Quantitative assessment of isolated rapid eye movement (REM) sleep without atonia without clinical REM sleep behavior disorder: clinical and research implications.
BACKGROUND
Rapid eye movement (REM) sleep without atonia (RWA) is observed in some patients without a clinical history of REM sleep behavior disorder (RBD). It remains unknown whether these patients meet the refined quantitative electromyographic (EMG) criteria supporting a clinical RBD diagnosis. We quantitatively evaluated EMG activity and investigated its overnight distribution in patients with isolated qualitative RWA.


METHODS
Fifty participants with an incidental polysomnographic finding of RWA (isolated qualitative RWA) were included. Tonic, phasic, and 'any' EMG activity during REM sleep on PSG were quantified retrospectively.


RESULTS
Referring to the quantitative cut-off values for a polysomnographic diagnosis of RBD, 7/50 (14%) and 6/50 (12%) of the patients showed phasic and 'any' EMG activity in the mentalis muscle above the respective cut-off values. No patient was above the cut-off value for tonic EMG activity or phasic EMG activity in the anterior tibialis muscles. Patients with RWA above the cut-off value showed higher amounts of RWA during later REM sleep periods.


CONCLUSIONS
This is the first study showing that some subjects with incidental RWA meet the refined quantitative EMG criteria for a diagnosis of RBD. Future longitudinal studies must investigate whether this subgroup with isolated qualitative RWA is at an increased risk of developing fully expressed RBD and/or neurodegenerative disease.
Department of Somnology, Tokyo Medical University, Tokyo, Japan; Japan Somnology Center, Neuropsychiatric Research Institute, Tokyo, Japan.
Taeko
T
Sasai-Sakuma
Department of Neurology, Innsbruck Medical University, Innsbruck, Austria.
Birgit
B
Frauscher
Department of Neurology, Innsbruck Medical University, Innsbruck, Austria.
Thomas
T
Mitterling
Department of Neurology, Innsbruck Medical University, Innsbruck, Austria.
Laura
L
Ehrmann
Department of Neurology, Innsbruck Medical University, Innsbruck, Austria.
David
D
Gabelia
Department of Neurology, Innsbruck Medical University, Innsbruck, Austria.
Elisabeth
E
Brandauer
Department of Somnology, Tokyo Medical University, Tokyo, Japan; Japan Somnology Center, Neuropsychiatric Research Institute, Tokyo, Japan.
Yuichi
Y
Inoue
Department of Neurology, Innsbruck Medical University, Innsbruck, Austria.
Werner
W
Poewe
Department of Neurology, Innsbruck Medical University, Innsbruck, Austria. Electronic address: birgit.ho@i-med.ac.at.
Birgit
B
Högl
D000293:Adolescent; D000328:Adult; D000368:Aged; D035843:Biomedical Research; D003937:Diagnosis, Differential; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009123:Muscle Hypotonia / Q000175:diagnosis*; D017286:Polysomnography; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D018570:Risk Assessment; D012815:Signal Processing, Computer-Assisted; D012895:Sleep, REM; D055815:Young Adult
Electromyography; Isolated qualitative REM sleep without atonia; Neurodegenerative disease; Polysomnography; REM sleep behavior disorder; SINBAR method