Neurology · Topic 12 of 22
Altered Mental Status & Coma
Neurology · the unresponsive patient
Altered Mental Status & Coma
Stabilize and reverse first — glucose, thiamine, naloxone — then localize with the pupils and image the head.
Key numbers
Thiamine 100 mg IV before dextroseThiamine 100 mg IV
GCS: eyes 4, verbal 5, motor 6GCS < 8 = coma
01 · FirstSecure ABCs and check fingerstick glucose
Stabilize airway, breathing and circulation while you diagnose: check pulse oximetry, cardiac rhythm, temperature and a fingerstick glucose at once, and immobilize the neck if trauma is possible.
02 · GiveThiamine 100 mg IV before dextrose
Give thiamine 100 mg IV or IM routinely in coma (risk of Wernicke encephalopathy); if glucose is low, give 50 mL of 50% dextrose IV — after the thiamine.
03 · Don't confuseFixed pupils early mean a structural lesion
Structural lesions fix one or both pupils early and cause asymmetric motor signs; in toxic-metabolic coma pupillary light reflexes are preserved until very late and findings are symmetric.
01
Presentation
What you'll seeUnilateral fixed dilated pupil: CN III herniationA unilateral dilated pupil unreactive to light usually means third-nerve compression from an ipsilateral mass (transtentorial herniation) — image and treat raised ICP emergently.
Pinpoint pupils: opioids, organophosphates or pontine bleedPinpoint (about 1 mm) pupils point to opioid or organophosphate/carbamate toxicity or a massive pontine hemorrhage; midposition fixed pupils suggest midbrain damage.
Decerebrate posturing means upper brainstem damageDecorticate (flexor) posturing indicates hemispheric damage with an intact upper brainstem; decerebrate (extensor) posturing indicates upper brainstem damage; flaccidity without movement is the worst motor response.
Asterixis or multifocal myoclonus suggests metabolic causeAsterixis and multifocal myoclonus suggest a metabolic or toxic cause — uremia, hepatic encephalopathy, hypoxic injury or drug toxicity.
02
Diagnosis & monitoring
Work-upGCS: eyes 4, verbal 5, motor 6The Glasgow Coma Scale scores eye opening (1–4), verbal (1–5) and motor (1–6) responses for serial tracking; totals below 8 are typically regarded as coma.
03
Do right now
In this orderFirst moves
1
→Secure ABCs and check fingerstick glucose
2
→Thiamine 100 mg IV before dextroseThiamine 100 mg IV
3
→Naloxone 0.4–2 mg IV for suspected opioids
4
Noncontrast head CT when the cause is unclear
Why each step
Secure ABCs and check fingerstick glucoseStabilize airway, breathing and circulation while you diagnose: check pulse oximetry, cardiac rhythm, temperature and a fingerstick glucose at once, and immobilize the neck if trauma is possible.
Thiamine 100 mg IV before dextroseGive thiamine 100 mg IV or IM routinely in coma (risk of Wernicke encephalopathy); if glucose is low, give 50 mL of 50% dextrose IV — after the thiamine.
Naloxone 0.4–2 mg IV for suspected opioidsIf opioid overdose is possible (pinpoint pupils, needle marks, history), give naloxone 0.4–2 mg IV and repeat as needed.
Noncontrast head CT when the cause is unclearIf the cause is not immediately clear, obtain a noncontrast head CT as soon as possible for hemorrhage, mass, edema or hydrocephalus; follow with MRI or a contrast study if CT is not diagnostic.
04
Management
OrdersCold calorics when doll's eyes are absentTest doll's eyes only after cervical injury is excluded; if absent, irrigate an ear (intact drum, head up 30°) with 50 mL ice water — tonic deviation toward that ear means the brainstem is intact.
Send chemistries, ammonia, ABG, toxicology and culturesOrder a metabolic panel with calcium, CBC, liver tests, ammonia, ABG (carboxyhemoglobin if CO is possible), blood and urine cultures, toxicology screen with ethanol level, ECG and chest radiograph.
EEG for possible nonconvulsive status epilepticusGet an EEG when coma remains unexplained or seizures are possible — nonconvulsive status epilepticus has no prominent motor signs and is found only on EEG.
Suspected meningitis: antibiotics before CT and LPIf coma is unexplained after imaging, perform a lumbar puncture; if meningitis is suspected, draw blood cultures and give antibiotics and dexamethasone before imaging — never delay them for CT.
Intubate for a reason, not for coma aloneIntubate comatose patients for respiratory distress, hypoxia despite oxygen, raised ICP, seizures, vomiting or shock; routine intubation of poisoned comatose patients without these increased harm in a randomized trial.
05
Red flags & don'ts
Avoid harmAvoid flumazenil in undifferentiated coma avoidFlumazenil can precipitate seizures, especially in long-term benzodiazepine users or cyclic antidepressant overdose — avoid it in unknown ingestions and use it only for known isolated benzodiazepine oversedation.
06
The rules
Know theseCorrect hypotension; lower severe hypertension cautiouslyCorrect hypotension promptly; lower severe hypertension carefully, because dropping blood pressure below the patient's usual level can cause brain ischemia.
07
Structural or toxic-metabolic coma?
Commonly confused| Pupils | Fixed or unequal early |
|---|---|
| Motor findings | Asymmetric (hemiparesis, one-sided posturing) |
| Classic clue | Unilateral fixed, dilated pupil (CN III compression) |
| Key test | Noncontrast head CT now |
08
Commonly confused
Tell apartPsychogenic unresponsiveness: normal tone, reflexes and fixationPsychogenic unresponsiveness keeps normal tone, reflexes and vital signs, preserves brainstem reflexes, maintains visual fixation on doll's-eye testing, and shows nystagmus away from a cold-irrigated ear.
09
More detail
ReferenceShow 5 reference facts
Coma requires bilateral hemispheric dysfunction or dysfunction of the brainstem arousal (reticular activating) system; a unilateral hemispheric lesion alone does not cause coma unless it compresses the other side.
Cheyne-Stokes breathing suggests bilateral hemispheric or diencephalic dysfunction; central neurogenic hyperventilation, midbrain or upper pontine injury; apneustic breathing, pontine or medullary injury that often progresses to arrest.
Coma: unarousable with eyes closed; vegetative state/unresponsive wakefulness: eye opening without awareness; minimally conscious state: inconsistent purposeful responses; stupor: arousable only by vigorous stimulation.
Basilar artery occlusion may cause up to 10% of unexplained nontraumatic coma and is missed by noncontrast CT in over 40% — add CT angiography when brainstem signs or coma remain unexplained.
Prognosis depends on cause, depth and duration — better when unresponsiveness lasts under 6 hours; absent pupillary responses predict poorly after cardiac arrest but not after sedative overdose.
Reverse before you localize: sugar, thiamine and naloxone come before the scanner.
Sources · Merck Manual Professional — Overview of Coma and Impaired Consciousness (Jul 2026) · Merck Manual Professional — Wernicke Encephalopathy · Flumazenil injection prescribing information — DailyMed (boxed seizure warning) · Sonneville R et al. The spectrum of sepsis-associated encephalopathy: a clinical perspective. Crit Care 2023;27:386 · Merck Manual Professional — Acute Bacterial Meningitis · Starter sheet built from the verified AGACNP fact map (facts reviewed 2026-10-15).