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Severe Brain Injury, Coma

Definition :
A coma is a state of prolonged unconsciousness in which the brain functions at its lowest level of alertness. A person in a coma can't be awakened and doesn't respond purposefully to physical or verbal stimulation.

Various causes can bring on a coma — a traumatic head injury, an underlying illness such as diabetes or infection, a stroke, or as the result of a brain tumor.

Occasionally a doctor may induce a coma with drugs to protect the brain and give it a chance to heal after brain surgery, or when someone is experiencing prolonged seizures. Doctors may also use drug-induced coma to control brain swelling caused by a brain injury from head trauma, a stroke or an infection.

People can recover from comas. Recovery depends on the cause, the severity of the injury or illness, and what part of the brain was affected. It's rare for a coma to last more than two weeks.

The level of care and assistance a person may need following recovery from a coma varies and may change over time. Many options for treatment and rehabilitation are available.

A coma is the result of widespread and diffuse injury to the brain, and there are many causes for the types of injuries resulting in coma. The causes of coma fall into two general categories — anatomic causes and metabolic causes.

Anatomic causes
Anatomic causes of a coma result in disruption of the normal physical structures of the brain responsible for consciousness. Often, alcohol is a contributing factor to injuries leading to an anatomic cause for coma. Some of the primary causes of injuries that result in a coma with an anatomic cause are :

  • Transportation accidents
  • Acts of violence, such as assaults and child abuse
  • Suicide attempts involving firearms
  • Sports activities

These injuries may cause a coma because of how they affect the brain. Skull fractures can result in pieces of the skull pressing into the brain. If a foreign object pierces the skull, localized injury to the brain can occur.

Fractures can also bruise the brain (contusion), causing brain tissue to swell. Damage to major blood vessels in the brain can cause bleeding into and around the brain (hematoma). Severe brain injury also can result from a lack of oxygen to the brain, common with near-drowning victims.

Anatomical causes of comas that aren't the result of physical trauma include brain tumors and strokes. When a stroke occurs at the base of the brain (brainstem), a common side effect is a coma.

Metabolic causes
Metabolic causes of a coma are those that adversely affect brain function by changing the chemical environment of the brain. Some examples of these causes are :

  • Diabetes. Blood sugar levels that get too high (hyperglycemia) and stay too high or get too low (hypoglycemia) and stay too low can result in a coma.
  • Infections. Certain viral and bacterial infections can cause encephalitis, an inflammation of the brain, and meningitis, an inflammation of the membranes and fluid surrounding the brain and spinal cord. Severe cases of encephalitis and meningitis can result in a coma.
  • Organ failure. Liver failure may disturb your metabolism to a degree high enough to cause a coma. Kidney failure also may cause a coma.
  • Reye's syndrome. This rare but serious condition that can affect the blood, liver and brain is linked to giving children aspirin and can result in coma.

Risk Factor :
A coma is often the result of a traumatic brain injury, and factors more likely to cause traumatic injuries are :

  • Socioeconomic factors. Poverty is a primary risk factor for all types of injuries, including traumatic brain injuries. For children especially, low-income living can mean a more dangerous environment. Overcrowded housing, unsafe play areas and increased exposure to physical danger and are some of the conditions that can lead to accidents resulting in head and brain injuries.
  • Transportation accidents. Many traumatic brain injuries are the result of accidents involving cars, motorcycles, bicycles and pedestrians. These accidents are the major cause of traumatic brain injury in people younger than 75.
  • Violence. Many traumatic brain injuries are due to violence, such as assaults, child abuse and sports injuries.
  • Alcohol use. Many incidents that result in traumatic brain injuries involve alcohol.
  • Age. Falls are the leading cause of traumatic brain injuries in people older than 75, but the very young (age 4 and under) also are at risk.
  • Sex. Males are twice as likely as females are to suffer a traumatic brain injury. At nearly all ages, males are at much higher risk of all types of injury because they participate more often in activities that result in injury. They're also more likely to engage in risky behavior and rougher play.
  • Developmental disabilities. Children with both physical and psychological disabilities are more likely to suffer injuries, including head injuries.

In addition, various medical conditions put some people at greater risk of going into a coma. These include :

  • Diabetes
  • Reye's syndrome
  • Encephalitis
  • Stroke
  • Brain tumor

When to seek medical advice :
A coma is a complication of a severe brain injury. Seeking medical assistance immediately when a severe head injury is sustained is extremely important.

