Monitoring of Anesthesia by Bispectral Analysis of EEG Signals.

BACKGROUND: In intensive care, monitoring the depth of anesthesia during surgical procedures is a key element in the success of the medical operation and postoperative recovery. However, despite the development of anesthesia thanks to technological and pharmacological advances, its side effects such as underdose or overdose of hypnotics remain a major problem. Observation and monitoring must combine clinical observations (loss of consciousness and reactivity) with tools for real-time measurement of changes in the depth of anesthesia. Methodology. In this work, we will develop a noninvasive method for calculating, monitoring, and controlling the depth of general anesthesia during surgery. The objective is to reduce the effects of pharmacological usage of hypnotics and to ensure better quality recovery. Thanks to the overall activity of sets of neurons in the brain, we have developed a BIS technique based on bispectral analysis of the electroencephalographic signal EEG. Discussion. By collecting the electrical voltages from the brain, we distinguish light sleep from deep sleep according to the values of the BIS indicator (ranging from 0 : sleep to 100 : wake) and also control it by acting on the dosage of propofol and sevoflurane. We showed that the BIS value must be maintained during the operation and the anesthesia at a value greater than 60. CONCLUSION: This study showed that the BIS technology led to an optimization of the anesthetic management, the adequacy of the hypnotic dosage, and a better postoperative recovery.

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.

IONM and thyroidectomy in benign thyroid disease. Analysis of adverse events.

OBJECTIVES: The aim of this study is to identify statistically significant differences in the onset of postoperative complications in patients undergoing thyroid surgery for benign pathology, following the systematic introduction of intraoperative neuromonitoring (IONM) of the laryngeal nerves. MATERIALS AND METHODS: In this study we have retrospectively analysed data of 604 consecutive patients underwent to thyroidectomy in the Unit of General Surgery - University Hospital of Parma between January 2011 and December 2017. All patients were divided in two groups: the first group of patients was operated without the use of IONM (Group A) the second group was operated after the introduction of the systematic use of IONM (Group B). We have compared the incidence of adverse events in these two groups, analysing the impact of IONM on the onset of the most frequent complications after thyroid surgery. We have considered the impact of other variables in both groups, such as thyroiditis, hyperfunction and gland sinking in mediastinum. RESULTS: No statistically significant differences in the incidence between Group A (patients operated without the use of IONM) and Group B (patients operated with the use of IONM) were detected, though a decreasing trend after the introduction of IONM was observed. No statistically significant differences were reported even analysing the influence of other patient's variables such as thyroiditis, hyperfunction and glandular sinking in mediastinum. CONCLUSION: Even if the number of patients considered is not sufficient to value statistically significant differences, the decreasing trend of the incidence of postoperative complications after introduction of IONM encourage us. The surgeon expertise is still the most relevant variable influencing the decreasing of postoperative complications, underlining the importance of the centralization of this kind of surgery in the high volume centres.

Accuracy of intraoperative electrophysiological testing in confirming correct cochlear implant electrode positions.

Objective: To investigate the accuracy of intraoperative electrophysiological studies in detecting incorrectly positioned electrodes in cochlear implant surgery. Study design: A retrospective chart review. Setting: Tertiary referral centre. Patients: In total, 104 consecutive patients with a mean age of 5 years underwent cochlear implant surgery at our centre between January 2012 and December 2013. All patients were implanted with Cochlear Nucleus Freedom implants. Method: A retrospective study to compare intraoperative neural response telemetry (NRT), impedance and electrode position using Stenver's transorbital plain X-ray view. Results: Intraoperative electrophysiological tests for patients with Cochlear Nucleus Freedom implants showed 97% sensitivity and 100% specificity compared with postoperative X-ray imaging. Conclusion: NRT results for the position of cochlear implants were very accurate when checked by X-ray imaging showing that this technique is sufficient in most cases. Stenver's plain X-ray view is needed in complicated cases with abnormal NRT testing or difficult electrode insertion.

