Incidence of intraoperative seizures during motor evoked potential monitoring in a large cohort of patients undergoing different surgical procedures

Chronologic Changes in Transcranial Motor Evoked Potential During Anterior Temporal Lobectomy in Patients with Temporal Lobe Epilepsy: A Single-Center Cross-Sectional Analytic Study

OBJECTIVE

Despite the benefits of anterior temporal lobectomy with amygdalohippocampectomy in patients with temporal lobe epilepsy (TLE), approximately up to 5% may have hemiparesis as its postoperative complication. This paper aims to describe which step/s of the anterior temporal lobectomy with amygdalohippocampectomy have the highest probability of having the greatest decrease in motor evoked potential (MEP) amplitude.

METHODS

This study used a cross-sectional design of obtaining data from TLE patients who underwent anterior temporal lobectomy with amygdalohippocampectomy with transcranial MEP monitoring. Each of the following steps were evaluated for reduction in MEP amplitude: 1) dural opening, 2) opening the inferior horn, 2) vertical temporal lobe resection 3) subpial dissection, 4) temporal lobe stem resection, 5) lateral temporal lobe resection, 6) hippocampal resection, 7) amygdala resection, 8) uncus resection, and 9) dural closure.

RESULTS

Nineteen patients were included in the study. Based on the Friedman Test, 1 or more steps had significantly different average MEP amplitude reductions (Friedman = 50.7, P = 0.0001). When compared with baseline (100%, cutoff P = 0.005), hippocampal resection (z = -3.81, P < 0.0001), T1 subpial dissection (z = -3.2, P = 0.0010), uncus resection (z = -3.48, P = 0.0002), temporal stem resection (z = -3.26, P = 0.001), lateral temporal lobe resection (z = -3.13, P = 0.002), and amygdalectomy (-z = -3.37, P = 0.0005) were significantly lower. Of these, hippocampal resection, uncus resection, and amygdalectomy were deemed highly significant.

CONCLUSIONS

MEP amplitude tends to decrease during amygdala, hippocampal, and uncal resection because of surgical manipulation of anterior choroidal arteries, which can potentially cause hemiparesis. Careful attention should be paid to changes in MEP during these steps.

Intraoperative Seizure Under General Anesthesia Not Detected by EEG: A Case Report

Intraoperative seizures under general anesthesia are infrequent. However, seizure activity under general anesthesia confirmed by contemporaneous EEG has been reported. We describe the case of a 39-year-old female undergoing right frontal brain tumor resection who experienced an intraoperative seizure. Intraoperative neuromonitoring was utilized and included four channels of EEG, somatosensory evoked potentials (SSEP), and transcranial motor evoked potentials (MEP). During this operation, characteristic motor manifestations of a seizure occurred. However, the EEG did not demonstrate seizure activity due to limitations in EEG lead placement. Post-operatively in the ICU, motor manifestations of seizure activity continued, and subsequent EEG recordings demonstrated classic seizure activity. Due to the previous hemicraniectomy, corkscrew EEG electrodes were not placed over the right skull defect, thereby failing to detect the intraoperative seizure. Anesthesiologists should be aware that limitations with EEG electrode placement can fail to detect intraoperative seizures, and treatment to extinguish the seizure should proceed in an emergent fashion.

Factors Affecting Transcranial Motor-Evoked Potential Measurements Using Single-Train Stimulation with an Increased Number of Pulses during Adolescent Scoliosis Surgery: A Prospective Observational Study

