Overview of coma and impaired consciousness

[Cami]

Coma is unresponsiveness from which the patient cannot be aroused and in which the patients eyes remain closed. Impaired consciousness refers to similar, less severe disturbances of consciousness; these disturbances are not considered coma. The mechanism for coma or impaired consciousness involves dysfunction of both cerebral hemispheres or of the reticular activating system (also known as the ascending arousal system). Causes may be structural or nonstructural (eg, toxic or metabolic disturbances). Damage may be focal or diffuse. Diagnosis is clinical; identification of cause requires laboratory tests and neuroimaging. Treatment is immediate stabilization and specific management of the cause. For long-term coma, adjunctive treatment includes passive range-of-motion exercises, enteral feedings, and measures to prevent pressure ulcers.
Decreased or impaired consciousness or alertness refers to decreased responsiveness to external stimuli. Severe impairment includes

Coma: The patient cannot be aroused, and the eyes are closed and do not open in response to any stimulation.
Stupor: The patient can be awakened only by vigorous physical stimulation.

Less severely impaired levels of consciousness are often labeled as lethargy or, if more severe, obtundation. However, differentiation between less severely impaired levels is often imprecise; the label is less important than a precise clinical description (eg, “the best level of response is partial limb withdrawal to nail bed pressure”).
Delirium differs because cognitive disturbances (in attention, cognition, and level of consciousness) fluctuate more; also, delirium is usually reversible. Patients with delirium may have periods of appropriate attention and cognition alternating with periods of impaired attention and cognition.