Intraoperative Monitoring Changes Research Articles

Microsurgical intraluminal obliteration of type IV perimedullary arteriovenous fistula with an in situ hemostatic agent: illustrative case.

Spinal arteriovenous fistulas (SAVFs) are underdiagnosed entities that can lead to severe morbidity from spinal cord dysfunction or hemorrhage. Treatment options include endovascular embolization or direct surgical obliteration at the level of the arteriovenous shunt. The authors present a case of intraluminal microsurgical access for occlusion with a hemostatic agent of a type IV SAVF near the conus medullaris as an alternative to clip occlusion to avoid nerve root compromise. Temporary microsurgical clipping of the SAVF led to nerve root compromise detected via intraoperative monitoring. Instead, the authors advanced elongated pieces of a hemostatic agent directly into the arterial lumen via arteriotomy to create direct obliteration of the fistula without intraoperative monitoring changes. In patients unable to tolerate clipping of the SAVF because of nerve root involvement and neurophysiological signal decline, open access of the vessels and direct intraluminal obliteration using a hemostatic agent should be considered as an alternative method of fistula occlusion.

Single-institution comparative analysis for odontoid resection: posterior transaxis versus anterior transnasal approach.

The resection of an upwardly migrated odontoid is most widely performed via an anterior endoscopic endonasal approach after the addition of posterior occipitocervical instrumentation. In patients with craniovertebral junction (CVJ) anomalies like basilar invagination (BI), surgery is usually achieved in two separate stages. However, the authors have recently introduced a novel posterior transaxis approach in which all the therapeutic goals of the surgery can be safely and effectively accomplished in a single-stage procedure. The aim of the current study was to compare the widely used anterior and the recently introduced posterior approaches on the basis of objective clinical results in patients who underwent odontoid resection for BI. Patients with BI who had undergone odontoid resection were retrospectively reviewed in two groups. The first group (n = 7) consisted of patients who underwent anterior odontoidectomy via the standard anterior transnasal route, and the second group (n = 6) included patients in whom the novel transaxis approach was performed. Patient characteristics, neurological conditions, and modified Rankin Scale (mRS) scores at admission were evaluated. Operative time, changes in intraoperative neurophysiological monitoring, blood loss during surgery, odontoid resection rate, postoperative complications, and mortality were compared between the patient groups. Data were retrospectively reviewed for 13 patients who underwent odontoid resection, posterior CVJ decompression, and occipitocervical instrumentation at the Ankara University School of Medicine Department of Neurosurgery between 2009 and 2022. In the first group (n = 7), patients who underwent anterior odontoidectomy via the standard endonasal route, two serious complications were observed, pneumocephaly and basilar artery injury. In the second group (n = 6), patients in whom the novel transaxis approach was performed, only one complication was observed, occipital plate malposition. This study represents the results of what is to the authors' knowledge the first comparison of a novel approach with a widely used surgical approach to odontoid resection in patients with BI. The preliminary data support the successful utility of the transaxis approach for odontoid resection that meets all the operative therapeutic demands in a single-stage operation. Considering the diminished surgical risks and operative time, the transaxis approach may be regarded as a primary approach for the treatment of BI.

Cardiovascular-related mortality after intraoperative neurophysiologic monitoring changes during carotid endarterectomy

ObjectiveWe examined significant intraoperative neurophysiologic monitoring (IONM) changes and perioperative stroke as independent risk factors of long-term cardiovascular-related mortality in patients who have undergone carotid endarterectomy (CEA). MethodsRecords of patients who underwent CEA with IONM at the University of Pittsburgh Medical Center between January 1, 2009 and December 31, 2019 were analyzed retrospectively. Cardiovascular-related mortality was compared between the significant IONM change group and no IONM change group and between the perioperative stroke group and no perioperative stroke group. ResultsOur final cohort consisted of 2,090 patients. Patients with significant IONM changes showed nearly twice the rate of cardiovascular-related mortality up to 10 years post-CEA (hazard ratio (HR) = 1.98; 95% confidence interval (CI) [1.20 – 3.26]). Patients with perioperative stroke were four times more likely than patients without perioperative stroke to experience cardiovascular-related mortality (HR = 4.09; 95% CI [2.13 – 7.86]). ConclusionsAmong CEA patients who underwent CEA and who experienced significant IONM changes or perioperative stroke, we observed long-term increased and sustained risk of cardiovascular-related mortality. SignificanceSignificant IONM changes are valuable in predicting the risk of long-term outcomes following CEA.

