Phase Reversal of Somatosensory Evoked Potentials Triggered by Gracilis Tract Stimulation: Case Report of a New Technique for Neurophysiologic Dorsal Column Mapping

Neurosurgery ◽  
2011 ◽  
Vol 70 (3) ◽  
pp. 783-783 ◽  
Author(s):  
Mirela V. Simon ◽  
Keith H. Chiappa ◽  
Lawrence F. Borges ◽  
Marc R. Nuwer ◽  
Vedran Deletis
Keyword(s):  
Spinal Cord ◽  
Evoked Potentials ◽  
Somatosensory Evoked Potentials ◽  
Spinal Cord Tumor ◽  
Tumor Resection ◽  
Dorsal Column ◽  
Intramedullary Spinal Cord ◽  
Phase Reversal ◽  
Dorsal Columns ◽  
A New Technique

Abstract Background and Importance: Reliable visual identification of the median raphae, essential for the preservation of function of the posterior dorsal columns during intramedullary spinal cord tumor resection, is not possible in many cases, because of distorted local anatomy. In such cases, intraoperative neurophysiologic mapping of the dorsal columns offers invaluable information to the surgeon, and guides the myelotomy. We hereby describe such a new technique. Clinical Presentation: A 41 -year-old man with a C3-C4 intramedullary spinal cord tumor underwent successful myelotomy and tumor resection. Dorsal column mapping was performed by use of an 8-contact minielectrode strip placed on the dorsal spinal cord. Direct electrical stimulation was applied via 2 adjacent contacts of the strip at a time, in an attempt to stimulate in succession the left and right dorsal columns. Somatosensory evoked potentials (SSEPs) were recorded after each stimulation, via scalp electrodes. A sharp change in polarity of the recorded scalp SSEPs (phase reversal) indicated when the stimulation of the opposite dorsal column occurred. Myelotomy was performed in between the minielectrode contacts identified as being situated closest to the raphe. The posterior tibial SSEPs were continuously monitored during and after myelotomy and until the dura closure. No changes from premyelotomy SSEPs were present. Postoperatively, the patient had preservation of the posterior column function. Conclusion: SSEP phase-reversal technique is a promising new method to identify the neurophysiologic midline in intramedullary tumor resection. Fast and easy to perform, its final role in neurophysiologic dorsal column mapping awaits confirmation in future applications.

Dorsal Column Mapping via Phase Reversal Method

Neurosurgery ◽  
2014 ◽  
Vol 74 (4) ◽  
pp. 437-446 ◽  
Author(s):  
Dinesh Nair ◽  
Vishakhadatta M. Kumaraswamy ◽  
Diana Braver ◽  
Ronan D. Kilbride ◽  
Lawrence F. Borges ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Evoked Potentials ◽  
Somatosensory Evoked Potentials ◽  
Spinal Cord Tumor ◽  
Tumor Resection ◽  
Dorsal Column ◽  
Neurological Deficits ◽  
Reliable Technique ◽  
Intramedullary Spinal Cord ◽  
Phase Reversal

ABSTRACT BACKGROUND: Safe resection of intramedullary spinal cord tumors can be challenging, because they often alter the cord anatomy. Identification of neurophysiologically viable dorsal columns (DCs) and of neurophysiologically inert tissue, eg, median raphe (MR), as a safe incision site is crucial for avoiding postoperative neurological deficits. We present our experience with and improvements made to our previously described technique of DC mapping, successfully applied in a series of 12 cases. OBJECTIVE: To describe a new, safe, and reliable technique for intraoperative DC mapping. METHODS: The right and left DCs were stimulated by using a bipolar electric stimulator and the triggered somatosensory evoked potentials recorded from the scalp. Phase reversal and amplitude changes of somatosensory evoked potentials were used to neurophysiologically identify the laterality of DCs, the inert MR, as well as other safe incision sites. RESULTS: The MR location was neurophysiologically confirmed in all patients in whom this structure was first visually identified as well as in those in whom it was not, with 1 exception. DCs were identified in all patients, regardless of whether they could be visually identified. In 3 cases, negative mapping with the use of this method enabled the surgeon to reliably identify additional inert tissue for incision. None of the patients had postoperative worsening of the DC function. CONCLUSION: Our revised technique is safe and reliable, and it can be easily incorporated into routine intramedullary spinal cord tumor resection. It provides crucial information to the neurosurgeon to prevent postoperative neurological deficits.

