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P158: Usefulness of cranial nerve motor evoked potential monitoring during skull base surgery
Abstracts of Poster Presentations / Clinical Neurophysiology 125, Supplement 1 (2014) S1–S339
P158 Usefulness of cranial nerve motor evoked potential monitoring during skull base surgery M. Fukuda, T. Takao, T. Hiraishi, Y. Fujii Brain Research Institute, University of Niigata, Department of Neurosurgery, Niigata-City, Japan Question: To determine whether monitoring of facial, pharyngeal, and lingual motor evoked potentials (MEPs) elicited by transcranial electrical stimulation during skull base tumor surgery can predict postoperative function. Methods: The authors analyzed facial MEPs in 104 patients during 112 surgical procedures, pharyngeal MEPs in 35 patients during 36 procedures, and lingual MEPs in 14 patients recieving treatment for skull base tumors. Corkscrew electrodes positioned at C3 or C4 and Cz were used to deliver supra-maximal stimuli. The correlation between the final to baseline amplitude ratio of each MEP and postoperative function was examined. Results: Twenty-nine (94%) of 31 patients with amplitude ratios in facial MEP of less than 50% had poor facial motor function outcomes (House and Brackmann (HB) grade III-VI). In contrast, in 73 (90%) of 81 patients with amplitude ratios exceeding 50%, postoperative facial function was good (HB grade I-II). Twelve (86%) of 14 patients with amplitude ratios of less than 50% in pharyngeal MEP after tumor resection experienced deterioration of swallowing function, whereas 18 (82%) of 22 with amplitude ratios exceeding 50% showed no swallowing function changes. In lingual MEPs, all 4 patients with amplitude ratios of less than 50% experienced lingual palsy postoperatively, whereas 9 (90%) of 10 maintainting ratios of more than 50% showed no lingual function changes. Conclusions: Intraoperative facial, pharyngeal, and lingual MEPs are potentially useful for predicting postoperative motor function after skull base surgery.
P160 The role of intraoperative neurophysiological monitoring during the intramedullary spinal cord tumors resection: protection of the anterior horn L. Vega-Zelaya 1 , J.R. Penanes 2 , O. Garnés-Camarena 1 , R.G. Sola 2 , J. Pastor 1 Hospital Universitario de la Princesa, Clinical Neurophysiology, Madrid, Spain; 2 Hospital Universitario de la Princesa, Neurosurgery, Madrid, Spain 1
Question: The surgical removal of intramedullary spinal cord tumors (ISCTs) may lead to significant risk of iatrogenic damage and postoperative neu-
S89
rologic dysfunction. Intraoperative neurophysiological monitoring (IONM) combining motor and somatosensory evoked potentials (MEP and SSEP respectively) is usually employed to minimize this risk. However, anterior horn (AH) function cannot be adequately assessed by means of D-wave or MEP recorded at members. So the electromyography (EMG) can be helpful to protect AH. Methods: IONM was performed in 19 patients (14 male and 5 female) who underwent surgical removal of ISCTs. A combination of SSEP/MEP/EMG was performed in all patients. The ASIA’s scale was used to assess the neurological outcome. Results: The mean age was 46±2.3 years. Total tumor resection was reached in 74% of cases. Pathology showed ependymoma (12) and hemangioblastoma (3) as the most frequent histological types. Significant MEP changes occurred in 11/19 (58%) and warning criteria for SSEP occurred in 17/19 (90%). Neurotonic discharges in EMG were seen in 11/19 (58%) during the attempt to detach the anterior part of the tumor from the spinal cord. All the changes were reversible and no new neurological deficit appeared, in fact, there was an improvement six months after the surgery in 6/19 patients. Conclusions: During the ISCT resection there is a true risk to selectively injury the dorsal columns, the corticospinal tract and the AH, thus the combination of SSEP, MEP and EMG should be employed during ISCT resection to minimize the risk of neurological injury.
