Vascular loops of the internal auditory canal: A diagnostic dilemma

Objective: To describe clinical and radiographic characteristics of vascular loops occupying the internal auditory canal. Study Design and Setting: A retrospective review of patients with lesions initially suggestive of neoplasm, such as acoustic neuroma, who were subsequently found to have vascular compression of the facial and/or cochleovestibular nerves. The symptoms suggestive of this retrocochlear pathology, including vertigo, tinnitus, hearing loss, hemifacial spasm, and facial paralysis, were assessed. Subsequent evaluation with MRI revealed findings suggestive of intracannalicular neoplasm in three patients. Main Outcome Measures: Vascular loops within the cerebellopontine angle have been reported to approach the facial and cochleovestibular nerves at the level of the porus acousticus or within the internal auditory canal in ~65% of postmortem specimens. Although presumably the majority of individuals are asymptomatic, several cases are presented where vascular loop compression created symptoms and radiographic findings suggestive of neoplasm. Results: Within this study, two patients underwent surgical exploration for expected neoplasm and were subsequently found to have pathology secondary to vascular loop compression. A third patient avoided surgical exploration due to radiographic confirmation with angiography. Conclusions: Although skepticism exists regarding true pathology occurring secondary to vascular loop compression, histologic confirmation of neural compression injury secondary to a vascular loop is presented. Further, diagnostic parameters and treatment are presented as well.