Impairment of sensory-motor integration in patients affected by RLS

Much evidence suggests that restless legs syndrome (RLS) is a disorder characterized by an unsuppressed response to sensory urges due to abnormalities in inhibitory pathways that specifically link sensory input and motor output. Therefore, in the present study, we tested sensory-motor integration in patients with RLS, measured by short latency afferent inhibition (SAI) and long latency afferent inhibition (LAI). SAI and LAI were determined using transcranial magnetic stimulation before and after 1month of dopaminergic treatment in RLS patients. Ten naive patients with idiopathic RLS and ten healthy age-matched controls were recruited. Patients with secondary causes for RLS (e.g. renal failure, anaemia, low iron and ferritin) were excluded, as well as those with other sleep disorders. Untreated RLS patients demonstrated deficient SAI in the human motor cortex, which proved revertible toward normal values after dopaminergic treatment. We demonstrated an alteration of sensory-motor integration, which is normalized by dopaminergic treatment, in patients affected by RLS. It is likely that the reduction of SAI might contribute significantly to the release of the involuntary movements and might account for the sensory urge typical of this condition.