From spinal shock to spasticity: neuronal adaptations to a spinal cord injury.
OBJECTIVE
To investigate the adaptational changes in excitability of spinal neuronal circuits below the level of lesion from spinal shock to spasticity in patients with spinal cord injury (SCI).


METHODS
More than 6 months after an acute SCI, clinical follow-up examinations were paralleled by electrophysiologic recordings with tibial nerve stimulation (M-wave, F-wave, H-reflex, and flexor reflex).


RESULTS
During spinal shock, the loss of tendon tap reflexes and flaccid muscle tone were associated with low persistence of F-waves and loss of flexor reflexes, whereas H-reflexes were already elicitable. During the transition to spasticity, the reappearance of tendon tap reflexes and muscle tone and the occurrence of spasms was associated with the recovery of F-waves and flexor reflex excitability, whereas the H-to-M ratio remained about stable over months. At later stages (2 to 6 months after SCI) when clinical signs of spasticity became established, the electrophysiologic measures showed little change. In paraplegic patients, in contrast to tetraplegic patients, M-wave and flexor reflex amplitudes even decreased.


CONCLUSIONS
The late decrease in M-wave and flexor reflex amplitude in paraplegic patients suggests a secondary impairment/degeneration of premotoneuronal circuits and of motoneurons. The divergent course of clinical signs of spasticity and their probable neuronal correlates indicates the occurrence of non-neuronal changes contributing to spasticity.
Hiersemenzel
L P
LP
Swiss Paraplegic Centre, University Hospital Balgrist, Zürich, Switzerland.
Curt
A
A
Dietz
V
V
D000222:Adaptation, Physiological; D000293:Adolescent; D000328:Adult; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D005500:Follow-Up Studies; D006181:H-Reflex; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009046:Motor Neurons; D009128:Muscle Spasticity / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D009129:Muscle Tonus; D018482:Muscle, Skeletal / Q000294:innervation; D009431:Neural Conduction; D010264:Paraplegia / Q000209:etiology / Q000503:physiopathology; D011446:Prospective Studies; D011782:Quadriplegia / Q000209:etiology / Q000503:physiopathology; D012026:Reflex, Stretch; D013119:Spinal Cord Injuries / Q000150:complications / Q000503:physiopathology*; D013979:Tibial Nerve / Q000503:physiopathology