Melatonin Effects in REM Sleep Behavior Disorder Associated with Obstructive Sleep Apnea Syndrome: A Case Series

REM sleep behavior disorder (RBD), with its main clinical symptoms of nightmares with dream-enacting behavior, is considered as a possible precursor of neurodegenerative disease. Obstructive Sleep Apnea Syndrome (OSAS) is known to be capable of provoking RBD-like symptoms by apneic event related arousals. The two sleep related pathologies must coincide in a relevant number of individuals because of overlapping prevalence in similar age groups. Until now RBD symptoms coexisting with OSAS are rarely described in scientific literature and in fact considered as OSAS mimicking RBD.We report four cases with a severe clinical RBD syndrome which were polysomnographically also diagnosed with concomitant OSAS (AHI range: 10.1 -53.2/h).Treatment with 2 mg prolonged release melatonin led to a relevant clinical improvement of RBD symptoms in all patients, so far untreated for the sleep related breathing disorder. Measure of REM sleep without atonia (RSWA) in polysomnography showed values ranging from 5.1 to 20.4% determined with the Montplaisir method. Surprisingly, RSWA values in PSG with melatonin were high, probably because of the still untreated OSAS.We presume that in patients with RBD and OSAS both pathologies contribute in varying degrees to the emergence of RBD symptoms by a destabilization of REM sleep. We suggest by consequence to consider a therapeutic strategy including the treatment of both disorders for an optimal therapeutic response.