Peripheral hypoxia in patients with restless legs syndrome

Abstract

Introduction Previous studies suggest that restless legs syndrome (RLS) may be associated with hypoxia in the skeletal muscles: biopsies have shown VEGF upregulation (Wahlin-Larsson 2009) and structural analysis of the muscle revealed high capillary tortuosity (Larsson 2007). In this study we measured oxygen and carbon dioxide partial pressure (pO2 and pCO2) in the legs of RLS patients and controls in order to evaluate the peripheral hypoxia suggested by these studies more directly. Materials and methods A total of 18 subjects (9 patients and 9 age and sex-matched controls) were included in the study. The tissue pO2 and pCO2 were estimated by transcutaneous measurements on the instep of the foot and on the chest. The measurements were performed in the evening, during two repeated suggested immobilization tests (SIT), two and four hours before bedtime. RLS patients went through the measurements once without medication and a second time with dopaminergic therapy. At the same time, arterial oxygen saturation (SaO2) was measured from the toe. Results The mean tissue pO2 during SIT was lower in the legs of RLS patients than controls (5.1 kPa vs. 7.4 kPa, p Conclusion Our results confirm that there is a significant peripheral hypoxia in the legs of RLS patients during the symptomatic period. Control subjects showed normal oxygen levels. The strong positive correlation with RLS severity suggests that the leg hypoxia could be a major factor in RLS pathophysiology. The finding that dopaminergic therapy abolishes both the symptoms and the hypoxia may suggest that the site of action of dopamine in RLS is in the periphery. Acknowledgement The study was supported by Tuberculosis Foundation of Tampere, Finland.