Practice Patterns in Parathyroid Surgery: A Survey of Asia-Pacific Parathyroid Surgeons.

BACKGROUND: Practice variations exist amongst parathyroid surgeons depending on their expertise and resources. Our study aims to elucidate the choice of surgical techniques and adjuncts used in parathyroid surgery by surgeons in the Asia-Pacific region. METHODS: A 25-question online survey was sent to members of five endocrine surgery associations. Questions covered training background, practice environment and preferred techniques in parathyroid surgery. Respondents were divided into three regions: Australia/New Zealand, South/South East Asia and East Asia, and responses were analysed according to region, specialty, case volume and years in practice. RESULTS: One hundred ninety-six surgeons returned the questionnaire. Most surgeons (98%) routinely perform preoperative imaging, with 75% preferring dual imaging with 99mTcsestamibi and ultrasound. Ten per cent of surgeons use parathyroid 4DCT as first-line imaging, more commonly in East Asia (p = 0.038). Minimally invasive parathyroidectomy is the favoured technique of choice (97%). Most surgeons reporting robotic or endoscopic approaches are from East Asia. Rapid intraoperative parathyroid hormone is accessible to just under half of the surgeons but less available in Australian/New Zealand (p < 0.001). The use of intraoperative neuromonitoring is not commonly used, even less so amongst Asian surgeons (p = 0.048) and surgeons with low case load (p = 0.013). CONCLUSION: Dual localisation techniques are the preferred choice of investigations in preparation for parathyroid surgery, with minimally invasive surgery without neuromonitoring the preferred approach. Use of adjuncts is sporadic and limited to certain centres.

Laryngeal force sensor metrics are predictive of increased perioperative narcotic requirements.

OBJECTIVES/HYPOTHESIS: To determine the relationship between force metrics measured by the laryngeal force sensor (LFS) during suspension microlaryngoscopy (SML) and perioperative narcotic requirements. STUDY DESIGN: Prospective observational study. METHODS: Compressive tissue forces were recorded during SML using the LFS and correlated with postoperative narcotic requirements in the postanesthesia care unit (PACU) at an academic tertiary center. Patients were prospectively enrolled and had force metrics recorded throughout each procedure including maximum force, average force, suspension time, and total impulse. Narcotic administration in the intraoperative period and PACU were also recorded and converted into intravenous morphine equivalents (ME). Surgeons were blinded to the force recordings during surgery to prevent operator bias. RESULTS: Eighty-two patients completed the study. Of these patients, the mean perioperative ME requirement was 16.96 mg (range, 0.15-79.82 mg). Univariate analysis demonstrated a positive correlation between perioperative narcotic requirements and total suspension time (P < .001) as well as total impulse (P = .007). A positive correlation was also seen with maximum force, although not significantly. On multiple linear regression, total suspension time was a significant predictive variable for perioperative narcotic use, with a marginal incremental increase of 0.273 mg of ME per minute of total suspension time (0.273 mg/min, 95% confidence interval: 0.040-0.507 mg/min, P = .022). CONCLUSIONS: Intraoperative force metrics including total suspension time are predictive of increased perioperative narcotic requirement after SML. Total impulse during SML may also correlate with increased perioperative narcotic requirements. LEVEL OF EVIDENCE: 2 Laryngoscope, 129:2563-2567, 2019.

Prediction of Postoperative Vocal Fold Function After Intraoperative Recovery of Loss of Signal.

