What happens during a coma?

Author:  Hoi See Tsao
Institution:  Wellesley College
Date:  July 2006

The Cause of Comas – Brain Swelling

Hit your arm hard against the wall, and you will notice a swollen bump there the next morning. Swelling due to leakage from damaged blood vessels is one of our body's responses to trauma, or serious injury or shock to the body. The same happens when the brain is traumatized. Just like any other tissue, it swells. Unfortunately, unlike other parts of the body, the brain is enclosed within the skull, a bony structure that provides structural support to the head. The brain has no space to expand into, leading to a rise in the pressure in the brain. When the rise in pressure equals the arterial pressure, or the pressure exerted by the transportation of oxygenated blood in blood vessels to various parts of the body, the blood flow to the brain is affected. The brain cells cannot metabolize normally and are unable to excrete toxins from the brain, causing them to accumulate and lead to further brain damage. This vicious cycle is the major cause for death in brain trauma patients. One of the major breakthroughs leading to patients' increased survival rate in recent years has allowed physicians to break this cycle.

Picture taken from: http://www.cbsnews.com/stories/2005/08/05/earlyshow/series/main760296.shtml

Picture taken from: http://www.cbsnews.com/stories/2005/08/05/earlyshow/series/main760296.shtml

If left untreated for a long period of time, water may begin to collect in the brain, leading to a condition called brain edema. The swelling of the brain and the accumulation of water lead to excessive pressure being exerted in the brain, commonly referred to as intercranial pressure.

To treat brain swelling, strong medications are often used to draw fluid back out of the brain and into blood vessels. Other medications decrease the brain's metabolic requirements. In certain cases, brain surgery is administered to remove small amounts of fluid or damaged brain tissue to alleviate the pressure in the brain and prevent further damage. If the intercranial pressure is not alleviated and causes sufficient damage to the brain, the results may be coma.

Coma - A Consequence of Brain Swelling:

So, what do some students think about comas? According to an undergraduate student at Haverford University, "It makes me think of humans dependent on machines." On the other hand, a student at Imperial College felt that, "I suppose that they're people who are in deep sleep."

From the medical point of view, a coma is a state of deep, prolonged unconsciousness which is usually the result of disease, poison or injury. Coma differs from sleep in that the individual is incapable of sensing or responding to external stimuli and internal needs and hence, cannot be aroused.

Many people believe that a coma is similar to deep sleep. However, contrary to popular belief, comatose patients may display signs of movement, make sounds and appear agitated. Occasionally, it is even necessary to restrain the activity of coma patients to keep them from interfering with medical equipment.

Reactivity refers to innate brain functions, such as our natural responses to pain or the turning of our heads towards the source of sound or movement. These actions are called reflexive movements. Perceptivity refers to the nervous system's responses to learned or acquired stimuli, such as our reaction to language or gestures. These actions are called conscious movements. When a person is in a coma, he does not exhibit reactivity or perceptivity. One example would be the person's inability to arouse in response to pain or when a close relative or nurse calls his nickname.

Often, a person who is emerging from a coma will begin to react to certain stimuli. Consciousness is said to be regained when both reactivity and perceptivity are present, as both of these functions are required for a state of awareness. In some cases, patients have to relearn areas of perceptivity such as speaking, going to the bathroom, or dressing. The progress or recovery from a coma is measured by the extent to which the patient is aware of external stimuli.

Some patients claim that they remember vivid or distinct events while they were in a coma. This claim has yet to be confirmed. However, the family and friends of comatose patients are often encouraged to speak positively to and in the presence of the patient. It is also possible that this positive atmosphere may hasten the patient's recovery.

In addition, different patients recover at different rates and to different degrees depending on their injury. Some patients have "locked in" syndrome, in which they are unable to react to their environment while they are awake. Others recover only certain capacities and require long-term care from family and friends.

Some comatose patients may even have to relearn the most basic human skills. "When I first woke up, I couldn't talk at all. I was crying and making baby noises for two weeks," said Glenn, a coma survivor, "When you come out of a coma, you're like three months old. Your life is starting over. You have to learn how to walk, talk, move your arms, and more through therapy. They started feeding me baby food. They toilet-trained me. I had a bunch of papers that I was trying to write on. My vocal chords started to come back about one month later" (Coma Recovery Association).

Scales to Assess Coma Severity

There are two different scales available to assess the coma levels of patients. These are the Glasgow Coma Scale and the Rancho Los Amigos Scale. The Glasgow Coma Scale assesses the degree of brain impairment and identifies the injury's seriousness depending on the patient's brain functionality after the injury. Responses elicited include eye opening, verbal responses and motor responses, such as movement. The responses are than ranked on a scale of 3 to 15, with 3 being low and 15 being a high degree of response.

The Rancho Los Amigos Scale is usually utilized in the first months after the brain injury, as it does not require the patient's cooperation. The Rancho Los Amigos Scale is based on trained personnel's observations of the patient's response to external stimuli. A description guideline of the patient's stages of recovery is provided as an indicator of the amount of brain damage inflicted.

What can we do about comas?

Often, the help of a neurosurgeon is enlisted. A neurosurgeon is a physician who specializes in the treatment and surgery of any part of the nervous system. The neurosurgeon's main role is to prevent further damage to the brain. One method is by removing any blood clots that form and press on the brain. Blood vessels may also be repaired to stop bleeding, and thereby reduce pressure in the skull. This allows for increased blood flow to the brain and helps to stop the cycle of compression and swelling. Portions of damaged brain may also be removed to increase the chances of recovery for the remaining portion of the brain.

The neurosurgeon may also insert pressure monitoring devices inside the brain, allowing medical personnel to intervene when the pressure in the brain increases. When this happens, a device called a ventricular drain is used to drain excess fluids. In more severe cases, surgery is required.

The main focus for neurosurgeons and medical personnel is to maintain blood flow and oxygen to all parts of the brain, allowing the brain to stop swelling. This will minimize brain damage and increase the patients' chances of survival and recovery.

According to neurosurgeon Dr. Jamshid Ghajar in an interview conducted by NOVA Online in 2000, "The key intervention point is right after the accident. That first week is absolutely key. If you do the right thing in that first week, then you won't have problems later on."

We as students also have the potential to change the lives of comatose patients and those around them by becoming neurosurgeons or researchers in the field of neuroscience – both careers greatly impacting the medical care that comatose patients receive. Marc J. Tetel, a Biology professor at Wellesley College specializing in neuroscience, says, "For me, learning about the brain is the most fascinating aspect of science to study. Understanding the brain (or at least trying to understand it) is at the core of understanding who we are. One of the things I love most about neuroscience (NS) is that it encompasses so many different disciplines: biology, psychology, biochemistry, chemistry, physics, computer science and more recently proteomics. NS never sits still. The field of NS is changing constantly and to enjoy it, one must be comfortable with change and enjoy the change."





- Hoi See Tsao