VISUAL AND BRAINSTEM AUDITORY-EVOKED POTENTIALS CORRELATE WITH SPECIFIC MOTOR AND NON-MOTOR SYMPTOMS IN PARKINSON'S DISEASE

Parkinson's disease (PD) is a common and complex neurodegenerative disease characterized by progressive motor and non-motor symptoms. The current study investigated the dysfunction of brain hemispheres and brainstem of PD patients and its relation to motor and non-motor symptoms using brainstem auditory evoked potentials (BAEP) and pattern reversal visual evoked potentials (p-VEP). We hypothesized that some motor and non-motor symptoms of PD due to specific dysfunctions of brainstem and brain hemispheres could be related to changes in p-VEP and BAEP. Accordingly, the aim of this study was to explore the abnormalities of BAEPs and p-VEPs in patients with PD and its correlation to the motor and non-motor symptoms of PD. Seventy-six nondemented PD patients took part in the p-VEP evaluations and 66 nondemented PD patients were included in BAEP evaluation. In order to compare the p-VEP performance of PD group, we included a control group comprising 32 age-matched participants. A BAEP substudy involved 29 age-matched healthy controls. All patients underwent a comprehensive motor and non-motor neuropsychological assessment. We found significant changes in all tested parameters of p-VEPs in PD patients compared to control subjects. In addition, these lower scores in p-VEP correlate with the results of some tests for cognition related to frontal-striatal dysfunction and contralateral rigidity, but not with the results of overall motor evaluation or other non-motor symptoms studied. In BAEP, PD patients have a significant prolongation of III and V wave latencies compared to controls. In addition, when examining the possible associations of BAEP with other non-motor manifestations of the disease, such association was observed only by the apathy scale. In conclusion, the current study confirms the visual and auditory abnormalities among PD patients that reflect brain hemispheres and brainstem pathological changes. It also correlates these abnormalities to some motor and non-motor features of the disease, providing a localizing tool for associated brain hemispheres and brainstem dysfunctions. Furthermore, abnormal visual evoked potentials are associated with motor and non-motor symptoms due to the basal ganglia dysfunction. In contrast, abnormal auditory evoked potentials are connected with apathy, which is considered to be related with brainstem raphe nuclei dysfunction.