Objective: To present a case of a cavernous malformation presenting with a subdural hematoma. Methods: A 27-year-old woman was admitted with progressively worsening headache, vomiting, weakness, and word-finding difficulties 1 week after she was discharged from an outside hospital, where she was managed conservatively for a presumed traumatic subdural hematoma. Computed tomography revealed an enlarging subacute left hemispheric subdural hematoma for which she underwent drill craniostomy. Postprocedural magnetic resonance imaging showed a posterior left temporal lobe mass consistent with a cavernous malformation juxtaposed with the subdural hematoma. Craniotomy for resection of the lesion was performed. She had an uncomplicated postoperative course and experienced a good recovery. Results: The signs and symptoms, diagnostic imaging, and intraoperative findings suggest that the subdural hematoma was caused by extralesional hemorrhage of the cavernous malformation, which is a rare finding associated with these malformations. Conclusions: The clinical course, radiologic, and intraoperative findings suggest that the subdural hemorrhage was caused by extralesional hemorrhage of the cavernous malformation