Measurement of transcranial motor-evoked potentials (TcMEPs) during scoliosis surgery helps detect postoperative new neurological defects. However, TcMEP interpretation is difficult owing to the influence of intraoperative physiological, pharmacological, and time-related factors as well as stimulation conditions. In this study, we aimed to investigate the effect of the abovementioned factors on TcMEP amplitude using single-train stimulation with an increased number of pulses (STS-INP) during adolescent scoliosis surgery; moreover, we evaluated the complications of TcMEP measurement. We included 50 patients and 706 TcMEP measurements. A total of 1412 TcMEP waveforms were analyzed, each on the bilateral abductor pollicis brevis, tibialis anterior, and abductor hallucis muscles. We estimated the mean difference (95% confidence interval (CI)) and predicted mean difference (95% CI) evaluated using the interquartile range of each factor, based on a mixed-effect model with random intercepts for TcMEP amplitude. The predicted mean differences in TcMEP amplitude were clinically small compared with the actual TcMEP amplitude, suggesting that each factor had a limited effect on TcMEP amplitude. No intraoperative bite injuries or seizures were observed. Using STS-INP during adolescent scoliosis surgery may enable accurate measurement of TcMEP amplitude with neither complications nor the influence of various intraoperative factors.

Utilization Trends of Intraoperative Neuromonitoring for Anterior Cervical Discectomy and Fusion in New York State

STUDY DESIGN

Retrospective cohort analysis.

OBJECTIVE

To elucidate trends in the utilization of intraoperative neuromonitoring (IONM) during anterior cervical discectomy and fusion (ACDF) procedures in NY state using the Statewide Planning and Research Cooperative System and to determine if utilization of IONM resulted in a reduction in postoperative neurological deficits.

SUMMARY OF BACKGROUND DATA

IONM has been available to spinal surgeons for several decades. It has become increasingly prevalent in all facets of spinal surgery including elective ACDF procedures. The utility of IONM for preventing a neurological deficit in elective spine procedures has recently been called into question.

MATERIALS AND METHODS

The Statewide Planning and Research Cooperative System database were accessed to perform a retrospective cohort study comparing monitored versus unmonitored ACDF procedures between 2007 and 2018 as defined by the International Classification of Disease-9 and 10 Procedural Coding System (ICD-9 PCS, ICD-10 PCS) codes. Patient demographics, medical history, surgical intervention, pertinent in-hospital events, and urban versus rural medical centers (as defined by the United States Office of Management and Budget) were recorded. Propensity-score-matched comparisons were used to identify factors related to the utilization of IONM and risk factors for neurological deficits after elective ACDF.

RESULTS

A total of 70,838 [15,092 monitored (21.3%) and 55,746 (78.7%) unmonitored] patients' data were extracted. The utilization of IONM since 2007 has increased in a linear manner from 0.9% of cases in 2007 to 36.7% by 2018. Overall, baseline characteristics of patients who were monitored during cases differed significantly from unmonitored patients in age, race/ethnicity, insurance type, presence of myelopathy or radiculopathy, and Charlson Comorbidity Index; however, only race/ethnicity was statistically significant when analyzed using propensity-score-matched. When comparing urban and rural medical centers, there is a significant lag in the adoption of the technology with no monitored cases in rural centers until 2012 with significant fluctuations in utilization compared with steadily increasing utilization among urban centers. From 2017 to 2018, reporting of neurological deficits after surgery resembled literature-established norms. Pooled analysis of these years revealed that the incidence of neurological complications occurred more frequently in monitored cases than in unmonitored (3.0% vs. 1.4%, P < 0.001).

CONCLUSIONS

The utility of IONM for elective ACDF remains uncertain; however, it continues to gain popularity for routine cases. For medical centers that lack similar resources to centers in more densely populated regions of NY state, reliable access to this technology is not a certainty. In our analysis of intraoperative neurological complications, it seems that IONM is not protective against neurological injury.

An Update of Neuroanesthesia for Intraoperative Brain Mapping Craniotomy

The perioperative multidisciplinary team approach has probably been best exemplified by the care of awake craniotomy patients. Advancement in anesthesia and meticulous perioperative care has supported the safety and complexity of the surgical and mapping efforts in glioma resection. The discussions in this review will emphasize on anesthetic and perioperative management strategies to prevent complications and minimize their effects if they occur, including current practice guidelines in anesthesia, updates on the applications of anesthetic medications, and emerging devices. Planning the anesthetic and perioperative management is based on understanding the pharmacology of the medications, the goals of different stages of the surgery and mapping, and anticipating potential problems.

