Electrodiagnostic investigation of motor neuron and spinal reflex arch (H-reflex) in spinal cord injury

Twenty patients with spinal cord injury underwent serial electromyographic examinations. Fibrillation potentials and positive waves were noted in six patients in the spinal shock phase. In another subject, these potentials were found 27 months after injury. Our finding of significant slowing in the NCV of both nerves, indicates that lower motor neurons are indeed affected by upper motor neuron lesions. The H-reflex studies showed an increase in the mean H/M ratio. This may indicate an increase of reflex motor neuron excitability. No clear correlation was found between this increase and the degree of clinical spasticity. With repeat investigations, after a period of physical activity, a trend to reduction of the H/M ratio was noted with no clinical confirmation of reduction in spasticity. These findings emphasise the need for not assigning diagnostic terms to EMC abnormalities, but rather identifying them as neurophysiological changes which must be interpreted in the light of the clinical picture.