Lipochoristoma of the Internal Auditory Canal

Neoplasms arising within the internal acoustic canal (IAC) and cerebellopontine angle (CPA) are most commonly of neuroepithelial origin. Vestibular schwannoma represents the most common lesion in the IAC (80–90%) with meningiomas comprising nearly all the rest (10%) of IAC tumors.1–3 Rare tumors include epidermoids, lipochoristomas, and metastatic tumors. Each of these lesions has typical imaging characteristics that frequently allow a diagnosis to be made with magnetic resonance imaging (MRI) scan alone. Lipochoristomas (lipomatous choristomas) comprise 0.1% of all CPA tumors. These rare tumors of the CPA and IAC are slow growing and often discovered incidentally. Classically, these tumors were thought to arise from cells of the meninx primitiva, the mesenchymal derivative of the neural crest, and thus they were referred to as lipomas of the IAC/CPA. However, research has since shown that these tumors arise from mesenchyme endogenous to the vestibulocochlear nerve and thus are more appropriately characterized as lipomatous choristomas.4 This theory offers an explanation for the failure of hearing conservation reported after surgical resection of these lesions. Patients with lipochoristomas may present with hearing loss, vestibular symptoms, or tinnitus. In this report we examine the appropriate work-up, diagnosis, and management of lipochoristoma of the IAC/CPA.