Polyneuropathy in levodopa-treated Parkinson's patients

Area of Science:

• Neurology
• Neuroscience
• Clinical Medicine

Background:

• Parkinson's disease (PD) patients exhibit a higher prevalence of polyneuropathy (PNP) compared to age-matched controls.
• The exact pathogenesis of PNP in PD remains controversial, with homocysteine (Hcy) toxicity linked to levodopa (LD) therapy being a major hypothesis.
• Understanding PNP prevalence and its relationship to clinical factors in PD is crucial for patient management.

Purpose of the Study:

• To determine the prevalence of PNP in levodopa-treated Parkinson's disease patients, excluding other etiologies.
• To investigate the relationship between PNP and demographic/clinical factors in PD patients.
• To explore the potential role of homocysteine in PNP development in PD.

Main Methods:

• A study involving 102 participants (51 PD patients, 51 age- and sex-matched controls) with strict exclusion criteria for other PNP risk factors.
• Clinical assessment of PNP using the Toronto Clinical Scoring System (TCSS).
• Objective assessment via electroneurography (ENG) examining motor and sensory nerves.
• Disease severity evaluated using the Unified Parkinson's Disease Rating Scale (UPDRS) and Hoehn-Yahr (H-Y) scale.
• Homocysteine (Hcy) levels were measured.

Main Results:

• Clinical and neurophysiological indicators of PNP were significantly more frequent in PD patients (43.1% and 15.7%) than in controls (13.7% and 2%).
• PNP in PD patients was characterized as a symmetrical, predominantly sensory axonal neuropathy.
• The presence of PNP correlated positively with patient age and Parkinson's disease severity.
• PD patients with PNP showed higher Hcy levels than those without PNP, though not statistically significant.
• A discrepancy between clinical and ENG findings suggested small fiber neuropathy (SFN) as a dominant form.

Conclusions:

• The prevalence of polyneuropathy is significantly higher in Parkinson's disease patients compared to controls.
• PNP in PD is associated with disease severity and age, and may predominantly involve small fiber neuropathy.
• Further research is needed to elucidate the role of homocysteine and other factors in PNP pathogenesis in PD.