Functional Recovery Following Brain Injury - 12/1996

Previous studies have demonstrated that after acute injury to the brain (e.g.: stroke, trauma), brain cells can die in a specific area of the brain. This generally results in the loss of function controlled by that part of the brain (e.g.: paralysis of a limb). However, surrounding that area of dead cells is a zone of injured tissue -- the penumbra -- which although alive, is barely functional. This injured but not dead area, also loses its ability to control function. Many of the treatments used are aimed at helping the recovery of this surrounding area of injured tissue. As this tissue recovers, the injured person begins to regain some function associated with that brain area. Thus, in the first several days after injury, we observe some return of function due to the recovery of the area injured but not dead.

However, after a longer period, there is often a second spurt of return of some additional function. Why?

Dr. R. J. Nudo and his colleagues have shown in an experimental model of stroke, that healthy brain areas adjacent to the injured area does indeed reorganize and take over some of the function of the "dead" area; however, this occurs more effectively if the healthy area is stimulated to take over that function. To put it in practical terms, by trying to use the injured part, the person "learns" to use it -- a possible biological explanation of the success of rehabilitation treatments in recovery of function. It is still uncertain whether such brain reorganization is due to growth of new processes from healthy nerve cells ("sprouting"; see Research Fact Sheet, How Does the Brain Heal?, August 1996) or to changes in existing nerve cell connections (activation of silent connections). In both instances, functional pathways are established that take over the role of a destroyed pathway. This information provides preliminary evidence of ways in which the function of damaged brain improves; also, how we may be able to increase functional improvement. We need to stimulate similar studies in injury of the developing brain.

Comment
How does this relate to the motor defect in cerebral palsy? The infant and child's developing brain is at an advantage in learning new skills and restoring lost function. The above paper gives us valuable information as to what is occurring in the damaged brain and the positive effect of activity on increasing the brain's ability to restore function. It also tells us what mechanisms of brain repair we need to address in order to increase the scope and quality of functional recovery. The applicability of this information in working with infants and young children remains to be seen; but it is an important lead that needs exploration. The Research Foundation is bringing this information to the attention of scientists studying infants with brain damage.

¹Nudo, R.J., Weise, B.M., et al; Neural Substrates for the Effects of Rehabilitative Training on Motor Recovery After Ischemic Infarct; Science; 272/1791-1794; June 21, 1996