Clinical and polysomnographic characteristics of high frequency leg movements

Abstract

Study Objectives: The aim of this study was to describe the clinical and polysomnographic characteristics of patients with high frequency leg movements (HFLM) on polysomnographic recording. Methods: Among 486 patients (male 232, female 254) referred for overnight diagnostic PSG over a 9-month period, 37 patients demonstrated HFLM: 19 males (8.2% of PSGs) and 18 females (7.1 % of PSGs). An equal number of age- and sex-matched consecutive patients who did not show HFLM were selected. HFLM was defined as ≥ 4 discrete leg movements occurring at a frequency of 0.3-4.0 Hz. Results: Two-thirds (64.3%) of all HFLMs occurred during waking; 35.7% occurred during sleep. Of those HFLM episodes occurring during sleep, 44.8% occurred during stage 1, 45.1% during stage 2, 0.6% during stages 3 and 4, and 9.5% during REM. The movements usually appeared unilaterally, but sometimes they showed a bilateral pattern. The mean frequency was 1.6 ± 0.6 Hz (range 0.4-3.7), the mean number of episodes of HFLM per subject per night was 26.5 ± 30.5 (range 2-111), and the mean duration per episode was 17.6 ± 35.4 sec (range 1.5 sec-6.1 minutes). The mean HFLM index, (total number of HFLM divided by the time in bed, in hours), was 107.7 ± 254.5 (range 2.0-1078.3). Patients with HFLM complained of RLS symptoms significantly more often than the group without HFLM (p < 0.05). Conclusion: Further studies are needed to establish criteria for scoring HFLM. Examination of other patient cohorts with HFLM will be needed to determine whether HFLM are in fact associated with RLS.