The brain can be injured in several traumatic ways, including an object that pierces the skull and enters the brain, bleeding such as a hemorrhage that increases pressure on the brain, lack of oxygen such as in a carbon monoxide exposure and sudden movement within the skull which is commonly referred to as a concussion. This article focuses on concussion because they are the most common traumatic injury that occurs in vehicular collisions.
A concussion can occur even without the head striking an object. A coup-contracoup trauma is a well-known mechanism of injury. You must first consider the anatomy of the brain’s environment to understand this type of injury, which may not exhibit any outward signs of injury, but which may manifest in memory issues, irritability, fatigues and personality change.
The adult brain, weighing about three (3) pounds, has a custard type consistency and is suspended in cerebral fluid within the skull. The skull is hard bone and has many sharp prominences, particularly in the lower areas of the skull. The skull is located on the neck, which is supported by spinal column and the neck muscles. When a force is applied to the human body, the skull can whip back and forth on the neck. When the skull whips back and forth in an unusually forceful motion that exceeds normal biological tolerances, then the brain’s impact on the skull, both in the initial impact and the secondary impact when the brain sloshes from front to back, or side to side, can bruise the brain.
Most people eventually recover from concussions however, many do not. The concussion may result in axonal stretching and breaking, resulting in a condition known as diffuse axonal injury, or DAI. Again, you need to understand the brain anatomy to understand this type of injury.
The brain is composed of approximately 86 billion neurons (brain cells) that extend from the brain’s exterior grey matter into the brain’s interior white matter. The axons are part of the neurons. When sudden force is applied to the brain, the grey matter which is a slightly different consistency than the white matter, moves at a different speed and direction. This forceful movement that is beyond the normal biological tolerances of the axons, causes the axons to stretch and break. However, the brain injury does not stop there. Once the axons are injured, they release materials into the brain that cause more injury to additional axons. This is called the metabolic cascade. The released materials continue the injury and is one reason that brain injuries are not initially recognized. The symptoms may not be recognized for days, weeks or even months.
The symptoms of brain injury from concussion, called post-concussion syndrome, can include memory problems, visual problems, fatigue, irritability and personality changes. For instance, activities that were once easy for the person can become difficult. That is because damage to the axons have interrupted the ability of the brain to carry information within its neurons. It’s like a town with a phone system that is hit by a hurricane and now half of the lines are down. Instead of being able to call your neighbor, you have to walk over to his house. This takes more effort. When a person suffers a brain injury, doing what could be easily done before, now takes more effort. This additional effort causes fatigue.
There are many methods to document brain damage. Measuring small eye movements, such as saccades, which are movements common to reading and switching focus from one item to another, is one method because eye movements are controlled by many areas of the brain. Measurements of other eye movements can also be consistent with brain injury. Imaging studies can also be done, although MRIs are often not sensitive enough to determine brain injury, there are other more sensitive measures, such as DTI, which is a more advanced form of MRI. However, most doctors treating brain injury rely on the clinical findings and patient history to make the diagnosis and determine the best treatment. Unfortunately, if problems persist after six months, the injury is likely permanent.