Intraoperative Neurological Monitoring Research Articles

Advanced perioperative assessment of neurological function in acute Stanford A aortic dissection

Objective Acute Stanford Type A aortic dissection (AAAD) is a critical condition in vascular surgery, and total aortic arch replacement surgery is the preferred method to save patients’ lives. In recent years, as clinical research has advanced, there has been a growing realization of the close association between poor postoperative outcomes in patients and neurological functional deficits. Neurological function monitoring is a medical technique used to evaluate and monitor the functional status of the nervous system. Methods This monitoring involves the assessment of various aspects of the nervous system, including but not limited to nerve conduction velocity, neuromuscular function, electroencephalographic activity, and sensory nerve transmission. Neurological function monitoring has broad clinical applications and can be used to diagnose and monitor many neurological disorders, helping physicians understand patients’ neurological functional status and guide treatment plans. During the postoperative recovery process, neurological function monitoring can assist physicians in assessing the potential impact of surgery on the nervous system and monitor the recovery of patients’ neurological function. Results Studies have shown that neurological function monitoring holds promise in predicting neurological functional prognosis and interventions for patients with aortic dissection. Conclusion Therefore, the primary objective of this study is to evaluate the effectiveness and reliability of various intraoperative neurological monitoring techniques, neuroimaging examinations, and biomarkers in predicting and assessing postoperative neurological outcomes in patients undergoing AAAD surgery.

Upper cervical intramedullary schwannoma of the spinal cord presenting with myelopathy: illustrative case.

Intramedullary schwannomas account for 1.1% of all spinal schwannomas. Preoperative diagnosis is best accomplished by thoroughly evaluating clinical and radiological characteristics, accompanied by a high index of suspicion. The authors report a case of C2-3 intramedullary schwannoma in a young male who presented with neck pain and vertigo. The current literature is also reviewed. The authors reviewed the data of a young male with a 2-month history of neck pain and vertigo. Magnetic resonance imaging of the brain and cervical spine showed an intramedullary mass at C2-3 with a syrinx extending into the cervicomedullary junction. Laminectomy, myelotomy, and microsurgical excision of the mass under intraoperative neurological monitoring (IONM) were done. Postoperative pathology reported the specimen as a schwannoma. Gross-total resection of a schwannoma using IONM is the treatment of choice because of the lesion's benign nature, a better prognosis, and defined cleavage plane. Schwannomas should be included in the differential diagnosis of intramedullary spinal tumors. Because of its progressive nature, early surgery is recommended in symptomatic patients.

Fluorescein-guided resection of a left frontal pre-rolandic cerebral metastasis: how I do it.

Cerebral metastases (CM) are the most common intracranial tumors; several studies have underlined the fundamental role of neurosurgical lesion removal. We describe the surgical resection of a left frontal single metastasis. We attempted to achieve a radical resection under the intraoperative guidance of fluorescein, with the aid of intraoperative neurological monitoring. This technique can be applied to each contrast enhancing, intra-axial, infiltrative lesion. Fluorescein-guided surgery is a valuable tool in CM surgery to increase the rate of resection; further prospective evaluation of the role of fluorescein in this field is in planning, aiming to study the prognostic impact.

Spine Deformity Associated with Chiari I Malformation and Syringomyelia.

The management of scoliosis in patients with Chiari I malformation and syringomyelia is a complex decision-making process, which is changing due to evolving evidence. Headache and scoliosis are common presenting symptoms of an underlying Chiari. History, physical examination, and screening with MRI are cornerstones of diagnosis. Posterior fossa decompression provides curve stabilization or regression in about half of patients. In those who require spinal fusion, careful attention must be paid to intraoperative neurological monitoring data to minimize risk of neurologic injury.

