Motor control in man after partial or complete spinal cord injury

The essential features of motor control in spinal man can be understood in terms of segmental reflexes interacting with, and controlled by, the influence of distant segments and even by the brainstem. Thus, overall motor control in patients with spinal cord lesions can be classified according to structure as: (1) simple segmental stretch and withdrawal reflexes; (2) plurisegmental gross reflex movement of paralyzed muscles; or (3) propriospinal processes with partial brain influence (i.e., severe spasticity and traces of position and postural control). Because of the variable nature of the injuries, there may be exceptions to this rule. However, the basic mechanisms can be understood by studying stretch reflex responses to various stimuli. The segmental reflexes are under a powerful influence of the propriospinal interneuron system which conducts impulses up and down the spinal cord. Finally, the apparently "isolated" spinal cord in which clinical signs indicate complete motor paralysis and lack of sensation below the lesion is not always isolated from supraspinal control of involuntary motor activity. In a significant proportion of the clinically complete spinal injuries we studied, it was possible to demonstrate the presence of preserved bulbospinal influences on spinal reflex responses.