Pergolide restores sleep maintenance but impairs sleep EEG synchronization in patients with restless legs syndrome

The treatment with the long-acting dopamine D1/D2 receptor agonist pergolide has been proven as very effective in lowering the frequency of periodic leg movements (PLM) in patients with restless legs syndrome (RLS). To further investigate the influence of this potent dopaminergic drug on the microstructure of rapid eye movement (REM) and non-REM sleep EEG we established a quantitative analysis of the EEG data.

The study group consisted of 15 patients with primary RLS (mean age 57.1+/-10.1 years) who were a subgroup of patients within a double-blind randomized crossover treatment study with pergolide versus placebo. The polysomnographic recordings were analyzed visually and submitted to a quantitative EEG analysis (fast Fourier transformation).

The pergolide treatment induced a significant reduction of the spectral power in the delta range (0.78-3.9 Hz; P<0.05; t-test) during SWS, as well as a significant reduction of PLMs. In addition, we observed a decrease in the sigma EEG activity (12.1-14.8 Hz; P<0.03) during non-REM sleep and stage 2 sleep. The visual sleep scoring revealed a significant increase in stage 2 sleep (P<0.005), whereas wakefulness was markedly diminished (P<0.001). The REM sleep parameters including the EEG power spectrum remained unchanged.

The treatment with pergolide markedly improved the sleep quality in RLS patients but did not restore SWS including the spectral power in the lower frequencies. Our results suggest that the dopamine agonist pergolide interferes with the subcortical mechanisms regulating the process of EEG synchronization during non-REM sleep.