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.
METHODS
This study involved a model of spinal claudication to assess the effect of single and double site compressions on blood flow in porcine cauda equina. Real-time monitoring of blood flow was achieved by using laser Doppler probes.


OBJECTIVE
To ascertain the difference 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 claudication.


BACKGROUND
The model used was based on that of K. Olmarker. Double as compared with single site compression of cauda equina showed impaired nerve impulse propagation and decreased blood flow.


METHODS
Pigs weighing 22-27 kg were anesthesized and the cauda equina was exposed by dorsal laminectomy of the sacral and first three coccygeal vertebrae. Polyethylene balloons were placed over the rootlets at the first and third coccygeal segments, and stimulating electrodes were positioned on the rootlets proximally to evoke motor activity. Electromyographic activity was monitored from tail musculature. Laser Doppler probes monitored blood flow in the cauda equina both between and distal to the two compression sites.


RESULTS
Single site, low level compression did not affect blood flow whereas double site compression decreased it profoundly. Proximal stimulation caused a marked increase in blood flow, which was not sustained during prolonged compression. Electromyographic activity diminished concomitantly during this compression.


CONCLUSIONS
Low pressure, double site compression significantly reduces cauda equina blood flow and prevents the sustained increase in blood flow required to maintain normal neurologic rootlet function. Local blood flow failure may therefore be responsible for claudication symptoms.
Baker
A R
AR
Department of Biomedical Sciences, University of Aberdeen, Scotland.
Collins
T A
TA
Porter
R W
RW
Kidd
C
C
D000818:Animals; D001783:Blood Flow Velocity / Q000502:physiology; D002420:Cauda Equina / Q000098:blood supply*; D004195:Disease Models, Animal; D004558:Electric Stimulation; D004576:Electromyography; D017078:Laser-Doppler Flowmetry; D013117:Spinal Cord Compression / Q000503:physiopathology*; D013130:Spinal Stenosis / Q000503:physiopathology*; D013552:Swine