Cases reported "Neuroma, Acoustic"

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1/143. Magnetic resonance cisternography using the fast spin echo method for the evaluation of vestibular schwannoma.

    neuroimaging of vestibular schwannoma was performed with the fat-suppression spoiled gradient recalled acquisition in the steady state (SPGR) method and magnetic resonance (MR) cisternography, which is a fast spin echo method using a long echo train length, for the preoperative evaluation of the lateral extension of the tumor in the internal auditory canal, and the anatomical identification of the posterior semicircular canal and the nerves in the canal distal to the tumor. The SPGR method overestimated the lateral extension in eight cases, probably because of enhancement of the nerves adjacent to the tumor in the canal. The posterior semicircular canal could not be clearly identified, and the cranial nerves in the canal were shown only as a nerve bundle. In contrast, MR cisternography showed clear images of the lateral extension of the tumor and the facial and cochlear nerves adjacent to the tumor in the internal auditory canal. The anatomical location of the posterior semicircular canal was also clearly shown. These preoperative findings are very useful to plan the extent to which the internal auditory canal can be opened, and for intraoperative identification of the nerves in the canal. MR cisternography is less invasive since no contrast material or radiation is required, as with thin-slice high-resolution computed tomography (CT). MR cisternography should replace high-resolution CT for the preoperative neuroradiological evaluation of vestibular schwannoma.
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2/143. Isolated metastases of adenocarcinoma in the bilateral internal auditory meatuses mimicking neurofibromatosis type 2--case report.

    A 56-year-old male with a history of lung cancer presented with isolated metastases of adenocarcinoma in the bilateral internal auditory meatuses (IAMs), mimicking the bilateral acoustic schwannomas of neurofibromatosis type 2, and manifesting as rapidly worsening tinnitus and bilateral hearing loss. magnetic resonance imaging showed small tumors in both IAMs with no sign of leptomeningeal metastasis. The preoperative diagnosis was neurofibromatosis type 2. Both tumors were removed and the histological diagnoses were adenocarcinoma. neuroimaging differentiation of a solitary metastatic IAM tumor from a benign tumor is difficult, although rapidly progressive eighth cranial nerve dysfunction suggests a malignant process. Metastases should be considered as a rare diagnostic possibility in a patient with small tumors in both IAMs.
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3/143. cerebellopontine angle pilocytic astrocytoma mimicking acoustic schwannoma.

    We describe a case of pilocytic astrocytoma of the cerebellum mimicking an acoustic schwannoma. The tumour protruded into the porus acusticus and enlarged the internal auditory meatus, which is a quite unusual characteristic of glial tumours.
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4/143. meningioma of the internal auditory canal with extension into the vestibule.

    Meningiomas account for approximately 18 to 19 per cent of all brain tumours. Although they can arise in numerous locations, meningiomas of the internal auditory canal (IAC) are rare. Most tumours that originate in the IAC are schwannomas of the VIIIth cranial nerve (acoustic neuromas). We report a case of a meningioma which appears to originate from the IAC and extends into the vestibule. The clinical findings and the radiographical features of meningiomas of the IAC are similar to those of acoustic neuromas. Pre-operative differentiation between acoustic neuromas and meningiomas of the IAC may be difficult.
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5/143. Pediatric acoustic schwannoma showing rapid regrowth with high proliferative activity.

    Acoustic schwannoma is a slow-growing tumor and usually occurs in adult patients. We report a rare pediatric case of acoustic schwannoma with high proliferative potential. A 10-year-old boy was diagnosed as having a right cerebellopontine angle tumor. The tumor was subtotally resected. Histological examination revealed a typical acoustic schwannoma with a few mitotic figures. Chromosomal analysis showed no abnormality on the long arm of chromosome 22 associated with neurofibromatosis type 2. The lesion re-grew rapidly as an acoustic schwannoma, necessitating subtotal resection on three occasions and CyberKnife radiosurgery. The immunohistochemical MIB-1 staining indices of the specimens obtained at the first, second, and third operations were 2.3%, 4.6% and 14.7%, respectively. The immunohistochemical proliferative potential of acoustic schwannoma is discussed.
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6/143. Intracranial sarcoma in a patient with neurofibromatosis type 2 treated with gamma knife radiosurgery for vestibular schwannoma.

    OBJECTIVE: To discuss the possible relationship between stereotactic radiation therapy and the development of a meningosarcoma. STUDY DESIGN: Retrospective case review. PATIENT: A 19-year-old woman with bilateral vestibular schwannomas (neurofibromatosis type 2). One large tumor was removed totally by the translabyrinthine approach; the other smaller tumor was treated with stereotactic radiation (SRT). Six years after SRT, a malignant tumor (meningosarcoma) developed at the exact site of radiation. The patient subsequently died of this tumor. OUTCOME MEASURE: On the basis of literature surveys, the possibility and risk of postirradiation neoplasia after SRT is discussed. Furthermore, the possible causal association between SRT and the development of the meningosarcoma in this case is evaluated. CONCLUSION: On the basis of statistical considerations, the development of the reported mesenchymal sarcoma was most likely caused by the stereotactic radiation therapy.
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7/143. Current surgical results of retrosigmoid approach in extralarge vestibular schwannomas.