Management of neurophysiological monitoring changes during carotid endarterectomy exposure

BackgroundCarotid endarterectomy (CEA) is a safe and effective operation in the management of carotid stenosis. Intraoperative neurophysiologic monitoring (IONM) changes during carotid clamping has been well studied, but there is scant evidence detailing IONM changes during carotid exposure. ObjectiveWe analyzed our experience with IONM changes during CEA exposure to determine whether multimodal IONM changes during exposure predict outcomes and how best to manage this challenging clinical scenario. MethodsWe reviewed all CEAs performed at our medical center between January 2015 and June 2020 and identified patients with multimodal IONM changes during exposure of the carotid artery. Our primary outcomes were perioperative stroke and functional outcomes. Functional outcomes were measured by modified Rankin scale (mRS), with good functional outcome defined at mRS scores 0–3. We also reviewed our intraoperative IONM change management strategies. ResultsFive patients (4 males, 1 female) with an average age of 67 ± 12 years had intraoperative IONM changes during carotid exposure. Among these, three patients were discharged with good functional outcome, and four patients had a good functional outcome at last follow-up. Two patients had perioperative stroke, half of which resulted in significant disability. One patient was transferred to the neuroendovascular suite intraoperatively for evaluation for thromboembolism followed by angioplasty and stenting with distal protection. ConclusionIntraoperative IONM changes during carotid exposure predict outcomes in CEA. We propose that transition to the neuroendovascular suite following significant IONM changes during carotid exposure may be a useful strategy for management of this challenging clinical scenario. This approach provides the opportunity to evaluate and treat thromboembolism and still complete carotid revascularization when appropriate. This algorithm may be particularly useful in the era of dual trained vascular neurosurgeons.

Intraoperative Lumbar Muscle Motor Evoked Potential Monitoring With Transcortical Stimulation

Stimulating electrodes for lower extremity motor-evoked potential (LE-MEP) monitoring with transcortical stimulation are usually placed on the medial side of motor cortex convexity, which is not lower extremity but lumbar motor area. Lumbar MEP may be elicited with lower stimulation intensity than LE-MEP through this location, and it is useful to monitor lower extremity motor function intraoperatively. Intraoperative lumbar and LE-MEP monitoring with transcortical stimulation during surgery of 12 patients with lesions involving the motor cortex from January 2012 to February 2019 at Shinshu University Hospital were reviewed retrospectively. Stimulations were delivered by a train of 5 pulses of anodal constant current stimulation. Stimulating electrode position was determined by motor cortex mapping. Recording needle electrodes were placed on bilateral lumbar muscles and contralateral leg muscles. The threshold-level stimulation method was used for MEP monitoring. The thresholds, monitoring result, and postoperative motor function of lumbar and lower extremities were compared. The mean baseline thresholds were 19.9 ± 8.9 mA for lumbar MEP and 26.5 ± 11.5 mA for LE-MEP (P= 0.02). Patterns of intraoperative monitoring changes were the same between lumbar and LE-MEP monitoring. Lumbar MEP was stimulated with lower stimulation intensity than the LE-MEP with the same intraoperative pattern of waveform changes in 12 patients. Lumbar MEP monitoring may be useful for preserving the corticospinal tract of lower extremities intraoperatively.

Risk Factor Analysis of Change in Intraoperative Neurophysiologic Monitoring During Cervical Open Door Laminoplasty

The aim of this study is to determine the risk factors affecting intraoperative neurophysiologic monitoring (IONM) changes, when such changes take place, and clinical outcomes associated with IONM change during cervical open door laminoplasty (COL) for cervical compressive myelopathy. Between 2010 and 2015, 79 patients who underwent COL with IONM recording were studied. Changes in motor evoked potentials or somatosensory evoked potentials over an alarm criterion were defined as IONM change. Patients with IONM change were assigned to the alarm group, and the others were classified as the control group. Baseline data and radiographic measurements were compared between the 2 groups. Radiologic parameters including maximal compression level (MCL), area and diameter of the spinal canal and ventral compressive lesion, stenosis grade, and occupying ratio of area (ORA) and length at the MCL were measured with magnetic resonance imaging. Thirteen patients were assigned to the alarm group and 66 patients were assigned to the control group. Multivariate analysis identified ORA at the MCL (odds ratio, 1.520; 95% confidence interval, 1.192-1.37; P= 0.001) as an independent risk factor for IONM change. Immediately after decompression, the IONM change occurred. One of 4 patients who did not fully recover from the IONM change had postoperative motor deficits. IONM change during COL occurred immediately after decompression, and a risk factor of IONM change was ORA at the MCL. If the IONM change was not fully recovered, a new motor deficit occurred after COL.

