Regeneration and Repair of the Nervous System: Clinical Aspects
In man, restoration of function after damage to the central nervous system (CNS) cannot be achieved by regeneration. It is, however, frequently accomplished by survival of the damaged neurons. This is only possible if the lesion is of a reversible nature. If the disease process or injury has caused irreversible damage, functional recovery can be achieved by compensatory mechanisms mediated by structures that have escaped damage. Restitution of function due to redundancy in a distributed system and substitution of function by the remaining part of the system represent further mechanisms underlying functional recovery after irreversible damage.
At the clinical level there are no reliable criteria for distinguishing reversible from irreversible lesions at the acute stage. It is therefore difficult to assess the extent of restoration of function after stroke or other acute lesions. Positron emission tomography seems to have the potential for making such a distinction. This would provide the basis for taking measures to prevent the progression of a potentially reversible into an irreversible lesion. The astonishing ability of the brain to survive complete ischemia for a time of as long as one hour and partial ischemia for much longer is an example of a potentially reversible lesion in acute stroke. The capacity for late structural repair is illustrated in the restoration of conduction in demyelinated central axons. At present, therapeutic strategies along these lines promise more benefit than attempts to achieve regeneration of destroyed tissue. However, the inroads made by experimental investigations into regeneration in the CNS justify intensive clinicopathological studies of this problem. In contrast to the poor regenerative capacity of the CNS, successful structural and functional repair mechanisms are illustrated by the remarkable ability of the peripheral neurons to regenerate.
KeywordsIschemia Neurol Cholin Tral Nism
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