Does the suggested immobilization test permit predicting the efficacy of dopaminergic agonists in the treatment of RLS

Introduction The etiology and pathophysiology of primary Restless Legs Syndrome (RLS) remain unknown. Although the diagnosis of RLS is based primarily upon interviews with the patient, it is sometime difficult to diagnose by interviews alone. The Suggested Immobilization Test (SIT) may be helpful in such cases. Dopamine agonists are symptomatically effective in the majority of RLS patients. However, efficacy of dopaminergic medication is not uniform in RLS patients. The relationship between the response to dopaminergic medication and the results of SIT has not been reported. Materials and methods The diagnosis of RLS was made based on the International Classification of Sleep Disorders 2nd edition criteria. Data from patients who were diagnosed from June 2005 to June 2012, with full polysomnography (PSG) and SIT recordings were analyzed. The subjects were divided into two groups according to the response to dopamine agonists: group A were treated with dopaminergic agonists only and group B required additional medication three months after the start of the treatment. We compared the PSG and SIT findings between the two groups. RESULTS In group A, 12 women and 13 men (mean age 66.2_}9.9 years) were included, and in group B, 15 women and 12 men (mean age 58.1_}15.8 years). Sleep efficiency was higher in group B, on the other hand, periodic limb movement index during sleep was significantly higher in group A. At SIT, subjects of group B had a higher index in both the leg movement and visual analog scale score. Conclusion In comparison between group A and B, results of the leg movement index in SIT were not concordant with the index from PSG findings. Efficacy of dopamine agonists was not clearly related to the results of SIT. Further studies are needed to clarify what indicators permit predicting the efficacy of dopaminergic agonists in RLS.