P95. REM sleep without atonia and REM sleep behavioral disorder in patients with amytrophic lateral sclerosis

Abstract

REM sleep behavioral disorder (RBD) is characterized by dream-enacting behavior arising from REM sleep. On polysomnography (PSG), physiological muscle atonia is absent during phasic REM sleep in patients with RBD. RBD reflects disinhibition of cortical motor impulses on the brainstem level during REM sleep. RBD comprises a prodromal or concomitant condition in neurodegenerative diseases characterized by α-synuclein deposition. In patients with amyotrophic lateral sclerosis (ALS) RBD has not been systematically been investigated. Since neurodegeneration in ALS spreads from the motor cortex to the bulbar reticular formation we retrospectively studied the presence of REM sleep without atonia (RSWA) and RBD in patients with ALS. Patients with possible, probable or definite ALS according to the revised El Escorial criteria were included in the study. Occurrence of nocturnal behavioral abnormalities was assessed by a standardized physician interview. Exlusion criteria were tetraplegia, home ventilatory support, continous positive airway pressure support for obstructive sleep apnea, concomitant PD or MSA, dementia, and medication with either benzodiazepines or tricyclic antidepressants. Video polysomnography was performed according to standard recommendations, and PSG records were validated manually by two independent scorers according to the AASM criteria. Tonic muscle activity during REM sleep was scored when 50% ore more of a single 30 s epoch showed an EMG amplitude higher than the smallest EMG amplitude during non-REM sleep. Phasic muscle activity during REM sleep was scored when 5 out of 10 3 s mini-epochs showed transient muscle activity for 0.5–1.0 s with an EMG amplitude at least 4-fold above background activity. Classification of behavioral abnormalities during REM sleep was performed based on the widely used RBD severity scale (RBD-SS). Video-polysomnography records of 12 patients underwent detailed analysis. Three patients were female. Mean age was 48.8 years. One patient was diagnosed to have familial ALS with a proven mutation in the FUS gene. Two patients had bulbar onset of ALS symptoms. Behavioral abnormalities or increased motor acitivity during sleep clearly not associated with nocturnal dyspnea were reported by two patients and their bed partners. Subtle clinical signs of parkinsonism were present in only one of these patients on admission (mild hyposmia, distal rigor). Both patients showed dream-enacting behavior in combination with RSWA on video-PSG confirming RBD. Four patients without self-reported symptoms of possible RBD exhibited non-physiologic motor activity during REM sleep including jerks and vocalisations. Violent behavior or vigorous movements did not occur. 9 out of 12 patients showed tonic or phasic musle activity on surface EMG reflecting RSWA. It is not known whether ALS predisposes to the development of RBD. In accordance to very few case reports in the literature our study suggests that both RSWA and mild RBD may be encountered in patients with ALS. Further studies in larger patient samples are necessary to elucidate the prevalence of RBD in patients with ALS.