Sensorineural hearing loss: more than meets the eye?

PURPOSE To assess the value of MR in patients with sensorineural hearing loss (SNHL) caused by lesions other than acoustic neuromas. METHODS MR studies of 51 patients with SNHL were retrospectively reviewed; patients with acoustic neuroma were excluded to focus on the more uncommon causes. RESULTS Twenty patients had labyrinthine lesions. Six patients had viral labyrinthitis, one patient had bacterial labyrinthitis, and one patient had luetic labyrinthitis. Three patients had hemorrhage in the labyrinth, two posttraumatic and one spontaneous from an adjacent temporal bone tumor. Only one of the two patients with traumatic labyrinthine hemorrhage had evidence of a fracture on high-resolution CT. In one patient with CT-proved cochlear otosclerosis, peri-cochlear foci of enhancement were seen on contrast-enhanced MR. Four patients had presumed labyrinthine schwannomas. A middle ear cholesteatoma in one patient invaded the cochlea and resulted in marked cochlear enhancement due to granulation tissue. Thirteen patients had intracanalicular and cerebellopontine angle lesions. The lesions included arteriovenous malformations (three patients), sarcoidosis (three patients), metastasis (two patients), lymphoma (two patients), lipomas (two patients), and postshunt meningeal fibrosis (one patient). Eighteen patients had intra-axial lesions responsible for SNHL. The most common intra-axial lesions were brain stem infarcts and multiple sclerosis. Traumatic lesions in the inferior colliculi, sarcoidosis, lymphoma, and extrinsic compression of the colliculi from a pineal tumor were also noted. CONCLUSION MR can demonstrate numerous lesions responsible for SNHL other than acoustic neuromas. The entire acoustic pathways, including the labyrinth, internal auditory canal, cerebellopontine angle, and brain stem should be carefully scrutinized for lesions in patients with SNHL. The use of contrast media markedly increases the yield of MR in this clinical situation by demonstrating inflammatory and neoplastic labyrinthine lesions and meningeal pathology (both neoplastic and inflammatory) in the internal auditory canal and cerebellopontine angle cistern.