The relevance of the wake-up test in scoliosis surgery: A narrative review

The corrective scoliosis surgery is associated with many complications; the neurologic complication is one of them. It is very important to assess spinal cord integrity intraoperatively to avoid postoperative damage and have a good outcome. Wake-up test was the standard of care in old generations but now with the availability of advanced neurophysiologic monitoring somatosensory and motor-evoked potentials; the relevance of wake-up test is questionable. This review aimed to assess the relevance of wake-up test in scoliosis surgery with availability of advanced technology. Comprehensive literature search was performed in PubMed, Google Search and Scopus, EndNote X6 version, and the keywords used for the search were scoliosis, neurophysiologic monitoring, and wake-up test. The different study results were interpreted to come to conclusion. This review gives us a detailed idea of the different tests available and pitfalls with each and finally what should be our stand. The review highlighted the good collaboration between surgeon, anesthesiologist, and neurologist to conclude the results of the tests of neurophysiologic monitoring. Intraoperative neurologic monitoring improves postoperative outcome. Wake-up test is only and strongly recommended, in case of unavailability of advanced monitoring, confusion on test results, and persistent signal reduction.

Anesthetic management of carotid endarterectomy: an update from Italian guidelines

Background and aimsIn order to systematically review the latest evidence on anesthesia, intraoperative neurologic monitoring, postoperative heparin reversal, and postoperative blood pressure management for carotid endarterectomy. The present review is based on a single chapter of the Italian Health Institute Guidelines for diagnosis and treatment of extracranial carotid stenosis and stroke prevention.Methods and resultsA systematic article review focused on the previously cited topics published between January 2016 and October 2020 has been performed; we looked for both primary and secondary studies in the extensive archive of Medline/PubMed and Cochrane library databases.We selected 14 systematic reviews and meta-analyses, 13 randomized controlled trials, 8 observational studies, and 1 narrative review. Based on this analysis, syntheses of the available evidence were shared and recommendations were indicated complying with the GRADE-SIGN version methodology.ConclusionsFrom this up-to-date analysis, it has emerged that any type of anesthesia and neurological monitoring method is related to a better outcome after carotid endarterectomy. In addition, insufficient evidence was found to justify reversal or no-reversal of heparin at the end of surgery. Furthermore, despite a low evidence level, a suggestion for blood pressure monitoring in the postoperative period was formulated.

Effects of compressive lesions on intraoperative human spinal cord elasticity.

Although evaluating tissue elasticity has various clinical applications, spinal cord elasticity (SCE) in humans has never been well documented. In this study, the authors aimed to evaluate the impact of compression on human SCE in vivo. The authors prospectively assessed SCE using intraoperative shear wave elastography (SWE). All consecutive patients undergoing spinal cord (SC) decompression (laminectomy or corpectomy) between June 2018 and June 2019 were included. After intraoperative exposure of the patient's dura mater, at least three SWE measurements of the SC and its coverings were performed. Intraoperative neurological monitoring in the form of motor and somatosensory evoked potentials was utilized. Cases were divided into two groups based on the state of SC compression following bone removal (laminectomy or corpectomy): patients with adequate decompression (the decompressed SC group [DCG]) following bone removal and patients with remining compression, e.g., compressing tumor or instability (the compressed SC group [COG]). A total of 25 patients were included (8 females and 17 males) with a mean age of 48.28 ± 21.47 years. Most cases were degenerative diseases (10 cases) followed by tumors (6 cases), and the compression was observed at cervical (n = 14), thoracic (n = 9), and conus medullaris (n = 2) levels. The COG (6 cases) expressed significantly higher elasticity values, i.e., greater stiffness (median 93.84, IQR 75.27-121.75 kPa) than the decompressed SC in DCG (median 9.35, IQR 6.95-11.22 kPa, p < 0.001). Similarly, the compressed dura mater in the COG was significantly stiffer (mean ± SD 121.83 ± 70.63 kPa) than that in the DCG (29.78 ± 18.31 kPa, p = 0.042). Following SC decompression in COG, SCE values were significantly reduced (p = 0.006; adjusted for multiple comparisons). Intraoperative monitoring demonstrated no worsening from the baseline. The current study is to the authors' knowledge the first to quantitatively demonstrate increased stiffness (i.e., elasticity value) of the human SC and dura mater in response to external compression in vivo. It appears that SCE is a dynamic phenomenon and is reduced following decompression. Moreover, the evaluation of human SCE using the SWE technique is feasible and safe. Information from future studies aiming to further define SCE could be valuable in the early and accurate diagnosis of the compressed SC.

