Abstracts

Rationale: Syncope can cause seizure-like convulsions, and seizures can cause cardiac arrhythmia leading to cardiogenic syncope. Cardiac arrhythmias solely confined to rapid eye movement (REM) sleep in the absence of underlying cardiac disease was first described in the early 1980s, and this is an increasingly recognized phenomenon. Seizures can also rarely occur during REM sleep. Differentiating between syncope and seizure during REM sleep can be challenging. We report for the first time a case of REM-induced cardiac arrhythmia leading to convulsive syncope.Methods: Case report.Results: A 41 year old right-handed male was referred for polysomnography due to suspected obstructive sleep apnea. The morning immediately after the test while waiting to leave hospital, he was found unresponsive with limbs extended, head extended, tongue protruding, and mouth frothing. There were generalized tonic-clonic movements prior to profound cyanosis. He was found to have no pulse and CPR was started. He quickly returned to sinus rhythm with no postictal confusion. He was subsequently readmitted during which the sleep laboratory urgently reported the finding of REM-induced bradyarrhythmia with significant episodes of Mobitz type II heart block. There was at least one episode of six successive P waves with no QRS complex or escape beats over a period of approximately 7 seconds (Figs. 1, 2). These events were solely confined to REM sleep. His 78 minutes of REM sleep occurred towards the end of the polysomnogram not too long before his pulseless convulsion later that morning. He was diagnosed with REM-induced cardiogenic convulsive syncope and received a permanent pacemaker within the week with no further convulsive events. In retrospect, the patient had been transiently diagnosed with epilepsy as a teenager after his parents found him in the midst of a generalized convulsion, also in the morning. He was prescribed Carbamazepine for a year. Despite coming off medication, he remained free of events for over 20 years until a transient bout of foreign accent syndrome led to a new prescription for Levetiracetam. He was still on Levetiracetam at the time of his polysomnogram. He had a number of EEGs, none of which demonstrated epileptiform activity. Cerebral neuroimaging was also unremarkable.Conclusions: This case emphasizes the importance of determining whether a convulsion in sleep is due to seizure or syncope, especially when it occurs in REM sleep. Because seizures are rare in REM sleep, one should consider the differential diagnosis of REM-induced heart block leading to cardiogenic convulsive syncope. One should have a high index of suspicion whenever a seizure occurs in the latter third of the night, or very early in the morning when REM is most prevalent.