Anyone with signs of brain injury — such as convulsions or seizures, weakness or numbness in the extremities, repeated vomiting, slurred speech, inability to awaken from sleep, or dilation in one or both pupils — needs emergency medical care. These types of brain injuries can quickly become life-threatening.

A person in a coma typically has the following signs and Symptoms:
  • Closed eyes
  • Lack of consciousness
  • No response to stimuli, such as pain or light
  • Inability to be aroused
  • Lack of sleep-wake cycles

The spectrum of human consciousness
To understand what a coma is and isn't, think of human consciousness as a spectrum. Complete awareness is at one end and brain death is at the other. Many of the altered states of awareness on this spectrum are the result of some type of brain malfunction or injury.

These conditions are in turn associated with different levels of consciousness. Some level of consciousness means a person can still respond — in varying degrees — to stimulation. A person in a coma, however, cannot.

In addition to coma, other states of consciousness as a result of brain injury — and signs and symptoms associated with them — are :

  • Stupor. Someone in a stupor is unresponsive but can be aroused briefly — for example, by sharp pain.
  • Vegetative state. People in a vegetative state are unconscious and unaware of their surroundings, but they have a sleep-wake cycle and may have brief times when they may appear to be alert. In a vegetative state, they may open their eyes, make noises and move. Like those in a coma, people may come out of a vegetative state after a few weeks.
  • Persistent vegetative state. A vegetative state lasting for more than 30 days is called a persistent vegetative state. The likelihood of recovery from this condition depends on the severity of the cause and the age of the person — younger people have a better chance of recovery. The longer someone is in a persistent vegetative state the more severe the resulting disabilities are likely to be.
  • Locked-in syndrome. People in this condition are aware and awake, but can't move or speak because of complete paralysis to their bodies.
  • Brain death. When brain death occurs, there is no sign of any brain functioning. This condition is not reversible.

If you visit a family member who is in a coma, talk to him or her in your regular tone of voice. If having a conversation with others nearby, assume that a comatose patient can hear you and understand what you're saying. Even though he or she may not respond to stimuli and appears to lack consciousness, some people who have emerged from a coma have reported remembering others' conversations.

When someone suffers a head injury, medical personnel first stabilize the condition and then evaluate how severe the injuries are by measuring reflexes, temperature, blood pressure, pulse, breathing rate and pupil size. Blood and urine samples are analyzed to determine if there's a metabolic cause of a coma.

A doctor or other medical professional determines the severity of a brain injury by assessing the level of consciousness and neurological functioning. The severity of a brain injury is determined by using the Glasgow Coma Scale. This test is often done at the scene of an accident or in the emergency room. This 15-point test measures eye opening, verbal response and motor response to document the level of neurological function.

Many kinds of assessments and tests can be done to distinguish between coma and other states of unconsciousness. Imaging tests help doctors pinpoint areas of brain injury. These locations also help determine the particular state of unconsciousness. Some of the tests and assessments that doctors may use include:

  • Cerebral angiogram. A cerebral angiogram is a type of X-ray. During this procedure, a flexible tube (catheter) is inserted into a large artery — usually in your groin — and threaded past your heart into the cerebral arteries in your brain. A special dye (contrast medium) is then injected into the catheter, and X-rays are taken as the dye fills these arteries. A cerebral angiogram provides a clear picture of the arterial blood flow, but the procedure isn't without risks, including bleeding at the catheter insertion site, infection and stroke.
  • Computerized tomography (CT). A CT scan uses a sophisticated X-ray machine linked to a computer to produce detailed, two-dimensional images of your brain. This is the best imaging test for assessing brain injuries because it can show bone fractures, hemorrhages or other bleeding and bruising, and brain tissue swelling. You lie still on a movable table that's guided into what looks like an enormous doughnut where the images are taken. A special dye may be injected into your bloodstream after a few CT scans are taken. CT scans are good for detecting blood clots, swelling, or compression in the brain. Not all types of brain injuries show up on CT scans. A CT scan generally takes less than 10 minutes.
  • Electroencephalography (EEG). An EEG measures the waves of electrical activity your brain produces. Small electrodes are attached to your scalp with paste or an elastic cap as you lie still. At times, a light may be flashed in your eyes. These actions are meant to stimulate your brain. The electrodes pick up the electrical impulses from your brain and send them to the EEG machine, which records your brain waves.
  • Magnetic resonance imaging (MRI) scan. This scan uses magnetic fields and radio waves to generate images of the brain. You lie inside a cylindrical machine for 15 minutes to an hour. MRI scans are particularly useful for examining the brainstem and deep brain structures. Sometimes a special dye is injected into your bloodstream during the procedure. The dye can help distinguish damaged brain tissue from healthy tissue.
  • Other brain scans. Other tests, such as magnetic resonance spectroscopy (MRS), single-photon emission computerized tomography (SPECT) and positron emission tomography (PET) scanning, help doctors gauge brain activity by studying brain metabolism and chemistry and blood flow within the brain. These scans can be combined with an MRI to help doctors understand the effects of a brain injury on brain activity and function.

