Smooth muscle choristoma of the internal auditory meatus.

Choristomas of the internal auditory meatus are very uncommon tumors. Because of their rarity and the lack of a consistent clinical and radiological pattern, they are usually misdiagnosed as vestibular schwannomas. Surgical exploration usually shows involvement of the vestibular, cochlear or facial nerve by the tumor, representing a diagnostic and therapeutic challenge to the surgeon. In this report, a case of a smooth muscle choristoma of the internal auditory meatus is presented. The lesion involved the vestibular and cochlear nerves and was extremely adherent to the facial nerve. Microscopic examination of the tumor revealed nerve fibers, smooth muscle and a small amount of adipose tissue. No striated muscle was found. The contemporary terminology, diagnosis and management of this infrequent lesion are analyzed.