Wednesday, March 4, 2009
Representing Mild TBI and Axonal Shearing
I had another client call today asking the same question I have heard dozens of times over the years, "I have a mild TBI case. How do I show that my client was really injured?" This is a very popular question that doesn't have a good straightforward answer, so I thought it would be a good topic to discuss here.
Let's start at the beginning. What is a mild TBI (traumatic brain injury)? The first thing you should know is that a TBI is categorized as mild only because there was only a brief loss of consciousness. This classification has nothing to do with how severe the actual injury is to the brain or to the function of the brain. Also, a TBI can occur even when the skull is not damaged (closed head injury) and no impact is required. The brain is made of soft spongy material and sudden or violent motion of the head can cause the brain to "slosh" around inside the skull. These sudden movements of the brain within the skull are at the heart of the majority of the TBI cases we see.
In most cases, no evidence of injury will show up on CT or MRI scans unless this injury results in hemorrhage from contusions or vascular injury. Usually, the injury is microscopic occurring to individual cells or clusters of cells. This is where axonal shearing comes into the conversation. The movement of the brain within the skull can cause disruption of the various nerve cells (neurons) that make up the brain tissue. These injuries to the neurons, and particularly to the long vulnerable axon portions of the neurons, are called axonal shearing or shear injuries.
Although traditional radiological techniques are not of much help in axonal shearing cases, PET scans can sometime be of assistance. A PET (positron emission tomography) scan shows the absorption rate of glucose in the tissues and can be helpful to show a functional deficit even when no structural defect can be seen. Of course, neuropsychological testing is also helpful to point out specific types of impaired function that did not exist prior to the injury. A skilled neuropsychologist can often isolate specific regions of brain injury based on lists of behavioral and cognitive dysfunction.
All in all, when pursuing a mild TBI case, you should be prepared to go beyond your efforts to locate a single source of evidence for your client's injury and be prepared to educate and enlighten as to the nature of the injury itself. These cases can be a challenge but they also can be very rewarding.