Evaluation of hearing loss in patients with Parkinson's disease

Parkinson's disease is a degenerative disorder of the central nervous system that primarily affects motor functions. It predominantly occurs in the elderly, typically between the ages of 50 and 65. The main symptoms arise from the loss of dopamine-producing neurons in the pars compacta region of the substantia nigra. However, neuronal degeneration in Parkinson's disease is not limited to the substantia nigra and locus coeruleus; it also involves the thalamus, cerebral cortex and the auditory system. In our study, we aimed to identify and evaluate the extent of hearing impairments that may occur in Parkinson's patients through audiological testing. The study included 90 patients diagnosed with Parkinson's disease, aged between 35 and 70, with no history of ear surgery, intact tympanic membranes, and no history of maxillofacial trauma or related surgeries. A control group of 90 healthy individuals without Parkinson's disease or any other conditions under the same criteria was also included. Hearing assessments were conducted using pure tone audiometry, otoacoustic emissions, and tympanometry Upon evaluating the pure tone audiometry results in our study, weak but statistically significant positive correlations were observed between Parkinson's disease and hearing threshold values. In particular, 500 Hz right bone conduction, 500 Hz right air conduction, and 1000 Hz right air conduction thresholds showed a significant but low-level positive correlation with Parkinson's disease. Stronger correlations were observed in the left ear frequencies; notably, 500 Hz and 2000 Hz left air conduction thresholds demonstrated significant low-level positive correlations with Parkinson's disease. In terms of otoacoustic emission results, more substantial and statistically significant correlations were found between the presence of Parkinson's disease and OAE outcomes. On the other hand, correlations involving tympanometry results were not found to be statistically significant. In conclusion, the findings of our study demonstrate that auditory function is adversely affected in individuals with Parkinson's disease compared to healthy controls. We recommend routine evaluation of the auditory system in Parkinson's patients. In particular, otoacoustic emission testing may serve as an objective and rapid method for early diagnosis. Key words: Parkinson's disease, hearing loss, audiometry, OAE