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.[1]References
- From spinal shock to spasticity: neuronal adaptations to a spinal cord injury. Hiersemenzel, L.P., Curt, A., Dietz, V. Neurology (2000) [Pubmed]
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