Coma

Coma is a profound state of unconsciousness from which a person cannot be awakened by external stimuli. Traumatic brain injury is a prominent cause of coma. Traumatic brain injury disrupts the brain functions that control consciousness and life support. Coma is a complex condition, as it has many causes and complications. Understanding coma and the many ways it is treated can help the families of brain injury victims cope with the troubling condition.

Causes of Coma

Coma is caused by a number of physiological disturbances that disrupt normal brain function. A common cause of coma is traumatic brain injury. Brain injury can damage parts of the brain that control consciousness. Two ways in which brain injury can result in coma are focal and diffuse axonal injury.

Focal brain injury is brain damage affecting a specific spot in the brain, such as the location where an object penetrates brain tissue. Open head injury may expose brain tissue to the environment and cause infection. A person can lose consciousness if the focal injury occurs in an area of the brain that controls consciousness (cerebrum and cerebral cortex).

Diffuse axonal brain injury is widespread damage affecting several areas of the brain. Whiplash is a common cause of diffuse axonal injury. During whiplash, the brain collides violently with the inside of the boney skull. Diffuse axonal injury shears neuron connections, which prevents areas of the brain from communicating with one another to promote consciousness. Closed head injury can increase intracranial pressure. An increase of pressure within the skull destroys delicate brain tissue and restricts blood and oxygen flow to the brain. Lack of blood and oxygen flow can cause a person to lose consciousness.

Coma Symptoms

Coma symptoms can appear suddenly or emerge slowly over time. Severe brain injuries produce coma symptoms more rapidly than do moderate brain injuries. If coma symptoms develop slowly, a person may feel mildly drowsy or confused. If brain tissue infection develops, a person may have migraines, body aches, fever, and dizziness prior to the coma onset.

As coma symptoms progress, a person may not respond to stimuli. A person may appear lethargic and may not be able to move his or her body. If a person is able to move, they may have tremors. It is important to note that while any movement may appear to reflect conscious acts, they are not; a comatose person may have injury to areas of the brain that control consciousness, thinking, or feeling, but not to areas of the brain that control simple movements.

A person may also lose gag reflex, fail to respond to noxious stimuli (foul odors), and fail to respond to pain.

Coma Diagnosis

A coma diagnosis requires a doctor to perform a complete physical and neurological evaluation. Doctors also use x-rays such as computed tomography scans (CT scans), magnetic resonance imaging (MRI), and electroencephalography (EEG) to locate injury in the brain.

Physical & Neurological Evaluation

During physical examination, doctors take the person's pulse and blood pressure. They also evaluate breathing patterns to ensure there is regular respiration. If there is irregular heart beat (arrhythmia) or labored breathing, the person is put on a respirator to help maintain normal blood and oxygen flow to the brain.

A doctor may also look into the person's eyes at the optic nerve. If the optic nerve is swollen, this may indicate increased intracranial pressure. Increased intracranial pressure is a troubling complication of traumatic brain injury. As an injured brain swells, pressure within the skull builds and destroys delicate brain tissue, compounding brain injury and complicating recovery.

Neurological evaluation is crucial to diagnose coma. Two widely-used scales for evaluation of brain activity and the presence of coma are the Glasgow Coma Scale and the Rancho Los Amigos Scale. The Glasgow Coma Scale is a simple, 15-point scale that evaluates a person's level of consciousness and chances for recovery. The Rancho Los Amigos Scale is a much more complex scale that categorizes a coma patient into one of eight separate levels and gives doctors insight into the patient's progression throughout treatment.

X-Rays and Imaging

CT scans and MRI's are used to see where in the brain injury occurs. An EEG may be performed to confirm or rule out seizures that may cause coma following brain injury. An EEG measures brain electrical activity. An absence of brain electrical activity indicates a lower state of consciousness, such as coma.

Coma Complications

Common coma complications include pressure or bed sores, and skeletal or muscular atrophy caused by lying in bed for long periods of time without moving. Multiple organ failure is a common complication, as an injured brain may not be able to control organ function.

Other coma complications result from secondary brain injuries caused by swelling and increased intracranial pressure. The brain often swells after injury. Water and blood may collect in the brain, increasing its size. The swelling causes excessive pressure in the skull. Increased intracranial pressure requires close monitoring and immediate treatment.

Coma Treatment

Coma caused by traumatic brain injury is treated by addressing the underlying brain injury. Treatment can involve decreasing intracranial pressure, administering strong medications, and hyperventilation.

Decreasing Intracranial Pressure

Treating brain swelling and intracranial pressure can be difficult. To relieve pressure, a surgeon may perform a craniotomy. During a craniotomy, a surgeon drills into the skull, creating an opening through which excess blood and fluid may drain, decreasing intracranial pressure. In more severe cases, a portion of the skull is removed. Once pressure has diffused, a surgeon will then replace the removed skull fragment with a synthetic skull fragment to protect the brain.

Another common procedure used to relieve intracranial pressure is hyperventilation. Hyperventilation involves using a ventilator to increase a person's breathing rate. An increase in breathing rate causes blood vessels to constrict, which prevents blood from pouring into the brain and increasing intracranial pressure. Hyperventilation temporarily treats intracranial pressure before surgeries are performed.

Other Coma Treatments

If seizures cause coma, doctors administer strong medications to control convulsions. If the coma is caused by brain tissue infection, antibiotics are administered.

Many coma patients are unable to breathe and are therefore put on a respirator. For hydration and nutrition, coma patients are given intravenous fluids.

Coma Prognosis

Coma prognosis depends on the severity of brain injury. Coma patients with more moderate brain injury and fewer complications have a better prognosis than do patients with severe brain injury.

A person can regain consciousness from coma within a few weeks; it is rare that a person stays comatose for more than five weeks. If a person does not regain consciousness within a few weeks, he or she is said to be in a vegetative state. The longer a person is comatose, the lower chances are for recovery. Many people die from underlying brain injury.

People who do regain consciousness may have problems with complex thinking and with emotional stability. A person may need assistance with self-care activities such as bathing. Even after regaining consciousness, some people are unable to live independently.

In addition to coma, other states of consciousness are associated with traumatic brain injury. To learn more about traumatic brain injury or other states of consciousness, please read other articles on this site.

[Last revision: March 2007]