Dorsal Column Mapping for Intramedullary Spinal Cord Tumor Resection Decreases Dorsal Column Dysfunction

2012 ◽  
Vol 25 (4) ◽  
pp. 205-209 ◽  
Author(s):  
Ankit Indravadan Mehta ◽  
Cindy A. Mohrhaus ◽  
Aatif M. Husain ◽  
Isaac O. Karikari ◽  
Betsy Hughes ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Tumor ◽  
Tumor Resection ◽  
Dorsal Column ◽  
Intramedullary Spinal Cord ◽  
Intramedullary Spinal Cord Tumor

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

2014 ◽  
Vol 13 (6) ◽  
pp. 591-599 ◽  
Author(s):  
Jason S. Cheng ◽  
Michael E. Ivan ◽  
Christopher J. Stapleton ◽  
Alfredo Quinones-Hinojosa ◽  
Nalin Gupta ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Evoked Potentials ◽  
Somatosensory Evoked Potentials ◽  
Motor Evoked Potentials ◽  
Dorsal Column ◽  
Motor Deficits ◽  
Intramedullary Spinal Cord ◽  
Sensory Deficits ◽  
Motor Strength ◽  
Transcranial Motor Evoked Potentials

Object 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. Methods 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. Results 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. Conclusions 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.

scholarly journals High-resolution direct microstimulation mapping of spinal cord motor pathways during resection of an intramedullary tumor

2015 ◽  
Vol 22 (2) ◽  
pp. 205-210 ◽  
Author(s):  
Ravi Gandhi ◽  
Corinne M. Curtis ◽  
Aaron A. Cohen-Gadol
Keyword(s):  
Spinal Cord ◽  
Evoked Potentials ◽  
Motor Evoked Potentials ◽  
Spinal Cord Tumor ◽  
Tumor Resection ◽  
Intramedullary Tumor ◽  
Intramedullary Tumors ◽  
Intramedullary Spinal Cord ◽  
Supratentorial Gliomas ◽  
Microsurgical Techniques

Despite the use of advanced microsurgical techniques, resection of intramedullary tumors may result in significant postoperative deficits because of the vicinity or invasion of important functional tracts. Intraoperative monitoring of somatosensory evoked potentials and transcranial electrical motor evoked potentials has been used previously to limit such complications. Electromyography offers an opportunity for the surgeon to map the eloquent tissue associated with the tumor using intraoperative motor fiber stimulation. Similar to the use of cortical simulation in the resection of supratentorial gliomas, this technique can potentially advance the safety of intramedullary spinal cord tumor resection. The authors describe the use of intraoperative motor fiber tract stimulation to map the corticospinal tracts associated with an intramedullary tumor. This technique led to protection of these tracts during resection of the tumor.

scholarly journals Continuous mapping of the corticospinal tracts in intramedullary spinal cord tumor surgery using an electrified ultrasonic aspirator

2017 ◽  
Vol 27 (2) ◽  
pp. 161-168 ◽  
Author(s):  
Ori Barzilai ◽  
Zvi Lidar ◽  
Shlomi Constantini ◽  
Khalil Salame ◽  
Yifat Bitan-Talmor ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Evoked Potentials ◽  
Spinal Cord Tumor ◽  
Tumor Resection ◽  
Continuous Mapping ◽  
Intramedullary Spinal Cord ◽  
Ultrasonic Aspirator ◽  
Corticospinal Tracts ◽  
Primary Treatment Modality ◽  
D Wave

