GPAtlas🧭 When to suspect
Transient loss of consciousness (TLoC) is spontaneous loss of consciousness with complete recovery – rapid onset, short duration, and no residual neurological deficit afterwards. It is extremely common, affecting up to half the UK population at some point in life, and presents as a ‘blackout’, ‘collapse’ or ‘funny turn’.
The whole task in primary care is to do three things well: confirm it really was TLoC (rather than a mechanical fall, vertigo or hypoglycaemia), separate benign reflex faints from dangerous cardiac causes, and never miss a red flag. The two non-negotiables on every patient are a meticulous eyewitness history (before, during and after) and a 12-lead ECG. A sobering point underpins all of this: a substantial proportion of people labelled and treated for epilepsy in fact have a cardiovascular cause for their blackouts.
| Category | Typical pointers | Examples |
|---|---|---|
| Reflex (neurally mediated) | The 3 P’s – Posture (prolonged standing), Provocation (pain, emotion, a procedure), Prodrome (warm, sweaty, nauseated, greying vision); rapid full recovery. | Vasovagal (simple) faint; situational (cough, micturition, swallow); carotid sinus syncope. |
| Orthostatic (postural) | On standing or after meals; older patients, autonomic disease; very commonly drug-induced. | Antihypertensives/diuretics; hypovolaemia; autonomic failure (e.g. Parkinson’s, diabetes). |
| Cardiac (do not miss) | Exertional or supine syncope; no or very short prodrome; palpitations beforehand; family history of sudden death < 40; abnormal ECG. | Arrhythmia (brady/tachy, heart block); structural (aortic stenosis, HCM); inherited (long QT, Brugada, WPW). |
| Neurological (mimic) | Lateral tongue-biting, head-turning to one side, prolonged limb-jerking, post-ictal confusion, prodromal déjà vu. | Epileptic seizure; dissociative (non-epileptic) seizures; psychogenic pseudosyncope. |
Source: NICE CG109 · NICE QS71
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