AXON REGENERATION AFTER DECOMPRESSION OF THE CONUS MEDULLARIS

Study Design. The effect of acute spinal stenosis (simulating fracture ) and decompression of stenosis on axon regeneration was evaluated in an animal model. Objectives. Clinical function and quantitative histom orphometry were used to gain insight into the clinicopathologic effect s of acute spinal stenosis and decompression. Summary of Background Da ta. Decompression of extrinsic compression after thoracolumbar fractur es has been suggested to maximize recovery of neurologic function. Cli nical studies seem to support this, but the histologic results of deco mpression are poorly understood. Methods. Experimental spinal stenosis was created in 5 female beagle dogs, followed by decompression in thr ee of the beagles at 6 weeks. Clinical function and histologic appeara nce were analyzed using a monoclonal antibody to neurofilaments. Resul ts. Stenosis consistently produced significant neurologic deficit and axon degeneration within motor roots distal to the stenosis. Decompres sion resulted in improved neurologic function and a tendency for the a xons to return to normal number and volume based on quantitative histo morphometry. Conclusion. This study provides an animal model and funct ional and histologic data that support the use of decompression of acu te spinal stenosis of 50% or more canal compromise at the level of the conus medullaris and a neurologic deficit. This may be seen clinicall y in thoracolumbar fractures.