Sternberg working memory performance following treatment with pramipexole in patients with moderate-to-severe restless legs syndrome.

Objectives: We recently reported that the P300 amplitude related to the Sternberg working memory (WM) task was significantly lower in drug-naïve severe restless legs syndrome (RLS) patients than controls. Here, we evaluated the effects of pramipexole on the Sternberg WM task performance by event-related potential (ERP) study.

Methods: Thirteen drug-naïve RLS patients (52.0 ± 9.48 years) were enrolled in the study. Pramipexole was administered over a period of 12 weeks every night 1 h before bedtime. Two ERP studies were carried out: the first was performed just before giving the first dose of pramipexole and the second was conducted at 12-16 weeks after commencement of pramipexole administration. P300 amplitudes and reaction times were compared before and after treatment considering brain regions and memory load as within-subject factors. Clinical and sleep-related variables were correlated with P300 amplitude.

Results: After treatment with pramipexole, the International RLS Severity Scale (IRLS) score was significantly decreased. Sleep quality and depression were also significantly improved. Omission error was significantly reduced without significant change of commission error. Reaction time was significantly shortened, regardless of memory load size, following treatment with pramipexole. Parietal P300 amplitude was significantly increased after treatment with pramipexole for all memory load sizes. Increase of frontal P300 amplitude was significantly correlated with improvement of sleep duration, IRLS, Insomnia Severity Index, and Pittsburgh Sleep Quality Index score.

Conclusion: Our study suggested that pramipexole improves WM performance in patients with RLS in addition to improving RLS symptoms, sleep disturbance, and depression.