P161 Elevated serum creatine kinase after intraoperative neuromonitoring in lateral position is associated with OP duration, BMI and age M. Neidert, M. Losa, L. Regli, J. Sarnthein University Hospital, Neurosurgery, Zurich, Switzerland Question: Highly elevated serum levels of creatine kinase (CK) following surgery may lead to renal dysfunction. High CK levels are known to occur after neurosurgical interventions, but a consensus on possible risk factors is still lacking. Here we investigate risk factors for excess CK in patients undergoing high risk surgical positioning with a special focus on the influence of motor evoked potentials (MEPs) as a modality of intraoperative neurophysiological monitoring (IONM). Methods: We included all patients undergoing elective surgery in lateral position (park bench) between 2010 and 2012 and where IONM was performed. In these patients, the anesthesia regimen excluded muscle relaxation. Medical charts were reviewed retrospectively for patient characteristics, CK levels and indicators of renal dysfunction. The MEP response intensity was estimated by the RMS of the EMG signals. Data were analyzed by multivariate logistic regression. Results: There were 96 patients (55 female, mean age 50 years) who met the inclusion criteria. The maximal CK level (CKmax) occurred on postoperative days 2 or 3 (mean 1763 U/L, range: 53-7172 U/L). In a multivariate linear regression model, log(CKmax) correlated positively with duration of surgery (p<0.001) and BMI (p=0.007), and negatively with age (p=0.007). There was no significant association between MEP response intensity of the muscles at risk and log(CKmax). We did not observe impaired renal function. Conclusions: MEP was not among relevant risk factors for elevated CK levels. Surgical positioning should be especially careful for long surgeries on young patients with high BMI, in particular if operated in lateral position.
P162 Intraoperative monitoring of visual evoked potentials Y. Luo, L. Regli, J. Sarnthein University Hospital, Neurosurgery, Zurich, Switzerland
Figure 1. Dorsal ependymoma. A) Left: MRI showing the tumor. Right: intraoperative image during the surgery. B) Bilateral and reversible alteration of SSEP during opening the dura. C) Reversible alteration of MEP in thorax muscles, while in the lower limbs are reduced yet. D) Bilateral neurotonic discharges in intercostal muscles during resection, by irritation of AH (middle). Left side corresponds to the previous time and the right to the residual activity. ADM: abductor digiti minimi. AH: abductor hallucis. Blue: left side. Red: right side. Grey: warning criteria.
Question: During surgeries that put the visual pathway at risk of injury, continuous monitoring of the visual function is desirable. However, there is no consensus in the literature on the usefulness of intraoperative monitoring of visual evoked potentials (VEPs). Only recently have stimulating devices with high luminance been introduced. Methods: We included 33 patients under total intravenous anesthesia for intraoperative VEP monitoring. Red LEDs provided flash stimulation at 1.1 Hz. VEPs were recorded at sites O1, O2, Oz against Fz, Cz, and linked A1 and A2 (A+). We analyzed the stability of the VEP features N75 and P100 and compared their distribution between patients with preoperative normal and impaired visual function. Their correlation to postoperative visual function was also examined.
P158 Usefulness of cranial nerve motor evoked potential monitoring during skull base surgery M. Fukuda, T. Takao, T. Hiraishi, Y. Fujii Brain Research Institute, University of Niigata, Department of Neurosurgery, Niigata-City, Japan Question: To determine whether monitoring of facial, pharyngeal, and lingual motor evoked potentials (MEPs) elicited by transcranial electrical stimulation during skull base tumor surgery can predict postoperative function. Methods: The authors analyzed facial MEPs in 104 patients during 112 surgical procedures, pharyngeal MEPs in 35 patients during 36 procedures, and lingual MEPs in 14 patients recieving treatment for skull base tumors. Corkscrew electrodes positioned at C3 or C4 and Cz were used to deliver supra-maximal stimuli. The correlation between the final to baseline amplitude ratio of each MEP and postoperative function was examined. Results: Twenty-nine (94%) of 31 patients with amplitude ratios in facial MEP of less than 50% had poor facial motor function outcomes (House and Brackmann (HB) grade III-VI). In contrast, in 73 (90%) of 81 patients with amplitude ratios exceeding 50%, postoperative facial function was good (HB grade I-II). Twelve (86%) of 14 patients with amplitude ratios of less than 50% in pharyngeal MEP after tumor resection experienced deterioration of swallowing function, whereas 18 (82%) of 22 with amplitude ratios exceeding 50% showed no swallowing function changes. In lingual MEPs, all 4 patients with amplitude ratios of less than 50% experienced lingual palsy postoperatively, whereas 9 (90%) of 10 maintainting ratios of more than 50% showed no lingual function changes. Conclusions: Intraoperative facial, pharyngeal, and lingual MEPs are potentially useful for predicting postoperative motor function after skull base surgery.
