Unconsciousness

Unconsciousness is a state of reduced or absent awareness of self and surroundings, often with diminished or absent responsiveness to stimuli. It can be transient or prolonged, and is not the same as sleep. It encompasses conditions such as syncope (fainting), stupor, coma, vegetative state, and minimally conscious state.

Mechanisms: Consciousness arises from interactions between the brainstem reticular activating system, thalamus, and cerebral cortex. Unconsciousness results when these networks are suppressed or disconnected, due to reduced blood flow or oxygen, metabolic disturbance, structural injury, seizures, or pharmacologic effects.

Causes: Cardiovascular (syncope from transient cerebral ischemia or hypotension), neurological (traumatic brain injury, stroke, tumor, seizures), metabolic/toxic (hypoglycemia, hepatic or renal failure, drug overdose, alcohol), infectious/inflammatory (meningitis, encephalitis), and postoperative anesthesia.

Clinical assessment and diagnosis: Immediate evaluation follows the ABCs. Consciousness level is commonly scored with the Glasgow Coma Scale. Additional evaluation includes pupils, motor responses, vital signs; imaging (CT, MRI), EEG, and laboratory tests to identify underlying causes. Distinctions among levels include coma (no wakefulness or purposeful response), vegetative state (wakefulness without awareness), minimally conscious state (limited inconsistent signs of awareness), and syncope (brief loss with rapid recovery).

Management and prognosis: Acute management focuses on securing the airway, ensuring adequate breathing and circulation, preventing further injury, and monitoring in a hospital setting. Treatment targets the underlying cause; for example, reversal of hypoglycemia, stabilization after stroke, administration of antidotes for overdose, or infection control. Recovery depends on cause and duration; some conditions resolve quickly, others result in permanent impairment. Complications may include aspiration, infections, and deconditioning.