The human brain is made up of billions of nerve cells that control all human activity...thinking, emotion, action, and movement. These microscopic nerve cells form bundles of nerve fibers that altogether form a gelatinous mass, the brain, which is cradled inside the skull. Brain tissue is very delicate, and even so much as poking it with your finger can cause disruption of neural pathways.

There are several forms of protection for the brain, which cushion the brain against injury from the normal bumps and scrapes of everyday life. First there is the skull, which provides a bony framework and totally encases the brain. Next there are 3 layers of membranes, and finally there is a cushion of fluid called cerebrospinal fluid.

The brain is comprised of three systems, any of which may sustain damage in a head injury:

1) The brainstem, which sits at the base of the brain, and continues on down to become the spinal cord, is responsible for maintaining arousal and tone, which is required for higher functioning areas of the brain. It is also responsible for maintaining certain autonomic functions such as regulation of breathing, swallowing, heart rate, and body temperature. The brainstem, due to the concentration of vital control areas, such as the respiratory, the cardiovascular, and the reticular activating system (responsible for alertness), can be the most important element to determined survival and level of function. (NOTE: This was a focal point of injury in Kimmie's case - so you can now appreciate why we were so scared that she may never wake from her coma state!)

2) Moving on up, the rear part of the brain is responsible for processing information that comes in from the sensory organs, like eyes, ears, taste, smell, and feel. 

3) Finally, the front of the brain is responsible for coordinating all of this information, and making decisions to do things. 

Ironically, the front of the brain is frequently injured in a traumatic brain injury. This is because of the structure of the skull, which is sharp and bony in the frontal region, resulting in contusion and bleeding in this area.

Another major cause of damage is shearing, or the stretching and tearing of the tiny nerve cells that comprise the brain. Shearing can occur throughout the brain, including the brainstem and the cortex, and can result in decreased arousal and attention, and slowed processing of information.

Q: What is "diffuse axonal injury"?

A: "Diffuse Axonal Injury" or "DIA" is a rather general term used to describe neural tissue injury that occurs in the cerebral hemispheres and in the brainstem following a head trauma. The mechanism of the injury is a "shearing" action between the different layers of the brain tissue, and between the brain tissue and the supplying blood vessels. Thus, the injured brain often displays multiple small hemorrhages within the white matter. A major determinant of the extent of diffuse axonal injury will be the nature and velocity of the impact force (how hard they were hit, how fast they were hit, and from what angle they were hit). Assessment of the damage is best achieved immediately after the event. Alteration of the level of consciousness is the primary factor for the gradation/ranking of the injury, and goes from: less than 5 mins (very mild), to more than 7 days (very severe). The prognosis and outcome in most patients depends on the severity of the primary damage, and in the most severe cases, on the extent of the brainstem involvement. The brainstem, due to the concentration of vital control areas, such as the respiratory, the cardiovascular, and the reticular activating system (responsible for alertness), can be the most important element to determined survival and level of function. The therapeutic management of these patients is largely supportive, so to provide appropriate cardiovascular, respiratory, renal, immunological, and nutritional support. (NOTE: This section also refers to injuries that Kimmie sustained in her accident. The doctors later told her that not one area of her brain was not injured...that there was extensive shearing of the brainstem as well as the rest of the brain tissues!)

Q: What is "cerebral edema" or "brain swelling"?

A: "Cerebral Edema" refers to brain swelling due to an accumulation of water. This is often caused by an excessive movement of fluid into the brain tissue from the blood vessels supplying that tissue. Both this condition and an increase in the amount of CSF surrounding the brain (hydrocephalus) can lead to a dangerous increase in the pressure within the skull (known as the intracranial pressure or "ICP"). Critical brain swelling can develop hours or days after a serious head injury, and can be detected with an intracranial pressure monitor. (NOTE: Kimmie suffered an increased ICP for days after the accident. If not caught and treated, this can often lead to even more brain injury.)

Q: What is a "coma"? 

A: "Coma" refers to a state of general "brain failure" characterized by severe depression of level of consciousness. Coma outwardly resembles sleep, but is physiologically very different. Sleep is characterized by highly organized and complex electrical brain activity, and can easily be reversed.  With stimulation, a sleeping person can be quickly aroused to a state of complete alertness. By contrast, coma is characterized by slowing and depression of electrical brain activity, and implies a neurologic deficit. No matter how much the patient is stimulated, he or she is incapable of becoming fully alert. Any serious injury to both cerebral hemispheres or the brainstem can produce coma. All causes of coma can be divided into two main categories: (1) structural (e.g. trauma, bleeding, stroke), or (2) toxic/metabolic (e.g. drug overdose, lack of oxygen). 

Q: My loved one is in a coma. Will he/she ever wake up?

A: Prognosis in coma can only be made on a case-by-case basis. However, certain general rules do apply. The cause of coma is probably the most important factor. Patients in coma because of toxic ingestions or metabolic abnormalities often have complete recovery whereas other etiologies such as vascular disease and anoxia tend to do worse. Head trauma falls between the two extremes. Younger people always have a better chance of recovering from coma. Regardless of cause, it is imperative that treatment and monitoring be initiated as soon as possible for the most desirable outcome. Because they are completely immobilized and have a weak ability to breathe, comatose patients are at high risk for secondary medical complications such as pneumonia, infection, and pulmonary embolism which can be fatal. The presence or absence of certain clinical signs of neurologic damage is also quite important in predicting outcome. Some studies have shown that patients with the best chance of recovery after a hypoxic-ischemic event had intact brain stem function and spontaneous roving eye movements on initial examination after onset of coma and evidence of intact cortical function (pattern of motor responses) at day 1 after the onset of coma. After several weeks in a coma patients will often progress to a "vegetative state". It is important to realize that "waking up" after coma does not simply mean opening one's eyes or moving spontaneously but rather meaningful response to stimuli such as following commands or conversing intelligibly. 

Q: Is there anything I can do to help my loved one who is in a coma? 

A: Although nobody knows for sure, it is now believed that patients in coma can and do respond to the presence of loved ones at the bedside. A familiar voice or touch may have a calming or reassuring effect on the patient, and certainly can't hurt. We encourage as much bedside contact between the patient and family members as is possible, as long as it does not interfere with medical care. Playing a patient's favorite music may also be helpful. The main rule of thumb is to be sure that your contact at the bedside does not lead to increased agitation, which can occur if the patient is semi-aware and frustrated by their inability to communicate or express himself or herself. If this occurs, it is probably best to leave the patient alone for awhile.

Q: What is "persistent vegetative state" or "PVS"? 

A: "Persistent vegetative state" describes the chronic condition that emerges after coma. It comprises a return of wakefulness (e.g. eye opening), sleep-wake cycles, and reflex movements (e.g. sucking, startle responses, grabbing), accompanied by a total lack of cognitive or mental activity of any type. The vegetative state is produced by intact function of the brain stem and "deeper" (i.e. subcortical) regions of the brain, without activity of the cerebral cortex itself. Persistent vegetative state refers to this condition in its permanent form and designates patients who survive for prolonged periods (sometimes years) following a severe brain injury without ever recovering any outward manifestations of higher mental activity. While these patients look awake and often alert they have no discernible meaningful interaction with their environment. Recovery of conscious awareness after one year in a vegetative state is exceedingly rare. It HAS happened, but it is rare, indeed. 

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