Penetrating head injury in young adulthood exacerbates cognitive decline in later years

Few investigators have studied whether the behavioral effects of brain insult in adulthood are stable after the period of maximum recovery. We addressed this issue in a 30-year longitudinal study of 84 veterans of World War II, 57 with penetrating head injury (HI) and 27 with peripheral nerve injury (PNI), matched with respect to age, premorbid intelligence, and premorbid education. Each subject was examined during the 1950s and during the 1980s; each examination included the largely verbal Army General Classification Test (AGCT) (with Vocabulary, Arithmetic, and Block Counting subscales) and the Hidden Figures Test (which measures figure-ground discrimination). HI exacerbated decline in performance over time, irrespective of lesion site or cognitive test. HI and PNI subjects differed significantly (p less than 0.05) in AGCT Total and Arithmetic change scores, and means were in the same direction for all other measures. In analyses contrasting subjects in each of the eight lesion groups to PNI subjects, those with left parietal lobe injuries showed significantly greater decline from the 1950s to the 1980s on the Vocabulary and Arithmetic subscales of the AGCT, as did those with left temporal lobe injuries on the Arithmetic subscale, whereas subjects with right parietal lobe injuries showed significantly greater decline on the Hidden Figures Test. We hypothesize that the observed reduction of cognitive capacities late in life was due to some combination of HI in young adulthood, secondary effects of the injury occurring with time, effects of stress on remaining brain tissue caused by functioning for decades in a compromised state, and changes in the brain occurring with age. Although the HI subjects were not demented, follow-up studies must assess whether exacerbated decline is a harbinger of dementia.