About This Page
This is a clinician-written, evidence-based guide aligned to the MCC Examination Objectives. It is structured by clinical presentation — the way the MCCQE tests and the way patients actually present. Management reflects current Canadian guidelines (CMA, CFPC, CPS). Always cross-reference with institutional protocols and clinical judgment.
Key points
- Confirm true loss of consciousness: abrupt onset, loss of postural tone and recovery pattern
- Differentiate syncope from seizure using prodrome, position, trigger, colour, movements, tongue bite and post-event confusion
- All unexplained transient LOC needs glucose, orthostatic vitals and ECG; CT head is not routine unless focal deficit, trauma or prolonged confusion
- Cardiac syncope red flags include exertional events, no prodrome, supine events, abnormal ECG, structural heart disease and family history of sudden death
- Neurological cross-ref: prolonged post-ictal state, lateral tongue bite or focal deficit should redirect toward seizures, stroke or intracranial pathology
Approach to the Presentation
Loss of consciousness sits at the interface of neurology, cardiology and emergency medicine. Start with immediate safety: ABCs, glucose, vital signs and trauma assessment. Then reconstruct the event from a witness: posture, trigger, prodrome, duration, colour, movements, injuries, recovery and confusion. The cardiovascular syncope page provides the detailed cardiac risk approach; this neurological page emphasizes the differential with seizure, metabolic coma, stroke, intoxication and functional episodes.
Differential Diagnosis
| diagnosis | likelihood | key features | distinguishing test |
|---|---|---|---|
| Cardiac syncope | must-not-miss | Exertional or supine LOC, no prodrome, palpitations, chest pain, abnormal ECG, structural heart disease, family history of sudden death | ECG, telemetry, troponin if ischemic symptoms, echo if structural disease suspected |
| Seizure | must-not-miss | Aura, head/eye deviation, tonic-clonic movements, lateral tongue bite, prolonged post-ictal confusion, focal Todd paresis | Witness history, glucose/electrolytes, EEG, brain imaging when indicated |
| Hypoglycaemia | must-not-miss | Diabetes therapy, missed meal, alcohol, sepsis; sweating, tremor, confusion, seizure or coma | Point-of-care glucose; response to dextrose |
| Stroke / intracranial haemorrhage | must-not-miss | Focal deficit, sudden severe headache, anticoagulation, persistent reduced consciousness | Urgent CT/CTA brain and stroke pathway |
| Vasovagal syncope | common | Pain, emotion, heat or prolonged standing; nausea, warmth, diaphoresis, tunnel vision; rapid recovery | Clinical; normal ECG and low-risk features |
| Orthostatic hypotension | common | Occurs after standing; dehydration, autonomic neuropathy, antihypertensives, diuretics | Orthostatic BP/HR measurements |
| Intoxication / overdose | common | Sedatives, opioids, alcohol, recreational drugs; miosis, respiratory depression or mixed toxidrome | Clinical toxidrome, glucose, ABG/VBG, toxicology where useful |
| Psychogenic non-epileptic event | less common | Fluctuating prolonged unresponsiveness, eye closure, inconsistent exam, emotional trigger; diagnosis requires care and exclusion of danger | Clinical pattern, video EEG when uncertain |
| Cataplexy / narcolepsy | rare | Sudden loss of tone triggered by emotion with preserved awareness | Sleep history; sleep specialist testing |
Red Flags & Key History
Symptoms
LOC during exertion or while supine
No prodrome with injury
Prolonged confusion after event
New focal neurological deficit
Chest pain, dyspnoea or palpitations preceding collapse
Warmth, nausea, tunnel vision and rapid recovery
Signs
Abnormal ECG
Orthostatic hypotension
Lateral tongue laceration
Focal neurological deficit or persistent GCS reduction
Signs of head trauma
Approach to Investigation
First-line
Point-of-care glucoseImmediate for any altered or collapsed patient.
12-lead ECGMandatory in unexplained LOC to detect arrhythmia, conduction disease, long QT, WPW, ischemia or Brugada pattern.
Orthostatic vitalsIdentify orthostatic hypotension and guide medication review.
Focused neurological and trauma examLook for focal deficit, meningism, head injury and post-ictal features.
Second-line
Canadian Syncope Risk ScoreFor ED syncope disposition when true syncope is likely.
CT headOnly when focal deficit, head trauma, anticoagulation, persistent altered mental status or suspected haemorrhage/structural pathology.
EEGIf seizure remains likely after history and initial assessment.
Telemetry / ambulatory monitoringFor suspected arrhythmia or recurrent unexplained events.
Specialist
Neurology/cardiology referralBased on suspected seizure, abnormal ECG, structural heart disease or recurrent unexplained LOC.
Management Principles
Canadian Syncope Risk Score + MCC Syncope objective1
Immediate care
- ABCs, cervical spine precautions if trauma, glucose and vital signs
- Treat hypoglycaemia, opioid toxicity, active seizure or shock immediately
2
Syncope likely
- Risk stratify using ECG, history and Canadian Syncope Risk Score
- Low-risk vasovagal: education, hydration, trigger avoidance and counterpressure manoeuvres
- High-risk features: telemetry/admission and cardiac evaluation
3
Seizure likely
- Follow seizure pathway, arrange EEG/imaging where indicated and counsel on driving/safety
4
Unclear episodes
- Avoid premature psychiatric labelling; arrange rhythm monitoring, neurology assessment or video EEG according to dominant features
Complications & Pitfalls
- CT head for every faint: uncomplicated syncope without neurological features usually does not need neuroimaging.
- Missing arrhythmia: syncope without prodrome is cardiac until proven otherwise.
- Confusing convulsive syncope with epilepsy: brief jerks can occur after cerebral hypoperfusion.
- Not asking witnesses: the witness history often provides the diagnosis.
MCCQE1 Exam Tips
- 1MCC framing: first decide whether the event is syncope, seizure or metabolic/toxic altered consciousness.
- 2ECG is essential for syncope; EEG is not first-line unless the story suggests seizure.
- 3Brief myoclonic jerks do not automatically mean epilepsy.
- 4Lateral tongue bite and prolonged post-ictal confusion favour seizure.
- 5Exertional syncope is a red flag for structural cardiac disease or malignant arrhythmia.
- 6CT head is reserved for neurological deficits, trauma, anticoagulation or persistent confusion.
Put your reading into practice
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Choose MCCQE Part I practiceAfter your session, return to this section to revisit the reading and choose your next review.
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