Effects of cervical spinal cord stimulation on cerebral blood flow in the rat

Object. Spinal cord stimulation (SCS) is frequently used for the treatment of chronic pain. Although the mechanisms by which SCS alleviates pain are u nclear, they are believed to involve changes within the dorsal horn of the spinal cord. Spinal cord stimulation has also been found to cause significa nt vasodilation in the peripheral vasculature. The mechanisms underlying th is effect are thought to involve sympathetic blockade. A rostral vasodilato ry effect has also bean described, but changes in cerebral blood flow (CBF) have been poorly delineated. Using laser Doppler flowmetry (LDF), the auth ors examined the effects of cervical SCS on CBF in rats. Methods. Cervical SCS was found to result in a significant increase in cort ical LDF values (83 +/- 11% [mean +/- standard error of the mean]). The inc rease in cortical LDF values was not accompanied by a significant increase in systemic blood pressure. Stimulation of the upper cervical spinal cord w as more effective in inducing LDF changes than was that of the lower cervic al cord. Changes in SDS-induced LDF values were significantly attenuated af ter spinal cord transection at the cervicomedullary junction and by the adm inistration of the sympathetic blocker hexamethonium. Conclusions. These results indicate that cervical SCS may induce cerebral v asodilation and that this effect may involve indirect effects on vasomotor centers in the brainstem as well as an alteration in sympathetic tone.