The Pathophysiology of Central Paresis
The pyramidal syndrome in man is characterized by four features: Spasticity with increased reflexes and muscle tone, release of flexor reflexes, weakness and loss of dexterity. This syndrome appears after lesions of the upper motor neurone and is commonly regarded as an entity. Although such a view has its great merits for practical purposes, the uniformity of this syndrome seems surprising when one considers the enormous range of possible lesions of descending motor fibres in the central nervous system. Leaving aside that extra-pyramidal lesions in the basal ganglia or cerebellum may also be associated with some weakness, lesions of descending motor fibres as the most common cause of the pyramidal syndrome will often affect different efferent projection systems. In one case, a lesion will mainly impair axons arising in the precentral gyrus, in another case those axons will be preserved and mainly axons arising from other motor areas will be damaged which may also course in the pyramidal tract.
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