The Percentage of Amplitude Decrease Warning Criteria for Transcranial MEP Monitoring

Journée, H. L.; Berends, Hanneke I.; Kruyt, Moyo C.

doi:10.1097/wnp.0000000000000338

Cited by 38 publications

(22 citation statements)

References 46 publications

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“…The trial-to-trial variability of amplitudes varies for TES between 1:1.3 and 1:6.5, and variations between 1:1.4 and 1:13 are observed for TMS. These values are somewhat higher than those reported in anesthetized human patients for stimulation intensities at supramaximal levels (range is 1:1.7 to 1:3.3) and are lower than the large variation of 1:26 at intensities just above ET ( Journée et al, 2017 ). The amplitude variations at supra-maximum intensity agree with those reported in a previous study ( Journée et al, 2015 ).…”

Section: Discussioncontrasting

confidence: 63%

Comparison of Muscle MEPs From Transcranial Magnetic and Electrical Stimulation and Appearance of Reflexes in Horses

Journée

Berends³

et al. 2020

Front. Neurosci.

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Introduction Transcranial electrical (TES) and magnetic stimulation (TMS) are both used for assessment of the motor function of the spinal cord in horses. Muscular motor evoked potentials (mMEP) were compared intra-individually for both techniques in five healthy horses. mMEPs were measured twice at increasing stimulation intensity steps over the extensor carpi radialis (ECR), tibialis cranialis (TC), and caninus muscles. Significance was set at p < 0.05. To support the hypothesis that both techniques induce extracranially elicited mMEPs, literature was also reviewed. Results Both techniques show the presence of late mMEPs below the transcranial threshold appearing as extracranially elicited startle responses. The occurrence of these late mMEPs is especially important for interpretation of TMS tracings when coil misalignment can have an additional influence. Mean transcranial motor latency times (MLT; synaptic delays included) and conduction velocities (CV) of the ECR and TC were significantly different between both techniques: respectively, 4.2 and 5.5 ms (MLT TMS – -MLT TES ), and −7.7 and −9.9 m/s (CV TMS -CV TES ). TMS and TES show intensity-dependent latency decreases of, respectively, −2.6 (ECR) and −2.7 ms (TC)/30% magnetic intensity and −2.6 (ECR) and −3.2 (TC) ms/30V. When compared to TMS, TES shows the lowest coefficients of variation and highest reproducibility and accuracy for MLTs. This is ascribed to the fact that TES activates a lower number of cascaded interneurons, allows for multipulse stimulation, has an absence of coil repositioning errors, and has less sensitivity for varying degrees of background muscle tonus. Real axonal conduction times and conduction velocities are most closely approximated by TES. Conclusion Both intracranial and extracranial mMEPs inevitably carry characteristics of brainstem reflexes. To avoid false interpretations, transcranial mMEPs can be identified by a stepwise latency shortening of 15–20 ms when exceeding the transcranial motor threshold at increasing stimulation intensities. A ring block around the vertex is advised to reduce interference by extracranial mMEPs. mMEPs reflect the functional integrity of the route along the brainstem nuclei, extrapyramidal motor tracts, propriospinal neurons, and motoneurons. The corticospinal tract appears subordinate in horses. TMS and TES are interchangeable for assessing the functional integrity of motor functions of the spinal cord. However, TES reveals significantly shorter MLTs, higher conduction velocities, and better reproducibility.

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Section: Discussioncontrasting

confidence: 63%

Comparison of Muscle MEPs From Transcranial Magnetic and Electrical Stimulation and Appearance of Reflexes in Horses

Journée

Berends³

et al. 2020

Front. Neurosci.

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“…Even though this finding were not reproduced in the substudy 2, a possible explanation could be the small sample size of the study. As has been previously described, 38‐40 tcMEP amplitude and morphology vary from trace to trace due to the mechanism of MEP generation and, moreover, there is considerable inter‐ and intra‐individual variability in patients under general anaesthesia 8 . The generation of tcMEPs requires synaptic transmission at the anterior horn cell, which is facilitated by a train of stimulus pulses 41 .…”

Section: Discussionmentioning

confidence: 96%

Effect of dexmedetomidine on evoked‐potential monitoring in patients undergoing brain stem and supratentorial cranial surgery

