Relationships among pre- and post-injury intelligence, length of coma and age in individuals with severe closed-head injuries

Relationships among pre-injury ability, post-injury verbal intelligence, duration of coma and age were analysed in 34 closed-head injury patients, 7-28 years of age, whose coma lengths ranged from 5 to 180 days. The results obtained suggest that moderate to severe closed-head injury uniformly impairs verbal intellectual functioning without regard to premorbid status. Premorbid ability test scores had a markedly low correlation (0.04) with Wechsler Verbal IQs, obtained after patients had plateaued in intellectual recovery. Even when the effects of coma and age were controlled, the correlation was not significant. Mean post-injury IQs for patients grouped according to pre-injury intelligence (above average, average, below average) were all in the 80s. The findings do not support the prevailing assumption that the greater the premorbid ability, the greater the potential for intellectual recovery and the better the outcome. This study instead suggests that the higher the pre-injury IQ, the greater the IQ point loss. This has important implications for rehabilitation, counselling, discharge planning and follow-up. The greater the disparity between pre- and post-injury IQs, the more profound the loss and, hence, the greater the need for patient and family adjustments, coping and modifications of future personal, educational and vocational plans.