Traumatic Brain Injury Levels of Consciousness
Loss of consciousness is a common but alarming consequence of traumatic brain injury. Traumatic brain injury victims may lose consciousness for minutes, for weeks, or forever. To help determine the extent of traumatic brain injury and the chance for regaining consciousness, doctors classify a traumatic brain injury victim into one of six abnormal conscious states: stupor, coma, vegetative state, persistent vegetative state, locked-in syndrome, and brain dead.
Stupor is an excessively long sleeplike state from which a person can be awakened only by loud noises or by intense pain. Traumatic brain injury can damage areas of the brain stem that control consciousness. Any bleeding or accumulation of blood puts pressure on these areas, causing further damage. Brain tumor or abscess also puts pressure on these areas. Cardiac arrest, aneurysms, cerebral infarction (stroke), seizures, hyperthyroidism, hypothermia, or hyperthermia can also cause stupor.
Coma is a profound state of unconsciousness in which a person cannot be awakened by pain or by vigorous stimulation. Interestingly, a person in a coma does not always lie still or quiet. Sometimes a person can talk or perform other functions that appear to be conscious acts but are not.
Doctors use the Glasgow Coma Scale or the Rancho Los Amigos Scale to measure a coma's severity. The Glasgow Coma Scale uses a 15 point scale to assess damage to the brain and to help establish a prognosis. The Rancho Los Amigos Scale is a complex scale that describes eight levels of coma and is used within the first weeks or months of coma.
As a coma deepens or progresses, brain responsiveness and chances for recovery decrease. For individuals who emerge from coma, recovery is slow and gradual. Many people emerge from a coma with physical, intellectual, and psychological impairments that require special treatments. Some people may never progress beyond very basic responses, while others recover with full awareness. Other people who do not recover slip from coma into vegetative or persistent vegetative states.
Traumatic brain injury victims in a vegetative state are unconscious and unaware of their surroundings. They may continue to have short periods of alertness and may move, groan, or show reflex responses. Vegetative state can be caused by damage to the parts of the brain that control thinking, memory, consciousness, and speech (cerebral hemispheres). A person with damage to these areas may not have damage to the part of the brain that coordinates movement and balance (cerebellum) or the part of the brain that controls breathing and heart rate (brainstem).
Many people can emerge from a vegetative state within a few weeks. However, if a person does not recover from a vegetative state, the person is deemed to be in a persistent vegetative state.
Persistent Vegetative State
Vegetative state that lasts for more than 30 days is referred to as persistent vegetative state. Persistent vegetative state recovery depends on the extent of brain injury and the person's age. Typically, younger people have a better chance of recovery than do older people. Adults have about a 50 percent chance of recovery, whereas children have about a 60 percent chance of recovery.
After a year, the chances of recovery from a persistent vegetative state are very low, and most patients who do recover consciousness will be severely disabled. The longer a patient is in a persistent vegetative state, the worse the disabilities are.
Locked-in syndrome is an exceptionally frustrating state of consciousness for a victim. Due to paralysis of the whole body, a person cannot communicate or move but is aware and awake. Unlike persistent vegetative state, in which only upper portions of the brain are damaged, locked-in syndrome is caused by damage to lower portions of the brain that control movement and mobility. Thinking, emotions, and memory are intact.
Most locked-in syndrome patients can communicate by blinking their eyes. Some people have the ability to move certain facial muscles as well. Most locked-in syndrome patients do not regain motor control.
A brain dead state reflects the absence of brain function. Before life support equipment was invented, the body would die as soon as the brain died. Brain death is irreversible. A brain dead person has no electrical activity and no clinical evidence of brain function on physical examination, with no response to pain, absent cranial nerve reflexes, and no spontaneous breathing. It is important to distinguish between brain death and states that mimic brain death like coma, hypothermia, and intoxication or drug overdose.
To pronounce a person brain dead, legal criteria usually require neurological exams by two independent doctors. Doctors rigorously test to determine if a person is brain dead or only appears to be brain dead. These tests must show complete absence of brain function, including a completely flat electroencephalogram (EEG), which measures electrical activity in the brain. Cranial blood flow scans and tests such as positron emission tomography (PET) or functional magnetic resonance imaging (fMRI) that show complete absence of brain blood flow can be used to confirm the diagnosis without performing an EEG. In 1980 the Uniform Determination of Death Act was proposed in the United States in an attempt to standardize the legal criteria across all the states.
Read more about the legal criteria to pronounce a person brain dead or other traumatic brain injury legal information. Read other articles on this site to learn more about traumatic brain injury causes, complications, and treatments.
[Last revision: July 2009]