In this sample of children, considerable individual night-to-night variability of PLMS indexes was observed. This finding has important clinical relevance for the diagnosis of restless legs syndrome and PLMD and may have an impact on future studies that correlate individual PLMS severity with frequently associated symptoms, such as negative affect, fatigue, and inattention. Our data, however, also suggest that individual PLMS variability is random and not likely to skew the group-level analysis of treatment outcome studies.

Background In a previous open-label study, dopaminergic agents improved Restless Legs Syndrome (RLS) and Periodic Limb Movements in Sleep (PLMS), as well as Attention-Deficit-Hyperactivity Disorder (ADHD) in children with both disorders. We therefore conducted a double-blind placebo-controlled trial of L-DOPA in ADHD children with and without RLS/PLMS. Methods Two groups of patients (total n=29), those with ADHD only or those with ADHD and RLS/PLMS were randomized to L-DOPA or placebo therapy. At baseline and after therapy patients were assessed with Conners' Parent and Teacher Rating Scales; polysomnography; RLS rating scale; and neuropsychometric measures of memory, learning, attention, and vigilance. Results L-DOPA improved RLS/PLMS symptoms in all patients with those disorders compared with placebo (p = .007). When assessed by the Conners' Scales before therapy, ADHD was more severe in children without RLS/PLMS than in children with RLS/PLMS (p=0.006). L-DOPA had no effect on Conners' scales, sleep, or neuropsychometric tests when all patients treated with drug were compared to those on placebo or when patients with ADHD only were compared to those with ADHD and RLS/PLMS. Conclusions In this first double-blind study of a dopaminergic therapy in children with RLS/PLMS, L-Dopa significantly improved RLS/PLMS but not ADHD. These results, however, should be interpreted carefully since they may have been influenced by the relatively small sample size and the baseline differences in severity of ADHD symptoms. Further work needs to be done to elucidate the relationship between dopamine, ADHD and RLS/PLMS.

Several previous studies have shown that Attention Deficit Hyperactivity Disorder (ADHD) is common in children with Restless Legs Syndrome and ADHD is more common in adults with this syndrome. This pilot study examined the prevalence of Restless Legs Syndrome in adults with ADHD, showing six of 30 adult ADHD participants (20%) had Restless Legs Syndrome. This estimate exceeds the prevalence (7.2%) for a previously published control group. These six adults had more severe ADHD symptomatology than those without Restless Legs Syndrome based on the overall Conners' Adult ADHD Rating Scale. Such results suggest that symptoms of Restless Legs Syndrome may occur often in adults with ADHD and might worsen the symptoms of ADHD. Replication with a larger sample size is in order.