Loss of Consciousness History

Table of Contents


This is a guide on how to take a history for a patient presenting with loss of consciousness

Presenting Complaint

In a patient presenting with loss of consciousness, you should get a detailed description of what happened before, during and after the episode.

It is good to ask if anyone witnessed the patient losing loss of consciousness as it can give you more clues as to what may have happened.


Was there any warning?

Yes – Aura preceding an epileptic seizure, dizziness prior to a vasovagal syncope

No – Cardiac cause e.g. arrythmia, aortic stenosis, hypertrophic obstructive cardiomyopathy

Were there any precipitating factors?

Standing Up – Orthostatic hypotension, vasovagal syncope

Head Turning – Carotid sinus hypersensitivity

Exercise – Cardiac causes

Sitting or Lying Down – Arrythmia

Was there any recent head trauma?

Days or Weeks Ago – Subdural haemorrhage


How long were you unconscious?

Seconds – Vasovagal syncope, arrythmia

Do you remember if you carried out any of the following acts while you were unconscious?

Tongue Biting – Epileptic seizure

Twitching/incontinence – Vasovagal syncope


How long did it take you to recover?

Slow recovery with confusion – Epileptic seizure

Spontaneous recovery is less likely to be a metabolic or neurological cause

Causes and Symptoms

Generally, the main causes can be summarised as either syncopal or non-syncopal.

Syncope is a form of loss of consciousness when you have a sudden, temporary drop in the amount of blood that flows through the brain.

Syncopal causes can be subdivided further by the mechanisms:

Reflex – A response to stimuli causing a drop in heart rate and and fall in blood pressure

Cardiac – Diseases causing a reduction in cardiac output

Orthostatic – A sudden drop in blood pressure on standing up

Cerebrovascular – Non-cardiac causes of reduced perfusion to the brain (relatively uncommon)

In any history you will ask about past medical history, medications, allergies, social history, and family history. In a history about loss of consciousness, you can show how much you know about the various causes by explicitly asking about the following things…

PMHx – Previous blackouts, epilepsy, diabetes, cardiac diseases, anaemia, psychiatric illness

DHx – Insulin, antihypertensives, vasodilators, antidepressants, anticoagulants

SHx – Alcohol, smoking, recreational drugs

FHx – Sudden death in any relations <65 years of age

When examining the patient, you should keep your differentials in mind and look for signs that confirm or refute your potential diagnoses.

Epileptic Seizure – Tongue bites or a sore tongue

Orthostatic Hypotension – Signs of dehydration (dry mucous membranes, tachycardia, hypotension) and lying/standing BP

Subdural Haemorrhage – Head trauma

Cardiac Causes – Slow or irregular pulse

Cardiac Artery Stenosis – Carotid bruits