Anesthesia considerations for patients with epilepsy: Findings of a qualitative study in the Palestinian practice

OBJECTIVE

This qualitative exploratory study was conducted to explore how anesthesiologists in Palestine provide perioperative care for patients with epilepsy and how they account for the unique challenges relevant to epilepsy while planning perioperative care for patients with epilepsy.

METHODS

This study was conducted in an explorative qualitative design. Purposive and snowball sampling approaches were used to recruit the study participants. Qualitative semi-structured in-depth interviews were conducted with anesthesiologists (n = 10) and a neurologist (n = 1). The qualitative data collected in this study were thematically analyzed using the interpretive description methodology to generate themes, subthemes, and patterns.

RESULTS

Three major themes emerged from the collected qualitative data with a total of 18 subthemes. The 3 themes were: 1) considerations/challenges while assessing patients, 2) anesthetic considerations, and 3) recovery considerations. Lack of epilepsy-specific assessment and anesthesia protocols, underuse of neurology referral services, and lack of neuromonitoring were identified.

CONCLUSION

Findings of this study highlighted the need to develop specific anesthesia protocols for patients with epilepsy. Anesthesiologists and planners of perioperative care should improve collection of patient information and assessment methods, ensure control over seizures, reduce triggers of seizures, and improve patient monitoring approaches. Findings of this study might be used to inform anesthesiologists and decision makers in professional groups, patient advocacy groups, and healthcare authorities to benchmark and improve anesthesia care and services offered to patients with epilepsy. More studies are still needed to quantitatively assess the quality of anesthesia care and services provided to patients with epilepsy.

Intraoperative neurophysiological monitoring in paediatric neurosurgery

Intraoperative neurophysiological monitoring (IONM) is commonly used in various surgical procedures in adults, but with technological and anaesthetic advancements, its use has extended to the paediatric population. The use of IONM in children poses a unique set of challenges considering the anatomical and physiological differences in this group of patients. The use of IONM aids in the localization of neural structures and enables surgeons to preserve the functional neural structures leading to decreased incidence of postoperative neurological deficits and better patient outcomes. In this article, we review the use of IONM in paediatric patients undergoing various spinal and cranial neurosurgical procedures. We discuss the patient characteristics, type of surgeries, and technical and anaesthetic considerations about IONM in this population.

A focal brain-cooling device as an alternative to electrical stimulation for language mapping during awake craniotomy: patient series

BACKGROUND

Functional mapping in awake craniotomy has the potential risk of electrical stimulation-related seizure. The authors have developed a novel mapping technique using a brain-cooling device. The cooling probe is cylindrical in shape with a thermoelectric cooling plate (10 × 10 mm) at the bottom. A proportional integration and differentiation-controlled system adjusts the temperature accurately (Japan patent no. P5688666). The authors used it in two patients with glioblastoma. Broca’s area was identified by electrical stimulation, and then the cooling probe set at 5°C was attempted on it.

OBSERVATIONS

Electrocorticogram was suppressed, and the temperature dropped to 8°C in 50 sec. A positive aphasic reaction was reproduced on Broca’s area at a latency of 7 sec. A negative reaction appeared on the adjacent cortices despite the temperature decrease. The sensitivity and specificity were 60% and 100%, respectively. No seizures or other adverse events related to the cooling were recognized, and no histological damage to the cooled cortex was observed.

LESSONS

The cooling probe suppressed topographical brain function selectively and reversibly. Awake functional mapping based on thermal neuromodulation technology could substitute or compensate for the conventional electrical mapping.

Navigated transcranial magnetic stimulation mapping of the motor cortex for preoperative diagnostics in pediatric epilepsy

OBJECTIVE

Navigated transcranial magnetic stimulation (nTMS) is a noninvasive technique often used for localization of the functional motor cortex via induction of motor evoked potentials (MEPs) in neurosurgical patients. There has, however, been no published record of its application in pediatric epilepsy surgery. In this study, the authors aimed to investigate the feasibility of nTMS-based motor mapping in the preoperative diagnostic workup within a population of children with medically refractory epilepsy.

