Experimental spinal cord injury produced by axial tension

Fifty cats underwent spine distraction with forces applied until the evoked potential (EP) amplitude was reduced 50 or 95%. Neurologic status and EPs were monitored for up to 6 weeks. Fifty percent reduction occurred at (x) = 4.2-kg distraction/kg body weight (BW); 95% at 7.4 kg distraction/kg BW: differences were significant (p less than .05). The 50% group showed quadriparesis at 24 hours (Tarlov 1), improving by 4 weeks (x = 3). Ninety-five percent-group animals were quadriplegic initially, progressing to Tarlov 2.2. Residual EP changes occurred, particularly in the 95% group. Early histologic changes included central necrosis and neuronal chromatolysis. Later, axon disruption was observed, with cystic degeneration and gliosis at 4-6 weeks. Tissue damage correlated with ultimate neurologic status. Correlations between latency changes and early neurologic status, and between amplitude and histology were observed. The axial tension model may be of value in the study of spinal cord injury mechanisms.