Intramedullary spinal cord tumors (IMSCTs) represent a rare entity, accounting for 4%–10% of all central nervous system tumors. Microsurgical resection of IMSCTs is currently considered the primary treatment modality. Intraoperative neurophysiological monitoring (IONM) has been shown to aid in maximizing tumor resection and minimizing neurological morbidity, consequently improving patient outcome. The gold standard for IONM to date is multimodality monitoring, consisting of both somatosensory evoked potentials, as well as muscle-based transcranial electric motor evoked potentials (tcMEPs). Monitoring of tcMEPs is optimal when combining transcranial electrically stimulated muscle tcMEPs with D-wave monitoring. Despite continuous monitoring of these modalities, when classic monitoring techniques are used, there can be an inherent delay in time between actual structural or vascular-based injury to the corticospinal tracts (CSTs) and its revelation. Often, tcMEP stimulation is precluded by the surgeon’s preference that the patient not twitch, especially at the most crucial times during resection. In addition, D-wave monitoring may require a few seconds of averaging until updating, and can be somewhat indiscriminate to laterality. Therefore, a method that will provide immediate information regarding the vulnerability of the CSTs is still needed.The authors performed a retrospective series review of resection of IMSCTs using the tip of an ultrasonic aspirator for continuous proximity mapping of the motor fibers within the spinal cord, along with classic muscle-based tcMEP and D-wave monitoring.The authors present their preliminary experience with 6 patients who underwent resection of an IMSCT using the tip of an ultrasonic aspirator for continuous proximity mapping of the motor fibers within the spinal cord, together with classic muscle-based tcMEP and D-wave monitoring. This fusion of technologies can potentially assist in optimizing resection while preserving neurological function in these challenging surgeries.

scholarly journals Intramedullary spinal cord tumor resection

2012 ◽  
Vol 33 (Suppl1) ◽  
pp. 1
Author(s):  
Mari L. Groves ◽  
Patricia L. Zadnik ◽  
Pablo F. Recinos ◽  
Violette Renard ◽  
George I. Jallo
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Tumor ◽  
Tumor Resection ◽  
Progression Free Survival ◽  
Low Grade ◽  
High Definition ◽  
En Bloc ◽  
Intramedullary Spinal Cord ◽  
Free Survival ◽  
Intramedullary Spinal Cord Tumor

The authors present a case of a 27-year-old patient who presented with spastic gait and worsening difficulty walking over a 6 month period. Spinal MR imaging revealed a heterogeneously enhancing intramedullary spinal cord tumor (IMSCT) with associated syrinx in the cervical spine. The lesion was resected through posterior en bloc laminotomy, durotomy, and microscopic resection of the intramedullary component followed by laminoplasty reconstruction. Surgical resections with a goal of gross total resection can significantly improve overall survival and progression free survival in patients with low-grade IMSCT. The procedure is presented in an edited, high-definition format with accompanying narrative. The video can be found here: http://youtu.be/Ui9bn82PtP8.

Spinal evoked potentials from the motor tracts

1983 ◽  
Vol 58 (1) ◽  
pp. 38-44 ◽  
Author(s):  
Walter J. Levy
Keyword(s):  
Spinal Cord ◽  
Evoked Potentials ◽  
Motor System ◽  
Evoked Potential ◽  
Motor Evoked Potential ◽  
Dorsal Column ◽  
Content Type ◽  
Dorsal Columns ◽  
Evoked Potential Monitoring ◽  
Potential Monitoring

✓ There is a need to monitor the motor system, but it has a different blood supply and a different location in the spinal cord from those measured by traditional somatosensory evoked potential monitoring. This paper reports a motor evoked potential monitoring system that uses direct spinal cord stimulation overlying the areas of the motor tract in the cord. In nine cats, evoked potentials were recorded from the dura, which gave a much faster main signal component than the traditional dorsal column evoked potentials, which were also recorded. This 100-m/sec signal was not affected by sectioning of the dorsal columns, which was verified histologically. This mode of monitoring the motor system can be used during surgery. It may also provide a better evaluation of patients after spinal cord trauma.

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