METHODS

A single-institution database was screened for preoperative nTMS motor mappings obtained in pediatric patients (aged 0 to 18 years, 2012 to present) with medically refractory epilepsy. Patient clinical data, demographic information, and mapping results were extracted and used in statistical analyses.

RESULTS

Sixteen patients met the inclusion criteria, 15 of whom underwent resection. The median age was 9 years (range 0-17 years). No adverse effects were recorded during mapping. Specifically, no epileptic seizures were provoked via nTMS. Recordings of valid MEPs induced by nTMS were obtained in 10 patients. In the remaining patients, no MEPs could be elicited. Failure to generate MEPs was associated significantly with younger patient age (r = 0.8020, p = 0.0001863). The most frequent seizure control outcome was Engel Epilepsy Surgery Outcome Scale class I (9 patients).

CONCLUSIONS

Navigated TMS is a feasible, effective, and well-tolerated method for mapping the motor cortex of the upper and lower extremities in pediatric patients with epilepsy. Patient age modulates elicitability of MEPs, potentially reflecting various stages of myelination. Successful motor mapping has the potential to add to the existing presurgical diagnostic workup in this population, and further research is warranted.

Consensus document for multimodal intraoperatory neurophisiological monitoring in neurosurgical procedures. Basic fundamentals

The present work aims to establish a guide to action, agreed by anaesthesiologists and neurophysiologists alike, to perform effective intraoperative neurophysiological monitoring for procedures presenting a risk of functional neurological injury, and neurosurgical procedures. The first section discusses the main techniques currently used for intraoperative neurophysiological monitoring. The second exposes the anaesthetic and non-anaesthetic factors that are likely to affect the electrical records of the nervous system structures. This section is followed by an analysis detailing the adverse effects associated with the most common techniques and their use. Finally, the last section describes a series of guidelines to be followed upon the various intraoperative clinical events.

A case report of several intraoperative convulsions while using the Narcotrend monitor: Significance and predictive use

INTRODUCTION

Intraoperative seizures under general anesthesia are rare and our observation is the first to demonstrate a distinct electroencephalogram (EEG) pattern on the Narcotrend monitor.

PATIENT CONCERNS

We present the case of a 30-year-old man undergoing craniotomy for glioblastoma resection under general anesthesia who suffered tonic-clonic seizures captured in a specific pattern by the intraoperative EEG.

DIAGNOSES

Our depth of anesthesia monitor recorded, before the seizure, a widening of the beta-wave performance in a distinct "triangular-shaped" pattern. This pattern was repeated before the second seizure. The patient had no previous history of seizures and following surgery no further seizures were recorded.

INTERVENTIONS

A spectrogram analysis showed a distinct increase in mean absolute beta power immediately prior to the first seizure. The EEG immediately prior to the second seizure was characterized by broadband noise. Both seizures were characterized by increased mean absolute delta, theta, and beta power.

OUTCOMES

The increase in EEG beta activity seen before the tonic-clonic movements may represent cortical irritability secondary to surgical manipulation, induced by electrical stimulation, reflecting progressive brain over-arousal. The attentive analysis of the relative beta power may have helped forecast the occurrence of the second seizure.

LESSONS

We report the use of a simple, inexpensive, and portable EEG-based monitoring device to assist seizure detection and decision making.

