Abstract Background Peripheral neuropathy has been described in Parkinson's disease (PD) patients receiving continuous levodopa delivery. Whether subcutaneous foslevodopa/foscarbidopa (fLD/fCD) infusion carries a similar risk remains unclear. Cases We report four PD patients treated with continuous subcutaneous fLD/fCD who experienced clinical and electrophysiological worsening of peripheral neuropathy after treatment initiation. At baseline, none reported functional neuropathic symptoms, although electrophysiological evidence of mild subclinical peripheral neuropathy and/or biochemical abnormalities was present. Neuropathic symptoms developed within a few months of fLD/fCD initiation and were associated with vitamin B6 and/or B12 deficiency and persistent hyperhomocysteinemia. In all cases, electrophysiological deterioration accompanied symptoms emergence. Conclusions Although causality cannot be established, these cases suggest that fLD/fCD infusion may be associated with aggravation of pre‐existing peripheral neuropathy, despite non‐enteral administration, supporting a potential systemic metabolic contribution. These findings underscore the importance of baseline assessment and longitudinal monitoring of peripheral nerve function and B‐vitamin status in patients receiving fLD/fCD. Optimal vitamin supplementation strategies in this setting remain to be defined.
Vial‐Daragon et al. (2026) studied this question.
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