P 35. Nerve conduction studies and their clinical relevance in a cohort of patients with Parkinson's disease

Abstract

Introduction. Previous studies have shown a high prevalence of up to 55% of axonal polyneuropathy (PNP) in patients with Parkinsońs disease (PD), for which the causes are not certainly identified (Toth et al. 2010; Szadjeko et al. 2016). Our recent study with 50 PD patients also suggests correlations between findings in the nerve conduction studies (NCS) and clinical severity (Kühn, Averdunk et al. 2020). By means of a lager cohort and extended NCS in this study, we aimed to characterise electrophysiological characteristics of PNP in PD patients. Methods. Nerve conduction studies, Hoehn&Yahr Scores and MDS-UPDRS Scores of 85 PD patients were evaluated. The cohort consisted of 49 men and 36 women, mean age was 68 ± 11 years, mean duration of disease was 6±5 years. Motor studies of tibial and median nerve and sensory studies of sural and median nerve were performed bilaterally in all patients and additional NCS of the fibular nerve, the ulnar nerve and the radial nerve were performed in 29 of the 85 patients. The NCS findings were analysed based on cut off normal values defined by Stöhr et. al. 2012 (Table 1), and were divided into five subgroups depending on the severity of peripheral nerve impairment. We further analysed correlations between the NCS and the PD symptom scores Hoehn&Yahr and MDS-UPDRS III. Results. According to our findings, 25 patients (24,9%) showed no signs of peripheral nerve impairment (group 0), 8 patients (9,4%) were diagnosed with a mild sensory PNP with sole axonal impairment of the fibular nerve (group 1a), 21 patients (24,7%) were diagnosed with a mild sensory PNP with reduced sNAP of fibular and sural nerve (group 1b), 17 patients (20%) were diagnosed with a moderate sensorimotor PNP with reduced amplitudes of tibial (group 3), sural and fibular nerve and 15 patients (17,6%)showed signs of a severe sensorimotor PNP with impairment of the nerves in lower and upper extremities (group 3). Strong inverse correlations were found between tibial cMAP ( r = −0,174, p = 0,042), sural sNAP ( r = −0,219, p = 0,01) and radial sNAP ( r = −0,383, p = 0,019) and MDS-UPDRS III scores independent of patients age and duration of disease. The tibial cMAP was significantly lower in late Hoehn&Yahr stages compared to earlier stages (8,9±4,4 vs 6,6±4,7 mV, p < 0,01). Patients without PNP were significantly younger than patients with severe PNP (60 ± 9 y.o. vs 76±7 yo., p < 0,001). Conclusion. Our findings could verify the results found in our recent study with a larger cohort that the severity of PNP correlates with the clinical severity of PD. Longitudinal examination is required to show dynamic alterations and if peripheral nerve impairment can be used as a predictor for clinical burden in PD patients. Table 1. mean values of examined nerve response amplitudes.