Continuous Monitoring of Corticobulbar Motor-Evoked Potentials of Vagus Nerve during Brainstem or Skull Base Surgery

Object The purpose of this study was to determine whether monitoring of pharyngeal motor evoked potentials (PhMEPs) elicited by transcranial electrical stimulation during skull base tumor surgery might be useful for predicting postoperative swallowing deterioration. Methods The authors analyzed PhMEPs in 21 patients during 22 surgical procedures for the treatment of skull base tumors. Corkscrew electrodes positioned at C3 or C4 and Cz were used to deliver supramaximal stimuli (220–550 V). Pharyngeal MEPs were recorded from the posterior wall of the pharynx through a modified endotracheal tube. The correlation between the final/baseline PhMEP ratio and postoperative swallowing function was examined. Results Postoperative swallowing function was significantly (p < 0.05), although not strongly (r = −0.47), correlated with the final/baseline PhMEP ratio. A PhMEP ratio < 50% was recorded during 4 of 22 procedures; in all 4 of these cases, the patients experienced postoperative deterioration of swallowing function. After 18 procedures, the PhMEP ratios remained > 50%; nevertheless, after 4 (22.2%) of these 18 procedures, patients showed deterioration of swallowing function. Conclusions Intraoperative PhMEP monitoring can be useful for predicting swallowing deterioration following skull base surgery, especially in patients with swallowing disturbances that are mainly due to reduction in the motor functions of the pharyngeal muscles.

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Facial nerve motor evoked potentials during skull base surgery to monitor facial nerve function using the threshold-level method

Neurosurgical FOCUS ◽

10.3171/2012.12.focus12386 ◽

2013 ◽

Vol 34 (3) ◽

pp. E7 ◽

Cited By ~ 8

Author(s):

Johannes Sarnthein ◽

Nader Hejrati ◽

Marian C. Neidert ◽

Alexander M. Huber ◽

Niklaus Krayenbühl

Keyword(s):

At Risk ◽

Facial Nerve ◽

Evoked Potentials ◽

Skull Base ◽

Skull Base Surgery ◽

Motor Evoked Potentials ◽

Threshold Level ◽

Nerve Function ◽

Facial Nerve Function ◽

Level Method

Object During surgeries that put the facial nerve at risk for injury, its function can be continuously monitored by transcranial facial nerve motor evoked potentials (FNMEPs) in facial nerve target muscles. Despite their advantages, FNMEPs are not yet widely used. While most authors use a 50% reduction in FNMEP response amplitudes as a warning criterion, in this paper the authors' approach was to keep the response amplitude constant by increasing the stimulation intensity and to establish a warning criterion based on the “threshold-level” method. Methods The authors included 34 consecutive procedures involving 33 adult patients (median age 47 years) in whom FNMEPs were monitored. A threshold increase greater than 20 mA for eliciting FNMEPs in the most reliable facial nerve target muscle was considered a prediction of reduced postoperative facial nerve function, and subsequently a warning was issued to the surgeon. Preoperative and early postoperative function was documented using the House-Brackmann grading system. Results Monitoring of FNMEPs was feasible in all 34 surgeries in at least one facial nerve target muscle. The mentalis muscle yielded the best results. The House-Brackmann grade deteriorated in 17 (50%) of 34 cases. The warning criterion was reached in 18 (53%) of 34 cases, which predicted an 83% risk of House-Brackmann grade deterioration. Sensitivity amounted to 88% (CI 64%–99%) and specificity to 82% (CI 57%–96%). Deterioration of FNMEPs and a worse House-Brackmann grade showed a high degree of association (p < 0.001). The impact of FNMEP monitoring on surgical strategy is exemplified in an illustrative case. Conclusions In surgeries that put the facial nerve at risk, the intraoperative increase in FNMEP stimulation threshold was closely correlated to postoperative facial nerve dysfunction. Monitoring of FNMEPs is a valid indicator of facial nerve function in skull base surgery. It should be used as an adjunct to direct electrical facial nerve stimulation and continuous electromyographic monitoring of facial nerve target muscles.

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Corticobulbar motor evoked potentials in skull base surgery

Neurophysiology in Neurosurgery ◽

10.1016/b978-0-12-815000-9.00010-1 ◽

2020 ◽

pp. 137-149

Author(s):

Isabel Fernández-Conejero

Keyword(s):

Evoked Potentials ◽

Skull Base ◽

Skull Base Surgery ◽

Motor Evoked Potentials

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Laryngeal Motor Evoked-potentials as a Biomarker of Vagus Nerve Stimulation in Epileptic Patients

Case Medical Research ◽

10.31525/ct1-nct03851770 ◽

2019 ◽

Author(s):

Keyword(s):

Evoked Potentials ◽

Vagus Nerve ◽

Nerve Stimulation ◽

Vagus Nerve Stimulation ◽

Motor Evoked Potentials ◽

Epileptic Patients

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157 Reinventing the Wheel: Intraoperative Continuous Flash Visual Evoked Potentials, a Novel Technique to Lessen Intraoperative Optic Nerves and Chiasmal Injury in Endoscopic Skull Base Surgery

Neurosurgery ◽

10.1093/neuros/nyx417.157 ◽

2017 ◽

Vol 64 (CN_suppl_1) ◽

pp. 239-239

Author(s):

Fahad A Alkherayf ◽

David Houlden ◽

Chantal Turgeon ◽

Charles B Agbi ◽

Andre Lamothe ◽

...

