MD Notes

creation date: 2026-08-16 23:58
tags: Workups

Altered Mental Status

Background

Altered mental status (AMS) is broadly defined as a change in cognitive function or level of consciousness. AMS is present in 5-10% of ED patients, with rates higher in the elderly.

Altered mental status involves some change to either the content of consciousness (how aware someone is relating to the environment and interacting with the environment) or the level of arousal (ranging from coma to unable to focus/easily distractible to fully awake).

Risk factors and precipitants for delirium is discussed separately.

Pathophysiology

AMS is due to either depression of both cerebral hemispheres, which play a major role in cognition, or dysfunction of the reticular activating system, which play a major role in sleep-wake cycle and wakefulness.

Differential Diagnosis

Vascular

Infection/Inflammation

Neoplasm

  • Large brain tumours
  • Carcinomatous meningitis
  • Paraneoplastic limbic encephalitis

Degenerative

Iatrogenic/Idiopathic/Intoxication

  • Intoxication and overdose
  • Withdrawal of alcohol, benzodiazepines, barbiturates, heroin
  • Medications with class effect:
    • Anticholinergics
    • Antiepileptics
    • Antihistamines (including H2 blockers such as cimetidine and famotidine)
    • Antipsychotics (via sedative effects or neuroleptic malignant syndrome
    • Benzodiazepines
    • Calcineurin inhibitors
    • Cephalosporins (especially in the setting of renal failure)
    • Dopamine agonists and levodopa
    • Fluoroquinolones
    • Monoamine oxidase inhibitors
    • Muscle relaxants (if centrally acting)
    • Opiates Steroids
    • Tricyclic antidepressants
  • Medications without class effect:
    • Antiemetics (promethazine)
    • Antihypertensives (clonidine, nifedipine)
    • Antidepressants (bupropion, mirtazapine, paroxetine, trazodone)
    • Antifungal agents (micafungin, voriconazole, posaconazole)
    • Antiparasitic agents (mefloquine)
    • Antiviral agents (amantadine, valacyclovir (especially in renal impairment))
    • Biological agents (bevacizumab (due to hypertensive encephalopathy), interferon alpha)
    • Chemotherapy agents (asparaginase, bicalutamide, cytarabine, decitabine, fluorouracil, ifosfamide, irinotecan, methotrexate, nelarabine, paclitaxel, thalidomide)
    • Mood stabilizers (lithium)
    • Sleep aids (zolpidem, eszopicione)
    • Others (acetazolamide, aspirin, digoxin, disulfiram, dronabinol)

Congenital

Autoimmune/Anatomic

  • Neuropsychiatric lupus
  • Behcet syndrome
  • Vasculitis
  • Acute disseminated encephalomyelitis
  • Hashimoto encephalopathy
  • Autoimmune limbic encephalitis
  • Hydrocephalus

Trauma

  • Concussion
  • Subdural hematoma

Endocrine/Metabolic/Emotion

  • Electrolyte imbalances (hyponatremia, hypernatremia, hypercalcemia, hypermagnesemia, hypophosphatemia)
  • Endocrine (hypothyroidism, hyperthyroidism, hypocortisolism, hypercortisolism, hypoglycemia, hyperglycemia)
  • Hepatic encephalopathy
  • Uremic encephalopathy
  • Acute pancreatitis
  • Hypoxia and hypercarbia
  • Vitamin deficiencies (thiamine, B12)
  • Hypothermia, hyperthermia
  • Marchiafava-Bignami disease
  • Porphyria

Mimics

Mimics which is not considered AMS but may appear as include:

  • Psychosis
  • Locked-in syndrome
  • Akinetic-mutism
  • Catatonia

Initial Evaluation

History

Important components of history to start with:

  • Acuity
  • Illness vs. injury
  • Focal vs. diffuse

It may be difficult to get a full history but EMS report and collateral interviewing should focus on:

  • Determining baseline cognitive function
  • Previous episodes of AMS
  • Symptoms of infection (eg. fever, headache, stiff neck, cough, dysuria)
  • Current medication and recent medication changes (especially anticholinergics, benzodiazepines, narcotics)
  • Recreational drug and alcohol use
  • History of recent trauma
  • Comorbid conditions that may contribute (cirrhosis, CKD, COPD, epilepsy, psychiatric disease, immune compromised status)

A number of tools exist for standardized evaluation:

  • Alert/Confused/Lethargic/Obtundation/Stupor/Coma
  • GCS
  • AVPU (quick form of GCS)
  • CAM (for delirium)
  • RASS & SAS (typically used for ICU)

Physical Exam

Physical includes:

  • ABCs
  • Vital signs
  • Focused neurological exam (initial presentation may just need an abridged version: vitals, GCS, motor, pupils)

Additionally, focus should be put on potential causes of AMS:

  • Signs of trauma
  • Evidence of toxidrome
  • Signs of infections
  • Evidence of tongue biting/incontinence
  • Signs of withdrawal
  • Percussion/auscultation (pneumonia, COPD)
  • Cardiovascular (endocarditis, CHF)
  • Skin (liver disease, needle marks)
  • Asterixis (metabolic encephalopathy)

Investigations

Initial investigation includes:

  • Serum glucose
  • CBC
  • Electrolytes, including calcium, magnesium, phosphorus
  • Liver and kidney function tests
  • Urinalysis and culture
  • Urine toxicology screen
  • Chest radiograph
  • ECG

Further investigations may be indicated depending on initial evaluation:

  • Brain imaging (if still unclear etiology, also mandatory for any with focal neurologic deficits or seizures)
  • Lumbar puncture (if meningitis suspected)
  • Serum ammonia, thyroid function tests, morning cortisol, vitamin B12, arterial blood gas
  • ESR, autoimmune serology
  • Blood cultures
  • Extended toxicology screen
  • EEG (for status epilepticus)

References

Tools / Guidelines

Additional Reading