Legal Update #22 When is Permanent Impairment Permanent: New Data on Recovery from Traumatic Brain Injury

NLBC LEGAL UPDATE: August, 2005 - Issue #22

Sam Goldstein, Ph.D., Editor
Complimentary Service of the Neurology, Learning and Behavior Center

When Is Permanent Impairment Permanent?
New Data On Recovery from Traumatic Brain Injury

The significant increase in the number of clinical neuropsychologists over the past twenty years has in part been fueled by the medical-legal/forensic arena. Armed with neuropsychological measures and an understanding of human behavior and development, neuropsychologists increasingly find themselves asked to render opinions about permanent neurocognitive impairment following traumatic brain injury. Unlike medical specialists such as physiatrists or neurologists, neuropsychologists are in a unique position to quantify and measure functioning skills and behaviors such as thinking, emotions, interpersonal abilities, vocational capability and impairing post accident changes. In this legal update I will provide a brief overview of an exciting, emerging trend in studies of traumatic brain injury suggesting that potential for recovery, particularly in light of the development of new medications, psychosocial strategies and an understanding of how to apply rehabilitative techniques may be significantly greater than traditionally thought.

The human brain is malleable in response to environment and life experience. The central nervous system is constantly adjusting to experience. This is true not just for growing children but throughout life. Stimulating environments lead to expanded cortical areas, greater neural organization, more branching of neurons and increased rates of neuronal survival. Multiple studies have demonstrated that the environment can and does have a profound influence on brain development. Animals raised in rich, stimulating environments have more dendritic branching and synapses per neuron than animals without this stimulation. In contrast, organisms placed at a young age in stimulus deprived environments, exposed to significant trauma or caretaker neglect suffer neurologically. Under-stimulating environments can and do cause less neuronal branching, less neurogenesis and neuronal loss. Cognitive stimulation at any age is an important predictor of enhancement and maintenance of cognitive functioning. Physical and mental exercise can increase levels of neurotrophic and other growth factors, stimulate neurogenesis, increase resistance to insult and improve mental performance. Conversely an impoverished environment appears to lead to detrimental effects on the organism.

At one time it was thought that the brains of young children may be more capable of recovery following injury because they were less developed, in particular less specified in the relationship of brain structure to cognitive or behavioral functioning. There appears to be compelling neuroscience findings, however, to suggest that the brain is in fact a vital, constantly changing organ capable of recovery throughout life. This phenomena in part can be explained through the concept of neuroplasticity. Neuroplasticity is defined as the capacity of brain cells to fight the chemical and structural changes that occur following trauma that can eventually kill them if not controlled. Neuroplasticity also refers to the ability of brain cells to modify their activity in response to change in the environment, to store information from the environment and to permit the organism to move about and survive. Thus, all functioning brains to some extent operate under the principle of neuroplasticity throughout life.

Researchers define three types of neuroplasticity. The first, developmental plasticity, reflects the shaping of the brain by early life experience. Children have more neurons and synapses than adults but lose a significant number of neurons and synapses through their adolescent years through a normal pruning process. Neuronal networks that are not sufficiently used are eliminated. Those frequently used are expanded and interconnected. Early plasticity may be greatest because many synapses and neurons have not yet been pruned.

The second, activity dependent plasticity, reflects pattern by which years of practice combined with learning and memory form new connections through experience and knowledge acquisition. Any individual competent in an activity from athletics to a specific vocation relies on this type of plasticity. Finally, injury induced plasticity reflects the altering of the balance of activity in the brain due to trauma in which some parts of the brain take up function for other damaged parts. This type of plasticity has been traditionally thought to operate more robustly in young brains. Defined as the Kennard Principle, this principle argues that recovery from a focal lesion to the brain is superior if the lesion occurs early in development rather than during adulthood. This concept also referred to as vicariation suggests that developing, immature central nervous systems have back-up neuronal connections, networks and fiber tracts that participate in the takeover of lost functions post brain injury. The concept of equipotentiality suggests that areas not normally involved in controlling certain types of behavior or function can take over those functions under the right circumstances. Researchers have demonstrated that other areas of the cortex can take over functioning for a damaged area. In mature brains, certain fiber tracts may become "unmasked" and functional following a brain injury. However, plasticity may not be without cost for the young brain. Increased plasticity of the young brain may allow it to compensate for one impairment but this may be at the expense of another, later developing function.

After brain injury, post-synaptic neurons attempt to adjust to reduced stimulation through several processes, including forming more receptors, slower re-uptake and receptor dysregulation. This pattern of hypersensitivity makes nerve cells more sensitive to incoming stimulation, particularly pain. However, brain injury alone may not be the only cause of decreased functioning. Depression and chronic stress result in elevated gluco steroid levels in humans which can over long periods cause premature aging as measured by atrophy in the hippocampus of the brain.

The once held belief that recovery from brain injury is limited to the first one to two years following injury has now been met with considerable challenge. Further, the idea that remediation of function can only be accomplished in the first eighteen months post accident is increasingly being challenged. The idea that the development of compensatory strategies many years post accident leading to improved daily functioning may have no direct impact on the structure and biochemistry of the brain is also increasingly in question. Neuroplasticity research suggests that people can recover for many years but on a continuum such that recovery is easier and faster early on and becomes increasingly more difficult as time progresses. A significant number of studies have now demonstrated that many people can make significant physical, cognitive and behavioral recovery as long as five years or more post brain injury. As Stein noted in 1995, "There is no rule of neuroscience that the processes of functional recovery must occur rapidly or that treatment should be terminated after a fixed period of time because the early results are unsatisfactory."

Neuro-rehabilitative therapy, in particular cognitive rehabilitation, may well facilitate the brain's plasticity. This theory has been demonstrated not only from the patient's perspective and observations of others, but even through SPECT and PET scanning. It also appears that neuro re-organization can be enhanced through specific training. Though compensatory strategies can be helpful post brain injury, plasticity research suggests that the appropriate timing of teaching these strategies is a critical and complex issue. If strategies are implemented too early, those potentially available, compensatory parts of the brain may not be capable of effectively taking over function. This may explain the significant problems many mild to low moderate brain injured patients experience when they return, often within a few days post injury, to every day activities, particularly work. Thus, too much activity too early post injury may lead to increased adverse outcome.

Despite the important and significant scientific gains being made in the understanding of brain function and recovery from brain injury, the current state of this science, I believe, still falls short of the needs of the legal system. The provision of quantified statistics relative to pre and post trauma functioning as well as a level of permanent impairment may not always be possible. Though in many cases post accident changes and recovery are obvious, easily observed, measured and reported, in many others the state of the science may not allow the provision of precise statistics. This may be particularly true in many mild to moderate brain injuries. Despite the needs of the legal system, it is the ethical responsibility of neuropsychologists to represent the current state of science in their forensic work. For the present, in these circumstances, clinical opinion will have to suffice.

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The Neurology, Learning and Behavior Center provides multi-disciplinary, clinical and forensic assessment, case management, trial consultation and treatment services for children and adults with brain injury and dysfunction, Attention-Deficit Hyperactivity Disorder, language disorders, learning disability, developmental delay, emotional disorders, Autism and adjustment problems. The Center is dedicated to the provision of treatment services.