Hearing Impairment in Parkinson's Disease: Expanding the Nonmotor Phenotype

The objective of this study was to evaluate hearing impairment in patients affected by Par- kinson's disease compared with hearing scores observed in normal age- and sex-matched controls. One hundred eighteen consecutive patients with a clini- cal diagnosis of Parkinson's disease were screened. Severity of motor symptoms and staging were meas- ured with the Unified Parkinson's Disease Rating Scale (section III) and the Hoehn and Yahr scale. Audiometric evaluation consisted of a comprehensive audiologic case history and questionnaire, visual otoscopic exami- nation, acoustic immittance measures (tympanogram and acoustic reflexes), pure tone audiometry, and mea- surement of brain stem auditory-evoked potentials. Healthy age- and sex-matched subjects were selected as the control group. One hundred six of 118 patients were enrolled. Pure tone audiometry revealed age-de- pendent high-frequency hearing loss in patients with Parkinson's disease compared with both normative values and values for healthy age- and sex-matched controls (75/106 (71%), v 2 5 5.959, P 5 .02; 92/106 (86.8%) vs 60/106 (56.6%), v 2 5 23.804, P < .001, respectively). Pure tone audiometry scores correlated with Hoehn and Yahr scale scores (P < .05). Brain stem auditory-evoked potentials were normal in all patients. Our patients with Parkinson's disease showed age-de- pendent peripheral, unilateral, or bilateral hearing impairment. Whether these auditory deficits are intrinsic to Parkinson's disease or secondary to a more complex impaired processing of sensorial inputs occurring over the course of illness remains to be determined. Because a-synuclein is located predominately in the efferent neuronal system within the inner ear, it could affect susceptibility to noise-induced hearing loss or presbycusis. It is feasible that the natural aging process combined with neurodegenerative changes intrinsic to Parkinson's disease might interfere with cochlear trans- duction mechanisms, thus anticipating presbycusis. V C 2012 Movement Disorder Society