Brainstem hyperintensity in patients with vestibular schwannoma is associated with labyrinth signal on magnetic resonance imaging but not vestibulocochlear tests

Abstract

Objectives Focal hyperintensity in the dorsal brainstem (HDB) has been described in large cerebellopontine angle tumours and is thought to represent vestibular nuclei degeneration, but its functional significance has not been thoroughly investigated. Our aim was to analyse its relationship to imaging characteristics of the tumour and inner-ear structures and to vestibulocochlear functional tests. Methods We retrospectively reviewed 54 patients with a histological diagnosis of vestibular schwannoma (VS). Magnetic resonance imaging tumour characteristics (size, cystic composition and distance from the cochlear aperture), signal intensity ratio of the cochlea and vestibule in fluid-attenuated inversion recovery (FLAIR) and fast imaging employing steady-state acquisition (FIESTA)/fast spin-echo imaging with variable flip angles (CUBE) and vestibulocochlear function tests (audiometry, auditory brainstem response (ABR) and video head impulse testing (vHIT)) were obtained. Statistical analyses were performed to evaluate their relation to focal HDB. Results Focal HDB was found in 22% of VS. It was significantly associated with large ( p < 0.001) and cystic ( p = 0.004) tumours and also with tumours located further from the cochlear aperture ( p = 0.039). The signal intensity ratio of the cochlea on FLAIR was higher in patients with HDB ( p < 0.014), but this difference was not observed in FIESTA/CUBE ( p = 0.981). Audiometry, ABR and vHIT results did not significantly differ in patients with HDB, but ABR results were worse in patients with higher cochlear signal intensity on FLAIR sequences ( p = 0.026). Conclusions Focal HDB in patients with VS was associated with increased signal intensity ratio of the cochlea on FLAIR in patients with VS but not directly to the results of vestibulocochlear function tests.