Lipomas of the internal auditory canal - Report of two cases and review of the literature

Objective: Lipomas of the internal auditory canal are extremely rare. So far, only 21 cases have been described in the literature. We present here two of our own cases and review the literature to date with special emphasis on the diagnostic and therapeutic options. Method: During the last seven years two lipomas of the internal auditory canal were surgically treated in our department. Despite native and gadolinium-enhanced MRI and a thin-sliced temporal bone CT scan they were misdiagnosed as intracanalicular acoustic neurinomas. Results: Total tumour removal could be achieved, the facial nerve function was conserved, but both patients were rendered functionally deaf after surgery. Conclusion: Lipomas' radiological behaviour may mimic acoustic neurinomas; without fat-supressed T-1-weighted images they are often preoperatively misdiagnosed as acoustic neurinomas. Although the postoperative morbidity with respect to cochlear and facial nerve function is much higher than in small acoustic schwannomas, early surgery may be justified, because complete removal is only possible in this stage. No reliable data are available concerning the natural history of this kind of lesion.