Threshold for pain from anterolateral quadrant stimulation as a predictor of success of percutaneous cordotomy for relief of pain.

A sensitive quantitative index for predicting optimal electrode position in percutaneous anterolateral cordotomy was determined by electrical stimulation through the lesioning electrode. If the threshold for pain elicited by the stimulation electrode was less than 300 muA, a 5-sec radiofrequency lesion of 50 mA would produce complete contralateral analgesia with no weakness. When the pain threshold exceeded 300 muA, incomplete or no analgesia would result with the standard single lesion. The results further suggested that the fibers in the anterolateral quadrant that transmit pain are discretely rather than diffusely localized.