Pacreu

Vilà

Moltó

et al. 2021

Acta Anaesthesiol Scand

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Background Dexmedetomidine is used as adjuvant in total intravenous anaesthesia (TIVA), but there have been few studies concerning its effect on intraoperative neurophysiological monitoring (IONM) during cranial surgery. Our aim was to study the effect of dexmedetomidine on IONM in patients undergoing brain stem and supratentorial cranial surgery. Methods Two prospective, randomized, double‐blind substudies were conducted. In substudy 1, during TIVA with an infusion of propofol and remifentanil, 10 patients received saline solution (SS) (PR group) and another 10 (PRD group) received dexmedetomidine (0.5 mcg/kg/h). Total dosage of propofol and remifentanil, intensity, latency and amplitude of motor‐evoked potentials following transcranial electrical stimulation (tcMEPs) as well as somatosensory‐evoked potentials (SSEP) were recorded at baseline, 15, 30, 45 minutes, and at the end of surgery. In order to identify differences in the same patient after dexmedetomidine administration, we designed substudy 2 with 20 new patients randomized to two groups. After 30 minutes with TIVA, 10 patients received dexmedetomidine (0.5 mcg/kg/h) and 10 patients SS. The same variables were recorded. Results In substudy 1, propofol requirements were significantly lower (P = .004) and tcMEP intensity at the end of surgery was significantly higher in PRD group, but no statistically significant differences were observed for remifentanil requirements, SSEP and tcMEP latency or amplitude. In substudy 2, no differences in any of the variables were identified. Conclusions The administration of dexmedetomidine at a dosage of 0.5 mg/kg/h may reduce propofol requirements and adversely affect some neuromonitoring variables. However, it can be an alternative on IONM during cranial surgeries. REDEX EudraCT: 2014‐000962‐23

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“…Thus, the preoperative nTMS risk stratification not only correlates with MEP amplitude alterations but also provides information that can improve the interpretation of IOM findings, especially for identifying false-positive amplitude changes. This is particularly important because recent studies have reported various neurosurgical as well as anesthesiologic causes that may affect MEP amplitude and could not be distinguished from phenomena induced by direct tissue lesions (39,(42)(43)(44). To our knowledge, our analysis is the first one that can help to distinguish true-positive from false-positive MEP amplitude alterations.…”

Section: Iom -Transcranial Mep Monitoringmentioning

confidence: 94%

Preoperative nTMS and Intraoperative Neurophysiology - A Comparative Analysis in Patients With Motor-Eloquent Glioma

et al. 2021

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BackgroundThe resection of a motor-eloquent glioma should be guided by intraoperative neurophysiological monitoring (IOM) but its interpretation is often difficult and may (unnecessarily) lead to subtotal resection. Navigated transcranial magnetic stimulation (nTMS) combined with diffusion-tensor-imaging (DTI) is able to stratify patients with motor-eloquent lesion preoperatively into high- and low-risk cases with respect to a new motor deficit.ObjectiveTo analyze to what extent preoperative nTMS motor risk stratification can improve the interpretation of IOM phenomena.MethodsIn this monocentric observational study, nTMS motor mapping with DTI fiber tracking of the corticospinal tract was performed before IOM-guided surgery for motor-eloquent gliomas in a prospectively collected cohort from January 2017 to October 2020. Descriptive analyses were performed considering nTMS data (motor cortex infiltration, resting motor threshold (RMT), motor evoked potential (MEP) amplitude, latency) and IOM data (transcranial MEP monitoring, intensity of monopolar subcortical stimulation (SCS), somatosensory evoked potentials) to examine the association with the postoperative motor outcome (assessed at day of discharge and at 3 months).ResultsThirty-seven (56.1%) of 66 patients (27 female) with a median age of 48 years had tumors located in the right hemisphere, with glioblastoma being the most common diagnosis with 39 cases (59.1%). Three patients (4.9%) had a new motor deficit that recovered partially within 3 months and 6 patients had a persistent deterioration (9.8%). The more risk factors of the nTMS risk stratification model (motor cortex infiltration, tumor-tract distance (TTD) ≤8mm, RMTratio <90%/>110%) were detected, the higher was the risk for developing a new postoperative motor deficit, whereas no patient with a TTD >8mm deteriorated. Irreversible MEP amplitude decrease >50% was associated with worse motor outcome in all patients, while a MEP amplitude decrease ≤50% or lower SCS intensities ≤4mA were particularly correlated with a postoperative worsened motor status in nTMS-stratified high-risk cases. No patient had postoperative deterioration of motor function (except one with partial recovery) when intraoperative MEPs remained stable or showed only reversible alterations.ConclusionsThe preoperative nTMS-based risk assessment can help to interpret ambiguous IOM phenomena (such as irreversible MEP amplitude decrease ≤50%) and adjustment of SCS stimulation intensity.

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The Percentage of Amplitude Decrease Warning Criteria for Transcranial MEP Monitoring

Cited by 38 publications

References 46 publications

Comparison of Muscle MEPs From Transcranial Magnetic and Electrical Stimulation and Appearance of Reflexes in Horses

Comparison of Muscle MEPs From Transcranial Magnetic and Electrical Stimulation and Appearance of Reflexes in Horses

Effect of dexmedetomidine on evoked‐potential monitoring in patients undergoing brain stem and supratentorial cranial surgery

Preoperative nTMS and Intraoperative Neurophysiology - A Comparative Analysis in Patients With Motor-Eloquent Glioma

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