Metastatic lesions involving the cerebellopontine angle.

PURPOSE To evaluate the clinical and MR findings of metastatic lesions involving the cerebellopontine angle (CPA), which may be useful in differentiating them from the more commonly occurring benign CPA lesions. METHODS Clinical and MR findings of 14 patients with clinical/radiologic (seven) or pathologic (seven) diagnoses of CPA metastasis were retrospectively reviewed. RESULTS Useful clinical findings included acute onset and rapid progression of cranial nerve symptoms, especially 7th and/or 8th cranial nerve deficits (92.9%). Cranial nerve symptoms could be unilateral (50%) and frequently involved multiple cranial nerves (64.3%). MR findings showed significantly more extensive disease than suggested by clinical presentation, with 100% of patients having multiple cranial nerve involvement and 85.7% bilateral. Useful MR findings included small and/or bilateral CPA-enhancing lesions with relative isointensity to brain parenchyma on precontrast MR, with associated findings of multiple and/or bilateral cranial nerve and/or leptomeningeal lesions. CONCLUSIONS These associated findings suggest that cerebrospinal fluid dissemination and/or leptomeningeal extension may be an important pathway for metastatic spread to the CPA. Because the CPA metastasis may be the initial or only site of metastasis, and may occur many years after the initial diagnosis of malignancy, MR findings with clinical correlation are not only useful for the detection of CPA metastases, but also for their differentiation from the more common benign CPA tumors.