Intraoperative changes in transcranial motor evoked potentials and somatosensory evoked potentials predicting outcome in children with intramedullary spinal cord tumors

Abstract

<jats:sec> <jats:title>Object</jats:title> <jats:p>Intraoperative dorsal column mapping, transcranial motor evoked potentials (TcMEPs), and somatosensory evoked potentials (SSEPs) have been used in adults to assist with the resection of intramedullary spinal cord tumors (IMSCTs) and to predict postoperative motor deficits. The authors sought to determine whether changes in MEP and SSEP waveforms would similarly predict postoperative motor deficits in children.</jats:p></jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>The authors reviewed charts and intraoperative records for children who had undergone resection for IMSCTs as well as dorsal column mapping and TcMEP and SSEP monitoring. Motor evoked potential data were supplemented with electromyography data obtained using a Kartush microstimulator (Medtronic Inc.). Motor strength was graded using the Medical Research Council (MRC) scale during the preoperative, immediate postoperative, and follow-up periods. Reductions in SSEPs were documented after mechanical traction, in response to maneuvers with the cavitational ultrasonic surgical aspirator (CUSA), or both.</jats:p></jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>Data from 12 patients were analyzed. Three lesions were encountered in the cervical and 7 in the thoracic spinal cord. Two patients had lesions of the cervicomedullary junction and upper spinal cord. Intraoperative MEP changes were noted in half of the patients. In these cases, normal polyphasic signals converted to biphasic signals, and these changes correlated with a loss of 1–2 grades in motor strength. One patient lost MEP signals completely and recovered strength to MRC Grade 4/5. The 2 patients with high cervical lesions showed neither intraoperative MEP changes nor motor deficits postoperatively. Dorsal columns were mapped in 7 patients, and the midline was determined accurately in all 7. Somatosensory evoked potentials were decreased in 7 patients. Two patients each had 2 SSEP decreases in response to traction intraoperatively but had no new sensory findings postoperatively. Another 2 patients had 3 traction-related SSEP decreases intraoperatively, and both had new postoperative sensory deficits that resolved. One additional patient had a CUSA-related SSEP decrease intraoperatively, which resolved postoperatively, and the last patient had 3 traction-related sensory deficits and a CUSA-related sensory deficit postoperatively, none of which resolved.</jats:p></jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>Intraoperative TcMEPs and SSEPs can predict the degree of postoperative motor deficit in pediatric patients undergoing IMSCT resection. This technique, combined with dorsal column mapping, is particularly useful in resecting lesions of the upper cervical cord, which are generally considered to be high risk in this population. Furthermore, the spinal cord appears to be less tolerant of repeated intraoperative SSEP decreases, with 3 successive insults most likely to yield postoperative sensory deficits. Changes in TcMEPs and SSEP waveforms can signal the need to guard against excessive manipulation thereby increasing the safety of tumor resection.</jats:p></jats:sec>

Differences in Multimodality Intraoperative Neurophysiological Monitoring Changes Between Spinal Intramedullary Ependymoma and Hemangioblastoma

“…In contrast, hemangioblastomas are located posteriorly (Mandigo et al, 2009) and should be removed in an en bloc fashion; debulking of the tumor should be avoided (Brotchi, 2002;Mandigo et al, 2009;Takami et al, 2015). However, previous studies on IONM for IMSCT did not separate tumors according to their specific pathology but instead grouped them together as IMSCT (Kothbauer, 2007;Hyun and Rhim, 2009;Cheng et al, 2014;Choi et al, 2014;Kobayashi et al, 2014).…”

Intramedullary spinal cavernoma: clinical presentation, microsurgical approach, and long-term outcome in a cohort of 48 patients

“…9,26 A microsurgical alternative to the CO 2 laser is the cavitational ultrasonic surgical aspirator (CUSA) in spinal cord tumor surgery. 4,7 Regarding the bony approach to the spinal cord, various strategies ranging from keyhole approaches (for example, hemilaminectomies) to more extensive multiple-level laminectomies in large ISC were applied in our cohort. Recent approaches focus on nondestructive, minimally invasive strategies if possible to obtain an adequate anatomical overview.…”

Feasibility and Predictability of Intraoperative Monitoring in Patients with Intradural Extramedullary and Epidural Metastatic Spinal Tumors

“…Morota et al reported a MEP sensitivity of 100% in all 3 patients, who showed more than 50% decrease of MEP amplitude resulted in paraplegia at immediate postoperative period [6]. Cheng et al also presented 100% sensitivity of transcranial MEP in all 6 patients with MEP changes out of 12 paediatric patients with intramedullary tumours [7]. And they evaluated SSEP changes and only 3 out of 7 patients with SSEP changes showed postoperative sensory deficit.…”

“…Later, MEP has played role in intramedullary spinal cord tumour surgery, where motor and sensory pathway could be separately dissected [6,7]. Among spinal tumours, intradural extramedullary (IDEM) and epidural (ED) metastatic spinal tumours are ideal for monitoring surgical manipulation of spinal cord as those tumours are free of both intrinsic pathologic condition of spinal cord and selective spinal cord dissection such as myelotomy.…”