Lesion size and recovery of function: some new perspectives.

The present article discusses the possibility that functional recovery following brain damage may be to a large degree dependent on the amount of nervous tissue destroyed, such that more neuronal destruction may lead to more and not (as commonly suggested) to less recovery. This assumption may derive from the neuropsychological and neurological literature: many cases with circumscribed brain lesions are implicated with severe functional losses. However, patients with dramatic and severe brain destructions often show astonishingly normal behavior regarding cognition, speech, visuospatial, motor and sensory functions. Animal experimentation as well shows that an extensive lesion of a brain area may be associated with equal or less functional detriment than a small lesion of the same area. Along with the well-known variables of age, lesion growth, or personality and environmental factors, the amount of tissue destroyed should be considered as a potent mediator of functional recovery. At least for some functions and brain regions, the likeliness of recovery may increase with the extent of the lesion and thus the necessity of the brain to fulfill plastic changes.