Effect of remimazolam on intraoperative neuromonitoring during thyroid surgery: a case series.

Intraoperative neuromonitoring is widely used to prevent accidental injury during thyroid surgery. Anesthesia should be performed without muscle relaxant or agents with high muscle-relaxant potency. Remimazolam, a novel intravenous anesthetic, became available for clinical use in 2020. Remimazolam is an ultra-short-acting benzodiazepine with a very high clearance rate. However, there are very few data regarding its effect on currently used intraoperative neurological monitoring. Five patients underwent thyroid surgery using intraoperative recurrent laryngeal neuromonitoring. In all cases, intubation was performed after the administration of rocuronium. Anesthesia was maintained by continuous administration of remimazolam at the recommended dose and remifentanil, and no additional rocuronium or sugammadex was administered. Recurrent laryngeal nerve activity could be detected at the first stimulus after surgery was started, and monitoring continued thereafter. Intraoperative monitoring was performed without problems and all surgeries were completed without any complications. Anesthesia with remimazolam at the normal dose did not prolong the time to first positive electromyogram in patients undergoing thyroid surgery, and enables intraoperative recurrent laryngeal nerve monitoring to be performed without any serious perioperative adverse events. Remimazolam may provide a comparable quality of anesthesia to that of existing drugs for neuromonitoring during thyroid surgery.

Intraoperative Neurological Monitoring in Lower Limb Surgery for Patients With Mucopolysaccharidoses

Background: There are reports of spinal cord injury (SCI) occurring after lower extremity (LE) surgery in children with mucopolysaccharidoses (MPS). Intraoperative neurological monitoring (IONM) has been adopted in some centers to assess real-time spinal cord function during these procedures. The aim of this investigation was to review 3 specialty centers’ experiences with MPS patients undergoing LE surgery. We report how IONM affected care and the details of spinal cord injuries in these patients. Methods: All pediatric MPS patients who underwent LE surgery between 2001 and 2018 were reviewed at 3 children’s orthopaedic specialty centers. Demographic and surgical details were reviewed. Estimated blood loss (EBL), surgical time, positioning, use of IONM, and changes in management as a result of IONM were recorded. Details of any spinal cord injuries were examined in detail. Results: During the study period, 92 patients with MPS underwent 252 LE surgeries. IONM was used in 83 of 252 (32.9%) surgeries, and intraoperative care was altered in 17 of 83 (20.5%) cases, including serial repositioning (n=7), aggressive blood pressure management (n=6), and abortion of procedures (n=8). IONM was utilized in cases with larger EBL (279 vs. 130 mL) and longer operative time (274 vs. 175 min) compared with procedures without IONM. Three patients without IONM sustained complete thoracic SCI postoperatively, all from cord infarction in the upper thoracic region. These 3 cases were characterized by long surgical time (328±41 min) and substantial EBL (533±416 mL or 30.5% of total blood volume; range, 11% to 50%). No LE surgeries accompanied by IONM experienced SCI. Conclusions: Patients with MPS undergoing LE orthopaedic surgery may be at risk for SCI, particularly if the procedures are long or are expected to have large EBL. One hypothesis for the etiology of SCI in this setting is hypoperfusion of the upper thoracic spinal cord due to prolonged intraoperative or postoperative hypotension. IONM during these procedures may mitigate the risk of SCI by identifying real-time changes in spinal cord function during surgery, inciting a change in the surgical plan. Level of Evidence: Level III—retrospective comparative series.