OBJECTIVES/HYPOTHESIS: This multicenter study aimed to 1) evaluate early postoperative vocal fold function in relation to intraoperative amplitude recovery, and 2) determine optimal absolute and relative thresholds of intraoperative amplitude recovery heralding normal early postoperative vocal fold function, both after segmental type 1 and after global type 2 loss of signal (LOS). STUDY DESIGN: Prospective outcome study. METHODS: This study, encompassing nine surgical centers from four countries, correlated intraoperative amplitude recovery with early postoperative vocal fold function using receiver operating characteristic analysis. RESULTS: Included in this study were 68 patients, 48 women and 20 men, who sustained transient recurrent laryngeal nerve injury during thyroid surgery under continuous intraoperative nerve monitoring. Early transient vocal fold palsy was seen in 18 (64%) of 28 patients with ipsilateral segmental LOS type 1, and in 10 (25%) of 40 patients with ipsilateral global LOS type 2. On receiver operating characteristic analysis, relative amplitude thresholds were superior to absolute amplitude thresholds in predicting vocal fold function after LOS type 2 (area under the curve [AUC]: 0.83 vs. 0.65; P = .01 vs. P = .15; Youden index 44% and 253 µV) and LOS type 1 (AUC: 0.96 vs. 0.97; P < .001 each; Youden index 49% and 455 µV). Amplitude recovery ≥50% of baseline after LOS always indicated intact vocal fold function. CONCLUSIONS: When the nerve amplitude recovers ≥50% of baseline after segmental LOS type 1 or global LOS type 2, it is appropriate to extend completion thyroidectomy to the other side during the same session. LEVEL OF EVIDENCE: 2b Laryngoscope, 129:525-531, 2019.

Recurrent laryngeal nerve paralysis after thyroid cancer surgery and intraoperative nerve monitoring.

OBJECTIVES/HYPOTHESIS: This study aimed to investigate the risk of postoperative recurrent laryngeal nerve paralysis (RLNP) with and without the use of intraoperative nerve monitoring (IONM) during thyroid cancer surgery. STUDY DESIGN: Retrospective cohort study. METHODS: This study utilized a nationwide claims database in Japan. Patients who underwent thyroid cancer surgery with and without IONM were included, and postoperative RLNP incidence was compared. RESULTS: The study included 5,804 patients. Multivariable logistic regression analysis revealed that use of IONM was not associated with increased RLNP risk (odds ratio: 1.15; 95% confidence interval: 0.67-1.96). There was no significant effect on RLNP prevention when stratified by tumor or nodal classification. Rather, the patients who had T4 or N1b classifications who received IONM had higher incidences of RLNP. CONCLUSIONS: Use of IONM did not significantly reduce the risk of RLNP. The results for the T4 and N1b populations may be explained by indication bias or unmeasured confounders. LEVEL OF EVIDENCE: NA Laryngoscope, 129:1954-1960, 2019.

The impact and value of uni- and multimodal intraoperative neurophysiological monitoring (IONM) on neurological complications during spine surgery: a prospective study of 2728 patients.

PURPOSE: We compared the value of different uni- and multimodal intraoperative neurophysiological monitoring (IONM) methods on the detection of neurological complications during spine surgery. METHODS: IONM data derived from sensory spinal and cortical evoked potentials combined with continuous electromyography monitoring, motor evoked potentials and spinal recording were evaluated in relation to subsequent post-operative neurological changes. Patients were categorised based on their true-positive or true-negative post-operative neurological status. RESULTS: In 2728 consecutive patients we had 909 (33.3%) IONM alerts. We had 8 false negatives (0.3%) with post-operative radicular deficit that completely recovered within 3 months, except for one. There was no false negative for spinal cord injury. 107 were true positives, and 23 were false positives. Multimodal IONM sensitivity and specificity were 93.0% and 99.1%, respectively. The frequency of neurological complications including minor deficits was 4.2% (n = 115), of which 0.37% (n = 10) were permanent. Analysis of the single IONM modalities varied between 13 and 81% to detect neurological complications compared with 93% when using all modalities. CONCLUSION: Multimodal IONM is more effective and accurate in assessing spinal cord and nerve root function during spine surgeries to reduce both neurological complications and false-negative findings compared to unimodal monitoring. We recommend multimodal IONM in all complex spine surgeries. These slides can be retrieved from Electronic Supplementary Material.

Usefulness of Ultrasound-Guided Microsurgery in Cavernous Angioma Removal.