Acute Focal Seizures Start As Local Synchronizations of Neuronal Ensembles

Understanding seizure formation and spread remains a critical goal of epilepsy research. We used fast in vivo two-photon calcium imaging in male mouse neocortex to reconstruct, with single-cell resolution, the dynamics of acute (4-aminopyridine) focal cortical seizures as they originate within a spatially confined seizure initiation site (intrafocal region), and subsequently propagate into neighboring cortical areas (extrafocal region). We find that seizures originate as local neuronal ensembles within the initiation site. This abnormal hyperactivity engages increasingly larger areas in a saltatory fashion until it breaks into neighboring cortex, where it proceeds smoothly and is then detected electrophysiologically (LFP). Interestingly, PV inhibitory interneurons have spatially heterogeneous activity in intrafocal and extrafocal territories, ruling out a simple role of inhibition in seizure formation and spread. We propose a two-step model for the progression of focal seizures, where neuronal ensembles activate first, generating a microseizure, followed by widespread neural activation in a traveling wave through neighboring cortex during macroseizures.SIGNIFICANCE STATEMENT We have used calcium imaging in mouse sensory cortex in vivo to reconstruct the onset of focal seizures elicited by local injection of the chemoconvulsant 4-aminopyridine. We demonstrate at cellular resolution that acute focal seizures originate as increasingly synchronized local neuronal ensembles. Because of its spatial confinement, this process may at first be undetectable even by nearby LFP electrodes. Further, we establish spatial footprints of local neural subtype activity that correspond to consecutive steps of seizure microprogression. Such footprints could facilitate determining the recording location (e.g., inside/outside an epileptogenic focus) in high-resolution studies, even in the absence of a priori knowledge about where exactly a seizure started.

A practical guide for anesthetic management during intraoperative motor evoked potential monitoring

Postoperative motor dysfunction can develop after spinal surgery, neurosurgery and aortic surgery, in which there is a risk of injury of motor pathway. In order to prevent such devastating complication, intraoperative monitoring of motor evoked potentials (MEP) has been conducted. However, to prevent postoperative motor dysfunction, proper understanding of MEP monitoring and proper anesthetic managements are required. Especially, a variety of anesthetics and neuromuscular blocking agent are known to attenuate MEP responses. In addition to the selection of anesthetic regime to record the baseline and control MEP, the measures to keep the level of hypnosis and muscular relaxation at constant are crucial to detect the changes of MEP responses after the surgical manipulation. Once the changes of MEP are observed based on the institutional alarm criteria, multidisciplinary team members should share the results of MEP monitoring and respond to check the status of monitoring and recover the possible motor nerve injury. Prevention of MEP-related adverse effects is also important to be considered. The Working Group of Japanese Society of Anesthesiologists (JSA) developed this practical guide aimed to help ensure safe and successful surgery through appropriate anesthetic management during intraoperative MEP monitoring.

Functional near-infrared spectroscopy for intraoperative brain mapping

Functional near-infrared spectroscopy (fNIRS) is a relatively new seizure-free technique and its value for intraoperative brain mapping is unknown. We examine the feasibility of fNIRS for intraoperative functional brain mapping. A 1 × 1    cm 2 density fNIRS probe specially designed for intraoperative use was used to map brain function in adult patients undergoing awake brain surgery and performing motor and/or language tasks. The ability of fNIRS for functional mapping was compared with direct cortical stimulation (DCS) and regression was used to determine if mean blood pressure (MBP) and blood hemoglobin influenced fNIRS measurements. Eighteen patients underwent awake craniotomy and performed 19 language- and 17 motor-related tasks. fNIRS mapping was highly correlated with DCS for 10 language- and 7 motor-related tasks. fNIRS was able to detect functional language ( p < 0.001 ) and motor areas ( p = 0.002 ). Compared to DCS, fNIRS was less accurate in determining both functional language (at least 22.64%, p < 0.001 ) and motor areas (at least 32.74%, p < 0.001 ). Higher MBP and blood hemoglobin were associated with better fNIRS results ( p = 0.045 and 0.007, respectively). No seizures or other complications occurred during fNIRS measurement. fNIRS is a promising seizure-free technique for intraoperative brain mapping. The accuracy of current technology needs further development for clinical use.

Incidence and Risk Factors for Intraoperative Seizures During Elective Craniotomy

BACKGROUND

Perioperative seizures may affect 1% to 50% of patients undergoing craniotomy and adversely impact outcomes. However, data on intraoperative seizures are limited. This retrospective case-control study investigated the incidence and risk factors for intraoperative seizures during elective supratentorial craniotomy involving evoked potential monitoring.