A rare intraoperative spinal cord injury caused by thoracic 8 nerve root interruption during posterior vertebral column resection surgery for severe congenital kyphoscoliosis: a case report

BackgroundTo our knowledge, the exposed nerve roots in thoracic spine are usually sacrificed to facilitate osteotomy during posterior vertebral column resection (PVCR) for severe spinal deformity. Currently we report a case with severe spine deformity in which intraoperative neurological monitoring (IOM) loss after interrupting T8 nerve root finally led to spinal cord injury during PVCR surgery.Case presentationThe patient was a 14-year-old female with severe congenital kyphoscoliosis (CKS) without preoperative neurologic deficits. The IOM events (MEP loss and SSEP latency prolong) were showed when T8 nerve root at concave side was interrupted. And then we reduce the scope of osteotomy to control bleeding, raised blood pressure (MAP, 65–80) to increase blood supply for spinal cord, placed the bilateral rod to stabilized the spinal cord, used the methylprednisolone, explored the presence or absence of spinal cord compression, and prepared to change the surgical plan from PVCR to PSO. After that the IOM signals partial recovered from the lowest point. Postoperatively the patients showed transient motor function deficits of left lower limbs weak without somatosensory deficits, and come back to preoperative status 6 months later.ConclusionsInterrupting the thoracic spine nerve root is danger to trigger the spinal cord injury during PVCR procedure of severe CKS. That probably because the increasing tension of contralateral anterior horn area of spinal cord via the nerve root pulling.

The usefulness of intraoperative neurological monitoring for esophageal cancer with double aortic arch; a case report

BackgroundDouble aortic arch (DAA) is a congenital anomaly of the aorta. Esophageal cancer with DAA is rare, and consequently, the appropriate surgical approach has not been standardized. Herein, we report the utilization of intraoperative neurological monitoring (IONM) system to preserve the function of the recurrent laryngeal nerve.Case presentationA 79-year-old man with esophageal cancer was diagnosed with DAA incidentally. The descending aorta was located on the right side of the thoracic vertebrae. Safe dissection of the mediastinal lymph nodes was difficult using the right transthoracic approach because of the anatomical abnormalities. During surgery, we used cervical mediastinoscopy combined with the IONM system to preserve the bilateral recurrent laryngeal nerves. Severe complications, including recurrent nerve palsy, were not observed postoperatively.ConclusionIONM may be useful for evaluation of the function of the recurrent laryngeal nerve, and it would be suitable for atypical cases of esophageal cancer.

Anaesthetic management of patients undergoing deep brain simulation: A retrospective review of 8 cases from a tertiary care center of Pakistan.

Objectives:To review anaesthesia related outcome, perioperative complications and overall length of stay (LOS) in hospital for patients who had deep brain stimulation (DBS).Methods:The study was retrospective review of patients medical records diagnosed with Parkinson disease (PD) and underwent DBS at The Aga Khan University Hospital, Karachi from 2017-2019. Data was reviewed from file notes and patient chart and recorded on predesigned Performa. Frequency and percentages were used to present the data.Results:All patients were anaesthetized using Sleep-Awake-Sleep technique (SAS). Dexmedetomidine was mainly used for conscious sedation. Bispectral index monitor (BIS) was used to monitor the depth of sedation, and kept between 70-85 during sedative phase. All patients had successful intraoperative neurological monitoring, stimulation, and placement of electrodes. Total duration of anesthesia varied significantly in between the patients. Maximum duration was 600 minutes. None of our patient had any intraoperative event related to anaesthetic management. Overall five patients had some adverse events during ward stay. Mean LOS in hospital was four days.Conclusion:Anaesthetic management of DBS is well-tolerated. It requires dedicated team. The SAS technique is excellent for intraoperative neurophysiological monitoring. Careful selection of sedative agents and monitoring depth of anaesthesia using BIS would be beneficial in terms of improving related outcomes.

