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Madjid Samii, Makoto Nakamura, Shahram Mirzai, Peter Vorkapic and Andres Cervio

Object

The aim of this study was to describe the symptomatology, radiological features, and surgical treatment of patients with cavernous angiomas within the internal auditory canal (IAC).

Methods

The authors reviewed the cases of seven patients with cavernous angiomas in the IAC that had been surgically treated in the 22-year period between 1983 and 2005. All the patients had presented with sensorineural hearing loss, and four suffered from tinnitus. Four patients also reported facial symptoms such as hemispasm or progressive palsy; one of these patients had presented with sudden facial paresis due to intrameatal tumor hemorrhage. According to computed tomography (CT) results, the lesions caused enlargement of the IAC. Interestingly, these same angiomas showed variable features on magnetic resonance (MR) imaging, making their differentiation from intrameatal vestibular schwannomas (VSs) sometimes impossible. In all patients the lesions were totally removed via the suboccipital retrosigmoid approach. They could be dissected away from the facial nerve in five cases, whereas in two cases, because of the location of the lesion, the seventh cranial nerve had to be sectioned and repaired with a sural nerve graft. Transient worsening of seventh cranial nerve symptoms occurred in two patients, with postoperative improvement in each of them. The cochlear nerve could not be functionally preserved because of its extreme adherence to the tumor, although its continuity was preserved in four patients. Complete deafness was the only postoperative complication.

Conclusions

Cavernous angiomas of the IAC are very uncommon lesions that can imitate the symptoms of VSs. Although it is the most sensitive study available, MR imaging does not show sufficiently specific findings to differentiate the two lesion types. Thus, the preoperative diagnosis must be based on patient symptoms plus the CT and MR imaging features.

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Makoto Nakamura, Florian Roser, Mehdi Dormiani, Madjid Samii and Cordula Matthies

Object. Meningiomas of the cerebellopontine angle (CPA) can either arise from or secondarily grow into the inner auditory canal (IAC). This location may have a great impact on hearing function following surgery to remove these lesions. The aim of this retrospective study was to investigate the reliability and predictive importance of auditory brainstem responses (ABRs) for the determination of postoperative auditory function in patients with CPA meningiomas in comparison with results obtained in patients who undergo surgery for vestibular schwannomas.

Methods. In a consecutive series of 1800 meningiomas surgically treated between 1978 and 2002, 421 lesions were located in the CPA. In 38 patients with CPA meningiomas involving the IAC, the findings of intraoperative ABR monitoring and the hearing status of each patient before and after surgery were retrospectively analyzed.

On analysis, ABR monitoring demonstrated stable findings in 24 patients throughout tumor resection and fluctuating signals in 10 patients. Among the 24 patients with stable ABRs, postoperative hearing function improved in three patients, remained the same in 15, and worsened in six patients, including one patient who displayed postoperative deafness. There was even one patient recovering from preoperative deafness. Among the 10 patients with unstable ABRs, intermittent decreases in amplitude and deformations of variable duration in the ABR wave were noted. The risk of deafness was considerably higher in patients with prolonged phases of intermittent ABR deterioration.

Conclusions. The presence and absence of ABRs during surgery for CPA meningiomas reliably predicted the presence and absence of postoperative auditory function. Intermittent deterioration of ABRs may result in postoperative deafness, depending on the duration of these events during surgery. Improvements in hearing are only seen when the ABRs are stable for amplitudes and latencies throughout surgery.

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Florian Roser, Makoto Nakamura, Mehdi Dormiani, Cordula Matthies, Peter Vorkapic and Madjid Samii

Object. Only some meningiomas of the cerebellopontine angle (CPA) extend into the internal auditory canal (IAC) or arise from its dural lining. The authors investigated cases of CPA tumors in which the meningioma was inserted in the dura mater in or at the ICA or infiltrated a cranial nerve.

Methods. The authors reviewed patient charts including surgical and clinical records, intraoperative recordings of auditory evoked potentials, records of postoperative auditory examinations, and imaging studies.

In a series of 421 patients harboring CPA meningiomas, 72 patients in whom there was dural involvement of the IAC were investigated. Total tumor resection was achieved in 86.1%. In 34 patients, opening of the IAC was required for total tumor removal; this procedure did not influence the patient functional outcome. Among patients with secondary involvement of the IAC, anatomical preservation of the facial and cochlear nerves was obtained in 94%, whereas among patients in whom the lesion arose from the dura in or at the IAC these values were 80 and 75%, respectively. Functional preservation of the seventh and eighth cranial nerves in cases of tumor extension within the IAC was 86 and 77%, respectively, whereas in cases in which the IAC was involved it was only 60%. In four of five patients in whom the tumor had its origin in the dura mater within the IAC, the seventh or eighth cranial nerve had to be sacrificed to achieve tumor removal because of the lesion's infiltrative behavior. Facial nerve reconstruction by sural grafting was performed in the same operative procedure.

Conclusions. Meningiomas of the CPA involving the IAC require special surgical management. Dural involvement of the IAC requires opening by using a diamond drill, a procedure that does not influence cranial nerve outcome. The increased rate of cranial nerve morbidity is attributed to the infiltrative behavior of these meningiomas. If affected nerve segments have to be sacrificed, immediate reconstruction enables satisfactory long-term results.

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Florian Roser, Makoto Nakamura, Almuth Brandis, Volkmar Hans, Peter Vorkapic and Madjid Samii

✓ The authors describe the first case of an intracranial transition of a melanocytoma into a primary malignant melanoma within a short time. A 37-year-old woman presented with progressive brainstem syndrome due to a tumor, originally diagnosed and treated 12 years earlier, that extended from the petroclival area to the anterior craniocervical junction. The histological workup following subtotal tumor resection of the initial tumor had revealed the typical features of a fibrous melanocytic meningioma without increased proliferation. Ten years after the patient had completed treatment for the melanocytic meningioma, control neuroimaging demonstrated growth of the residual tumor with compression of the brainstem. Another neurosurgical intervention revealed a dark tumor of hard consistency. At this time immunohistochemical examinations demonstrated melanocytic features (expression of vimentin, S100 protein, and melan A) of the lesion with focally increased proliferation (5% of Ki-67—positive cells) but no higher mitotic activity. Clinical signs of deterioration along with imaging-confirmed tumor progression precipitated another operation within 7 months. A neuropathological examination revealed epithelial and anaplastic changes and indicated that the MIB-1 indices were greater than 25%. Pleomorphic changes and a focal high mitotic activity led to the diagnosis of a primary cerebral malignant melanoma. The patient's later clinical course consisted of a rapid diffuse meningeal spread of the lesion throughout the entire brain and spine. Despite whole-brain and stereotactic radiation therapy as well as chemotherapy, the patient died 4 months after the last neuropathological diagnosis. Although grossly resembling a meningioma, melanocytomas lack the former's histological and immunohistochemical features. The biological behavior of a melanocytoma is variable and recurrence may happen after subtotal resection, but intracranial transition into a malignant melanoma has not been observed previously.