BACKGROUND: Primary elements of surgical treatment of cavernous angiomas (CAs) are precise lesion identification and optimal trajectory determination. Navigation techniques allow for better results compared to microsurgery alone. In this study, we examined the benefits of intraoperative ultrasound (IOUS) use as an adjunct to standard localization systems. METHODS: We retrospectively analyzed 59 CAs, comparing outcomes in 2 groups of patients: 34 who underwent frame-based or frameless navigation-assisted microsurgery (no-IOUS group) and 25 who underwent IOUS-guided microsurgery associated with these techniques (IOUS group). RESULTS: The use of IOUS did not significantly increase the surgery time (mean, 172 ± 1.7 minutes in the IOUS group and 192.6 ± 11.5 in no-IOUS group; P = 0.08). In all 25 patients in the IOUS group, IOUS allowed for ready identification of CA as a hyperechoic mass. At the last follow-up (mean, 41.7 ± 3.5 months postsurgery), 95.2% of the IOUS group and 80.8% of the no-IOUS group had a modified Rankin Scale score of 0-1 and an Extended Glasgow Outcome Scale score of 7-8 (P = 0.2), with 100% and 64%, respectively, included in Engel outcome scale class IA (P = 0.006). Complete removal, as confirmed on postoperative magnetic resonance imaging, was achieved in all patients in the IOUS group and in almost all (97.1%; P = 0.4) patients in the no-IOUS group. CONCLUSIONS: IOUS is a valid tool for the intraoperative identification of CAs. Implementation of standard localization methods with IOUS guidance was associated with complete resection in all cases, without increasing surgical time. Compared with microsurgery without IOUS guidance, long-term functional outcomes showed better trends, and the epilepsy-free rate was significantly higher.

Safeness and Utility of Concomitant Intraoperative Monitoring with Intraoperative Magnetic Resonance Imaging in Children: A Pilot Study.

BACKGROUND: High-field intraoperative magnetic resonance imaging (MRI) has become increasingly available in neurosurgery centers. There is little experience with combined intraoperative MRI and intraoperative neurophysiologic monitoring (IONM). We report the first series, to our knowledge, of pediatric patients undergoing brain tumor surgery with 3T intraoperative MRI and IONM. METHODS: This pilot study included all consecutive children operated on for brain tumors between October 2013 and April 2016 in whom concomitant intraoperative MRI and somatosensory evoked potentials and motor evoked potentials were used. Neuromonitoring findings and related complications of all cases were retrospectively analyzed. RESULTS: During a 30-month period, 17 children (mean age 8.4 years; 3 girls) undergoing surgery met the study criteria. During intraoperative MRI, 483 IONM needles were left in place. Of these needles, 119 were located on the scalp, 94 were located above the chest, and 270 were located below the chest. Two complications with skin burns (first degree) were observed. In all patients, neuromonitoring was still reliable after MRI. In 1 case, a threshold increase for motor evoked potential stimulation (20 mA) was necessary after intraoperative MRI; in 2 cases, a reduction of 50% of the somatosensory evoked potential amplitude at the end of the surgery was observed compared with the values obtained before intraoperative MRI. CONCLUSIONS: The combination of intraoperative MRI and IONM can be safely used in pediatric patients. IONM data acquisition after intraoperative MRI was feasible and remained reliable.

Somatosensory evoked potentials after decompressive craniectomy for traumatic brain injury.

Somatosensory evoked potentials (SSEPs) are used for neuroprognosis after severe traumatic brain injury (TBI). However decompressive craniectomy (DC), involving removal of a portion of the skull to alleviate elevated intracranial pressure, is associated with an increase in SSEP amplitude. Accordingly, SSEPs are not available for neuroprognosis over the hemisphere with DC. We aim to determine the degree to which SSEP amplitudes are increased in the absence of cranial bone. This will serve as a precursor for translation to clinically prognostic ranges. Intra-operative SSEPs were performed before and after bone flap replacement in 22 patients with severe TBI. SSEP measurements were also performed in a comparison non-traumatic group undergoing craniotomy for tumor resection. N20/P25 amplitudes and central conduction time were measured with the bone flap in (BI) and out (BO). Linear regressions, adjusting for skull thickness and study arm, were performed to evaluate the contribution of bone presence to SSEP amplitudes. Latencies were not different between BO or BI trials in either group. Mean N20/P25 amplitudes recorded with BO were statistically different (p = 0.0001) from BI in both cohorts, showing an approximate doubling in BO amplitudes. For contralateral-ipsilateral montages r2 was 0.28 and for frontal pole montages r2 was 0.62. Cortical SSEP amplitudes are influenced by the presence of cortical bone as is particularly evident in frontal pole montages. Larger, longitudinal trials to assess feasibility of neuroprognosis over the hemisphere with DC in severe TBI patients are warranted.

