Brain Injury Newsroom

How Does a Traumatic Brain Injury Affect Consciousness

A TBI can cause problems with arousal, consciousness, awareness, alertness, and responsiveness. Generally, there are five abnormal states of consciousness that can result from a TBI: stupor, coma, persistent vegetative state, locked-in syndrome, and brain death.

Stupor is a state in which the patient is unresponsive but can be aroused briefly by a strong stimulus, such as sharp pain. Coma is a state in which the patient is totally unconscious, unresponsive, unaware, and unarousable. Patients in a coma do not respond to external stimuli, such as pain or light, and do not have sleep-wake cycles. Coma results from widespread and diffuse trauma to the brain, including the cerebral hemispheres of the upper brain and the lower brain or brainstem. Coma generally is of short duration, lasting a few days to a few weeks. After this time, some patients gradually come out of the coma, some progress to a vegetative state, and others die.

Patients in a vegetative state are unconscious and unaware of their surroundings, but they continue to have a sleep-wake cycle and can have periods of alertness. Unlike coma, where the patients eyes are closed, patients in a vegetative state often open their eyes and may move, groan, or show reflex responses. A vegetative state can result from diffuse injury to the cerebral hemispheres of the brain without damage to the lower brain and brainstem. Anoxia, or lack of oxygen to the brain, which is a common complication of cardiac arrest, can also bring about a vegetative state.

Many patients emerge from a vegetative state within a few weeks, but those who do not recover within 30 days are said to be in a persistent vegetative state (PVS) . The chances of recovery depend on the extent of injury to the brain and the patient's age, with younger patients having a better chance of recovery than older patients. Generally adults have a 50 percent chance and children a 60 percent chance of recovering consciousness from a PVS within the first 6 months. After a year, the chances that a PVS patient will regain consciousness are very low and most patients who do recover consciousness experience significant disability. The longer a patient is in a PVS, the more severe the resulting disabilities will be. Rehabilitation can contribute to recovery, but many patients never progress to the point of being able to take care of themselves.

Locked-in syndrome is a condition in which a patient is aware and awake, but cannot move or communicate due to complete paralysis of the body.