Auditory pathway abnormalities in Parkinson's disease

Parkinson's disease (PD) is a degenerative, progressive, chronic disease that mainly affects the central nervous system, caused by dopamine deficiency. One of the ways to evaluate the central nervous system is with auditory evoked potentials (AEP).

To characterize the audiometric responses, and the auditory brainstem response (ABR), and cortical auditory evoked potentials (CAEP) in individuals with PD.

Thirty-two patients aged between 40 and 81 of both sexes were assessed, 16 with PD (study group [SG]) and 16 without PD (control group [CG]) matched for sex and age. The subjects were assessed using pure tone audiometry, ABR with click stimuli, and CAEP using the oddball paradigm with tone burst and speech stimuli. The results were compared between the groups using a repeated measures analysis of variance (ANOVA) test.

In pure-tone audiometry, significantly higher hearing thresholds were found in the SG at 6 and 8 kHz. For the ABR, no differences were observed between groups. The CAEP analysis did not find statistical differences in the latencies between the groups, however, the SG presented smaller amplitudes of P1-N1, P2-N2, and N2-P3 than the CG.

The results of this study showed a significantly higher threshold in higher frequencies in PD. Although no differences were observed at the brainstem level, the decrease in amplitude of all components in patients with PD in the CAEP suggests a deficit in both automatic and attentional cortical processing of acoustic stimuli.