Intraoperative Neuromonitoring Alarms: Relationship of the Surgeon's Decision to Intervene (or Not) and Clinical Outcomes in a Subset of Spinal Surgical Patients with a New Postoperative Neurological Deficit.

BACKGROUND: The goal of intraoperative neurophysiologic monitoring (IONM) is to minimize neurologic injury during surgery, yet patients still emerge with postoperative deficits. Few studies focus on outcomes relative to IONM alarms and interventions in this population. The authors sought to analyze the influence of IONM alarms with and without surgical intervention on patient outcome in spinal surgical patients who suffered immediate postoperative neurologic deficits. METHODS: Of 62,038 spinal surgeries with multimodality IONM, 90 patients with new or worsened postoperative neurologic deficits and whose outcomes were reported immediate to the surgery and at discharge were analyzed. Outcomes at discharge were compared for surgeries in which an IONM alarm versus no alarm occurred. Outcomes where surgical intervention was performed versus not performed were also compared. RESULTS: By discharge, 48 (53.3%) of 90 patients had complete or partial recovery of their postoperative deficit. Patients with IONM alarms and surgical interventions had an 80% (39/49) recovery rate overall versus only 26% (7/27) recovery rate of patients with IONM alarms but no interventions, and only 14% (2/14) of patients without IONM alarms and without interventions (P < 0.001). CONCLUSIONS: These data showed significantly more patients recovered by the time of discharge when a surgical intervention was precipitated by an IONM alarm versus when it was not. The authors conclude that surgical interventions based on IONM alarms do improve patient outcomes despite immediate postoperative deficit.

Intraoperative nerve monitoring reduces recurrent laryngeal nerve injury in geriatric patients undergoing thyroid surgery.

OBJECTIVE: This research was aimed to investigate whether the intraoperative nerve monitoring (IONM) can reduce the incidence of recurrent laryngeal nerve (RLN) injury in geriatric patients undergoing thyroid surgery. METHODS: This retrospective cohort study included 522 geriatric patients undergoing thyroid surgery between January 2013 and June 2016 in the Sun Yat-sen Memorial Hospital. Patients with IONM during the surgery (n = 340) were compared with patients without IONM (n = 212). RLN injury was verified by direct or indirect laryngoscope and relative factors for injury would be retrospectively analyzed. RESULTS: The use of IONM group showed significant reduction in both total and transient RLN injury incidence, when compared with that in control group (1.76 versus 4.72%, p = .01 and 1.32 versus 3.67%, p = .03, respectively). However, the permanent RLN injury incidence did not show difference between the two groups (p = .3). CONCLUSIONS: Our finding showed the use of IONM resulted in significantly reduction in RLN injury incidence. The technology of IONM is safe and convenient to detect, track and monitor the complete function of RLN and to provide the guidance for the surgeons during the thyroid surgery in geriatric patients, who are at high risk of RLN injury.

Prognosis of Significant Intraoperative Neurophysiologic Monitoring Events in Severe Spinal Deformity Surgery.

