Arch Phys Med Rehabil, 2004 · DOI: · Published: May 1, 2004
Spasticity, common after spinal cord injury (SCI), is often blamed on overly sensitive stretch reflexes. This study aimed to see if this is due to increased excitability in the spinal cord connections responsible for these reflexes. The researchers used the H-reflex, a way to test spinal cord excitability, on people with and without SCI to see if there were any differences in how easily their muscles were activated. The results showed no significant difference in H-reflex measures between the groups, suggesting that factors other than simple spinal cord excitability might be responsible for spasticity after SCI.
The findings challenge the common assumption that spasticity after SCI is primarily due to increased excitability of monosynaptic reflex connections.
The study suggests that future research should focus on factors extrinsic to these connections, such as gamma motor activity and musculotendonous properties, to better understand the mechanisms underlying spasticity.
The results highlight the need for caution when using H-reflex measures to assess the effectiveness of spasticity treatments, as these measures are not abnormal in persons with chronic SCI.