Primary or idiopathic restless legs syndrome (RLS) is a sensorimotor disorder of unknown neurophysiologic origin.

Ten patients with RLS and 10 healthy control subjects were investigated. Postmovement beta oscillations (event-related synchronization, ERS) induced by movement of the right index finger were measured by electroencephalography and analyzed.

We found differences between patients and controls for ERS values at electrode positions C3 and Cz. At C3, the lower beta band ERS (14-20 Hz) in the RLS group was 101.2% compared with 27.5% in the control group (P < .05); in the upper beta band, (20-32 Hz) the findings were 97.8% and 29.0% , respectively, for the RLS and control groups (P < .01). At electrode Cz, no significant difference could be found in the lower beta band, but, for the upper beta band, patients showed significantly higher values than did the healthy control subjects (68.5% vs 25.6%, P < .05).

We interpret these findings as a higher need for motor-cortical inhibition in RLS patients due to an increased level of excitation by motor-cortex activation and input from neighboring functionally interrelated cortical areas (hand and foot region). These results reveal new potentially important findings of the neurophysiologic and pathophysiologic origin of primary RLS.