BACKGROUND: Intraoperative neurophysiologic monitoring has become a standard tool for mitigating neurologic injury during spinal deformity surgery. Significant monitoring changes during deformity correction are relatively uncommon. This study characterizes precipitating factors for neurologic injury and relates significant events and postoperative neurologic prognosis. METHODS: All spinal deformity surgeries at a West African hospital over a 12-month period were reviewed. Patients were included if complete operative reports, monitoring data, and postoperative neurologic examinations were available for review. Surgical and systemic triggers of monitoring events were recorded and neurologic status was followed for 6 weeks postoperatively. RESULTS: Eighty-eight patients met inclusion criteria. The average age was 14 years (3-28). The average kyphosis was 108° (54°-176°) and average scoliosis was 100° (48°-177°). There were 44 separate neurologic events in 34 patients (39%). The most common triggers were traction or positioning (16), posterior column osteotomies/vertebral column resections (9/1), and distraction, corrective maneuvers, or implant placement (12). On surgery completion, 100% (12/12) of events from non-osteotomy-related surgical procedures, 75% (12/16) of events from traction or positioning resolved; however, 0% (0/10) of events from osteotomies resolved completely. Eight percent (7/88) had new neurologic deficits postoperatively, all with intraoperative monitoring changes. In 6 of these 7 patients, the event was attributed to an osteotomy; in 1 patient the cause was not determined. At 6-week follow-up, all patients had some preserved motor function bilaterally with the ability to walk (ASIA D/E) or recovered completely. CONCLUSIONS: Intraoperative signal changes were most frequently from traction or positioning. However, the most common cause of persistent neurologic deterioration and the only cause of postoperative neurologic deficit was the performance of osteotomies. Unlike traction- or instrument-related correction, osteotomies produce irreversible changes, from canal intrusion or sudden localized deformity change. The incidence of postoperative neurologic deficit is very low when the inciting cause is reversed; however, osteotomy-related events are irreversible, with a high incidence of associated lasting neurologic injury.

Sensitivity and Specificity of Intraoperative Neuromonitoring for Identifying Safety and Duration of Temporary Aneurysm Clipping Based on Vascular Territory, a Multimodal Strategy.

BACKGROUND: Patients who undergo clipping of cerebral aneurysms face an inherent risk for new postoperative neurologic deficits. Intraoperative neuromonitoring (IONM) is used often for early detection of ischemic changes, while it is still potentially reversible. However, the value, safety, and efficacy of temporary clipping and multimodal IONM to minimize risks are debated. Our retrospective series examined the sensitivity and specificity of IONM using transcranial motor evoked potentials and somatosensory evoked potentials and quantified the safety of temporary clipping by duration and vascular territory. METHODS: Our prospectively collected database (2010-2013) included 123 consecutive patients who underwent clipping of 133 cerebral aneurysms with use of IONM. We determined postoperative deficit rate and sensitivity and specificity of monitoring to predict these changes intraoperatively. The rate of permanent deficit after temporary clipping was correlated with duration, vascular territory, and IONM findings. RESULTS: Of 133 clipped aneurysms, 15 instances of IONM changes occurred, including 12 temporary without new postoperative deficit and 3 permanent with new postoperative deficit. Somatosensory evoked potential monitoring predicted one of the permanent deficits and transcranial motor evoked potentials predicted the other 2 deficits. CONCLUSIONS: Multimodal IONM was highly specific and sensitive for detecting new deficits. Three patients with new deficits had temporary clipping, including 2 patients with IONM changes not temporally associated with clip placement. Our 1.1% rate of permanent neurologic deficit attributed to temporary clipping support its safety. Differences in patterns of IONM changes among vascular territories warrant further investigation.

Intraoperative Neurophysiologic Monitoring for Adult Patients Undergoing Posterior Spinal Fusion.

