Dopamine Transporter Density Profiles in Patients With Periodic Limb Movements

Overview

Restless legs syndrome and periodic limb movement (PLM)are sleep-related movement disorders and studies have shown changes in striatal dopaminergic activity in patients with these disorders. Physical exercise has been shown to improve the symptoms of restless legs syndrome and PLM, as has treatment with dopamine agonists. However, the mechanism by which physical exercise acts as a non-pharmacological treatment in improving symptoms of restless legs syndrome and PLM remains unknown. The investigators evaluated dopamine transporter density profiles in 16 sedentary patients (control and experimental - with PLM, groups) and the influence of acute physical exercise on its concentration after a maximal exercise test. Each patient underwent baseline polysomnography to evaluate sleep patterns and PLM index values. After obtaining the polysomnography baseline, the single photon emission computer tomography baseline was determined. Subsequently, the volunteers performed a maximal exercise test in the morning, followed by a single photon emission computer tomography two hours later and polysomnography that night, to assess the effect of acute physical exercise on dopamine transporter and sleep patterns. The results showed significant lower dopamine transporter baseline densities in the striatum region for the experimental group. The results also showed a significant reduction in the periodic leg movement rate in the experimental group and a significant increased percentage of stage-1 non-REM sleep in both groups after maximal exercise test. Significant differences between the groups were only observed for Stage 2 sleep and slow wave sleep. Our results show that patients with PLM had a lower dopamine transporter density in the left putamen region compared to the control group and an acute physical exercise (maximal exercise test) did not alter this profile, providing evidence that this improvement is the result of chronic physical exercise.

Experimental Design Each volunteer (in both control and experimental groups) underwent Polysomnography (PSG) adaptation. After one week, a baseline cerebral SPECT was performed (1-3pm) and a baseline PSG was performed that night to evaluate the sleep pattern and the PLM index. Subsequently (after one week), each subject underwent a maximal exercise test (MET) in the morning (11am to 1pm) after which SPECT examination was performed in the afternoon (1-3 pm). A PSG was then performed that night to evaluate the effect of acute exercise on DAT density and sleep pattern (Figure 1).