What are the causes of altered sensorium?

Causes of Altered Sensorium

Altered sensorium is most commonly caused by neurological disorders, metabolic derangements, infections, toxins, and cardiovascular conditions that affect brain function. 1

Neurological Causes

• Cerebrovascular events - Strokes (both ischemic and hemorrhagic), intracranial hemorrhage, and transient ischemic attacks can lead to altered sensorium 2
• Central nervous system infections - Encephalitis, meningitis, and brain abscesses can cause inflammation and altered mental status 1
• Head trauma - Concussions, contusions, and intracranial bleeding following trauma 1, 2
• Seizures and post-ictal states - Both during seizures and in the recovery period afterward 1
• Brain tumors - Primary or metastatic lesions causing increased intracranial pressure or direct brain tissue involvement 2
• Neurodegenerative disorders - Advanced stages of dementia, Parkinson's disease, and other degenerative conditions 3

Metabolic and Endocrine Causes

• Diabetic emergencies - Diabetic ketoacidosis (particularly with severe acidosis pH <7.2), hyperosmolar hyperglycemic state, and severe hypoglycemia 1, 4, 5
• Electrolyte abnormalities - Particularly:
  • Hyponatremia or hypernatremia (sodium <130 or >150 mmol/L) 1, 6, 2
  • Hypocalcemia or hypercalcemia 1
  • Hypokalemia (<2.0 mEq/L) or hyperkalemia (>6.0 mEq/L) 1
• Acid-base disturbances - Severe metabolic acidosis (the primary determinant in diabetic ketoacidosis) 5, 6
• Hepatic encephalopathy - Due to liver failure and accumulation of toxins 2
• Uremic encephalopathy - Due to renal failure 1
• Hypoxia - Insufficient oxygen delivery to the brain from any cause 2
• Vitamin deficiencies - Particularly B12 and vitamin E deficiencies affecting neurological function 3

Infectious Causes

• Systemic infections - Sepsis with or without septic shock 6
• Central nervous system infections - Encephalitis, meningitis, and brain abscesses 1
• Tick-borne diseases - Rocky Mountain spotted fever, ehrlichiosis, and anaplasmosis can cause altered mental status 1
• Endocarditis - Can lead to altered sensorium through embolic phenomena or metabolic derangements 1

Toxins and Substances

• Medication effects - Particularly sedatives, opioids, anticholinergics, and certain antipsychotics 2
• Alcohol - Both intoxication and withdrawal states (delirium tremens) 2
• Recreational drugs - Stimulants, hallucinogens, and depressants 2
• Carbon dioxide narcosis - Due to respiratory failure and CO2 retention 2
• Other toxins - Including heavy metals, industrial chemicals, and certain plant toxins 2

Cardiovascular Causes

• Shock states - Particularly when systolic blood pressure falls below 90 mmHg 6
• Cardiac arrhythmias - Leading to decreased cerebral perfusion 1
• Hypertensive emergencies - With end-organ damage affecting the brain 2
• Hypoperfusion states - Due to heart failure or other causes of reduced cardiac output 2

Special Considerations

• Combined factors often worsen altered sensorium - For example, the combination of severe acidosis and hyperosmolarity in diabetic ketoacidosis has a synergistic effect on depressing consciousness (61% sensitivity, 87% specificity) 5
• Severity indicators - White blood cell count >25 x 10^6/L, systolic blood pressure <90 mmHg, and serum osmolality >320 mOsm/kg are independent predictors of altered sensorium severity 6
• Neuroimaging findings - MRI and CT scans often reveal cerebrovascular accidents (both hemorrhagic and ischemic) as common structural causes of altered sensorium 2

Diagnostic Approach

• Prioritize rapid assessment of treatable causes - Particularly hypoglycemia, hypoxia, and drug overdose 2
• Laboratory evaluation - Complete blood count, comprehensive metabolic panel, arterial blood gases, toxicology screen, and blood cultures when indicated 5, 6, 2
• Neuroimaging - CT or MRI of the brain to identify structural causes 1, 2
• Lumbar puncture - When central nervous system infection is suspected, with examination of cerebrospinal fluid for cells, protein, glucose, and potential pathogens 1