Contrast enhancement of the labyrinth on MR scans in patients with sudden hearing loss and vertigo: evidence of labyrinthine disease.

The sudden onset of hearing loss and vertigo presents a difficult diagnostic problem. We describe the finding of labyrinthine enhancement on MR images in five patients with sudden unilateral hearing loss or vertigo or both and correlate the MR findings with audiologic and electronystagmographic studies. All patients were studied with T2-weighted axial images through the whole brain, contrast-enhanced 3-mm axial T1-weighted images through the temporal bone, and enhanced T1-weighted sagittal images through the whole brain. Cochlear enhancement, on the side of hearing loss only, was found in all five patients. The presence of associated vestibular enhancement correlates with objective measures of vestibular function on the electronystagmogram. In two patients, the resolution of symptoms 4-6 months later correlated with resolution of the enhancement on gadopentetate dimeglumine-enhanced MR images. Two patients had luetic labyrinthitis. No labyrinthine enhancement was seen in a series of 30 control subjects studied with gadopentetate dimeglumine-enhanced MR using the same protocol. Labyrinthine enhancement in patients with auditory and vestibular symptoms is a new finding and is indicative of labyrinthine disease. While abnormalities on electronystagmograms and audiograms are nonspecific and indicate only a sensorineural problem, gadopentetate dimeglumine-enhanced MR may separate patients with retrocochlear lesions, such as acoustic neuromas, from those in whom the abnormal process is in the labyrinth or is intraaxial. This group of patients underscores the importance of identifying and commenting on the structures of the membranous labyrinth when evaluating MR studies of the internal auditory canal and the cerebellopontine angle in individuals with hearing loss.