Evoked potential response in patients with idiopathic Parkinson’s disease and atypical parkinsonian syndromes: A comparative study

Patients with idiopathic Parkinson’s disease (IPD) and atypical parkinsonian syndromes (APSs) suffer from a range of disorders, especially in balance and locomotion, which necessitate visual, auditory, and somatosensory inputs. In this study, IPD patients, APS patients, and healthy controls (HCs) (n = 50 per group) underwent a series of assessments for visual evoked potentials (VEP), brainstem auditory evoked response (BAER), and short-latency somatosensory evoked potentials (SSEP). Results showed that VEP P100 latency was prolonged in multiple system atrophy-cerebellar type (MSA-C), multiple system atrophy-parkinsonian type (MSA-P), and corticobasal ganglionic degeneration (CBD) patients. The latency of peaks III and V was prolonged in IPD, MSA-C, dementia with Lewy bodies (DLB), and Parkinson’s disease dementia (PDD). BAER I-III and I-V interpeak latency were prolonged in IPD, DLB, and PDD, whereas BAER I-III, III-V, and I-V interpeak latencies were increased and the V/I amplitude ratio was decreased in MSA-C. The central sensory conduction time (N20-N13) was increased in MSA-P and MSA-C in SSEP. IPD patients had prolonged VEP P100 latency (P < 0.001), lower VEP N75-P100 amplitude (P < 0.001), prolonged BAER I, II, II, IV, V peak latencies (P < 0.001), I-III, I-V interpeak latencies (P < 0.001), lower BAER V/I amplitude ratio (P < 0.001), and prolonged SSEP N13, N20, central sensory conduction time (N20-N13) (P < 0.001) than HCs. IPD patients also had prolonged BAER I, II, II, IV, V peak latencies (P < 0.001), prolonged I-III, I-V interpeak latencies (P < 0.001), and shorter SSEP N13, N20, central sensory conduction time (N20-N13) (P < 0.001) than APS patients. Moreover, APS patients had prolonged VEP P100 and N145 latencies (P < 0.001) and decreased N75-N145 amplitude (P < 0.001) compared to HCs. APS patients also had prolonged BAER II, II, IV, V peak latencies (P < 0.001), prolonged I-III, III-V, I-V interpeak latencies (P < 0.001), decreased V/I amplitude ratio, and prolonged SSEP N13, N20, central sensory conduction time (N20-N13) (P < 0.001) than HCs. Postural instability and gait disorder (PIGD) IPD had significantly prolonged BAER III, V peak latencies (P < 0.05), and prolonged III-V interpeak latencies (P < 0.05) compared to tremor-dominant IPD. Overall, the IPD and APS patients had significant VEP, BAER, and SSEP abnormalities of demyelination and axonal variety in the visual, auditory, and somatosensory pathways. The changes were also correlated with the disease duration and severity. Although the diseases are predominantly motor disorders with significant non-motor components, these electrophysiological abnormalities might open a new avenue to assess the non-motor symptoms.