Lipomas of the Internal Auditory Canal

Abstract

Lipomas of the internal auditory canal (IAC) are rare, benign neoplasms occurring in the third to fifth decade of life predominately in Caucasian males. Eleven cases of IAC lesions have been previously reported; we report four more. Two of four cases showed atypical findings on preoperative radiographic evaluation. These two patients had surgery. Two patients with small tumors elected for observation with close follow-up. Fat suppression of T1-weighted images on magnetic resonance imaging (MRI) offers the most precise preoperative diagnostic tool of IAC lipomas. Because of the infiltrative nature of these tumors, hearing conservation surgery is unlikely to succeed. We recommend observation for those patients with small tumors and serviceable hearing.

Lipomas of the Internal Auditory Canal and Cerebellopontine Angle

“…Lipomas do not usually enhance with gadolinium. 1,6,11 A missing signal on fat suppression sequences confirms the diagnosis of lipoma. Lower-intensity areas inside the mass may be found and are usually consistent with neurovascular structures.…”

“…We identified only 6 articles (Table 2) reporting series of 4 or more well-documented cases. 1,[5][6][7][8]12 There were 38 patients and a male predominance (male-to-female ratio of 3 to 1). The age of initial presentation ranged between 7 months and 74 years (mean, 42.6 years; SD, 16.4 years).…”

“…These findings are consistent with those reported in the literature. 1,[4][5][6][7][8]12 The most important radiologic differential diagnosis of these tumors includes vestibular schwannomas, meningiomas, arachnoid cysts, cholesterol granulomas, hemangiomas, and epidermoid tumors. 1,11 Table 3 shows the MRI features of lipomas as compared with other, more common IAC/CPA lesions.…”

“…Since that original report, fewer than 150 cases have been reported in the literature worldwide. Only a few studies have reported more than 4 patients, 1,[4][5][6][7][8] and the majority of articles still present case reports. Because of the small number of patients in each of the series reported, it has been difficult to make recommendations for the management of IAC and/or CPA (IAC/CPA) lipomas.…”

Rare Bilateral Lipoma of the Internal Auditory Canals

“…The signal pattern was consistent with and specific for that of a lipoma: it was hyperintense on T1 images, hypointense on T2 images (not shown), and did not enhance after the administration of Gadolinium. The diagnosis was made specific on the fat suppression sequence which is commonly used to characterize lipomas 2,19 .…”