No association between neuropathy and restless legs in Parkinson's disease

Background The prevalence of restless legs syndrome (RLS) has been studied extensively in Parkinson's disease (PD), with conflicting findings. More recently, both neuropathy and leg motor restlessness (LMR) have been found to be significantly more prevalent in PD patients than in controls. Aims Our objective was to determine whether RLS or LMR may be secondary to neuropathy, or its currently postulated determinants, cumulative levodopa usage and vitamin B12 metabolism, in patients with PD. Materials and Methods We compared prevalence of RLS, LMR and neuropathy in 37 PD patients and 37 age- and gender-matched controls. Correlations between RLS/LMR and neuropathy and symptomatic neuropathy, cumulative levodopa usage and vitamin B12 levels were ascertained. Results RLS prevalence was comparable in PD patients and controls (16.2% vs 10.8%; P=0.30). LMR was significantly more common in PD patients than in controls (40.5% vs 16.2%; P=0.038), as was neuropathy (37.8% vs 8.1%; P=0.005). Neither RLS, nor LMR correlated with neuropathy or symptomatic neuropathy, cumulative levodopa exposure or serum vitamin B12 levels in patients with PD. There was a non-significant trend for a correlation between LMR and earlier age of onset of PD (P=0.069). Conclusions RLS and LMR appear unrelated to neuropathy or symptomatic neuropathy, cumulative levodopa usage, or serum vitamin B12 levels in patients with PD. The occurrence of LMR may relate to the earlier onset of PD, raising the possibility of common pathophysiological mechanisms for PD and RLS, of which LMR may be an early manifestation in some patients.