Evaluation of peripheral and autonomic nervous systems dysfunctions in patients with Parkinson’s disease

Abstract

Background: Peripheral neuropathy (PN) is increasingly recognized in Parkinson’s disease (PD). This study aimed to evaluate peripheral nerve and autonomic nervous system dysfunction in PD. Forty patients with PD (20 drug-naïve, 20 on treatment) and 20 controls underwent neurological examination, Toronto Clinical Neuropathy Score (TCNS), nerve conduction studies, autonomic function tests including (heart rate variability, Blood pressure changes with standing and sustained handgrip, and sudomotor pathways. The Ewing classification system scored each test to quantify autonomic failure severity). Laboratory tests (B12, homocysteine, methylmalonic acid). Results: Treated patients with PD had higher MDS-UPDRS scores than drug-naïve (p = 0.001). TCNS indicated mild PN in some drug-naïve patients, and mild–moderate PN in treated patients. Nerve conduction studies showed significant sensory and motor neuropathy in treated versus drug-naïve PD and controls. Treated patients had lower B12, higher homocysteine/methylmalonic acid than other groups. Across autonomic tests, controls had the most normal results, followed by drug-naïve patients, with treated patients being most abnormal. Autonomic dysfunction correlated with disease duration, severity, L-dopa dose. Lower B12, higher homocysteine/methylmalonic acid levels were associated with greater neuropathy and disease severity. Conclusion: Patients with PD show evidence of PN and autonomic dysfunction, which is milder in drug-naïve patients but worsens with disease progression and treatment. Peripheral nervous system assessments may help diagnose and monitor PD neuropathy and effects of interventions.