1034. Brainstem Arteriovenous Malformation Masquerading as an Intracranial Metastasis

Authors: Karam Atli; Jonathan Pace; Mickey Smith; Berje Shammassian; Yin Hu (Cleveland, OH)

Introduction: Brain arteriovenous malformations (BAVM) are rare, primarily congenital lesions, involving an abnormal direct fistula between arterial and venous vasculature without an interposed capillary network. Herein, we discuss an unusual case of a BAVM that presented as a brainstem mass lesion with surrounding vasogenic edema, and the widely varying management algorithms of intracranial metastatic lesions compared with BAVMs. Methods: A retrospective case study was performed for a patient diagnosed with a BAVM, that originally appeared radiographically as hepatocellular carcinoma intracranial metastasis. Results: Patient is in their 60's with a history notable for smoking, chronic hepatitis C, and hepatocellular carcinoma (HCC). The HCC was diagnosed 1 year previously on workup for inguinal lymphadenopathy. Three months later the patient was seen in clinic, where he endorsed new numbness in his right face, and a constant, throbbing, non-positional headache for two weeks. Neurologic exam at that time was notable for numbness in the right maxillary and mandibular divisions and a right sided facial droop. Subsequent MRI demonstrated a 12mm right pontine mass with heterogeneous signal intensity on T1 and T2, homogenous contrast enhancement, and significant surrounding vasogenic edema. Due to the patient’s history of HCC and radiographic appearance of the lesion, HCC metastasis was at the top of the differential. However, subsequent angiography identified the lesion as a brainstem AVM with large venous varix, not a tumor. Conclusion: Careful evaluation of imaging, history, and physical exam is required for proper diagnosis and management of patients presenting with brainstem mass lesions. The treatment algorithm is vastly different for HCC metastasis compared with brainstem AVMs, and thus a tailored, multidisciplinary approach is warranted.