MATERIALS AND METHODS

Patients aged 18 years or above undergoing elective supratentorial craniotomy with evoked potential monitoring who experienced intraoperative seizures at our institution between December 2008 and March 2014 were compared with a control group generated using a random number generator. Six controls were used for each case from among the patients who underwent elective supratentorial craniotomy during the same calendar year. Multivariate analysis was conducted using logistic regression to identify the risk factors for intraoperative seizures.

RESULTS

Among the 1916 patients who met the inclusion criteria, 45 (2.3%) had intraoperative seizures. The majority of seizures occurred during burr-hole placement or craniotomy, before lesion manipulation. Timing of seizures relative to motor evoked potential runs and stimulus intensity was variable. Significant risk factors for intraoperative seizures were seizure history (odds ratio [OR], 2.18; 95% confidence interval [CI], 1.07-4.46; P=0.03), diagnosis of brain tumor (OR, 2.41; 95% CI, 1.16-4.19; P=0.02), and temporal craniotomy (OR, 5.18; 95% CI, 2.03-13.25; P=0.001). Intraoperative prophylactic use of phenytoin/fosphenytoin and levetiracetam was protective against seizure (phenytoin/fosphenytoin: OR, 0.12; 95% CI, 0.04-0.35; P<0.001 and levetiracetam: OR, 0.40; 95% CI, 0.17-0.94; P=0.04). Phenytoin/fosphenytoin was more protective than levetiracetam (OR, 0.31; 95% CI, 0.10-0.99; P=0.048).

CONCLUSIONS

The overall incidence of intraoperative seizures was 2.3%. Independent risk factors for intraoperative seizures were seizure history, diagnosis of intracranial tumor, and temporal craniotomy. Intraoperative prophylactic anticonvulsant use was protective.

Iatrogenic Seizures during Intraoperative Transcranial Motor-Evoked Potential Monitoring

Intraoperative neurophysiological monitoring (IONM) is an important tool for early detection of inadvertent damage and guide intra-operative manipulation during complex neurosurgical procedures. However trans-cranial stimulation can evoke an iatrogenic seizure and it remains a real concern while using Tc-MEP. We report a case of intra-operative seizure during transcranial electrical stimulation for motor evoked potential monitoring in a patient without seizure disorder, who underwent surgery for thoracic intra-medullary tumor excision.

Treatment of cavernous malformations in supratentorial eloquent areas: experience after 10 years of patient-tailored surgical protocol

BACKGROUND

Eloquent area surgery has become safer with the development of intraoperative neurophysiological monitoring and brain mapping techniques. However, the usefulness of intraoperative electric brain stimulation techniques applied to the management and surgical treatment of cavernous malformations in supratentorial eloquent areas is still not proven. With this study, we aim to describe our experience with the use of a tailored functional approach to treat cavernous malformations in supratentorial eloquent areas.

METHODS

Twenty patients harboring cavernous malformations located in supratentorial eloquent areas were surgically treated. Individualized functional approach, using intraoperative brain mapping and/or neurophysiological monitoring, was utilized in each case. Eleven patients underwent surgery under awake conditions; meanwhile, nine patients underwent asleep surgery.

RESULTS

Total resection was achieved in 19 cases (95%). In one patient, the resection was not possible due to high motor functional parenchyma surrounding the lesion tested by direct cortical stimulation. Ten (50%) patients presented transient neurological worsening. All of them achieved total neurological recovery within the first year of follow-up. Among the patients who presented seizures, 85% achieved seizure-free status during follow-up. No major complications occurred.

CONCLUSIONS

Intraoperative electric brain stimulation techniques applied by a trained multidisciplinary team provide a valuable aid for the treatment of certain cavernous malformations. Our results suggest that tailored functional approach could help surgeons in adapting surgical strategies to prevent patients' permanent neurological damage.

Neuroanesthesiology Update

We provide a synopsis of innovative research, recurring themes, and novel experimental findings pertinent to the care of neurosurgical patients and critically ill patients with neurological diseases. We cover the following broad topics: general neurosurgery, spine surgery, stroke, traumatic brain injury, monitoring, and anesthetic neurotoxicity.