Tuesday, July 24, 2012

Axonal Shearing

Presenting cases of mild traumatic brain injury (TBI) has always been more of a challenge than more severe brain injuries that may include open skull fractures, large areas of intracranial hemorrhage or visible cerebral contusions. Of course this is because of the lack of clear physical evidence of injury in the various types of radiological studies. A case with a massive depressed skull fracture, a huge subdural hematoma or large areas of bruising in the brain have pathologies that are clear in the CT or MRI films, even to a lay audience. Closed head injury or concussion cases most likely do not have such clear and obvious physical manifestations.

The injuries in a mild TBI case that lead to long term or permanent neurological deficits and symptoms in the patient occur on the microscopic level affecting individual brain cells and the connections between these cells. The impact forces that occur when the brain impacts the inner wall of the skull can displace or shear these connections leading to injury and death to the affected nerve cells. Traditionally, this mechanism had to be discussed theoretically since these microscopic injuries could not be seen in the post-accident radiological studies. This discussion was often a challenge since it had to involve a description of the neurons, the connecting axons, the gelatinous nature of the brain tissue, the shearing forces and the final disruption and death of the affected cells.

Thankfully, MRI technology has improved dramatically over the years. Modern MRI studies have a resolution so fine that the small lesions created by a shear injury can often be demonstrated. These lesions primarily result from petechial (pinpoint) hemorrhages or the small regions of scarring that develops after this bleeding has resolved. The following image is a good example of the type of lesion that I often see in these cases.

Certainly a legal case argued before an average jury can be more effectively presented when there is physical evidence of the injury. These small microscopic injuries may not be as dramatic or clear to the uneducated viewer as other larger pathologies, but at least the attorney presenting this evidence does not have to rely solely on a discussion of a theoretical process in a brain that remains completely normal in appearance. Who knows what the future may hold. I believe that the technology will only continue to improve and that soon we will have routine studies that can show these injuries in even greater and greater detail.

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