Periodic limb movements (PLM) are characterized by repetitive leg movements, detected by surface EMG of tibialis anterior muscles, during sleep. EEG arousals are considered to be associated with leg movements if they occurred before, simultaneously or 10 s after a PLM. Studies have indicated that PLM’s are not primary but rather an epiphenomenon associated with an underlying arousal disorder. Recently O’Malley et. al. 2003 postulated that the addition of a single frontal EEG lead yielded additional respiratory related arousals that were physiologically relevant. We hypothesized that PLM related arousals detected by an additional Fz-A2 EEG lead would correlate with a measure of excessive daytime sleepiness(EDS) and offer clarity when reporting PLM’s.
12 subjects (6 males) who had symptoms of excessive daytime sleepiness (EDS) with an apnea-hypopnea index of < 10 and a PLM index > 10 were recruited. A full overnight polysomnography (with additional Fz -A2) was performed using a complete computerized system (Sandman). Sleep was staged as per standard criteria (Rechtschaffen A, Kales A.1968) EEG arousals were scored as per the report from Sleep Disorders Atlas Task Force of the American Sleep Disorders Association (1992). Daytime sleepiness was measured by the Epworth Sleepiness score (ESS).
The age of our subjects were 54 ± 15(mean ± SD), ESS 11 ± 5 (mean ± SD), mean total PLM’s 201, mean PLM index 36. More PLM arousals were detected by Fz-A2 than C3-A2 EEG leads (456 vs 257).There was a significant correlation between ESS and total PLM’s (Pearson correlation, r=0.57, p=0.05), however there was no difference between C3-A2 or Fz-A2 related PLM arousals during specific sleep stages, CPAP usage or by severity (PLM index > or < 20).
There was a significant relationship between total PLM’s and a clinical measure of EDS.
In reporting PLM’s, the absolute number of PLM is more relevant than the commonly reported PLM arousal index, and measures to improve arousal detection by an additional frontal EEG lead may not be relevant.
E.A. DeSousa, None.