    BACKGROUND: Vestibular schwannomas (VS) are common tumors that can be cured; they are reported to comprise 6 approximately 8% of all intracranial tumors. The primary objective in the surgery of extralarge VS is total removal of the tumor mass while preserving the facial nerve. In extralarge tumors, complete excision of the tumor carries a significant risk of injuring the facial nerve and adjacent vital brain structures. The authors are reporting the techniques and results of operation on extralarge VS. methods: The material consisted of 30 patients during the last 6 years with surgically treated VS that had a maximal extrameatal diameter exceeding 4 cm. Suboccipital craniotomy and tumor removal was performed with patients in the lateral position. Results and complications of the surgical technique will be reviewed. RESULTS: Average age of patients was 45.2 years; there was a slight female predominance (1.5:1). Size of the mass ranged from 41 to 70 mm; all were removed by the retrosigmoid transmeatal approach. Peritumoral edema on MRI was seen in 50% (15/30). Total removal was achieved in 73.3% (22/30) with no significant relationship to peritumoral edema. In the cases of total removal, the facial nerve preservation rate was 86.4% (19/22). There was no mortality. Surgical complications were hemorrhage and CSF leakage in 1 case (3%) and 8 cases (26.7%), respectively, but in most of these cases, conservative treatment was adequate. In patients in whom anatomic preservation of the facial nerve was achieved, facial nerve function improved progressively within a year. In all cases except for one with gait disturbance, a good outcome was achieved.CONCLUSIONS: Our surgical techniques, including the prediction of facial nerve displacement, not using retractors, and replacement of bone, contributed to good surgical results in a series of extralarge VS.
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8/143. Acoustic schwannoma and arachnoid cyst colocated in the cerebellopontine angle--case report.

    A 50-year-old female presented with a right acoustic schwannoma colocated with a cerebellopontine angle arachnoid cyst. The arachnoid cyst was distinct from the arachnoid cap surrounding the acoustic schwannoma. Initial excision of the arachnoid cyst created the space required to excise the schwannoma. The acoustic schwannoma had surprisingly dense adhesions to the brainstem, probably due to the constant pressure exerted by the cyst displacing the tumor towards the brainstem. The acoustic schwannoma was excised by meticulous dissection. Such a coexisting lesion should be suspected when a large cystic collection surrounds an acoustic schwannoma. Initial excision of the arachnoid cyst will prevent excessive cerebellar retraction.
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9/143. Focal amyotrophy in neurofibromatosis 2.

    Neurofibromatosis type 2 (NF2) is an autosomal dominant disorder characterised by bilateral vestibular schwannomas and other CNS tumours including meningiomas and spinal schwannomas. Occasionally, peripheral neuropathy occurs in these patients but this is the first report of focal amyotrophy. Clinical, electrophysiological, and imaging data from four NF2 patients seen at a specialist neurofibromatosis clinic over a 4 year period are described in whom symptomatic focal amyotrophy preceded the diagnosis of NF2. Two presented with wasting and weakness of a single muscle group, several years before NF2 was diagnosed. In one patient a mononeuritis multiplex was the presenting feature of NF2, and in one patient focal wasting and weakness developed after the diagnosis of NF2 was made. In none of the four cases could a focal peripheral nerve or root neurofibroma be identified despite extensive imaging with MRI, and the limitations of neuroimaging for identifying a structural cause in patients with NF2 with a focal peripheral nerve lesion is discussed. It is likely that NF2 may affect peripheral nerve structures in a manner distinct from a compressive schwannoma.
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10/143. Lesions of the internal auditory canal and cerebellopontine angle in an only hearing ear: is surgery ever advisable?

    OBJECTIVE: To define the indications for surgery in lesions of the internal auditory canal (IAC) and cerebellopontine angle (CPA) in an only hearing ear. STUDY DESIGN: Retrospective case series. SETTING: Tertiary referral center. patients: Seven patients with lesions of the IAC and CPA who were deaf on the side opposite the lesion. Five patients had vestibular schwannoma (VS), and one each had meningioma and progressive osseous stenosis of the IAC, respectively. The opposite ear was deaf from three different causes: VS (neurofibromatosis type 2 [NF2]), sudden sensorineural hearing loss, idiopathic IAC stenosis. INTERVENTION(S): Middle fossa removal of VS in five, retrosigmoid resection of meningioma in one, and middle fossa IAC osseous decompression in one. MAIN OUTCOME MEASURE: Hearing as measured on pure-tone and speech audiometry. RESULTS: Preoperative hearing was class A in four patients, class B in two, and class C in one. Postoperative hearing was class A in three patients, class B in one, class C in two, and class D in one. CONCLUSIONS: Although the vast majority of neurotologic lesions in an only hearing ear are best managed nonoperatively, in highly selected cases surgical intervention is warranted. Surgical intervention should be considered when one or more of the following circumstances is present: (1) predicted natural history of the disease is relatively rapid loss of the remaining hearing, (2) substantial brainstem compression has evolved (e.g., large acoustic neuroma), and/or (3) operative intervention may result in improvement of hearing or carries relatively low risk of hearing loss (e.g., CPA meningioma).
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