IMMOBILIZATION TESTS AND PERIODIC LEG MOVEMENTS IN SLEEP FOR THE DIAGNOSIS OF RESTLESS LEG SYNDROME

Patients with restless leg syndrome (RLS) complain of motor restlessne ss, usually occurring while they rest in the evening. Two immobilizati on tests have been described to assess leg restlessness in these patie nts. In the first test, the patient sits in bed with his or her legs o utstretched while electromyograms are recorded from right and left ant erior tibialis muscles for an hour (Suggested Immobilization Test [SIT ]); in the second test: the legs are immobilized in a stretcher (Force d Immobilization Test [FIT]). In the current study, the SIT and the FI T were compared in patients with RLS and normal control subjects match ed for age and sex. More leg movements were seen in patients than in c ontrols during immobilization tests, especially the SIT. These movemen ts were periodic, occurring at a frequency of approximately one every 12 seconds. The SIT (index > 40) was found to discriminate between RLS and control subjects better than the FIT (index > 25). Patients were also recorded during two consecutive nights to measure periodic leg mo vements in sleep (PLMS). A SIT index greater than 40 and a PLMS index greater than 11 (highest PLMS index of 2 consecutive nights) were foun d to discriminate patients with RLS from control subjects with similar power. With each of these two measures, the clinical diagnosis was co rrectly predicted in 81% of patients and 81% of the control subjects. The SIT has several advantages over the measure of the PLMS index, it does not require an all-night polygraphic recording and can be adminis tered several times a day to measure circadian fluctuation of motor re stlessness.