Recent developments in neurosurgical spinal cord monitoring

In a review 8 years ago, the then current status of intraoperative spinal cord monitoring (SCM) was discussed. Concerning future developments, that article concluded that the major challenge lay in (a) the improvement of the reliability and clinical relevance of somatosensory evoked potential (SEP) monitoring, where the incidence of false-negative and false-positive results had to be reduced, and (b) the application of new techniques like motor evoked potential (MEP) monitoring, which might turn out to be a method complementary to the SEP approach. Since that time, there has been a considerable amount of newly published results from intraoperative SCM, although clinical articles on exclusively neurosurgical SCM are rare (Table I). A selective literature search for the present review (primarily for the time from 1988 to 1992) yielded more than 200 citations. Eighty-one studies entered into the final evaluation; among these were 3 conference proceedings, 6 book chapters, and 10 review articles. Further, 40 clinical articles, and 22 articles on experimental work were counted. In particular, experimental studies in animals have given support to clinical monitoring by exploring the usefulness of new stimulation and recording techniques. This reappraisal only considers recent work on SEP and MEP in neurosurgical SCM with some experimental studies relevant to clinical SCM. Spinal cord monitoring in orthopaedic surgery is not evaluated in this review for reasons detailed in the article.