LAUSR

A rare case of a lipoma within the internal auditory canal (IAC) extending to the basal turn of the cochlea is presented. A 70-yearold female presented with a worsening left sided sensorineural hearing loss (SNHL). She reported no associated tinnitus or vertigo with a background of bilateral hearing loss for over 10 years and previous industrial noise exposure. Her audiogram demonstrated a moderate to severe SNHL with corresponding ‘roll over’ on speech perception, that is, reduced speech recognition with increased amplification of sound. This feature can be seen in patients with vestibular nerve schwannoma. Magnetic resonance imaging (MRI) was requested to exclude retro-cochlear pathological causes for her worsening unilateral hearing loss, commonly used to exclude vestibular schwannoma. Initial unenhanced MRI study demonstrated a 4 mm × 3.6 mm intracanalicular hyperintense focus on T1 weighted imaging extending to the base of the cochlea (Fig. 1). This oval mass displaced both the facial nerve and the vestibular nerve superiorly, with otherwise normal bilateral vestibulocochlear apparatuses. Subsequent T1 MRI with gadolinium contrast and fat suppression demonstrated complete signal loss (Fig. 2). The case was discussed at a multidisciplinary meeting, and the working diagnosis of IAC lipoma was made. The patient was subsequently managed conservatively with monitoring of the lipoma. A repeat MRI organized 12 and 24 months after demonstrated no change in the lipoma dimensions. The patient’s hearing remained stable during 2 years of monitoring. Intracranial lipomas have been described as a rare entity comprising fewer than 0.5% of intracranial tumours. Of these rare intracranial lipomas, reports indicate that less than 9% are found at the IAC or the cerebellopontine angle (CPA). When considering all tumours of the IAC or CPA, only 0.14–1% are lipomas. In addition, lipomas involving the cochlea are rare even in the literature. CPA or IAC lipomas may present with symptoms similar to those caused by vestibular schwannomas, with hearing deficits, tinnitus and dizziness being the most commonly reported.