⚠️ Must-Not-Miss Diagnoses
Hypoglycemia (always check first), hypertensive encephalopathy, meningitis/encephalitis, intracranial hemorrhage, status epilepticus (nonconvulsive), Wernicke's encephalopathy, carbon monoxide poisoning.
Differential Diagnosis by Key Features
| Clinical Feature | Think Of | Priority |
|---|---|---|
| Glucose <60 mg/dL | Hypoglycemia | HIGH — treat immediately |
| Fever + meningismus + photophobia | Meningitis/encephalitis | HIGH |
| Sudden onset, focal neuro deficits, headache | Intracranial hemorrhage/stroke | HIGH |
| Alcohol use, thiamine-deficient, ataxia + ophthalmoplegia | Wernicke's encephalopathy | HIGH |
| Gradual onset, elderly, fluctuating, recent illness/hospitalization | Delirium | Moderate |
| Medication change, polypharmacy, elderly | Drug-induced encephalopathy | Moderate |
| Liver disease, asterixis, elevated ammonia | Hepatic encephalopathy | Moderate |
Systematic Approach
Immediate
Glucose first — always
Check fingerstick glucose immediately. Hypoglycemia is the most treatable and most commonly missed cause of AMS. Give D50 empirically if glucose unavailable and patient has altered consciousness.
Airway
Assess and protect airway
GCS ≤8 or inability to protect airway requires immediate consideration of intubation. Don't proceed to detailed workup without first ensuring airway safety.
History
AEIOU-TIPS framework
Alcohol/toxins, Epilepsy, Infection, Opioids/overdose, Uremia/metabolic, Trauma, Insulin (glucose), Psychiatric, Stroke/structural. Collateral history from family/EMS is often more reliable than patient history.
Exam
Focused neurological exam
Level of consciousness (GCS), pupil symmetry and reactivity, focal deficits, meningismus, asterixis (hepatic), myoclonus (uremic, drug-induced), seizure activity.
Testing
Glucose, BMP, CBC, LFTs, ammonia, drug screen, CT head, LP if indicated
Non-contrast CT head first if focal deficits, anticoagulation, or concern for herniation. LP after CT to evaluate for meningitis if infectious cause suspected.
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