The auditory system involvement in Parkinson disease: electrophysiological and neuropsychological correlations

In the course of Parkinson disease (PD), apart from motor symptoms, presence of mental disturbances such as dementia and depression is common. The aims of this study were to assess the auditory system involvement in patients with PD using electrophysiological and neuropsychological tests and to correlate the cognitive impairment and the auditory evoked potentials tests results. The auditory and cognitive functions were studied in 53 patients with idiopathic PD, mean age 65.8 +/- 9.1 years; mean disease duration 7.8 +/- 5.0 years; mean motor disability score 2.5 +/- 0.8 points in Hoehn-Yahr scale compared with a control group matched for age and sex. In patients and controls, cognitive functions were analyzed electrophysiologically using middle latency auditory evoked potentials (MLAEP) and long latency (event-related potentials, P300) auditory evoked potentials. Neuropsychological testing consisted of Wisconsin Card Sorting Test (WCST). According to WCST results, patients with PD were divided into 2 subgroups: patients with normal and abnormal WCST performance (WCST(-) and WCST(+) subgroups, respectively). Sixteen of 46 patients (34.8%) showed cognitive impairment when evaluated with WCST. Statistically significant differences in middle latency auditory evoked potentials and P300 results between WCST(-) and WCST(+) groups were found consisting of P300 abnormalities in 93.8% patients in WCST(+) and 57.7% in WCST(-) group. Middle latency auditory evoked potentials were abnormal in 71.4% and 63% patients in WCST(+) and WCST(-) group, respectively. P300 was absent significantly more often (P < 0.01) in the subgroup with cognitive impairment. The difference in middle latency auditory evoked potentials results between these subgroups was statistically insignificant. The auditory evoked potentials changes were more common among patients with abnormal WCST performance. According to our results, the auditory evoked potentials of different latencies are helpful in the assessment of cognitive changes accompanying PD.