Small fiber function in drug naïve patients with idiopathic restless legs syndrome

To assess whether idiopathic restless legs syndrome (RLS) is associated with small fiber abnormalities, we evaluated somatic and autonomic small fiber function in 56 patients with idiopathic RLS and 36 age-matched and sex-matched healthy controls using quantitative sensory testing and quantitative sudomotor axon reflex tests. The warm detection thresholds (WDT) of the hands (p = 0.017) and feet (p = 0.008) were higher in patients with RLS than in controls. Cooling detection thresholds (CDT) were higher in the feet of patients with RLS than controls (p < 0.001), but CDT in the hands did not differ between groups (p = 0.161). There were no significant between-group differences in total sweat volume and sweat production in the forearms, proximal legs, distal legs, and feet (p > 0.1 each). These findings suggest that abnormal sensory perception in patients with idiopathic RLS may result from impairment of central somatosensory processing rather than small fiber neuropathy.