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Coma: Definition, Causes, Clinical Features & Prognosis

Coma is a state of profound unconsciousness from which a person cannot be aroused by any stimulus (voice, pain, light). It reflects bilateral cerebral hemisphere dysfunction or brainstem (reticular activating system) failure.

Common Causes

CategoryExamples
StructuralTBI, stroke (ischemic/hemorrhagic), tumor, hydrocephalus, herniation
Metabolic/ToxicHypoglycemia, hepatic encephalopathy, uremia, hyper/hyponatremia, overdose (opioids, benzos, alcohol), carbon monoxide
InfectiousMeningitis, encephalitis, brain abscess, sepsis
Hypoxic-ischemicCardiac arrest, asphyxia, severe anemia, CO poisoning
Seizure-relatedStatus epilepticus, post-ictal

Clinical Assessment

  • Glasgow Coma Scale (GCS): Eye (1–4) + Verbal (1–5) + Motor (1–6) = 3–15. ≤8 = coma.
  • Pupils: Size, symmetry, reactivity (cranial nerve III, brainstem).
  • Motor patterns: Decorticate (flexion), decerebrate (extension), flaccid.
  • Respiratory pattern: Cheyne-Stokes, central neurogenic hyperventilation, apneustic, ataxic.

Workup (Emergent)

  1. ABCs, glucose, naloxone/thiamine if indicated.
  2. Stat labs: CBC, BMP, LFTs, coagulation, toxicology, ABG, lactate.
  3. CT head (non-contrast) → MRI if CT negative.
  4. LP if infection suspected (after imaging).
  5. EEG if non-convulsive status epilepticus considered.

Prognosis

  • Depends on etiology, GCS, age, pupillary response, duration.
  • Metabolic/toxic comas often reversible; structural/hypoxic carry higher mortality.
  • Vegetative state / minimally conscious state may follow prolonged coma.

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