Surgery for intramedullary spinal cord tumors: the role of intraoperative (neurophysiological) monitoring

Abstract

In spite of advancements in neuro-imaging and microsurgical techniques, surgery for intramedullary spinal cord tumors (ISCT) remains a challenging task. The rationale for using intraoperative neurophysiological monitoring (IOM) is in keeping with the goal of maximizing tumor resection and minimizing neurological morbidity. For many years, before the advent of motor evoked potentials (MEPs), only somatosensory evoked potentials (SEPs) were monitored. However, SEPs are not aimed to reflect the functional integrity of motor pathways and, nowadays, the combined used of SEPs and MEPs in ISCT surgery is almost mandatory because of the possibility to selectively injury either the somatosensory or the motor pathways. This paper is aimed to review our perspective in the field of IOM during ISCT surgery and to discuss it in the light of other intraoperative neurophysiologic strategies that have recently appeared in the literature with regards to ISCT surgery. Besides standard cortical SEP monitoring after peripheral stimulation, both muscle (mMEPs) and epidural MEPs (D-wave) are monitored after transcranial electrical stimulation (TES). Given the dorsal approach to the spinal cord, SEPs must be monitored continuously during the incision of the dorsal midline. When the surgeon starts to work on the cleavage plane between tumor and spinal cord, attention must be paid to MEPs. During tumor removal, we alternatively monitor D-wave and mMEPs, sustaining the stimulation during the most critical steps of the procedure. D-waves, obtained through a single pulse TES technique, allow a semi-quantitative assessment of the functional integrity of the cortico-spinal tracts and represent the strongest predictor of motor outcome. Whenever evoked potentials deteriorate, temporarily stop surgery, warm saline irrigation and improved blood perfusion have proved useful for promoting recovery, Most of intraoperative neurophysiological derangements are reversible and therefore IOM is able to prevent more than merely predict neurological injury. In our opinion combining mMEPs and D-wave monitoring, when available, is the gold standard for ISCT surgery because it supports a more aggressive surgery in the attempt to achieve a complete tumor removal. If quantitative (threshold or waveform dependent) mMEPs criteria only are used to stop surgery, this likely impacts unfavorably on the rate of tumor removal.

Ependimomas del filum terminal. Análisis de 20 casos consecutivos

“…Cuando existe buen plano de disección la resección completa es posible sin necesidad de aplicar tratamientos posteriores 3 . Aunque en nuestra experiencia, únicamente se ha utilizado monitorización neurofisiológica en 4 casos, pensamos, al igual que otros autores, que el empleo de potenciales evocados somatosensoriales y motores, electromiografía de los músculos de miembros inferiores así como de los esfínteres anal y uretral, contribuyen a obtener un estricto control funcional del cono medular y del filum terminal, permitiendo exéresis más amplias y seguras, reduciendo de forma significativa las secuelas neurológicas 9,36 .…”

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

“…Because MEP has potentials to spontaneously recover after suspension of surgical manipulation of cord. Also, we carefully irrigate surgical field with warm saline help to keep surgical field warm [15]. We need to verify these results after correction of bias (i.e.…”

A survey of the “surgical and research” articles in the European Spine Journal, 2007

“…We are introduced to the concept of multimodal intraoperative monitoring, and that it consists of intraoperative spinal and cortical-evoked potentials combined with continuous EMG and motor evoked potentials of muscles [50]. We are provided with an American view, by a neurologist, anesthesiologist and spine surgeon [36], and then a number of papers dealing with its use and results in various types of spinal surgery, principally from the Schulthess Clinic Zurich, Switzerland [14][15][16]51], from Italy [43] and Saudi Arabia [33]. These papers cover the use of MIOM in the thoracolumbar spine, the thoracic spine, the cervical spine, dealing with stenosis and deformity, and also intramedullary tumors [43,51].…”

“…We are provided with an American view, by a neurologist, anesthesiologist and spine surgeon [36], and then a number of papers dealing with its use and results in various types of spinal surgery, principally from the Schulthess Clinic Zurich, Switzerland [14][15][16]51], from Italy [43] and Saudi Arabia [33]. These papers cover the use of MIOM in the thoracolumbar spine, the thoracic spine, the cervical spine, dealing with stenosis and deformity, and also intramedullary tumors [43,51]. I particularly enjoyed the paper by Sala, as it indicated the particular value of each monitoring system as one dissected into the cord in removing a tumor, allowing one to understand the necessity for a multimodal system.…”