Neural monitoring during ultrasound-guided radiofrequency ablation of thyroid nodules

Background Intraoperative neurological monitoring is important in locating and assessing nerves during surgery. This study aimed to investigate the feasibility of neural monitoring during ultrasound-guided radiofrequency ablation (RFA) of thyroid nodules. Methods From February 2019 to August 2019, 16 patients (age, 42.8 ± 15.9 years; range, 17–74 years) with benign thyroid nodules who underwent ultrasound-guided RFA with neural monitoring in Zhongshan Hospital, Xiamen University, were included. A neuromonitoring system stimulated the vagus nerve to obtain electromyographic (EMG) signals and predict the function of recurrent laryngeal nerves (RLNs) during RFA. The hydrodissection technique was used to protect the RLN area. Thyroid nodules were treated with the moving-shot technique. The EMG signal value results were recorded and analyzed. All patients underwent laryngoscopic investigation 1 day after the procedure. Results Twenty vagus nerves were stimulated preprocedure and postprocedure, and the EMG signals were successfully recorded (100%). The mean initial (before ablation) and final (final ablation) vagus nerve amplitudes were 612.7 ± 130.4 μV (range, 455–882 μV) and 592.7 ± 127.3 μV (range, 410–817 μV), respectively. Based on the EMG signals, all 20 RLNs were judged to be in good condition, consistent with the postprocedure laryngoscopic results. The maximum lesion size and volume at 6 months after RFA were significantly lesser than those at baseline (p < 0.05). The volume reduction rate was 68.5% ± 21.5% (range, 13.0–97.3%). Cosmetic and symptom scores were significantly lower than those at baseline. No complications from neural monitoring occurred. Conclusions Neural monitoring during ultrasound-guided RFA of thyroid nodules is feasible to predict RLN function.

Carotid Access for Aortic Interventions: Genius or Madness?

The endovascular-first approach remains is omnipresent ubiquitous amongst in the vascular community today. However, several key issues have ensued remain, one of which involves the choice of vessel site. Although the transfemoral route is the first-line approach has been established as first-line approach in endovascular interventions of the aorta (endovascular aortic repair [EVAR], thoracic endovascular aortic repair [TEVAR], and transcatheter aortic valve implantation [TAVI]), there remains a select some group of patients who are contraindicated for the aforementioned this as well as for alternatives vessel routes such as the transapical approach. The carotid artery, first used in aortic aneurysm repair, is potential alternative for these patients. Emerging evidence appears to support this relatively unpopular approach in EVAR, TEVAR and TAVI. Sporadic case reports and series have reported the transcarotid approach for EVAR and TEVAR, and collectively show relatively low rates of mortality and neurological complications. For TAVI, the carotid artery appears to be a safe and effective route of access compared to the transapical and even the transfemoral approach. However, technical aspects have not been ironed out; there are procedural variations, for example, in type of anaesthesia used, intraoperative neurological monitoring and choice of common carotid artery. The overall quality of evidence is poor, since the majority of it consists of case reports, and retrospective and prospective cohort studies. Although a randomised controlled trial (RCT) is needed to compare the transcarotid against the transfemoral approach, this is unlikely to take place because of ethical considerations. Therefore, the authors recommend future research to consider cohort studies with adequately powered sample sizes to establish any firm conclusions. However, as transcarotid procedures are performed infrequently, most institutions will have relatively small sample sizes. Therefore, it is recommended that collaborative efforts are undertaken to increase the overall sample size in the cohort analysis.

Effect of neurological monitoring in postoperative 5-15 days residual thyroidectomy after primary thyroid cancer surgery.

