Altered Level of Consciousness Causes

Aka: Altered Level of Consciousness Causes, Altered Mental Status Differential Diagnosis, ALOC Causes

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II. Causes: Pitfalls - critical diagnoses that are easily missed

  1. Toxicologic Pitfalls
    1. See Drug Induced Altered Level of Consciousness Causes
    2. Carbon Monoxide Poisoning
    3. Toxic Alcohol ingestion
    4. Alcohol Withdrawal Syndrome
    5. Chronic Salicylate Toxicity
    6. Anticholinergic drug toxicity
    7. Neuroleptic Malignant Syndrome or Serotonin Syndrome
    8. Envenomation
    9. Opioid Overdose
    10. Benzodiazepine Overdose
  2. Endocrine Pitfalls
    1. Hypoglycemia
    2. Thyroid emergencies (Myxedema Coma, Thyroid Storm)
    3. Addisonian Crisis (Adrenal Insufficiency)
    4. Wernicke's Encephalopathy
  3. Infectious Pitfalls
    1. Cerebral Malaria
    2. Herpes Encephalitis
  4. Organ Failure Related Pitfalls
    1. Hypercarbia (CO2 Narcosis in COPD)
    2. Hepatic Encephalopathy
    3. Uremic encephalopathy
  5. Miscellaneous Pitfalls
    1. Non-convulsive Status Epilepticus
    2. Occult Trauma
    3. Thrombotic Thrombocytopenic Purpura

III. Causes: Mnemonics

  1. Mnemonic: AEIOU TIPS
    1. Alcohol (or Toxic Alcohols) or Abdominal Aortic Aneurysm
    2. Epilepsy (Status Epilepticus), Electrolytes, Hepatic Encephalopathy (or PRESS), endocrine problems
    3. Insulin (Hypoglycemia), Intussusception or Inborn Errors of Metabolism
    4. Opiates or Overdose
    5. Uremia
    6. Trauma (Closed Head Injury), Temperature (Hypothermia, hyperthermia), or Toxemia, Brain Tumor
    7. Infections (Sepsis, Meningitis, Encephalitis)
    8. Psychogenic, Pulmonary Embolism, Poisoning (Toxin Ingestion)
    9. Space occupying lesions, Stroke (including Intracranial Pressure), Shock, Seizure, shunt (ventriculoperitoneal)
  2. Mnemonic: I WATCH DEATH
    1. Infection
    2. Withdrawal
    3. Acute metabolic causes
    4. Trauma
    5. CNS Causes
    6. Hypoxia
    7. Deficiencies (Nutritional)
    8. Endocrinopathies (Adrenal Insufficiency, Myxedema, Hyperthyroidism)
    9. Acute Vascular Causes
    10. Toxins or Drugs
    11. Heavy Metals
  3. Mnemonic: SMASHED
    1. Sepsis or Substrates (abnormal Glucose, Thiamine deficiency)
    2. Meningitis or Mental Illness (acute Psychosis)
    3. Accident (Head Trauma, CVA) or Alcohol Intoxication or withdrawal
    4. Seizing or Stimulants
    5. Hypertension, Hyperthyroidism, Hypercarbia or Hypotension, Hypothyroidism, Hypoxia
    6. Electrolytes (Sodium, Hypercalcemia) or Encephalopathy
    7. Drugs (Drug Withdrawal, Carbon Monoxide, Lithium, steroids, Salicylates...)

IV. Causes: Neurologic - Supratentorial

  1. Unilateral hemispheric disease AND Brainstem Herniation
  2. Closed Head Injury (Concussion or Contusion)
  3. Meningitis or Encephalitis
  4. Hypertensive Encephalopathy
  5. Subarachnoid Hemorrhage or other Intracranial Hemorrhage (e.g. Epidural Hematoma, Subdural Hematoma)
  6. Ventriculoperitoneal Shunt Malfunction
  7. Cerebrovascular Accident
  8. Parkinsonism
  9. Myasthenia Gravis
  10. Intracranial Mass
  11. Demyelinating Disease (e.g. Multiple Sclerosis)
  12. Seizure
    1. Post-ictal State
    2. Non-convulsive Status Epilepticus

V. Causes: Neurologic - Infratentorial

  1. Basilar Artery Occlusion
  2. Brainstem tumor
  3. Cerebellar Hemorrhage
  4. Pontine Hemorrhage
  5. Traumatic posterior fossa Hemorrhage

VI. Causes: Toxins

  1. See Toxin Induced Altered Level of Consciousness Causes (includes medication causes)
  2. See Unknown Ingestion
  3. See Date Rape Drug
  4. Carbon Monoxide Poisoning
  5. Toxic Alcohol ingestion (e.g. Ethylene Glycol, Methanol)
  6. Alcohol Intoxication or Alcohol Withdrawal Syndrome
  7. Chronic Salicylate Toxicity
  8. Anticholinergic drug toxicity
  9. Neuroleptic Malignant Syndrome
  10. Serotonin Syndrome
  11. Envenomation
  12. Excited Delirium (Cocaine, Methamphetamine, PCP, or other psychostimulant induced)
  13. Opioid Overdose
  14. Benzodiazepine Overdose

VII. Causes: Cardiopulmonary

  1. Hypoxia
  2. Hypercarbia
  3. Congestive Heart Failure (CHF)
  4. Pulmonary Embolus
  5. Hypertensive Encephalopathy

VIII. Causes: Gastrointestinal and Renal

  1. Hepatic Encephalopathy
  2. Wernicke's Encephalopathy
  3. Uremic encephalopathy
  4. Peritonitis

IX. Causes: Electrolyte disturbance

  1. Hypercalcemia
  2. Hypermagnesemia
  3. Hyponatremia
  4. Hypernatremia
  5. Hypophosphatemia

X. Causes: Endocrine

  1. Adrenal Insufficiency (Addisonian Crisis)
  2. Diabetes Mellitus
    1. Hypoglycemia
    2. Diabetic Ketoacidosis
    3. Hyperosmolar Hyperglycemic Nonketotic Coma
  3. Thyroid disease
    1. Myxedema Coma (severe Hypothyroidism)
    2. Thyroid Storm

XI. Causes: Infectious

  1. Meningitis or Encephalitis
  2. Sepsis
  3. Urinary Tract Infection
  4. Pneumonia
  5. Severe Viral Infection (e.g. Covid19)

XII. Causes: Miscellaneous

  1. Heat Stroke or Malignant Hyperthermia
  2. Hypothermia
  3. Vasculitis
  4. Hyperviscosity Syndromes (e.g. Thrombotic Thrombocytopenic Purpura)

XIII. References

  1. Herbert et al. in Herbert (2014) EM:Rap 14(11): 10-12
  2. Veauthier (2021) Am Fam Physician 104(5): 461-70 [PubMed]

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