Painful polyneuropathy associated with restless legs syndrome. Clinical features and sensory profile

The association of restless legs syndrome (RLS) with polyneuropathy, and its prevalence, have been evaluated differently throughout various studies. As subtypes of polyneuropathy characterized by neuropathic pain seem to be preferentially associated with RLS, we intended to investigate the prevalence and the features of RLS occurring with painful neuropathy, and to define whether there is a specific sensory phenotype.

We prospectively investigated 58 consecutive patients with distal symmetric polyneuropathy and neuropathic pain or dysesthesia, using a bedside protocol for sensory assessment. RLS was diagnosed with an interview assessing the International RLS Study Group diagnostic criteria.

Overall, RLS was reported by 21 patients (36.2%), but it was occurring at the time of the evaluation in 12 patients (20.7%), significantly more than in controls. RLS was chronic in nine patients and remitting-intermittent in 12 patients. No difference was demonstrated between patients with or without RLS. Comparing patients with chronic RLS and remitting-intermittent RLS, the latter had more severe electrophysiological changes, whereas hyperalgesia, suggesting central sensitization, was significantly more frequent in chronic RLS patients.

RLS is frequently associated with painful polyneuropathy, in keeping with the hypothesis that its occurrence is favored by small fiber involvement. It represents a heterogeneous entity, differentiated in chronic and remitting-intermittent subtypes, possibly conditioned by indolent or aggressive neuropathy course and phenomena of central sensitisation.