To explore the application of intraoperative neurological monitoring in residual thyroidectomy 5-15 days after thyroid cancer operation and the influence on postoperative serum thyroglobulin (Tg), recurrent laryngeal nerve and function of parathyroid glands. Material of patients receiving thyroid surgery from January 2010 to December 2016 was retrospectively analyzed. Cases meeting with standards were enrolled for analysis and the patients were divided into neurological monitoring group and non-neurological monitoring group in line with the use of neurological monitoring during the operation. Recurrent laryngeal nerve-injured hoarseness, hypoparathyroidism and concentration of serum Tg before and after the surgery were collected and analyzed. Four-hundred and thirty-five patients met with standards, among which 227 from neurological monitoring group and 208 from non-neurological monitoring group. Temporary hoarseness rate of non-neurological monitoring group and neurological monitoring group was 8.67% and 2.2%. Permanent hoarseness rate of non-neurological monitoring group and neurological monitoring group was 1.92% and 0.44%. Temporary hypoparathyroidism rate of non-neurological monitoring group and neurological monitoring group was 18.75% and 7.48%. Permanent hypoparathyroidism rate of non-neurological monitoring group and neurological monitoring group was 1.92% and 0.88%. Average Tg concentration 1 month after the surgery in non-neurological monitoring group and neurological monitoring group was 2.82 and 1.37ng/mL, respectively. Rate of average Tg concentration less than 1ng/mL 1 month after the surgery in non-neurological monitoring group and neurological monitoring group was 45.06% and 67.4%. Intraoperative neurological monitoring can be adopted in residual thyroidectomy in postoperative 5-15 days after primary thyroid cancer surgery, as to reduce incidence rate of recurrent laryngeal nerve injury and hypoparathyroidism and to enhance thorough removal of thyroid tissues and cancer tissues.

High-Risk Surgical Maneuvers for Impending True-Positive Intraoperative Neurologic Monitoring Alerts: Experience in 3139 Consecutive Spine Surgeries

Intraoperative neurologic monitoring (IONM) has become an essential component for decreasing the incidence of spinal cord injury during spine surgeries. Many high-risk surgical maneuvers that result in significant IONM alerts have not been reported systematically. Our objective was to thoroughly summarize some common high-risk surgical points associated with IONM alerts in various spine surgeries. Between November 2010 and April 2017, 62 patients with true-positive IONM alerts from 3139 spine surgeries were enrolled. Transcranial motor evoked potentials, somatosensory evoked potentials, and free-run electromyography were used for IONM. All 62 patients were identified as true-positive IONM cases. Of 3139 patients, 101 demonstrated significant IONM changes-62 true-positive cases, 14 false-positive cases, and 25 indeterminate IONM results. IONM alerts most often occurred in thoracic screw placement (n= 10, 16.1%), osteotomy (n= 22, 35.5%), correction (n= 19, 30.6%), and spinal cord decompression (n= 11, 17.8%). Appropriate timely measures are indicated in response to IONM alerts during high-risk surgical maneuvers. Ten (10/62, 16.1%) patients showed permanent postoperative neurologic deficits. IONM alerts are often associated with some specific high-risk surgical maneuvers. Careful and timely observation is crucial.

A case of spinal surgery that could rescue iatrogenic peripheral neuropathy in intraoperative neurological function monitoring

A case of spinal surgery that could rescue iatrogenic peripheral neuropathy in intraoperative neurological function monitoring

Patients Without Intraoperative Neuromonitoring (IONM) Alerts During VEPTR Implantation Did Not Sustain Neurological Injury During Subsequent Routine Expansions: A Retrospective Multicenter Cohort Study.

