Altered mental status and coma

Last updated: October 17, 2022

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Altered mental status (AMS) is an acute change in cognitive function, psychological function, and/or level of consciousness and can manifest with confusion, behavioral changes, and changes in alertness ranging from hyperalertness to somnolence or even coma. There are many potential causes of altered mental status, including primary CNS processes, general medical conditions, substance use, and psychiatric illness. Initial management includes stabilization (e.g., definitive airway management) and screening for life-threatening acutely reversible causes (e.g., hypoglycemia, opioid overdose). Coma scores are used to assess and monitor the level of neurological dysfunction. Once stabilized, a full diagnostic evaluation should be performed based on the suspected underlying etiology; this may include basic laboratory studies, ECG, head imaging, and lumbar puncture. Treatment is focused on the management of the underlying etiology in addition to providing supportive care and preventing complications.

General principles

  • Use coma scores (e.g., GCS, AVPU scale, FOUR score) for a more objective and reproducible assessment.
  • Document the score upon presentation.
  • Frequently reassess to detect changes early.

AVPU scale

An abbreviated scale that helps rapidly classify and communicate a patient's level of consciousness in emergency settings. [1][2]

  • A: Alert
  • V: responsive to Verbal stimuli
  • P: responsive to Painful stimuli
  • U: Unresponsive

Glasgow coma scale (GCS) [3]

A standardized scale used to assess the level of consciousness and neurological status in multiple settings, e.g., TBI classification. GCS is less useful in intubated patients and does not provide a detailed assessment of brainstem function.

Glasgow coma scale (GCS) [4]
Criteria Response Score
Eye opening (E) Spontaneous 4
To verbal command 3
To pain 2
No response 1
Closed due to local factor (e.g., ocular injury) Nontestable
Verbal response (V)
Oriented 5
Confused 4
Inappropriate words 3
Incomprehensible sounds 2
No response 1
Other factor(s) interfering with communication (e.g., intubation) Nontestable
Best motor response (M) Follows instructions 6
Localizes pain stimulus 5
Withdraws from pain (normal flexion to pain) 4
Decorticate posturing (abnormal flexion to pain) 3
Decerebrate posturing (extension to pain) 2
No motor response 1
Preexisting factor(s) causing paralysis Nontestable


Full Outline of UnResponsiveness (FOUR) score [3]

The FOUR score is equally useful in nonintubated and intubated patients and is more discriminatory than GCS in patients with very low levels of consciousness [5][6]

Full Outline of UnResponsiveness (FOUR) score [7]
Criteria Response Score
Eye response (E)

Tracking or blinking to command

Eyelids open spontaneously or to command 3
Eyelids closed but open in response to loud voices 2
Eyelids closed but open in response to pain 1
Eyelids remained closed in response to pain 0
Motor response (M) Can make thumbs up, fist, or peace sign 4
Localizes pain stimulus 3
Flexion response to pain 2
Extension response to pain 1
No response to pain or generalized myoclonus status epilepticus 0
Brainstem reflexes (B) Pupil and corneal reflexes present 4
One pupil wide and fixed 3
Pupil OR corneal reflexes absent 2
Pupil AND corneal reflexes absent; cough reflex present 1
Absent pupil, corneal, and cough reflexes 0
Respiration (R) Not intubated; regular breathing pattern 4
Not intubated; Cheyne-Stokes breathing pattern 3
Not intubated; irregular breathing pattern 2
Intubated; breathing above ventilator rate 1
Intubated; breathing at ventilator rate or apnea 0

Consider using the FOUR score instead of GCS to assess intubated patients, as it does not rely on verbal responses. [3]

The goal of initial management is to identify and treat rapidly reversible and/or time-sensitive critical causes of AMS prior to a full diagnostic evaluation.

Initial evaluation [3][8]

See also: “Evaluating disability in the ACBDE approach.”

Use coma scores to quickly assess and document neurological function at presentation and regularly reassess to detect changes.

In patients with abrupt-onset AMS or coma, consider seizure, stroke, cardiac event, overdose, or intoxication. [8]

Managing critical causes of AMS [3][8]

Perform the following concurrently with the initial evaluation, based on clinical suspicion:

Next steps [3][8]

Obtain EEG monitoring for patients with suspected nonconvulsive status epilepticus.

Critical causes include potentially rapidly reversible etiologies and conditions that may pose an imminent threat to life.

Critical causes of AMS or coma and their immediate management

Condition Suggestive features Immediate intervention
Hypoxic respiratory failure
Hypercapnic respiratory failure


  • Serum or fingerstick glucose ≤ 70 mg/dL (≤ 3.9 mmol/L)
Opioid overdose
  • Administer IV naloxone for respiratory depression. [8][10]
Carbon monoxide poisoning
  • Prodrome of headache, nausea, and fatigue
  • Possible history of smoke inhalation
  • Sick household members
Cyanide poisoning


  • Core body temperature < 35.0°C (95.0°F)


  • Elevated body temperature
  • Environmental exposure and/or excessive physical activity
  • Clinical features of drug-induced hyperthermia


Sepsis and/or meningitis

  • Symptoms of infection
  • ≥ 2 positive SIRS or qSOFA criteria
  • Meningococcal rash may be present


Hypertensive encephalopathy
Imminent brain herniation

Perform diagnostic studies based on clinical evaluation in tandem with the initial management of AMS and coma. More thorough targeted diagnostics can be obtained once the patient is stabilized.

Routine laboratory studies [3][11][12]

ECG findings [3][11][12]

Neuroimaging [3][11][12]

Additional studies

May be indicated based on the clinical presentation and the suspected underlying etiology. For further information, see:

The following are possible causes of AMS and coma. See “Coma mimics” for differential diagnoses in which consciousness is preserved (e.g., locked-in syndrome, akinetic mutism).

Causes of altered mental status and coma [8][11][13]
Possible causes
Primary CNS dysfunction
Hypoxia and/or hypoperfusion
Endocrine and/or metabolic



Causes of altered mental status and coma: AEIOU TIPS (Alcohol, Epilepsy/Electrolytes/Endocrine, Insulin, Overdose/Oxygen, Uremia, Trauma/Temperature, Infection, Poisons/Psychiatric, Stroke/Seizures/Shock) [14]

Gradual onset of AMS or coma suggests infection, metabolic processes, or an enlarging space-occupying lesion. [8]

Depends on the site of initial assessment (e.g., ED vs. ward), clinical stability, expected course, and individual patient factors. [8]

  • Consider ICU admission for patients requiring frequent monitoring, hemodynamic stabilization, and/or respiratory support.
  • Consider urgent interfacility transfer for neurosurgical intervention if not available locally.
  • Consider discharge home in patients with all of the following:
    • Identified and treated acute and reversible causes (e.g., hypoglycemia, opiate overdose)
    • Return to baseline mental status
    • Stability on observation
    • No other medical issues requiring inpatient treatment

In patients with altered mental status due to long-acting agents (e.g., opioid overdose from methadone, hypoglycemia from sulfonylureas), consider admission for observation even if the mental status has returned to baseline.

The following conditions can mimic coma. See “Causes of AMS and coma” for underlying etiologies.

The differential diagnoses listed here are not exhaustive.

All of the relevant financial relationships listed for the individuals below have been mitigated. For details, please review our full conflict of interest (COI) policy.

  • Alexandra Willis, copyeditor, was previously employed by OPEN Health Communications.
  1. Cooksley T, Rose S, Holland M. A systematic approach to the unconscious patient. Clin Med (Lond). 2018; 18 (1): p.88-92. doi: 10.7861/clinmedicine.18-1-88 . | Open in Read by QxMD
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