Recovery of function after brain injury in man.

Late after-effects of cerebral trauma are difficult to study because patients tend to be seen for persisting symptoms, and not simply for their lesions. We have tried to avoid this bias by recalling periodically, over the years, 520 men with known brain injuries incurred in World War II or in Korea or Vietnam. These men are seen irrespective of clinical need and all undergo intensive behavioural and neurological assessment, which still continues. For such groups, recovery is impressive, though one third shows persistent intellectual loss. In addition, some tasks reveal specific deficits enduring unchanged, after th first 2-3 yr, for the 20-30 yr of follow-up (e.g. visual field defects, certain auditory discrimination losses, trouble on various complex perceptual tasks). These lasting deficits are linked to the site and size of focal injury, often representing remnants of more severe initially-present disorders. The extent of recovery is correlated with age at the time of trauma, the youngest faring best. Extension of such studies to cases of early brain damage (birth to five years), as indicated by hemiparesis, shows the familiar 'escape' of language after early left-hemisphere lesions but this is achieved at a price, the price being borne by non-verbal functions that normally depend on the integrity of the right hemisphere.