Keyword(s):

Optic Nerve ◽

Evoked Potentials ◽

Skull Base ◽

Visual Evoked Potentials ◽

Skull Base Surgery ◽

Optic Nerves ◽

Novel Technique ◽

Endoscopic Skull Base Surgery ◽

Flash Visual Evoked Potentials ◽

Visual Evoked

Abstract INTRODUCTION Optic nerve/chiasmal injury is a devastating outcome that may happen during endoscopic surgery. A key goal of endoscopic skull-base surgery is visual improvement. Currently, however, there is limited intraoperative visual pathway monitoring. We examine a novel technique that uses continuous flash visual evoked potentials (FVEPs). METHODS Eyes were stimulated by light stimulators (3 LEDs on each side, 640 nm peak wavelength, 10 ms pulse width, 3000 mCd of luminous intensity). Uniform illumination was placed over eyelids. Recording electrodes were placed at Oz-Fz. The filter cuts were = 5 Hz and 100 Hz with amplifier gain 20,000 or 50,000. EEG was recorded. Recordings were correlated to pre and post operative VFs and acuity. Dropping in the FVEP was examined in relation to intraoperative events. A drop of 50% from the base line was considered positive. RESULTS >101 patients had FVEPs in addition to other neurophysiologic monitoring. Patients demographic data, co-morbidities, diagnosis, surgical approach, length of surgery, MAP, and blood loss during surgery were recorded. All patients' visual acuity and field deficits were evaluated by neuro-ophthalmologist before their surgery and within 30 days after surgery. In our cohort, one patient had true positive pre-chiasmatic while another patient had false negative test result. However, the latter patient's deficit was post chiasmatic with no optic nerve or chiasmal injury. Another patient had false positive test (drop of 60%). Eight patients had transient changes related to traction of the chiasm or optic nerves. For predicting optic nerve or chiasmal injury, our study showed sensitivity of 100% (CI2.5-100), specificity of 99% (CI94.5-99.97) and negative predicted value of 100%. CONCLUSION FVEP is reproducible throughout surgery and can predict the post surgical outcome. Additionally, we found that FVEP is transiently affected by different stages of surgery. Further validation is required given the small number of optic/chiasmal injuries in our study.

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A Preclinical Study of Laryngeal Motor-Evoked Potentials as a Marker Vagus Nerve Activation

International Journal of Neural Systems ◽

10.1142/s0129065715500343 ◽

2015 ◽

Vol 25 (08) ◽

pp. 1550034 ◽

Cited By ~ 7

Author(s):

Annelies Grimonprez ◽

Robrecht Raedt ◽

Leen De Taeye ◽

Lars Emil Larsen ◽

Jean Delbeke ◽

...

Keyword(s):

Minimally Invasive ◽

Evoked Potentials ◽

Vagus Nerve ◽

Motor Evoked Potentials ◽

Reference Electrode ◽

Preclinical Study ◽

Invasive Technique ◽

Laryngeal Muscles ◽

Effective Current ◽

Electrophysiological Responses

Vagus nerve stimulation (VNS) is a treatment for refractory epilepsy and depression. Previous studies using invasive recording electrodes showed that VNS induces laryngeal motor-evoked potentials (LMEPs) through the co-activation of the recurrent laryngeal nerve and subsequent contractions of the laryngeal muscles. The present study investigates the feasibility of recording LMEPs in chronically VNS-implanted rats, using a minimally-invasive technique, to assess effective current delivery to the nerve and to determine optimal VNS output currents for vagal fiber activation. Three weeks after VNS electrode implantation, signals were recorded using an electromyography (EMG) electrode in the proximity of the laryngeal muscles and a reference electrode on the skull. The VNS output current was gradually ramped up from 0.1 to 1.0 mA in 0.1 mA steps. In 13/27 rats, typical LMEPs were recorded at low VNS output currents (median 0.3 mA, IQR 0.2–0.3 mA). In 11/27 rats, significantly higher output currents were required to evoke electrophysiological responses (median 0.7 mA, IQR 0.5–0.7 mA, [Formula: see text]). The latencies of these responses deviated significantly from LMEPs ([Formula: see text]). In 3/27 rats, no electrophysiological responses to simulation were recorded. Minimally invasive LMEP recordings are feasible to assess effective current delivery to the vagus nerve. Furthermore, our results suggest that low output currents are sufficient to activate vagal fibers.

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