Electrophysiological technique for evaluating lesions of the conus medullaris and cauda equina

The authors describe the use of evoked electromyographic responses recorded in the anal sphincter induced by stimulation of the bladder wall and urethra in evaluating lesions of the conus medullaris and cauda equina in 110 patients. This reflex response took effect by way of the pelvic nerves and cauda equina to the sacral cord where the pudendal nerve nucleus was activated, resulting in a contraction of the external anal sphincter. Various lesions along this pathway have been shown to produce either increased latencies and depressed responses or complete loss of response depending on the extent of the lesion. The correlation of results of this technique with clinical, myelographic, and operative findings indicate it to be a useful clinical tool.