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.


  1. What is the lowest vehicular speed needed to produce a traumatic brain injury for a driver hit in a rear end collision? Do you have any exhibits or other resources depicting a low speed brain injury?

  2. I believe that I have read articles that claim that TBI can be caused in impacts with speeds as low as 2.5 m.p.h. Keep in mind that impacts up to 10 m.p.h. may result in no visible damage to either vehicle so substantial brain injury could occur without any evidence of impact.

    For more information on low speed vehicular impact, I suggest you check out the 4 Speeds Video product available online ( This 5 minute video uses the Hybrid II crash test dummy to demonstrate key facts about rear impact automobile collisions, while dispelling often used myths such as: - No property damage means low speed - Bumpers are damaged in any collision over 5 m.p.h. - Damage analysis can prove a collision was a low speed impact - Forces on the body in an automobile crash are like sitting in a chair.

    The video also demonstrates that, in a rear impact, there are forces applied to the occupant that match the locations of commonly diagnosed injuries of the back and neck. While automobile collisions vary, the tests shown in this video are applicable to most rear end crashes. Variation from the baseline depicted in this test will typically result in greater injury potential.

    The product also includes a full Engineer's Report prepared by Four Speeds supervising engineer, John Smith, P.E. The video was produced by renowned medical-legal consultant and presenter Janabeth Fleming Evans (Taylor), R.N., R.N.C., of Attorney's Medical Services, named by the Association of Trial Lawyers of America as Paralegal of the Year 2002.

  3. Ben, I believe the article is thorough and concise. I think it would be helpful to have an image of the axonal shearing that can occur in these types of injuries. The inside of the skull base is not a clean smooth surface and can cause damage to the brain tissue in addition to the contracoup injury imaged above. I think your article appropriately points out that these are not always easy cases to prove, but with the right evidence it is possible to convince a jury that a true injury has occurred. Neuropsychological testimony is usually key in these cases. Brenda Szynaka, LNC Phoenix, AZ

  4. Brenda, thanks for your suggestions. I agree with your comments completely!

  5. Hi

    This is a wonderful opinion. The things mentioned are unanimous and needs to be appreciated by everyone


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