COMA

Coma is a state of deep unconsciousness characterized by the inability to be awakened and the absence of meaningful responses to external stimuli. People in a coma do not exhibit awareness of themselves or their surroundings, and purposeful movement is not possible. The sleep-wake cycle is typically disrupted, although reflexive responses may persist. Coma results from widespread dysfunction of the brain, most often involving the reticular activating system in the brainstem and thalamocortical circuits. It is distinct from vegetative and minimally conscious states, as well as from locked-in syndrome.

Common causes include traumatic brain injury, stroke, brain hemorrhage, and severe reduction of blood flow or oxygen to the brain (hypoxia). Other etiologies are infections such as meningitis or encephalitis, metabolic disturbances (for example severe hypoglycemia, liver or kidney failure, electrolyte abnormalities), intoxication with drugs or toxins, and complications related to anesthesia.

Diagnosis relies on rapid assessment and investigations. Initial management focuses on airway, breathing, and circulation. Neurological examination and the Glasgow Coma Scale provide initial severity. Imaging with computed tomography or magnetic resonance imaging identifies structural injuries or lesions. Electroencephalography assesses brain electrical activity. Laboratory tests screen for metabolic or infectious causes; lumbar puncture may be performed if infection is suspected.

Treatment targets the underlying cause and prevention of complications. Supportive care in an intensive care unit is common, including protection of the airway, ventilation if needed, control of intracranial pressure, seizure prevention, and prevention of infections, ulcers, and blood clots. Prognosis varies widely and depends on the cause, duration of coma, age, and early brainstem reflexes. Some patients regain consciousness within days to weeks, while others remain in coma or transition to vegetative or minimally conscious states.