Meningiomas arise from the arachnoid cap cells and form an encapsulated mass that is usually slow growing, eventually creating mass effect on the brain (see Figure 5). Histologically, they classically manifest a whorled cellular pattern, psammoma bodies with differing degrees of fibrous connective tissue, blood vessels, and, if malignant, mitotic activity and invasion of cortex.
Generally, meningiomas are classified on a four-grade system:
The great majority of meningiomas (94%) are benign.158
Meningiomas most commonly arise on the brain convexity or in a parasagittal location (36%), with 50% located between the coronal and lambdoid sutures and 20% anterior to the coronal suture.157
Complete surgical resection should be the goal for accessible tumors. A 4.2-fold excess risk of death has been reported with partial resection compared to gross total resection.163 Adjuvant radiation treatment, although controversial, has been used with some success. In one study the time to recurrence after nonradiated subtotal resections was 66 months, versus 125 months for radiated subtotal resections.164
Stereotactic radiosurgery (SRS) is now used to treat meningiomas that are nonoperable, small, recurrent, or a result of a subtotal resection. The goal is to prevent further tumor growth and preserve normal neurologic function. This is a safe and effective primary or adjuvant therapeutic strategy.165–168 SRS is not indicated for large tumors (>3 cm) or those less than 5 mm from the optic nerve or chiasm.
Few studies focus on seizure outcomes after resections of meningiomas. Flyger and colleagues studied the neogenesis of seizure disorders postresection.161 They observed that 41.1% of patients with no preoperative seizure disorder developed epilepsy postoperatively. Similarly, Foy et al. reported a 22% risk of postoperative seizures after meningioma resection.162 Parietal tumors were the most epileptogenic, followed by frontal and occipital tumors.
Predicting recurrence is related to tumor grade and degree of resection. Benign tumors recur in 3% at 5 years, compared to 78% recurrence at 5 years for anaplastic tumors.159 Gross total resection has a reported recurrence rate of 7% at 5 years, compared to 37% if the resection is partial.160
Reviewed and revised March 2004 by Steven C. Schachter, MD, epilepsy.com Editorial Board.
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