Premeatal and retromeatal cerebellopontine angle meningioma. Two distinct clinical entities

Objective. Meningiomas represent the second most common type of neoplasm of the cerebellopontine angle (cpa). Their relationship to critical neural or vascular structures of the cpa is variable and they present with different signs and symptoms. Materials and Methods. A retrosigmoid craniotomy was performed in 31 cpa-me ningiomas from January 1981 to February 1997. The mean age of the 25 women (81%) and the 6 men (19%) was 53 +/- 13 years. According to their location within the posterior fossa and with special reference to the internal audit ory canal (IAC), they were classified in 17 cases (55%) as retromeatal (pos terior to the iac) and in 14 cases (45%) as premeatal (anterior to the iac) . Results. The retromeatal group showed a significantly larger tumour size (2 1 +/- 15 vs 29 +/- 20 mm) and the diagnosis was made later (2.7 +/- 3.2 vs 1.1 +/- 0.9 years) compared to premeatally located meningiomas. Before the operation, a reduction of the facial nerve function (64% vs 0%) and hearing function (100% vs 25%) was present significantly more often in premeatal m eningiomas. The clinical appearance of the retromeatal group was dominated by cerebellar symptoms (44% vs 0%). Both preoperative and postoperative imp airment of facial nerve and auditory function prevailed in the premeatal gr oup. Conclusion. The topological classification of CPA-meningiomas according to their location anterior or posterior to the ICA is important, because the c linical presentation, the surgical strategy to be applied, and the function al outcome of critical neural structures differ between the two subtypes. O ur results provide substantial evidence for the paradoxical observation tha t premeatal meningiomas have a significantly worse postoperative functional outcome compared to retromeatal meningiomas although premeatal meningiomas become symptomatic earlier and at smaller sizes.