DESCRIPTION

Coma is defined as a sleep-like state in which the patient shows no awareness of their surroundings, has no purposeful response to environmental stimulus, and cannot be aroused. Coma may be a transient state from which patients emerge but may also progress to a permanent disorder of consciousness or to death. Often a medical emergency, immediate intervention may be required to preserve life and brain function.

• Coma is at the far end of a spectrum of acute impaired consciousness, which also includes the following:
  • Somnolence or lethargy: patient arousable but confused or drowsy; impaired responses to commands; poorly attentive
  • Delirium: a confused, agitated, or disoriented patient; often with significant fear and visual hallucinations
  • Stupor: deep sleep or unresponsiveness from which the patient can only be temporarily and transiently aroused
• Coma may progress to
  • Persistent vegetative state: chronic state (>1 month) with preserved autonomic functions and sleep–wake cycles but no awareness of self or surroundings
  • Brain death: complete lack of cortical and brainstem responses

EPIDEMIOLOGY

Incidence varies by age, season (infection), and ethnicity (inborn errors of metabolism [IEM]).

ETIOLOGY

Coma etiology can be traumatic or nontraumatic. Infection is a common cause of nontraumatic coma.

PATHOPHYSIOLOGY

Dysfunction of the reticular activating system in the brainstem or bilateral cerebral dysfunction causes impaired arousal and consciousness.