Time structure analysis of leg movements during sleep in REM sleep behavior disorder.
OBJECTIVE
To compare the time structure of leg movements (LM) during sleep of patients with rapid eye movement (REM) sleep behavior disorder (RBD) with that of patients with restless legs syndrome (RLS) or control subjects.


METHODS
The polysomnographically recorded tibialis anterior activity during sleep was analyzed by means of a new approach able to consider duration, intermovement interval, sleep stage and time of night distribution, and periodicity.


METHODS
Twenty patients with idiopathic RBD, 37 with idiopathic RLS and 14 age-matched control subjects were consecutively recruited.


RESULTS
Most patients with RBD (85%) presented periodic leg movements during sleep (PLMS). PLMS occurred more frequently during non-REM sleep in patients with RLS and during REM sleep in patients with RBD. PLMS were shorter in duration, less often bilateral, and with a higher intermovement interval in patients with RBD compared to those with RLS. The number of PLMS decreased across the night in patients with RBD and in those with RLS, but not in control subjects. In all subjects, LM periodicity clearly depended on sleep state, with higher values during non-REM than during REM sleep. Patients with RBD showed a lower LM periodicity, compared with patients with RLS, in each of the sleep states.


CONCLUSIONS
Significant differences, together with some similarities in LM time structure, were observed between patients with RBD and those with RLS; for this reason, our approach seems to indicate that their phenotype might be dependent on 2 factors: disease and sleep stage.
Manconi
Mauro
M
Sleep Disorders Center, Department of Neurology, H San Raffaele Scientific Institute, Università Vita-Salute San Raffaele, Milan, Italy. manconi.mauro@hsr.it
Ferri
Raffaele
R
Zucconi
Marco
M
Fantini
Maria Livia
ML
Plazzi
Giuseppe
G
Ferini-Strambi
Luigi
L
D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology; D020189:Nocturnal Myoclonus Syndrome / Q000175:diagnosis* / Q000503:physiopathology; D017286:Polysomnography; D020187:REM Sleep Behavior Disorder / Q000175:diagnosis* / Q000503:physiopathology; D012148:Restless Legs Syndrome / Q000175:diagnosis* / Q000503:physiopathology; D012894:Sleep Stages / Q000502:physiology