Evoked potential testing.

Abstract

Electrophysiologic tests of the sacral neuromuscular system and its suprasegmental control may be divided into EMG and methods involving stimulation (i.e., evoked potential and sacral reflex testing). The latter group of methods tests the function of defined parts of the motor or sensory nervous system, or reflex arcs. There already is ample experience with testing the somatic sensory pathways (pudendal SEP) and the (somatic) sacral reflex arc, whereas other methods (testing the motor system and tests involving visceral afferents and sympathetic efferents) need further study to establish their proper place in everyday clinical diagnostics. The application of these methods in research has led to important advances in our understanding of nervous system involvement in different pathologic conditions leading to neurogenic sacral dysfunctions. If applied in individual patients, these methods should however, be used and interpreted with restraint; they should be considered in patients with probable or proved nervous system lesions, those in whom additional clarification regarding proof of, localization of, and the nature (i.e., axonal versus demyelinative) of the lesion is relevant for diagnosis and prognosis. If applied in patients with central nervous system involvement, evoked potential studies may be used on their own; but, in the author's opinion, in patients with putative peripheral nervous system involvement these tests should be considered, as a rule, only as an extension of a needle EMG exploration. It is expected that further experience will clarify the sensitivity and specificity of the available methods. The already available methods certainly will gain a place in the operating room helping the surgeon in selected procedures involving the pelvis and particularly conus and cauda equina better to identify neuromuscular structures and to monitor their function throughout the operation in order to prevent subsequent development of lesions.