case report: trigeminal neuralgia caused by a minute meningioma with hyperostosed suprameatal tubercle

Cerebellopontine angle tumors might occasionally provoke trigeminal neuralgia but are usually large enough to be diagnosed radiographically. We present a case of trigeminal neuralgia caused by a very small meningioma covering the suprameatal tubercle that displayed hyperostosis at the entrance of Meckel's cave and was not obvious on routine magnetic resonance (MR) images. A 72-year-old woman with intractable trigeminal neuralgia in the left V3 territory was referred to our institution. Preoperative imaging studies revealed that the left trigeminal nerve was medially distorted at the entrance of Meckel's cave by a laterally seated bone bulge covered by a minute enhanced lesion. Trigeminal nerve decompression surgery was performed via a retrosigmoid intradural suprameatal approach. We found a small meningioma that had compressed and flattened the trigeminal nerve root at the entrance of Meckel's cave, which was grossly and totally removed by suprameatal tubercle resection. There was no vascular compression of the trigeminal nerve root. The trigeminal neuralgia ceased completely after the operation. Accurate preoperative determination of the causative pathologies is essential to achieve adequate surgical results after microvascular decompression for neurovascular compression syndrome. Because conventional MR sequences are inadequate for the precise interpretation of complex neurovascular anatomy in the cerebellopontine angle and such small tumors can be overlooked on routine MR studies, high-resolution thin-slice MR examinations and careful radiological interpretations are required for correct diagnosis and treatment.