Neuromuscular choristoma of the internal auditory meatus.

Choristomas of the internal auditory meatus are exceedingly rare tumors. In most cases, neuromuscular choristomas have initially been misdiagnosed as vestibular schwannomas (VS). No known characteristics in the clinical presentation or in imaging exist distinguishing these tumors from VS, which are the most common tumors at this location [Smith et al.: AJNR Am J Neuroradiol 1997;18:327-329]. We present a case of a neuromuscular choristoma of the 8th cranial nerve that was operated because of growth demonstrated on two MRI scans 3 months apart. We were convinced that this young patient would require treatment sometime in the future, and we believed that an operation at that time had higher chances to preserve the anatomical structures. Histomorphological examination of the tumor revealed a nodular lesion with fascicular and nodular assembled smooth muscle cells, connective tissue and nerve fibers.