Inner Ear Signal Abnormalities of Adjacent Intracranial Lipochoristoma

BACKGROUND AND PURPOSE: Inner ear signal abnormalities commonly develop in cases of vestibular schwannoma and are associated with hearing loss. Whether such signal alterations occur in other masses of the internal auditory canal (IAC), however, remains unknown. Here, we assessed inner ear signal abnormalities of lipochoristomas, historically termed “lipomas,” involving the IAC and cerebellopontine angle (CPA).

MATERIALS AND METHODS: A retrospective review was completed of patients with an MRI of an IAC and/or CPA intracranial lipochoristoma. The signal intensity of the ipsilateral labyrinthine structures was both subjectively and objectively compared with the contralateral side on FLAIR, FSE, T2 sampling perfection with application-optimized contrasts by using different flip angle evolution (SPACE sequence) and gradient recalled-echo (CISS) images by 2 neuroradiologists. Any initial disagreements were resolved by joint review to establish a consensus.

RESULTS: Fourteen patients were included. The average age was 53.1 (SD, 11.7) years, and 6 patients (42.9%) were women. Twelve of 14 (86%) of the lipochoristomas were in the IAC; the remaining masses were in the CPA. Regarding subjective assessment of abnormal labyrinthine signal, there was perfect interobserver agreement using FLAIR and T2 SPACE images; the Fleiss κ for CISS images was 0.7379. After consensus review, abnormal signal was noted in the adjacent labyrinthine structures in most cases on FLAIR (75%) and T2 CISS (73%); only 8% of patients had abnormal signal on T2 SPACE. Objective measurements of the cochlear signal similarly demonstrated relatively increased ipsilateral signal on FLAIR (P = .011) and relatively decreased signal on T2 CISS (P = .046). No significant difference was noted between ipsilateral and contralateral measurements on T2 SPACE (P = .093).

CONCLUSIONS: Abnormally increased FLAIR signal and decreased T2 CISS signal are present in most ipsilateral labyrinthine structures in patients with IAC and/or CPA lipochoristomas. Thus, these labyrinthine signal alterations are not exclusively restricted to vestibular schwannomas.