Syncope

Syncope is a brief loss of consciousness caused by temporary reduction in blood flow to the brain, followed by spontaneous recovery.

Cerebral hypoperfusion: Inadequate blood flow to the brain, reducing its supply of oxygen and glucose. A temporary fall in cerebral blood flow is the defining mechanism of syncope.
Consciousness: The state of awareness of oneself and the surrounding environment. Syncope temporarily interrupts awareness, then restores it spontaneously.
Electrocardiography: A recording of the heart’s electrical activity from electrodes placed on the body. An ECG can reveal rhythm or conduction abnormalities linked to fainting.
Epileptic seizure: A seizure caused by abnormal electrical activity in the brain associated with epilepsy. It can cause loss of consciousness, but is not caused by transient cerebral hypoperfusion.
Vasovagal syncope: A reflex faint involving vasodilation, a slowed heart rate, or both. This common subtype follows an exaggerated autonomic reflex.
Presyncope: A sensation of impending faint without complete loss of consciousness. It can share syncope’s warning symptoms without progressing to unconsciousness.
Tilt table test: A test that monitors cardiovascular responses while a person is moved from lying to upright. It can reproduce symptoms and help identify reflex or orthostatic syncope.
Psychogenic pseudosyncope: An apparent faint without the blood-pressure or heart-rate changes that cause syncope. It resembles syncope while lacking its defining circulatory mechanism.
Orthostatic hypotension: A sustained fall in blood pressure after standing or sitting upright. Blood pooling after a posture change can briefly impair brain perfusion.
Transient loss of consciousness: A brief episode of unresponsiveness with loss of awareness and subsequent recovery. Syncope is one cause of this broader clinical presentation.

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