抄録
Twenty-one cases of meningiomas of the posterior fossa were reported.
They were located in the cerebellopontine angle (9 cases), over the cerebellar convexity (7 cases), and in the tentorial attachment (5 cases). Of the 21 patients, 18 were female. The most common subjective symptoms were headache (95%) and unsteady gait (81%). Loss of hearing and tinnitus were the initial symptoms in 4 of 9 patients with the cerebellopontine angle meningiomas. Papilledema was present in 15 patients. Cerebellar signs, although observed in all cases, were not prominent in those patients with the cerebellar convexity or tentorial meningiomas. Except in the cases of cerebellopontine angle meningiomas, cranial nerve involvement was not a consistent finding. False localizing signs (FLS) of the cranial nerves were present in 6 (29%) of 21 cases of posterior fossa meningiomas including 4 (44%) of 9 patients with cerebellopontine angle meningiomas, whereas only 7 (16%) of 45 patients with acoustic neurinomas showed FLS. CT scan, performed in 15 patients, was the most useful examination in the diagnosis of this meningioma. In precontrast CT, the tumor frequently appeared iso or high dense. Calcifications were located in the tumor in 4 patients. Contrast CT revealed huge tumors in all of the cases and homogenous enhancement was seen in 13 patients (87%). Tumor stains in angiograms were demonstrated in 12 (57%) of 21 patients. Operative treatments were performed in all cases; total removal-12 (including 2 cases with second stage operation); subtotal removal-4; partial removal-5. Total removal was not easy except in cases of cerebellar convexity meningioma. There were 4 hospital deaths after the first operation. Follow-up revealed only three cases in good condition in the cerebellopontine angle meningiomas group, good results were obtained in the cerebellar convexity and the tentorial meningiomas groups.
The mechanism of the development of false localizing signs was discussed with a review of the literature.
