Auditory temporal resolution in multiple sclerosis

Disturbances of hearing in multiple sclerosis patients have been variably reported, likely because standard audiologic testing emphasizes assessment of peripheral, rather than central, auditory function. This study investigated a group of patients with multiple sclerosis (MS), prospectively selected on the basis of magnetic resonance imaging (MRI) scans. Five of these patients had demyelinating lesions that included the rostral auditory fibre tracts, while another seven patients had lesions restricted to brainstem auditory sites. A further four had no lesions in the distribution of their auditory pathways. A comprehensive battery of audiometric tests, including standard audiometry and retrocochlear testing, was performed. In addition, their findings on electrophysiologic testing, including auditory brainstem responses (ABR) and middle latency responses (MLR), were studied. Finally, their performances in gap detection and speech recognition in continuous and interrupted background noise were examined to assess their auditory temporal resolution. The MS patients were found to be selectively impaired under the interrupted masker of this speech-in-noise paradigm, confirming a temporal processing defect. Furthermore, these patients' performances suggested a predominant role of forebrain pathways in mediating auditory temporal resolution.