Electrophysiological and biochemical evaluations of neuropathy risk in oral levodopa versus levodopa/carbidopa intestinal gel treatment

The association between levodopa treatment and neuropathy in Parkinson's disease (PD) remains controversial, particularly when comparing the oral and intestinal administration routes.To compare the electrophysiological and biochemical changes in patients receiving oral levodopa or levodopa/carbidopa intestinal gel (LCIG) and to determine their association with neuropathy development.The current prospective cross-sectional study included 32 PD patients (18 oral and 14 LCIG). Demographic features, disease duration, Hoehn and Yahr (H&Y) stage, Unified Parkinson's Disease Rating Scale (UPDRS) scores, biochemical parameters (vitamin B12, folate, homocysteine), and electrophysiological values were recorded. Nerve conduction studies (NCSs) of the median, ulnar, peroneal, tibial, and sural nerves were performed unilaterally, using reference values from our neurophysiology laboratory.The LCIG group presented significantly higher doses of levodopa (<i>p</i> < 0.001), levodopa equivalent daily dose (LEDD; <i>p</i> < 0.001), and homocysteine levels (<i>p</i> = 0.002) compared with the oral group. Electrophysiological tests revealed significantly reduced motor amplitudes and sensory conduction velocities in the median, ulnar, tibial, and sural nerves in the LCIG group. The median and tibial F-wave latencies were prolonged in the LCIG group. Correlation analyses indicated significant associations involving homocysteine elevation and conduction abnormalities.Patients receiving LCIG presented higher homocysteine levels and more frequent electrophysiological abnormalities than those on oral treatment, suggesting a higher risk of polyneuropathy. These findings highlight the importance of biochemical monitoring and individualized treatment strategies in advanced PD.