Early-Onset Spinal Deformity in Skeletal Dysplasias: A Multicenter Study of Growth-Friendly Systems

PurposeSevere, early-onset spinal deformity is common in patients with skeletal dysplasia. These deformities often present at young ages and are associated with significant pulmonary dysfunction. The objective of this study is to verify the effectiveness of growth-friendly spinal instrumentation systems in promoting growth in patients with skeletal dysplasia and early-onset kyphoscoliosis. MethodsA retrospective, multicenter comparative cohort study was performed. Twenty-three patients identified to have a skeletal dysplasia (SKD) were evaluated for diagnosis, age at treatment, gender, and type of growing rod construct (spine vs. rib constructs). Patients were matched by age and construct type with similarly treated patients with early-onset scoliosis (CON) without skeletal dysplasia. Radiographic parameters including maximum coronal and sagittal Cobb angle with levels, T1–S1 height, and T1–T12 height were measured. ResultsT1–T12 (12.8 vs. 15.2 cm, p = .01) and T1–S1 (21.2 vs. 24.5 cm, p = .05) heights were significantly shorter for the SKD group at implantation, and kyphosis tended to be more severe in children with SKD (p = .80 and .07, respectively). Kyphosis did not improve with treatment. Scoliosis improved (p < .01), and ΔT1–T12 and ΔT1–S1 significantly increased in both groups (p < .01). Complication rates were similar between the two groups; however, patients with SKD had more intraoperative monitoring changes and hardware failures (p < .005). ConclusionAlthough patients with SKD start with shorter spine lengths, gains in spine length appear to be comparable to other forms of EOS. Neuromonitoring changes and implant failures are more common in the SKD group. SignificanceThe effectiveness of growth-friendly techniques in promoting growth in early-onset spinal deformities in patients with skeletal dysplasia has not been previously studied. We report the first comprehensive review of this topic. Growth-friendly techniques are an appropriate treatment option in this patient population.

The influence of anaesthesia on intraoperative neuromonitoring changes in high-risk spinal surgery

Abstract Background: The use of intraoperative neuromonitoring is a well-established method of detecting neurologic injuries during spine surgery. Anaesthesia, especially inhalational agents, influence motor evoked potential (MEP) monitoring. The aim of our study was to compare the effect of balanced anaesthesia (BA) (intravenous plus inhalational anaesthesia) and total intravenous anaesthesia (TIVA) on the incidence of intraoperative neuromonitoring changes, interventions performed and neurological outcomes of patients following high-risk spinal surgery. Methods: After Research and Ethics Board approval, a retrospective review of 155 patients who underwent spinal surgery with MEP was performed. Data were collected on changes in MEP and/or somatosensory evoked potential, interventions performed and neurological outcomes. Patients were divided into BA and TIVA groups and data were analysed. Results: A total of 152 patients were eligible for the study (mean age 54 ± 17, male: female 45:55). A BA technique was used in 62% and TIVA in 38%. Desflurane (&lt;0.5 minimum alveolar concentration [MAC]) was used in 85% BA cases. Intraoperative neuromonitoring changes occurred in 11.8% (18/152) of cases. There was no statistical difference in the incidence of monitoring changes between BA (78%) and TIVA (22%) groups (P = 0.197). Anaesthetic or surgical interventions were performed in 12 patients, with a resolution of changes in 50% (P = 0.455). All 5 patients with persistent MEP changes had worsening of existing neurological deficits postoperatively; 8 had transient MEP changes, and 2 experienced worsening of existing neurological deficits. Conclusions: We found that intraoperative neurophysiological monitoring can be performed with both BA (MAC &lt;0.5) and TIVA in high-risk spinal surgery with no statistical difference in the incidence of intraoperative monitoring changes.

