+ Site Statistics
+ Search Articles
+ PDF Full Text Service
How our service works
Request PDF Full Text
+ Follow Us
Follow on Facebook
Follow on Twitter
Follow on LinkedIn
+ Subscribe to Site Feeds
Most Shared
PDF Full Text
+ Translate
+ Recently Requested

Crossover Phenomena in Motor Evoked Potentials During Intraoperative Neurophysiological Monitoring of Cranial Surgeries

Crossover Phenomena in Motor Evoked Potentials During Intraoperative Neurophysiological Monitoring of Cranial Surgeries

Journal of Clinical Neurophysiology 36(3): 236-241

Transcranial motor evoked potentials (TcMEPs) are used to assess the corticospinal tract during surgery. Transcranial motor evoked potentials are elicited by preferentially activating the anode over the target cortex. Crossover occurs when stimulation also induces activation of ipsilateral motor evoked responses. These responses are believed to be generated by activation of corticospinal tract on more caudal neural structures. The presence of cross activation poses a problem in craniotomy surgeries because activation of neural structures occurs distal to the area of interest leading to false negatives. Eliminating crossover may lead to activation of the motor pathway proximal to the surgical site, thus potentially reducing false-negative responses. There are no data on how often crossover signals occur or the conditions in which they take place. This study examines the frequency of crossover, the surgical procedures in which they occur, and their stimulation parameters. We reviewed all the TcMEP data files for intracranial procedures performed in 2016 at Keck Hospital of USC. We recorded demographic information about the surgical side, lobe, diagnosis, age, and sex. Only baseline TcMEPs were analyzed. Crossover responses were deemed present if recorded amplitudes were greater than 25μv on the ipsilateral side. We evaluated the rate of crossover presence, the lowest voltage associated with crossover, the highest voltage without crossover, if crossover resolved, and the last muscles to remain present when crossover is eliminated. Transcranial motor evoked potentials were divided into four groups. Group A: crossover present and was not resolved, group B1: crossover present but resolved with desired signals, group B2: no crossover seen with desired signals in both limbs, and group C: crossover resolved with loss of signals in either limb. The Difference between lowest amplitude with crossover and highest amplitude without crossover was obtained for each patient, and the mean of this difference was calculated using paired t-test. We analyzed 186 TcMEPs. Forty-four TcMEPs were in group A, 52 in B1, 68 in B2, and 22 TcMEPs were in group C. Of total crossovers (118), 63% resolved at baseline, whereas 37% did not resolve. The mean difference between minimum value with crossover and maximum value without crossover was 50 V (P < 0.0001). In five TcMEPs, this difference was 0 and the median was 250 V. There was no significant difference between surgical site, stimulation side, pathology, or sex between crossover (A) and noncrossover (B + C) groups. There was a significant association found between age group ≤50 years versus >50 years and being in crossover versus noncrossover groups (P = 0.01). For 95% of the cases in group C, the last muscles to stay were hand muscles. Transcranial motor evoked potential crossover may pose a problem during surgeries leading to false-negative results. Crossover is a frequent phenomenon that should not be overlooked. Stimulation intensity is the main factor contributing to the reduction of crossover. Crossover can be reduced in most TcMEPs performed (63%) leading to adequate monitoring in 76% of TcMEPs. Despite best efforts, there are still one quarter (24%) of TcMEPs where crossover cannot be eliminated. Newer strategies should be sought to reduce crossover. Teams should focus their efforts on reducing crossover of TcMEPs to make monitoring of intracranial surgeries more reliable.

Please choose payment method:

(PDF emailed within 1 workday: $29.90)

Accession: 066609149

Download citation: RISBibTeXText

PMID: 30893247

Related references

Reliability of intraoperative neurophysiological monitoring using motor evoked potentials during resection of metastases in motor-eloquent brain regions: clinical article. Journal of Neurosurgery 118(6): 1269-1278, 2013

Significance of intraoperative motor function monitoring using transcranial electrical motor evoked potentials (MEP) in patients with spinal and cranial lesions near the motor pathways. British Journal of Neurosurgery 23(1): 48-55, 2009

Predictive value and safety of intraoperative neurophysiological monitoring with motor evoked potentials in glioma surgery. Neurosurgery 70(5): 1060-70; Discussion 1070-1, 2012

Intraoperative neurophysiological monitoring of corticobulbar muscle motor evoked potentials in children younger than 2years. Clinical Neurophysiology 127(4): e157-e158, 2016

P31-20 Intraoperative cranial nerve monitoring with corticobulbar motor evoked potentials. Clinical Neurophysiology 121: S290-S291, 2010

An Electrode Configuration for Recording Muscle Motor Evoked Potentials in the Upper Extremities during Intraoperative Neurophysiological Monitoring. Journal of Korean Neurosurgical Society 60(4): 475-480, 2017

Intraoperative Neurophysiological Monitoring (Motor and Somatosensory Evoked Potentials) in Dorsal Root Entry Zone Lesioning for Brachial Plexus Avulsion Pain. Stereotactic and Functional Neurosurgery 95(5): 330-340, 2017

Noninvasive intraoperative monitoring of motor evoked potentials under propofol anesthesia: effects of spinal surgery on the amplitude and latency of motor evoked potentials. Neurosurgery 29(4): 551-557, 1991

Intraoperative Neurophysiological Monitoring for Spinal Cord Tumor Surgery: Comparison of Motor and Somatosensory Evoked Potentials According to Tumor Types. Annals of Rehabilitation Medicine 41(4): 610-620, 2017

The Efficacy of Intraoperative Neurophysiological Monitoring Using Transcranial Electrically Stimulated Muscle-evoked Potentials (TcE-MsEPs) for Predicting Postoperative Segmental Upper Extremity Motor Paresis After Cervical Laminoplasty. Clinical Spine Surgery 29(4): E188-E195, 2016

Intraoperative monitoring with visual evoked potentials for brain surgeries. Journal of Neurosurgery 130(2): 654-660, 2018

Comparison of Intraoperative Motor Evoked Potentials Monitoring with Direct Cranial Stimulation by Peg-Screw and Transcranial Stimulation by Corkscrew for Supratentorial Surgery. World Neurosurgery 127: E1044-E1050, 2019

Intraoperative neurophysiological monitoring of somatosensory evoked potentials during hip arthroscopy surgery. Neurodiagnostic Journal 52(4): 312-319, 2012

Localized transcranial electrical motor evoked potentials for monitoring cranial nerves in cranial base surgery. Neurosurgery 57(1 Suppl.): 78-85; Discussion 78-85, 2005

Intraoperative motor tract monitoring using transcranial magnetic motor evoked potentials. Neurology 43(4 Suppl. 2): A262, 1993