Convulsive Syncope

Definition and Pathophysiology

The European Society of Cardiology states that convulsive syncope is an episode of loss of consciousness caused by cerebral hypoperfusion, accompanied by involuntary myoclonic movements, but it is not an epileptic seizure 1, 2
Convulsive syncope occurs when cerebral hypoperfusion during a syncopal episode produces involuntary muscle movements called myoclonias, which appear when the electroencephalogram (EEG) shows slowing but is not completely flat 1
The presence of myoclonias in syncope is common enough to assert that the mere presence of movements is not sufficient evidence of an epileptic seizure 1, 2

The European Heart Journal recommends that few movements (approximately 10 movements) are characteristic of convulsive syncope 3
Asymmetric and asynchronous movements (although they can be symmetric rarely) are typical of convulsive syncope 3, 4
Movements that begin after loss of consciousness (usually some seconds after, average 20 seconds) are characteristic of convulsive syncope 3, 4
A duration of unconsciousness <30 seconds makes syncope more likely than epilepsy 3
Many movements (20-100 in generalized seizures) are more suggestive of epileptic seizures than syncope 1, 4
Symmetric, synchronous, and rhythmic movements are more characteristic of epileptic seizures than syncope 3, 4
Movements that begin at the onset of unconsciousness or before the fall are more suggestive of epileptic seizures than syncope 3, 4
A duration of unconsciousness >1 minute suggests epileptic seizures rather than syncope 3
Movements restricted to one side or one limb suggest epilepsy rather than syncope 3

The European Society of Cardiology guidelines state that the term "convulsive syncope" does not imply epileptic seizures 1, 2
The term "convulsions" should be reserved for epilepsy, while "myoclonias" or "myoclonic jerks" are used for both syncope and certain types of epilepsy 3

Convulsive syncope is frequently misdiagnosed as epilepsy, which can lead to unnecessary antiepileptic treatment and potentially delay the diagnosis of potentially life-threatening cardiac causes 1, 2

Position at the onset (standing/sitting favors syncope) is an important factor in diagnosing convulsive syncope 3
Triggers such as pain, emotions, heat, and prolonged bipedalism (favor vasovagal syncope) should be considered in the clinical history 3
Prodromal symptoms such as nausea, sweating, pallor, blurred vision, and distant sounds (favor syncope) are important to note in the clinical history 3
Witness accounts, including a detailed description of the type, number, and synchrony of movements, are crucial in diagnosing convulsive syncope 3, 4
Time to recovery, with rapid recovery (<1 minute) favoring syncope and prolonged confusion favoring epilepsy, is an important factor in diagnosing convulsive syncope 3