Clinical and neurophysiological features of the augmentation phenomenon in restless legs syndrome

Abstract

Anxiety and depressive disorders are common in restless legs syndrome (RLS); in some cases, the disease is accompanied by cognitive impairment and a deterioration in quality of life. The most important treatment method for RLS is the use of dopaminergic medications. In some cases, the use of these drugs leads to a complication - the phenomenon of augmentation, which manifests itself in an increase in RLS symptoms as the dose of medication increases.Objective: to determine the clinical and neurophysiological characteristics of RLS patients with the augmentation phenomenon.Material and methods. 40 patients with RLS were examined: 20 with augmentation (main group, MG; 5 men and 15 women) and 20 without augmentation (comparison group, CG; 7 men and 13 women). The median age of the patients in the MG was 63.5 [56; 71] years, and 62.0 [43.5; 71.5] years in the CG. Clinical assessment was performed using the RLS Severity Rating Scale (RS), Montreal Cognitive Assessment Scale (MoCA), Beck Anxiety Inventory, Beck Depression Inventory, Quality of Life Scale (SF-36), Insomnia Severity Index (ISI), Trail Making Test (Part A), Trail Making Test (part B), phonemic and semantic speech activity tests. All patients underwent suggested immobilization test (SIT) to assess the urge to move on a 10-point numerical rating scale (NRS) and periodic limb movements (PLM) while awake, as well as a polysomnographic examination.Results. Augmentation significantly more frequently resulted in an expansion of the area of distribution of the urge to move and other unpleasant sensations over the entire surface of the legs (p=0.01), painful discomfort in the legs (p=0.001), early onset of symptoms (04:00—18:00; p=0.04), shortening of the latency period for the onset of symptoms (p=0.001), twitching in the legs while awake (p=0.04), taking higher doses of dopaminergic medications (p=0.004). In augmentation, the MoCA score is lower (p=0.01), such patients use fewer words in the semantic speech activity test (p=0.049), have a higher score on the RS (p=0.001) and ISI (p=0.02), a greater number of PLMs while awake according to SIT (p=0.01) compared to CG. No significant differences were found between groups in terms of age, gender, ferritin level, total score on the Beck Anxiety and Depression Inventory, SF-36 Quality of Life Scale, Trail Making Test (Part A), Trail Making Test (part B), phonemic speech activity test, polysomnography indicators (including motor activity during sleep).Conclusion. From a clinical and neurophysiological point of view, the phenomenon of augmentation is not simply a manifestation of a more severe course of RLS but has features that reflect the pathogenesis of this disorder. During augmentation, patients tend to describe the sensations as painful and their involuntary motor activity increases. This reflects changes in the activity of the diencephalospinal tract due to excessive dopaminergic stimulation.