Teaching Case

A 35-year-old female patient presented with a 2-year history of progressive left sided facial numbness and left trigeminal neuralgia.

A 35-year-old female patient presented with a 2-year history of progressive left sided facial numbness and left trigeminal neuralgia. She had a medical treatment with the presumed diagnosis of microvascular compression of trigeminal nerve. However her symptoms persisted. An MRI of the cranium was ordered. MRI study of the cranium, especially for trigeminal nerve with thin-slices (3 mm slices) on axial, coronal, sagittal planes with T1, T2 spin-echo sequences, and post-gadolinium T1 spin-echo sequences were performed. A soft tissue mass of the left Meckel's cave, isointense to gray matter and with uniformly contrast enhancement was detected. The mass was removed totally with surgery.

Schwannomas constitute approximately one third of primary trigeminal and Meckel's cave tumors. The second place for schwannomas within the cranium is the course of trigeminal nerve, following eight nerve. The tumors of the trigeminal nerve may be seen along the course of the nerve, involving its pontine cisternal segment, Meckel's cave, and the cavernous sinus.Schwannomas with isolated Meckel's cave localization are not common entities. Neurinoma, schwannoma, neurilemoma are the names for tumors arising from the Schwann cells of nerve sheaths. Grossly, they are circumscribed encapsulated tumors that may be lobulated, but frequently ovoid or tubular in shape. Histopathologically many of the lesions are composed of two distinct types of tissue. Antoni A tissue has a compact texture composed of interwoven bundles of bipolar spindle cells, whereas Antoni B tissue has a loose texture containing tumor cells. On MRI the tumors are usually well demarcated with almost isointense signal intensity characteristics with cortical gray matter, and they enhance uniformly following contrast administration. However they may reveal heterogeneous signal intensity and contrast enhancement characteristics, depending on the cystic, necrotic, hemorrhagic components within the tumors. Differential diagnosis should include meningioma, epidermoid, lymphoma, amyloidoma, perineural spread of malignancy, metastasis, granulomatous inflammations at the cisternal segment and Meckel's cave. Unfortunately most of the lesions encountered herein may mimic schwannomas both clinically and radiographically.