Lipomas of the cerebellopontine angle and internal auditory canal: Primum Non Nocere

Objectives/Hypothesis To describe the presentation and clinical course of cerebellopontine angle (CPA) and internal auditory canal (IAC) lipomas. Study Design Retrospective cohort study at a tertiary academic referral center. Methods All patients presenting with a CPA or IAC mass radiographically consistent with a lipoma on high-resolution magnetic resonance imaging (MRI) were identified. Data including presenting symptomatology, tumor characteristics, management strategy, and patient course were collected. Results Between 1996 and 2012, 15 patients were diagnosed with a CPA or IAC lipoma at the authors' institution and were included in the analysis. The mean duration of radiological and clinical follow-up was 3.4 years and 5.1 years, respectively. Eight lesions were confined to the IAC, while seven involved the CPA. The median tumor size at diagnosis was 7.2 mm; one patient demonstrated tumor growth on serial MRI while the remaining subjects did not have radiological progression. The most common presenting symptoms were sensorineural hearing loss (40%) and tinnitus (33%); five patients were diagnosed after incidental discovery on MRI. Fourteen patients were managed with observation, while one subject underwent subtotal resection. None of the observed patients reported worsening symptoms at last follow-up. Conclusions While rare, lipomas should be included in the differential diagnosis of CPA and IAC lesions. Owing to a generally benign clinical course and high morbidity associated with resection, microsurgery should only be considered in cases of definite tumor enlargement with intractable symptoms from mass effect. Careful radiological evaluation is critical for establishing an accurate diagnosis in order to prevent unnecessary morbidity associated with resection.