Monaural tinnitus from a contralateral inferior colliculus hemorrhage.

A 48-year-old man presented with sudden right ear tinnitus and showed no other otoneurologic signs or symptoms. Auditory brainstem response revealed prolonged III-V interpeak latencies from stimulating either ear. MRI revealed a small, circumscribed lesion of the left inferior colliculus, probably from an acute hemorrhage leading to a small cavernous malformation. Circumscribed lesions of the inferior colliculus are rare with no prior reports of contralateral tinnitus.