Objective: To assess the frequency of neuropathy and its neurophysiological characteristics in orally and levodopa/carbidopa intestinal gel (LCIG) treated patients with advanced idiopathic Parkinson´s disease (IPD) and the influence of levodopa on vitamin levels and neuropathy.

Background: LCIG is an established treatment option in advanced IPD with motor fluctuations. Recently, (subacute) development of neuropathy has been described sporadically in patients treated with LCIG, and hypotheses as to the pathogenesis range from immune-mediated causes to deficiency of B-vitamins, especially cobalamin, but also cases of pyridoxine deficiency have been reported. On the other hand, neuropathy has been reported also in orally treated advanced IPD patients.

Methods: In a retrospective data analysis serum levels of pyridoxine, cobalamin, folate, and homocysteine as well as neurographic Features and daily levodopa doses (LDD) of 8 LCIG and 13 orally treated patients matched for age, H&Y, and UPRDS III were collected and analyzed for correlations.

Results: Compared to the oral group, LICG patients had a longer disease duration and higher LDD. All individuals of the LCIG group and most of the oral group had electrophysiologically sensorimotor axonal neuropathy, which was more, but not significantly pronounced, in the LCIG Group. Pyridoxine levels were significantly lower in the LCIG group, and LDD correlated inversely with pyridoxine levels irrespective of the route of application. LDD above 2000 mg generally resulted in pyridoxine deficiency. In both groups, homocysteine levels were elevated without significant difference, again with an almost significant correlation with LDD. Only in the LCIG group, neurographic amplitudes correlated to pyridoxine and homocysteine levels. Levels of cobalamin and folate were low, but within the normal range in both groups without significant difference and without correlation to neither LDD nor neurographies.

Conclusions: Axonal sensory neuropathy is frequent in advanced IPD treated with levodopa irrespective of the route of application. LDD correlates with pyridoxine deficiency and homocysteine elevation, but not with cobalamine or folate. The data set is too small to prove or rule out an association of pyridoxine deficiency and hyperhomocysteinemia with neuropathy, but the results deserve further investigations.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/levodopacarbidopa-intestinal-gel-neuropathy-and-b-vitamins-is-there-an-association/