P160 The role of intraoperative neurophysiological monitoring during the intramedullary spinal cord tumors resection: protection of the anterior horn L. Vega-Zelaya 1 , J.R. Penanes 2 , O. Garnés-Camarena 1 , R.G. Sola 2 , J. Pastor 1 Hospital Universitario de la Princesa, Clinical Neurophysiology, Madrid, Spain; 2 Hospital Universitario de la Princesa, Neurosurgery, Madrid, Spain 1
Question: The surgical removal of intramedullary spinal cord tumors (ISCTs) may lead to significant risk of iatrogenic damage and postoperative neu-
S89
rologic dysfunction. Intraoperative neurophysiological monitoring (IONM) combining motor and somatosensory evoked potentials (MEP and SSEP respectively) is usually employed to minimize this risk. However, anterior horn (AH) function cannot be adequately assessed by means of D-wave or MEP recorded at members. So the electromyography (EMG) can be helpful to protect AH. Methods: IONM was performed in 19 patients (14 male and 5 female) who underwent surgical removal of ISCTs. A combination of SSEP/MEP/EMG was performed in all patients. The ASIA’s scale was used to assess the neurological outcome. Results: The mean age was 46±2.3 years. Total tumor resection was reached in 74% of cases. Pathology showed ependymoma (12) and hemangioblastoma (3) as the most frequent histological types. Significant MEP changes occurred in 11/19 (58%) and warning criteria for SSEP occurred in 17/19 (90%). Neurotonic discharges in EMG were seen in 11/19 (58%) during the attempt to detach the anterior part of the tumor from the spinal cord. All the changes were reversible and no new neurological deficit appeared, in fact, there was an improvement six months after the surgery in 6/19 patients. Conclusions: During the ISCT resection there is a true risk to selectively injury the dorsal columns, the corticospinal tract and the AH, thus the combination of SSEP, MEP and EMG should be employed during ISCT resection to minimize the risk of neurological injury.
P161 Elevated serum creatine kinase after intraoperative neuromonitoring in lateral position is associated with OP duration, BMI and age M. Neidert, M. Losa, L. Regli, J. Sarnthein University Hospital, Neurosurgery, Zurich, Switzerland Question: Highly elevated serum levels of creatine kinase (CK) following surgery may lead to renal dysfunction. High CK levels are known to occur after neurosurgical interventions, but a consensus on possible risk factors is still lacking. Here we investigate risk factors for excess CK in patients undergoing high risk surgical positioning with a special focus on the influence of motor evoked potentials (MEPs) as a modality of intraoperative neurophysiological monitoring (IONM). Methods: We included all patients undergoing elective surgery in lateral position (park bench) between 2010 and 2012 and where IONM was performed. In these patients, the anesthesia regimen excluded muscle relaxation. Medical charts were reviewed retrospectively for patient characteristics, CK levels and indicators of renal dysfunction. The MEP response intensity was estimated by the RMS of the EMG signals. Data were analyzed by multivariate logistic regression. Results: There were 96 patients (55 female, mean age 50 years) who met the inclusion criteria. The maximal CK level (CKmax) occurred on postoperative days 2 or 3 (mean 1763 U/L, range: 53-7172 U/L). In a multivariate linear regression model, log(CKmax) correlated positively with duration of surgery (p<0.001) and BMI (p=0.007), and negatively with age (p=0.007). There was no significant association between MEP response intensity of the muscles at risk and log(CKmax). We did not observe impaired renal function. Conclusions: MEP was not among relevant risk factors for elevated CK levels. Surgical positioning should be especially careful for long surgeries on young patients with high BMI, in particular if operated in lateral position.
P162 Intraoperative monitoring of visual evoked potentials Y. Luo, L. Regli, J. Sarnthein University Hospital, Neurosurgery, Zurich, Switzerland
Figure 1. Dorsal ependymoma. A) Left: MRI showing the tumor. Right: intraoperative image during the surgery. B) Bilateral and reversible alteration of SSEP during opening the dura. C) Reversible alteration of MEP in thorax muscles, while in the lower limbs are reduced yet. D) Bilateral neurotonic discharges in intercostal muscles during resection, by irritation of AH (middle). Left side corresponds to the previous time and the right to the residual activity. ADM: abductor digiti minimi. AH: abductor hallucis. Blue: left side. Red: right side. Grey: warning criteria.
Question: During surgeries that put the visual pathway at risk of injury, continuous monitoring of the visual function is desirable. However, there is no consensus in the literature on the usefulness of intraoperative monitoring of visual evoked potentials (VEPs). Only recently have stimulating devices with high luminance been introduced. Methods: We included 33 patients under total intravenous anesthesia for intraoperative VEP monitoring. Red LEDs provided flash stimulation at 1.1 Hz. VEPs were recorded at sites O1, O2, Oz against Fz, Cz, and linked A1 and A2 (A+). We analyzed the stability of the VEP features N75 and P100 and compared their distribution between patients with preoperative normal and impaired visual function. Their correlation to postoperative visual function was also examined.