Lymphomatous involvement of the trigeminal nerve and Meckel cave: CT and MR appearance.

A 49-year-old woman presented with a 3-week history of headaches and numbness of the face, mouth, and ear on the left side. Her medical history was significant for diffuse large cell lymphoma, first diagnosed 6 years previously. She was in her third remission and had been free of disease for 2 years. A contrast-enhanced CT scan showed an enhancing mass in the anterior aspect of the cerebellopontine cistern on the left, extending into Meckel cave, which was thought to represent a trigeminal neurinoma or meningioma (Fig. 1 A). Bone windows showed the foramen ovale to be normal in size and appearance. On MR , the T1-weighted images showed an isointense dumbbell-like appearance of the left trigeminal nerve in its cisternal segment extending into Meckel cave (Figs. 1 B and 1 C). On T2-weighted images, the lesion appeared hyperintense, and abnormal signal was seen in the left foramen ovale (Fig . 1 D). Since the bones appeared normal , CSF cytology was suggested to rule out leptomeningeal metastasis. This revealed abnormal lymphocytes suggestive of lymphoma. An open biopsy of the proximal portion of the mandibular branch of the trigeminal nerve (V3) at the gasserian ganglion was performed , and perineural diffuse large cell lymphomatous involvement of the mandibular branch of the trigeminal nerve was confirmed (Fig . 1 E). After intrathecal chemotherapy via an Omaya reservoir , the trigeminal symptoms improved but did not completely resolve. Posttreatment T1-weighted images showed a normal-appearing cisternal segment of the trigeminal nerve (Fig . 1 F).