Multimodality intraoperative monitoring during complex lumbosacral procedures: indications, techniques, and long-term follow-up review of 61 consecutive cases

Abstract

<jats:p content-type="fine-print"><jats:italic>Object.</jats:italic> The purpose of this study was to examine the neurological outcomes after complex lumbosacral surgery in patients undergoing multimodality neurophysiological monitoring.</jats:p> <jats:p content-type="fine-print"><jats:italic>Methods.</jats:italic> Sixty-one patients were consecutively enrolled in this study. These patients underwent complex intra- and extradural lumbosacral procedures with concomitant intraoperative electromyography (EMG) monitoring of the lower-limb muscles, external anal and urethral sphincters (EAS and EUS), and lower-limb somatosensory evoked potentials (SSEPs). Long-term (minimum 2-year) clinical follow-up data were obtained in all cases.</jats:p> <jats:p content-type="fine-print">Most patients were treated for spinal/spinal cord tumors (61%) or adult tethered cord syndrome (25%). Recordable lower-extremity SSEPs were reported in 54 patients (89%). New postoperative neurological deficits occurred in only three patients (4.9%), and remained persistent in only one patient (1.6%) at long-term follow-up examination. In only one of these cases was a significant decrease in SSEP amplitude detected. Spontaneous EMG activity was observed in the lower-extremity muscles and/or EAS and EUS in 51 cases (84%). Intraoperatively, EMG demonstrated activity only in the EUS in 5% of patients and only in the EAS in 28%. In seven patients (11%) spontaneous intraoperative EMG activity was observed in both the EAS and the EUS; however, in only three of these cases was EMG activity recorded in both sphincters simultaneously. In addition to spontaneously recorded EMG activity, electrically evoked EMG activity was also used as an intraoperative adjunct. A bipolar stimulating electrode was used to identify functional neural tissue before undertaking microsurgical dissection in 58 individuals (95%). In the majority of these patients, evoked EMG activity occurred either in one (33%) or in two muscles (9%) simultaneously. The presence of electrically evoked EMG activity in structures encountered during microdissection altered the plan of treatment in 24 cases (42%).</jats:p> <jats:p content-type="fine-print"><jats:italic>Conclusions.</jats:italic> The authors conclude that the combined SSEP and EMG monitoring of lower-limb muscles, EAS, and EUS is a practical and reliable method for obtaining optimal electrophysiological feedback during complex neurosurgical procedures involving the conus medullaris and cauda equina. Analysis of the results indicates that these intraoperative adjunctive modalities positively influence decision making with regard to microsurgery and reduce the risk of perioperative neurological complications. Validation of the clinical value of these approaches, however, will require further assessment in a larger prospective cohort of patients.</jats:p>

Complications associated with the treatment for spinal ependymomas

“…65 While the advantages of neurophysiological monitoring have been demonstrated in a number of studies regarding thoracolumbar spinal lesions, data regarding its use for operations involving the cervical spine are limited. 3,31,50,65,69 Given the low incidence of new postoperative neurological deficits for surgeries in this region, SSEP inaccuracy and suboptimal sensitivity make this a poor choice for single-modality monitoring. 65,75 In fact, isolated injury to the motor tracks with sparing of the sensory pathways may allow false-negative responses and result in postoperative deficits.…”

“…Additionally, EMG monitoring is also considered a very sensitive technique, but it lacks specificity. 50,65,69 Given the potentially devastating impact of a neurological injury at the cervical level, Kelleher and colleagues 65 recommended intraoperative monitoring in all operations with neurological risk despite the low incidence of neurological complications. As no single monitoring modality appears optimal alone, multimodal monitoring may be the best approach.…”

Intraoperative somatosensory evoked potentials to facilitate peripheral nerve release

“…Ultimately, the best clinical prospect could be to combine SSEP and EMG, rather than excluding one technique from another. 11 Regarding the LFCN, one limitation lies in the fact that this nerve is purely sensory, precluding the use of usual motor nerve stimulation patterns. Nevertheless, LFCN cutaneous supply zone stimulation is possible 7,12 according to techniques published previously, 13 and recently refined.…”

Editorial

“…Previous studies have demonstrated the utility of electrophysiological monitoring in the treatment of complex lumbosacral pathological conditions. 2,3 It is possible that the relatively high number of false-negative results reported by Sansur et al reflect institutional heterogeneity in the way intraoperative electrophysiological monitoring is performed, or failure to use both electromyography and somatosensory evoked potentials to monitor the integrity of neural structures. J Neurosurg: Spine / Volume 13 / November 2010 It is clear that the surgical management of DS and IS remains challenging.…”