Abstract
(1) Background: Increased attention has lately been given to polyneuropathy in Parkinson’s Disease (PD). Several papers postulated that large-fiber neuropathy (PNP) in PD is related to vitamin B12 deficiency and L-Dopa exposure. (2) Methods: Using a cross-sectional, observational study, we evaluated 73 PD patients without a previously known cause of PNP using clinical scores (UPDRS II and III and Toronto Clinical Scoring System), biological evaluation of vitamin B12 and folic acid, and nerve conduction studies to assess the prevalence and features of PNP. (3) Results: The prevalence of PNP was 49.3% in the study group. In the L-Dopa group, the frequency of PNP was 67.3% as compared to PNP in the non-L-Dopa group, where one subject had PNP (χ2 = 23.41, p < 0.01). PNP was predominantly sensory with mild to moderate axonal loss. Cyanocobalamin correlated with L-Dopa daily dose (r = −0.287, p < 0.05) and L-Dopa duration of administration (r = −0.316, p < 0.05). L-Dopa daily dose correlated with the amplitudes of sensory nerve action potentials of the superficial peroneal and radial nerves (r = −0.312, p < 0.05) (r = −0.336, p < 0.05), respectively. (4) Conclusions: PNP is more frequent in L-Dopa-treated patients than in L-Dopa-naïve patients. The results imply that longer exposure to high doses of L-Dopa may cause vitamin B12 and folate imbalance and PNP, secondarily.
Highlights
Parkinson’s disease (PD) is a neurodegenerative condition that affects the whole nervous system, but above all, the central nervous system [1,2]
The amplitude of sensory action potential (aSNAP) of the sural nerve correlated with the vitamin B12 seric value (r = 0.444, p < 0.01) and folic acid (r = 0.314, p < 0.01) and the aSNAP of the superficial peroneal nerve correlated with the B12 plasmatic value (r = 0.349, p < 0.01) and folic acid (r = 0.347, p < 0.01), while the aSNAP of the radial nerve correlated only with cyanocobalamin (r = 0.375, p < 0.01)
In the L-dopa group, the aSNAP of the sural nerve correlated with the vitamin B12 seric value (r = 0.401, p < 0.01) and folic acid (r = 0.329, p < 0.05) and the aSNAP of the superficial peroneal nerve correlated with the B12 plasmatic value (r = 0.405, p < 0.01) and folic acid (r = 0.430, p < 0.01), while the aSNAP of the radial nerve correlated only with cyanocobalamin (r = 0.327, p < 0.05)
Summary
Parkinson’s disease (PD) is a neurodegenerative condition that affects the whole nervous system, but above all, the central nervous system [1,2]. Hyperhomocysteinemia, low plasma levels of B12, B6, and folic acid, along with disease duration, age, and L-Dopa daily intake are considered to be the key factors in PD patients developing PNP [3,4,5,6,7,8,9,10,12,13,14,15,16]. Several studies found that PNP prevalence was higher in PD than in age-matched controls, ranging from 15% to 73% in patients treated orally with L-Dopa [5,6,7,12,13,15,16], depending on the criteria used for the diagnosis of PNP. Data published on the prevalence of PNP in L-Dopa-naïve groups revealed a lower frequency of PNP when compared to L-Dopa-treated groups, ranging from 4.82% to 12.1% [7,15,23] and similar to the one in age-matched controls [9,12,15]
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