Binaural hearing, neurological disability and brain imaging in Multiple Sclerosis

Multiple sclerosis is an inflammatory autoimmune disease characterized by focal destruction of myelin within the central nervous system. Auditory deficits are a relatively frequent, but often underdiagnosed symptom. This study examined sound detection threshold and functional hearing ability in a cohort of patients with multiple sclerosis. Thirty adults with relapsing-remitting multiple sclerosis and 30 age, gender and hearing-level matched controls underwent peripheral and central auditory assessments. These included audiometric (sound detection threshold) measurement, binaural speech perception, spatial hearing (Listening in Spatialized Noise test) and self-perceived hearing/communication disability rating (Speech, Spatial and Qualities of Hearing Questionnaire). Correlations with neurological disability, white matter lesion count, lesion volume and whole brain volume were evaluated. Average sound detection levels for individuals with multiple sclerosis were abnormal in one or both ears for 18/30 participants and outside age-based population norms in 17/60 ears. Binaural speech perception was significantly poorer (P<.001) in listening conditions requiring localization of sound sources and participants rated their everyday hearing/communication ability lower than matched controls (P=.001). Importantly, peripheral hearing loss did not account for the observed speech deficits. Rather, poorer speech perception moderately correlated with greater disability and lower brain volume, and poorer binaural processing was strongly correlated with increased lesion and lower brain volumes. The findings of this study are consistent with disruption of auditory neural activity occurring as a result of demyelination in the central pathways and global neurodegeneration. Clinicians should be aware that both peripheral- and central deficits severe enough to affect the quality of life of patients are common in multiple sclerosis.