The purpose of this study was to determine the rate of intraoperative neurological monitoring (IONM) alerts and neurological injury during vertical expandable prosthetic titanium rib (VEPTR) treatment and evaluate the utility of IONM during VEPTR expansion procedures in patients who have not previously had neurological injury or IONM alerts. After institutional review board approval, VEPTR procedures and IONM records were reviewed at 17 institutions for patients treated with VEPTR from 2005 to 2011. All consecutive cases in patients with minimum 2-year follow-up were included. Patients with prior history of growing rods or other invasive spine-based surgical treatment were excluded. Surgeries were categorized into implant, revision, expansion, and removal procedures. Cases with IONM alerts or neurological injury had additional detailed review. Descriptive statistics were used for data analysis. In total, 2355 consecutive VEPTR procedures (352 patients) consisting of 299 implant, 377 revision, 1587 expansion, and 92 removal procedures were included. In total, 620 VEPTR procedures had IONM, and 539 of those had IONM records available for review. IONM alerts occurred in 9/539 procedures (1.7%): 3/192 implants (1.6%), 3/58 revisions (5.2%), and 3/258 expansions (1.2%). New neurological injury occurred in 3/2355 procedures (0.1%), 3/352 patients (0.9%). All 3 injuries were in implant procedures, only 1 had an IONM alert. All 3 had upper extremity motor deficits (1 had sensory deficit also). All had full recovery at 17, 30, and 124 days postinjury. One patient without prior neurological injury or IONM alert had an IONM alert during expansion that resolved after an increase in blood pressure. The remaining IONM alerts during expansions were all in children with prior IONM alerts during implant, revision, or exchange procedures. The highest rate of neurological injury in VEPTR surgery was found for implant procedures. There were no instances of neurological injury during VEPTR expansion, revision, or removal procedures. IONM did not identify new neurological injuries in patients undergoing VEPTR expansion who did not previously have a history of IONM signal change or neurologic injury. Level IV-diagnostic study.

False-negative transcranial motor evoked potentials (TcMEPs) during surgery for congenital lumbar kyphoscoliosis: a case report.

Transcranial motor evoked potential (TcMEP) monitoring is the gold standard for intra-operative neurological monitoring (IOM) of motor pathways during complex spine surgery because of its high sensitivity and specificity. However, although it is very low, the rate of false-negatives in TcMEP monitoring is not zero. Therefore, over-reliance on TcMEP monitoring can cause potentially preventable motor deficits. We report a case of motor deficits due to nerve root stretch after surgical correction of a congenital lumbar kyphoscoliosis in a 56-year-old woman. TcMEPs did not show any significant changes during surgery, whereas free-run electromyography (EMG) demonstrated a long-lasting train activity in the left quadriceps femoris muscle (QF) after correction at the osteotomy area. According to the normal findings on TcMEP monitoring, we did not release the correction. Postoperatively, a significant decrease (grade 2-) in the manual muscle test for the left QF and iliopsoas muscle and hypesthesia of the left anterior thigh was revealed. Fortunately, muscle strength was fully recovered without revision surgery at 6 months postoperatively; however, numbness in the left anterior thigh persisted at 2 years after surgery. Our report suggests that the possibility of false-negative TcMEPs should be kept in mind, especially during surgery with a risk of nerve root injury. When abnormal findings in the free-run EMG, including long-lasting train activity, are observed, surgeons should consider performing appropriate responses, such as the release of the correction, even when no substantial changes are seen in the TcMEPs.

Current Status of Neuromonitoring in Cardiac Surgery

Brain injury often complicates cardiac surgery with a wide spectrum of neurologic dysfunction running from evidence of stroke to cognitive impairment. Global or regional brain hypoxia represents the common cause of brain injury as the consequence of a mismatch between the oxygen demand and supply to the brain tissue. Whatever the etiological mechanism of the brain damage (cerebral embolism, hypo and/or hyper cerebral perfusion, hypoxia, and the systemic inflammatory response), the continuous intraoperative neuromonitoring should assess the cerebral blood flow and oxygenation and the brain function. The expanded role of the intraoperative neurologic monitoring in cardiac surgery setting has allowed the neurologic adverse events to be promptly detected. The main advantage of the intraoperative neuromonitoring is that they are noninvasive, portable, and reliable. The current literature, though showing low grade of evidence, suggests that intraoperative neuromonitoring may be protective against neurologic adverse events.