LASER-DOPPLER STUDY OF PORCINE CAUDA-EQUINA BLOOD-FLOW - THE EFFECT OF ELECTRICAL-STIMULATION OF THE ROOTLETS DURING SINGLE AND DOUBLE SITE, LOW-PRESSURE COMPRESSION OF THE CAUDA-EQUINA

Study Design. This study involved a model of spinal claudication to as sess the effect of single and double site compressions on blood flow i n procine cauda equina. Real-time monitoring of blood flow was achieve d by using laser Doppler probes. Objectives. To ascertain the differen ce between single and double site compressions on blood flow and nerve conduction in the cauda equina. Also to provide possible explanations for the mechanisms underlying the pathophysiology of neurogenic claud ication. Summary of Background Data. The model used was based on that of K. Olmarker. Double as compared with single site compression of cau da equina showed impaired nerve impulse propagation and decreased bloo d flow. Method. Pigs weighing 22-27 kg were anesthetized and the cauda equina was exposed by dorsal laminectomy of the sacral and first thre e coccygeal vertebrae. Polyethylene balloons were placed over the root lets at the first and third coccygeal segments, and stimulating electr odes were positioned on the rootlets proximally to evoke motor activit y. Electromyographic activity was monitored from tail musculature. Las er Doppler probes monitored blood flow in the cauda equina both betwee n and distal to the two compression sites. Results. Single site, low l evel compression did not affect blood flow whereas double site compres sion decreased it profoundly. Proximal stimulation caused a marked inc rease in blood flow, which was not sustained during prolonged compress ion. Electromyographic activity diminished concomitantly during this c ompression. Conclusions. Low pressure, double site compression signifi cantly reduces cauda equina blood flow and prevents the sustained incr ease in blood flow required to maintain normal neurologic rootlet func tion. Local blood flow failure may therefore be responsible for claudi cation symptoms.