[Early functional and structural changes in the nerve tissue following contact with chymopapain]

Using magnetic resonance imaging, conventional histology, and spinal evoked potentials, the authors studied the short-term effects of chymopapain on nerve tissue in the lumbar vertebral canal region in rats. Chymopapain in different concentrations was injected into the subarachnoid space in 31 rats. As early as 20 minutes later latency changes in the evoked potentials were observed; the histologic examinations after two hours showed bleeding, swelling of the myelin, and vascular changes. Magnetic resonance imaging of the lumbar spine, performed after six hours, showed a markedly stronger signal, indicative of an intraspinal edema, as compared to the control group. The authors' studies are clear proof that changes in nerve tissue following contact with chymopapain occur considerably faster than hitherto assumed in the literature.