Traumatic Brain Injuries: A Primer

The brain is our most complex organ and perhaps the most difficult to help heal. The biggest challenge is its protective covering: the skull. Management of acute traumatic brain injury, or TBI, typically involves manipulating the three components within the skull: the brain, the blood, and the cerebrospinal fluid (CSF).

What is the purpose of each of these components? The brain is the body’s supercomputer. The blood delivers oxygen and nutrients to feed the cells or neurons. The CSF nourishes the brain, helps remove waste products, and keeps the brain buoyant.

What happens when something is significantly injured? It swells. Think about a time you saw someone with a really bad sprained ankle. What happened? It blew up like a balloon. The same thing happens to the brain with a traumatic injury. It swells.

Unlike an ankle, brain swelling is inhibited by the skull but the pressure inside the head can continue to rise if swelling is unchecked. Too much pressure inside the skull (it can’t move) and blood flow diminishes, thereby starving cells of oxygen, which then swell more.

We can measure the pressure inside your skull, or intracranial pressure (ICP), by placing a sensor into a ventricle (a ventriculostomy).  A normal ICP is 7-15mmHg. Cerebral edema can be insidious as swelling peaks 48-72 hours post injury. A patient can initially present following commands. Then in 2-3 days, develop cerebral edema to the point of herniation (which means brain contents shifting) and die.

What happens when a patient develops significant cerebral edema and ICP pressures skyrocket?

First bad thing: Blood flow is reduced. The brain is very sensitive to blood flow and greedy for oxygen. If there is diminished blood flow, neurons (brain cells) begin to die. If there is no blood flow, the brain will die. You may have heard the term brain death. This is determined by several factors but the definitive one is by taking the patient to radiology and doing a brain flow study. Roughly, a dye is injected into the blood and x-rays are taken. If there is no blood flow, the patient is declared brain dead.

Second bad thing: Brain contents shift into areas where they’re not supposed to be. This is called herniation. When neurons are compressed, they don’t function properly and will begin to die as well. When brain cells die, machines and medications have to take over their function to keep the patient alive.

Unfortunately, if brain death has occurred, the medical team will start discussing withdrawal of care with the family.

***Content reposted from January, 12, 2011.***

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