As part of the Vietnam Head Injury Study (VHIS; see Chapter 5 for description of the study and the cohort), Grafman et al. (1988) studied the nature of intellectual function after penetrating missile wounds. The cohort consisted of 263 men who had penetrating brain injuries—96 with lesions in the right hemisphere, 78 in the left hemisphere, and 89 in both—and 64 uninjured controls who met the inclusion criteria: they served in Vietnam during the same years as the brain-injured, and they were stratified according to preinjury Armed Forces Qualification Test (AFQT) to be matched with the brain-injured. There were no significant differences between the groups in age, education, or preinjury AFQT percentile scores. Although Grafman and colleagues stratified head-injured subjects by location of brain injury, the study data clearly indicate that the head-injured showed worse change than the controls in performance on the AFQT. The authors also assessed whether brain-volume loss correlated with changes in cognitive function. As expected, greater total brain-volume loss correlated with greater declines in AFQT scores from before to after injury (p < 0.0001). The authors examined whether lesion location was associated with cognitive decline. No significant effects on AFQT scores by lesion location (right, left, or bilateral) were observed. Preinjury education level also did not correlate with AFQT. The results indicated several factors that influence cognitive decline after brain injury as measured with the AFQT: preinjury intelligence was the strongest predictor of postinjury intelligence scores, followed by the size of the lesion, and then the location of the lesion. Preinjury education level did not correlate with cognitive decline.

Raymont et al. (2008) examined 182 Vietnam veterans as part of phase 3 of the VHIS. All were identified from the VHIS registry and had a history of penetrating head injury although an additional 17 patients who were assessed for phase 3 had not participated in phase 1 or 2. Controls were 32 veterans who had participated in phase 2 and an additional 23 who were recruited through advertisements in veteran publications; none of the controls had a history of head injury. All the veterans were assessed over 5–7 days at the National Naval Medical Center in Bethesda, Maryland. There were no significant differences between cases and controls with regard to age, years of education, or preinjury induction intelligence level (as measured with the AFQT). Brain lesions were identified with computed tomography. The median AFQT score in the entire sample was 65.0; in the penetrating-injury group, it was 54.0, and in the controls, 74.0. The penetrating-injury veterans had a significantly greater decrease in AFQT score than controls from phase 2 to phase 3 and from before injury to phase 3. The scores of the controls improved from before injury to phase 2 compared to those with penetrating head injuries. If officers were excluded from the sample, the AFQT scores of those with penetrating head injuries decreased significantly more than the scores of the controls over the entire period from before injury to phase 3. Those with penetrating injuries had lower AFQT scores at phase 3 (mean, 52.58) than the controls (mean, 68.50). The authors examined several risk factors for AFQT outcome at followup and for declining AFQT scores, including dementia, location of brain lesion, and genetic markers. They found that preinjury intelligence was the most consistent predictor of cognitive outcome at all followup times and of decline over time. There was no evidence that laterality of the lesion affected overall intelligence or decline. Specific brain regions, the degree of local and global atrophy, and some genetic markers were found to be associated with exacerbated decline. Thus, the long-term followup of Vietnam veterans with penetrating head injury found that exacerbated decline in intelligence is a significant risk.

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