BACKGROUND: Somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) are frequently used to monitor neurologic function during spinal deformity surgery. The sensitivity and specificity of intraoperative neurophysiologic monitoring (IONM) in patients undergoing posterior spinal fusion (PSF) is debatable. METHODS: A retrospective review of all patients undergoing PSF with IONM from October 2008 to December 2012 was performed. Factors including sex, operative time, and spinal levels of posterior fusion were analyzed as risk factors for intraoperative alerts. RESULTS: A total of 784 consecutive patients who underwent PSF with IONM without any baseline deficits were analyzed. Patients included 45% men (n = 356) and 55% women (n = 428), with a mean age of 56 years. The mean procedure time was 7 hours. Intraoperative alerts were noted for 3.3% (n = 26) of patients. In this cohort, the average number of levels involved per procedure was approximately 7, ranging from 1 to 16 levels. Of all the spinal levels, the cervicothoracic region had the highest incidence of intraoperative alerts (6 of 97 cervicothoracic cases, P = 0.06). Among these patients, age (P = 0.32), sex (P = 0.66), and procedure time (P = 0.63) were not predictive factors. Four out of 26 (15%) patients had neurologic deficits despite surgeon intervention after neuromonitoring alerts. CONCLUSIONS: SSEP and MEP changes occurred in 3.3% of patients undergoing PSF, with the highest incidence at the cervicothoracic level. Twenty-three out of 26 patients with intraoperative neuromonitoring changes had improvements in IONM signals after interventions during surgery. Further studies using larger patient numbers may be useful in establishing the utility of neuromonitoring in PSF.

Intraoperative seizures during craniotomy under general anesthesia.

PURPOSE: An acute symptomatic seizure is a clinical seizure occurring at the time of or in close temporal association with a brain insult. We report an acute symptomatic seizure occurring during a surgical procedure in a patient who did not have a prior history of epilepsy and who did not have a lesion associated with an increased risk of epilepsy. To characterize the incidence and clinical features of intraoperative seizures during craniotomy under general anesthesia, we reviewed cases where continuous EEG was acquired during craniotomy. METHOD: Records of 400 consecutive cases with propofol as general anesthesia during craniotomy were reviewed. Demographic data, indication for surgery, clinical history, history of prior seizures, duration of surgery and duration of burst suppression were recorded. Cases where seizures were observed were analyzed in detail. RESULTS: Two out of 400 patients experienced intraoperative seizures, including one patient who appeared to have an acute symptomatic seizure related to the surgical procedure itself and a second patient who experienced two seizures likely related to an underlying diagnosis of epilepsy. CONCLUSIONS: This is the first report of an acute symptomatic seizure secondary to a neurosurgical procedure. Overall, 0.5% of patients monitored experienced seizures, indicating that intraoperative seizures are rare, and EEG monitoring during craniotomies is of low yield in detecting seizures.

Exploration of the Intraoperative Motor Evoked Potential.

STUDY DESIGN: Prospective study. OBJECTIVE: The objectives of the study was to (1) seek a relation between motor evoked potential (MEP) and corresponding cervical cord function in cervical compression myelopathy (CCM) and (2) explore a high-sensitive MEP range that can predict the intraoperative monitoring change ahead in cervical spine surgery. SUMMARY OF BACKGROUND DATA: There have been lots of controversies concerning the application of transcranial MEP in cervical spine surgery. METHODS: We prospectively investigate 86 consecutive patients with CCM who underwent posterior laminoplasty or laminectomy from December 2012 to September 2014. The 18-point modified Japanese Orthopedic Association (mJOA) score and intraoperative MEP were used for neurological and electrophysiological assessment. Statistical correlation analysis and curve fitting were used to definite the relationship between MEP and corresponding cervical cord function. And a novel concept of high-sensitive MEP range was firstly addressed for predicting the intraoperative monitoring change ahead in CCM. RESULTS: Our results showed that the preoperative mJOA score of lower extremity presented a significant correlation with MEP parameters in CCM, and the correlation was expressed in an exponential relationship. The monitoring change in CCM often appeared at a high-sensitive MEP range (amplitude <159 µV or latency >36.1 ms). In addition, the high-sensitive MEP ranges not only included MEP degeneration but also a larger number of MEP improvement cases. CONCLUSION: Intraoperative MEP may imply an exponential correlation with the corresponding cervical cord function in CCM. And we first characterize a high-sensitive MEP range which may indicate high risk for the impending monitoring change during cervical cord decompression and we must watch more closely.