Complications :
A coma usually lasts only a few days or weeks. Although some people gradually recover, others enter a vegetative state or die.

Complications that a person in a coma may experience commonly include pressure sores on the skin from lying in a bed, bladder infections, pneumonia and sometimes progressive multiple organ failure.

A coma is a medical emergency, and attention first is given to maintaining the person's respiration and circulation. Assistance with breathing, administration of fluids and blood, and other supportive care may be necessary. If head trauma hasn't been ruled out as the cause, emergency personnel will stabilize the person's neck in case there's a fracture.

Treatment of anatomic causes
Ideally doctors can determine the cause of the coma quickly in order to treat potentially reversible conditions. If the coma's cause is anatomic, surgery may be performed to repair the skull or remove a foreign object. Many people with severe head injuries need surgery to repair or remove bleeding or bruised parts of the brain.

Treatment of metabolic causes
If the coma's cause is a metabolic disorder, doctors make attempts to correct the underlying disorder. Antibiotic treatment may be used for a suspected or confirmed infection. Other treatments may focus on addressing an underlying disease, such as diabetes, asthma, kidney failure or liver disease. If the cause of a coma is a drug overdose, then glucose, a B vitamin (thiamine) and a medication that counteracts narcotic-type drugs may be given. Medication may also be given to counteract seizures, if they are present.

Lasting effects of comas
Sometimes the cause of a coma can be completely reversed, and the person will regain normal function. This is often the case for people who suffer a coma from a drug overdose. But depending on how severe the brain damage is, where the damage is located, and the duration of the condition causing the coma, the person may sustain permanent disabilities or may never regain consciousness.

The disabilities that may occur after being in a coma can be physical, such as partial paralysis. There may also be changes in the person's personality or mental ability. People who suffer a coma from head injuries tend to recover better than those in whom illness is the cause of the coma.

With the exception of people whose coma was caused by drug poisoning, only a small percentage of people who are in a coma for more than a few hours make a good recovery. Age may play a role in how well, and whether, a person recovers after a coma. Adults who stay in a coma for more than four weeks have a slim chance of regaining their previous level of functioning. On the other hand, children and young adults have regained functioning even after two months in a coma.

Maintaining physical fitness
Another aspect of treatment that's important for people who may be unconscious for extended periods is maintaining a healthy physical state. This includes taking measures to prevent pneumonia and bedsores and providing balanced nutrition. The person may also receive physical therapy to prevent permanent muscle contractures and deformities of bones, joints and muscles. These measures will make recovery less difficult if the person regains consciousness.

A coma that is the result of a brain injury is usually preventable. Here are some ways to help prevent brain injury :
  • Use seat belts and safety seats. Whenever you get into a car, put on your seat belt. Place your child into a properly installed safety or car seat and fasten his or her seat belt every time your child rides in the car.
  • Wear a helmet. When engaging in sports or activities that involve contact or may involve falls, wear a helmet and make sure your child wears one.
  • Be careful with firearms. Make sure firearms and bullets are stored in a safe, locked place, inaccessible to children.
  • Protect yourself from falling. To prevent head injury from falling, use a stepstool, install handrails on stairways, install window guards to protect small children, and use safety gates on stairs.
  • Work for safer playgrounds. Talk with administrators at your child's school and with other parents to make sure your child's playground is as safe as possible, including using a shock-absorbing material on the playground's surface.

If you have an underlying illness, such as diabetes, that can result in a coma if left untreated, make sure you take day-to-day control of your medical condition.

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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