Different periodicity and time structure of leg movements during sleep in narcolepsy/cataplexy and restless legs syndrome.
OBJECTIVE
To analyze periodic leg movements (PLM) during sleep in patients with narcolepsy and compare the results with those obtained in normal controls and subjects with restless legs syndrome (RLS).


METHODS
We recruited 40 HLA DQB1*0602-positive patients with narcolepsy/cataplexy, 22 with RLS, and 22 controls. The time structure of their polysomnographically recorded LMs was analyzed by means of an approach particularly able to consider their periodicity.


RESULTS
Nineteen patients with narcolepsy had a PLM index greater than 15. The distribution of inter-LM intervals was clearly bimodal in RLS and narcoleptics, with 1 peak at 2 to 4 seconds and another at around 22 to 26 seconds; in the range 22 to 40 seconds, patients with RLS had values significantly higher than patients with narcolepsy. All periodicity parameters were significantly lower in the narcolepsy group. Finally, the distribution of the number of PLM per hour of sleep was bell shaped in normal controls and patients with narcolepsy, whereas patients with RLS showed a progressive decrease throughout the night.


CONCLUSIONS
Most narcoleptic patients show a high number of LMs that are significantly less periodic than those of patients with RLS. PLM are in functional interrelationship with the cyclic alternating pattern, which is reduced in patients with narcolepsy; decreased arousal fluctuations during sleep may be one of the factors influencing the reduction in periodicity of LMs during sleep in narcolepsy.
Ferri
Raffaele
R
Sleep Research Centre, Department of Neurology I.C., Oasi Institute for Research on Mental Retardation and Brain Aging (IRCCS), Troina, Italy. rferri@oasi.en.it
Zucconi
Marco
M
Manconi
Mauro
M
Bruni
Oliviero
O
Ferini-Strambi
Luigi
L
Vandi
Stefano
S
Montagna
Pasquale
P
Mignot
Emmanuel
E
Plazzi
Giuseppe
G
D000328:Adult; D004569:Electroencephalography; D004576:Electromyography; D006801:Humans; D008390:Markov Chains; D009290:Narcolepsy / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology*; D010507:Periodicity; D017286:Polysomnography; D015995:Prevalence; D012148:Restless Legs Syndrome / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology*; D012720:Severity of Illness Index; D012895:Sleep, REM / Q000502:physiology; D013997:Time Factors