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Meningioma of the internal auditory canal
A W Langman1, R K Jackler, S R Althaus
1Department of Otolaryngology-Head and Neck Surgery, University of California, San Francisco.
Abstract:
The great majority of tumors that arise in the internal auditory canal are schwannomas of the eighth cranial nerve (acoustic neuromas). Meningiomas constitute the second largest group of posterior fossa tumors. Meningiomas arise from arachnoid villae, the apparatus responsible for cerebrospinal fluid absorption, in proximity to a major vein or dural sinus in most cases. Arachnoid villae are also present along neural foramena at the base of the skull. They have been observed histologically in the internal auditory canal (IAC), and are the probable site of origin of meningiomas in this location. Larger cerebellopontine angle meningiomas occasionally possess a significant intracanalicular component; however, these lesions usually originate from the meningeal lining of the posterior petrous face adjacent to the sigmoid, superior petrosal, or inferior petrosal sinuses and prolapse into the IAC. Two meningiomas have recently been observed that extensively involved the IAC, one of which arose from the lining of the IAC. The clinical manifestations of these meningiomas mimicked those of acoustic neuromas. Preoperative radiographic studies, including magnetic resonance imaging, were unable to differentiate these from acoustic neuromas. Meningiomas have a higher rate of recurrence than acoustic neuromas and should be excised with surrounding dura and several millimeters of subjacent bone. Meningiomas that extensively involve the IAC have a tendency to invade the inner ear and the deeper portions of the temporal bone. In meningiomas that involve the lateral portion of the IAC, consideration should be given to exenteration of the cochlea and semicircular canals.
Insights
Meningiomas in the internal auditory canal (IAC) can mimic acoustic neuromas, posing diagnostic challenges. Early surgical intervention with dural and bone margins is crucial due to their higher recurrence rate and invasive potential.
Area of Science:
- Neurosurgery
- Oncology
- Otolaryngology
Background:
- Schwannomas of the eighth cranial nerve (acoustic neuromas) are the most common tumors in the internal auditory canal (IAC).
- Meningiomas are the second most frequent posterior fossa tumors, typically arising from arachnoid villae near venous structures.
- Arachnoid villae are also found in the IAC, suggesting a potential origin for meningiomas in this location.
Observation:
- Two meningiomas extensively involving the IAC were identified, with one originating within the IAC itself.
- Clinical presentation and standard preoperative imaging (including MRI) failed to distinguish these meningiomas from acoustic neuromas.
- These meningiomas demonstrated a propensity to invade the inner ear and adjacent temporal bone structures.
Findings:
- Meningiomas in the IAC can present clinically similar to acoustic neuromas.
- Radiographic studies are often insufficient to differentiate IAC meningiomas from acoustic neuromas.
- Meningiomas exhibit a higher recurrence rate compared to acoustic neuromas.
Implications:
- Surgical excision of IAC meningiomas requires removal of surrounding dura and subjacent bone to minimize recurrence.
- Extensive IAC meningiomas may necessitate en bloc resection, potentially including the cochlea and semicircular canals.
- Accurate preoperative diagnosis is critical for appropriate surgical planning and management of IAC meningiomas.