The left temporal bone pathology consisted primarily of a large vestibular schwannoma occupying the internal auditory meatus. The organ of corti was well preserved in each turn. In the modiolus, the numbers of spiral ganglion cells and cochlear nerve fibres in each turn were decreased. These histological findings suggest that clear compound action potentials were recorded from the distal portion of the cochlear nerve in spite of the presence of the vestibular schwannoma, but ABR could not be detected because of the blockade of the proximal portion of the cochlear nerve by the vestibular schwannoma.
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