Asymmetric hearing loss and tinnitus

A 56 year old man was referred by his general practitioner with a 10 year history of progressive hearing loss and tinnitus, mainly in his right ear. He did not describe otalgia or dizziness. After thinking about it more carefully, however, he admitted that he occasionally felt slightly unsteady but had attributed this to tiredness. His medical history was otherwise unremarkable, and there was no family history of deafness. Clinical examination showed normal tympanic membranes bilaterally, with unremarkable pharynx and nasal cavity. There were no obvious neurological deficits, and clinical balance tests, including Romberg’s test, Unterberger’s test, and head impulse tests, were normal. Audiological assessment confirmed moderate right sensorineural hearing loss in all frequencies and a mild drop in high frequencies in the left ear. Because of the asymmetry of his symptoms, magnetic resonance imaging (MRI) of the brain and internal auditory canal was performed (fig 1⇓). Fig 1 Axial magnetic resonance imaging of the brain and internal auditory canal. (A) T2 weighted image, (B) non-contrast T1 weighted image, (C) post-gadolinium T1 weighted image ### 1. What does the MRI scan show? #### Short answer Figure 1 shows a well delineated lesion of the right internal auditory canal extending into the cerebellopontine angle. The lesion is hypointense on T2 weighted imaging (A), isointense on non-contrast T1 weighted imaging (B), and it enhances strongly on T1 weighted imaging after administration of intravenous contrast (C). #### Long answer The axial MRI shows a well defined lesion (arrow) arising from the right internal auditory meatus and extending about 1.5 cm into the cerebellopontine angle (fig 2⇓). The lesion seems to abut the brainstem (white X) and the cerebellum (white star), without compressing them. It is characteristic …