Differential diagnosis of cardiogenic syncope and seizure disorders

Abstract

Transient loss of consciousness is a dramatic symptom, which has many possible mechanisms and hence different therapeutic, psychosocial, and prognostic implications. It is a common cause both for emergency room visits and for hospitalisation, and has recently been the topic of a task force within the European Society of Cardiology (ESC). Syncope is a symptom, defined as a transient, self limited loss of consciousness with a relatively rapid onset and usually leading to falling; the subsequent recovery is spontaneous, complete, and usually prompt. The underlying mechanism is a transient global cerebral hypoperfusion. Seizure is, according to the same document, synonymous with an epileptic fit, which is the manifestation of a paroxysmal discharge of abnormal rhythms in some part of the brain, and "Epilepsy is then defined as a condition in which seizures recur, usually spontaneously". The diagnosis thus requires that the episodes are spontaneous or unprovoked and recurrent. In order to differentiate between syncope and seizure, videotelemetry with simultaneous electroencephalographic (EEG) and electrocardiographic (ECG) recording with multiple scalp and chest electrodes is required - a situation that is rarely fulfilled. There are clinically important relations between cardiovascular causes of syncope and seizure disorders (fig 1). Involuntary movements, often referred to as myoclonic jerks, may accompany syncope due to cardiovascular causes and create a differential diagnostic problem against seizure with important therapeutic and prognostic implications. These implications are basically: the underlying disease may not receive proper treatment, and some cardiac causes of syncope carry a considerable mortality risk; bradycardias might be aggravated by some (ion channel active) anti-epileptic drugs (AEDs); and a diagnosis of epilepsy may also lead to significant psychosocial consequences. Put slightly differently: "Hardly anyone with epilepsy will come to any harm from a delay in diagnosis whereas a false positive diagnosis is gravely damaging". Therefore seizure-like or convulsive syncope from the cardiovascular perspective has been chosen as the topic for this article. "Convulsive syncope" is not a recommended term by the ESC task force," ...because it carries the risk of increasing confusion between syncope and epilepsy". Unfortunately, there is no simple term to denote syncope accompanied by "myoclonic jerks" or "jerking movements", which are preferred; therefore, for linguistic reasons and because it is used in some of the references, "convulsive syncope" is used in this article, which focuses on cardiovascular or cardiogenic syncope.