Vietnam Head Injury Study Reveals Late Cognitive Decline
Veterans the Vietnam War who received penetrating brain injuries are demonstrating continuing late effects with a faster decline in cognitive function than vets who returned uninjured. Jordan Grafman, Ph.D., of the National Institute of Neurological Disorders and Stroke, made on online report of his veterans study in Brain, 2007. Grafman was able to differentiate the TBI group with penetrating injuries from individuals with dementia.He cautioned clinicians to evaluate their patients neurobehavioral status carefully to avoid confusion with the frank signs of dementia. Individuals with higher intelligence as measured on the Armed Forces Qualification Test (AFQT) were found to be "protective in terms of later decline" according to Grafman. Specific areas of brain atrophy in the left parietal and right frontal regions were associated with greater decline. Other indicators were: severity and location of injury, education, intellectual development and genetic endowment.Laterality (left, right or bilateral) was not a factor in AFQT scores . Injuries to the caudate nucleus was found to be as important as AFQT scores in predicting score changes from baseline to the present.
In another study which focused on a swapping of information between the front and back of the brain, conducted by Randy Buckner, Ph.D. of Harvard's Center for Brain Science and reported in the December 6, 2007 issue of Neuron, the reduced communication was associated with degradation of white matter linking elements known as the default network. This network is associated with the functions of remembering and planning.
While these two studies are not related, the reality is that brain injury hastens cognitive decline, particularly the features that are associated with the functional loss of aging. As the injury has caused a disruption of neural tracts, as the person ages the effects of the injury may trigger the loss of more functions.
The issues associated with the aging process for individuals with a brain injury is becoming more important as the number of people living with the long term effects of brain injury increases. Can these studies help us to identify treatment which can slow the cognitive decline or identify strategies to preserve function? The group of young men and women returning from Iraq and Afghanistan will increase the number of brain injury survivors who are likely to experience age related functional changes. We need to learn as much as we can from studies involving older survivors to address the future needs.