Hemiparesis and other types of motor weakness

© Cambridge University Press 1995, 2001, 2012. Motor weakness concepts Motor weakness has been defined as a difficulty in generating the necessary voluntary muscle force for effective motor and movement performance. Movement (to be in motion) means spatial moving of any part of the body. It is produced by muscle contraction, usually of striated muscle, and may be voluntary, automatic (involuntary), or reflex, as a result of muscle strength involving the pyramidal tract, the motor nerves, the muscles, and the joints. For a movement to be correct, it is necessary that it involve functions of the many parts of the nervous system, specifically the senses, sensory nerves, cerebellum, and extrapyramidal system, to provide adequate muscle tone, coordination, and equilibrium. Disturbances of voluntary movement in the form of paresis or paralysis are the usual consequence of pyramidal tract dysfunction, cerebrovascular disease being one of the causes. Voluntary movement disorders may also be due to non-pyramidal causes, such as loss of sensory or afferent pathways, coordination disorders related to cerebellar lesions, lesions of the extrapyramidal tracts, and alteration of cortical motor programming, causing apraxia or lack of initiative [1].