Auditory spatial deficits in brainstem disorders

Purpose Brainstem disorders seem to negatively influence the central auditory system, causing spatial hearing deficits. Material and methods We tested 11 patients with brainstem lesions due to ischemic stroke (IS), multiple sclerosis (MS), or cerebellopontine angle tumor (CPAT) together with 50 age- and sex-matched healthy volunteers. We used pure tone audiometry (PTAud), brainstem auditory evoked potentials (BAEPs) and the horizontal minimum audible angle test (HMAAT) for 8 azimuths with binaural stimulation. Results The chosen patients and the controls had normal or near normal hearing in PTAud. BAEPs interaural wave I–V latency difference was over 7 times longer in the patients group compared to the controls. Additionally, 9 of the 11 patients (81.1%) had abnormal HMAAT results. The biggest quantitative disturbances in HMAAT were present in the CPAT and the MS patients. The sound localization ability in HMAAT was significantly worse in the patients in 0° azimuth in comparison with the controls, and in 45° and 90° azimuth in patients with auditory pathway involvement compared with the ones without the involvement. Conclusions Our study confirms the strong relationship between various brainstem pathologies and sound localization disability and sheds some light on the complexity of the relationship