Syncope is a transient, self limited loss of consciousness with loss of postural tone, followed by spontaneous, complete recovery, caused by temporary global cerebral hypoperfusion.
Syncope can result from many different disorders, commonly grouped into:
Reflex (neurally mediated) syncope
Vasovagal (most common)
Situational (cough, micturition, defecation)
Carotid sinus hypersensitivity
Orthostatic hypotension
Volume depletion
Autonomic dysfunction
Medications (e.g., antihypertensives)
Cardiac syncope (highest risk)
Arrhythmias (bradyarrhythmias, tachyarrhythmias)
Structural heart disease (e.g., aortic stenosis, HCM)
Ischemia
Cerebrovascular causes (rare)
Subclavian steal syndrome
Vertebrobasilar insufficiency (uncommon)
Syncope is a red-flag symptom, especially when cardiac in origin.
The clinician’s task is not to diagnose “syncope”, but to identify the underlying cause and stratify risk.
If you’d like, I can also provide a diagnostic approach, red flags, or a comparison with seizures and other causes of transient loss of consciousness.