PC1184: Convulsive Syncope Caught Red-handed on Video EEG! Neurological Manifestations of a Cardiac Disease

Introduction: Convulsive syncope or complex vasovagal syncope is a variant of syncope that is accompanied by tonic activity, occurring in about 10% of vasovagal syncope patients. Pain and phobic stress during invasive procedures can trigger an increase in parasympathetic tone, leading to bradycardia and rarely asystole. Asystole is thought to be secondary to complete withdrawal of sympathetic activity. The neurological sequelae caused by cerebral hypoperfusion can manifest as flattening of electroencephalography waves, often mistaken for epilepsy. We were fortunate to catch one such rare occurrence live in action.

Case Description: A 17-year-old-female presented to the emergency department (ED) due to multiple incidences of loss of consciousness over 2 weeks, with possible seizure-like-activity in the most recent episode. She experienced two witnessed episodes in the ED, described as generalized tonic-clonic movements and unresponsiveness while getting lumbar puncture and venous cannulation (IV). Patient reported prodromal symptoms including generalized fatigue, diaphoresis and vision loss prior to both episodes. Lab work and orthostatic vital signs were unremarkable. Patient was admitted for close monitoring with video electroencephalography (vEEG) given the presentation with seizure-like activity. Next morning, she started complaining of lightheadedness while getting her IV fixed. Within a few seconds, patient had central cyanosis, eye deviation and full body twitching. The entire episode was caught on vEEG. Patient went into cardiac asystole for 15 seconds and vEEG showed brain flat lining 5 seconds into the asystole and return of neuronal activity after 8 seconds. (Figures 1 and 2). Asystole resolved spontaneously and patient was started on fludrocortisone for vasovagal syncope given acute onset of cardiac dysfunction with possible future consideration of cardiac pacemaker if symptoms persist.

Discussion: During syncopal events, electroencephalography (EEG) usually demonstrates generalized slowing followed by high-voltage frontal delta activity. It is theorized that the flattening of the EEG is based on the severity and duration of cerebral hypoperfusion that occurs after asystole and it is the stage where nonepileptic, seizure-like movements are often described. Cerebral hypoxia leads to the loss of cortical inhibition of normally suppressed brainstem activity; known as brainstem release phenomena. The loss of inhibition leads to a brief episode of non-epileptic pathological myoclonus. Typically, diagnosis can be made from history of cardiac manifestations, however it can easily be misdiagnosed as epilepsy in the acute settings. The brainstem release phenomenon has been demonstrated in studies where patients underwent a head-upright tilt table test with continuous electroencephalographic recording.

Conclusion: Exact pathophysiology of convulsive syncope is unknown but believed to be secondary to cerebral hypoperfusion. Our case provides a live demonstration of the association between asystole and EEG flattening and exemplifies the importance of considering a cardiac etiology as a differential diagnosis in patients presenting with paroxysmal episodes of seizure-like-activity.