Vasovagal syncope (VVS) is the most common form of fainting, characterized by a temporary loss of consciousness often triggered by specific environmental or emotional factors. The involuntary movements that sometimes accompany these fainting spells are frequently mistaken for a true seizure. These episodes can cause brief jerking movements that visually resemble an epileptic event, raising concern for an underlying neurological condition. This article clarifies the distinct physiological processes behind vasovagal fainting and epileptic seizures.
Understanding Vasovagal Syncope
Vasovagal syncope occurs due to a temporary malfunction in the autonomic nervous system. When exposed to certain triggers, the nervous system overreacts, causing a sudden shift in activity. This involves the simultaneous enhancement of parasympathetic (vagal) tone and a withdrawal of sympathetic tone.
The result is a rapid drop in heart rate (bradycardia) and a widening of blood vessels (vasodilation), causing blood pressure to plummet. This leads to a significant decrease in blood flow to the brain. Common triggers include prolonged standing, heat exposure, intense emotional distress, or the sight of blood or needles. This transient reduction in cerebral blood flow (cerebral hypoperfusion) causes the momentary loss of consciousness, which resolves quickly once the person falls or is laid down.
The Difference Between Convulsive Syncope and Epilepsy
Vasovagal syncope does not cause a true epileptic seizure. The involuntary movements that occur during a severe faint are categorized as “convulsive syncope” or “anoxic seizures.” These movements are a secondary consequence of the acute lack of oxygen reaching the brain due to the severe drop in blood pressure.
During a convulsive syncopal event, the brain’s medullary reticular formation is triggered by the global cerebral hypoperfusion. This can result in brief myoclonic jerks, tonic posturing (stiffening), or eye rolling. The movements are typically short, lasting only a few seconds, and cease immediately once blood flow to the brain is restored.
In contrast, a true epileptic seizure is a primary electrical event that can last for several minutes. It is frequently followed by a prolonged period of confusion and disorientation, known as the post-ictal state. Convulsive syncope is rarely associated with lateral tongue biting, and syncope-related movements typically involve fewer than ten jerks, unlike true convulsive seizures.
Diagnostic Tools Used to Distinguish Episodes
Medical professionals rely on patient history, witness accounts, and diagnostic tests to distinguish between convulsive syncope and epilepsy. Noting presyncope symptoms like lightheadedness, nausea, and pallor strongly suggests a syncopal event. Conversely, an aura (such as a strange smell or feeling) preceding the event suggests an epileptic seizure.
The Electroencephalogram (EEG) measures the electrical activity of the brain. An EEG during or immediately after a true epileptic seizure typically shows abnormal electrical patterns, such as spikes or sharp waves. During a syncopal episode, the EEG usually shows a pattern consistent with decreased brain activity due to hypoperfusion, rather than an intrinsic electrical event.
Head-Up Tilt Test
The Head-Up Tilt Test (Tilt-Table Test) is a definitive test for diagnosing VVS. This procedure monitors a person’s heart rate and blood pressure as they are tilted upright on a table. If the test provokes a reflex drop in blood pressure and heart rate that reproduces the patient’s symptoms, it confirms the diagnosis of vasovagal syncope. Long-term cardiac monitoring is also used to rule out heart rhythm disturbances as a cause of syncope.
Strategies for Managing Vasovagal Syncope
Management of VVS focuses on preventing episodes by recognizing and responding to early warning signs (prodromal symptoms). Individuals should increase their daily fluid intake and, in some cases, increase salt consumption to raise blood volume and blood pressure, though this requires medical consultation.
Learning to recognize the onset of lightheadedness, sweating, or nausea allows the use of physical counter-pressure maneuvers to abort the faint. These maneuvers temporarily increase venous return to the heart, boosting blood pressure and maintaining cerebral blood flow. Effective techniques include crossing the legs and tensing the leg and abdominal muscles or interlocking the hands and pulling them apart.