Functional changes in motoneurones of hemiparetic patients

Forty-six patients have been studied after upper motor neurone lesions of cerebrovascular origin. The numbers of functioning motor units in extensor digitorum brevis muscles were reduced to approximately half between the second and sixth months after a hemiplegic episode. The surviving motor units tended to have slow twitches and appeared to increase their sizes after the lesions had been present for about 20 months. The findings are explained on the basis of transsynaptic changes in alpha-motoneurones after degeneration of corticospinal fibres.