The subject under consideration is a rather difficult and extensive one, and I agree with most of the authors, especially S. A. K. Wilson, that nearly all problems in connection with it are still unsolved. I will, however, attempt to explain my own conception of the extrapyramidal system and of its lesions.
DISORDERS OF MOTILITY
It is well known that all extrapyramidal diseases have this factor in common—they all present characteristic disturbances of motility associated with changes in muscle tonus. These disorders of motility can be definitely differentiated from the pyramidal tract, and three forms can be distinguished, all of which are manifested in the course of voluntary, automatic and reflex movements. These three forms are: (1) hypokinesia; (2) diminished or increased muscletone states, manifesting themselves in either hypotonia or hypertonic rigidity: (3) hyperkinesia.1. The hypokinesiae consist of failure of innervation during voluntary movements (mild paralysis), consisting of
JAKOB A. THE ANATOMY, CLINICAL SYNDROMES AND PHYSIOLOGY OF THE EXTRAPYRAMIDAL SYSTEM. Arch NeurPsych. 1925;13(5):596-620. doi:10.1001/archneurpsyc.1925.02200110053005