Intraoperative neurophysiologic monitoring (IONM) changes associated with a case of delayed thalamic infarct: Implications for postoperative management

Treatment of cerebral aneurysms poses a risk of cerebral hemorrhage and/or ischemia; these potential sequelae are usually associated with changes in intraoperative neurophysiologic monitoring (IONM) modalities. Our case demonstrates a patient with significant changes in IONM during the treatment of a right posterior cerebral artery aneurysm who did not develop neurologic deficits until three days postoperatively. IONM changes can represent a guide in postoperative patient management and may pose grounds for closer monitoring of patients with IONM changes that do not develop immediate postoperative deficits.

O3-6-21. Time-dependent changes in intraoperative monitoring findings during microvascular decompression for hemifacial spasm

We analyzed time-dependent changes in the intraoperative monitoring of abnormal muscle responses (AMRs) and facial motor evoked potentials (FMEPs) elicited by transcranial electrical stimulation during microvascular decompression (MVD) in 26 patients with hemifacial spasm. In the orbicularis oculi muscle, the AMRs disappeared in 11 patients before MVD, in six after MVD, and in three during dural closure. The AMRs persisted in six patients. FMEP amplitudes decreased to less than 50% in two patients before MVD, in four after MVD, and in six during dural closure. FMEP amplitudes did not decrease in 14 patients ( p p

Predictors of cross-clamp-induced intraoperative monitoring changes during carotid endarterectomy using both electroencephalography and somatosensory evoked potentials

ObjectiveThe efficacy of selective shunting during carotid endarterectomy (CEA) using intraoperative monitoring (IOM) for detection of cerebral ischemia is well established. There is mounting evidence that monitoring of both electroencephalography (EEG) and somatosensory evoked potentials (SSEPs) increases the sensitivity of cerebral ischemia detection. Predictors of cerebral ischemia requiring selective shunt placement using IOM of both EEG and SSEPs have not been previously identified. MethodsConsecutive patients who underwent CEA between January 1, 2000, and December 31, 2010, were retrospectively analyzed. Primary end points were IOM changes at any time during the operation or IOM changes with carotid cross-clamping. Risk factors assessed included demographics; baseline comorbidities; severity of ipsilateral and contralateral disease; symptomatic status; and use of statin, antiplatelet, and beta-blocker medications. Univariate and multivariate logistic regression was used for analysis. ResultsDuring the 11-year study period, a total of 758 patients underwent 804 CEAs (mean age, 70.6 ± 9.5 years; 59.8% male; 39.2% symptomatic) using IOM of both SSEPs and EEG for selective shunting guidance. Postoperative stroke rate was 1.37%; 27.1% of patients had significant SSEP or EEG changes, and 49.1% of these were clamp induced (within 5 minutes of cross-clamping). Of these patients, 83.2% received a shunt (11.4% overall). The most common reason that a shunt was not placed after cross-clamp-induced changes was that the changes resolved with further blood pressure elevation (8 of 17 patients). Clamp-induced IOM changes were predictive of postoperative stroke (odds ratio [OR], 5.5; P = .005). Risk factors for clamp-induced IOM changes were contralateral carotid occlusion (OR, 2.5; P = .01), symptomatic stenosis (OR, 1.8; P = .006), and diabetes (OR, 1.6; P = .03), whereas there was a trend toward increased risk with female sex (OR, 1.5; P = .08). Risk factors for any IOM change (clamp and nonclamp induced) were symptomatic carotid stenosis (OR, 1.8; P < .001), use of beta blockers (OR, 1.5; P = .03), and female sex (OR, 1.5; P = .02). ConclusionsWhereas some patients can be expected to experience IOM changes by monitoring of SSEPs and EEG, a much smaller percentage will receive a shunt. Contralateral carotid occlusion, symptomatic stenosis, diabetes, and female sex increase the risk of clamp-induced IOM changes and should be anticipated to need a shunt. Patients receiving beta blockers are likely to experience IOM changes during the operation that are not associated with clamping.

Somatosensory Evoked Potentials During Temporary Arterial Occlusion for Intracranial Aneurysm Surgery: Predictive Value for Perioperative Stroke.

Temporary arterial occlusion (TAO) is valuable for minimizing intraoperative rupture risk during intracranial aneurysm microsurgery; however, it may be associated with ischemic injury. This study aims to identify surgical and intraoperative neurophysiologic monitoring factors that predict perioperative stroke risk after TAO. We performed a retrospective chart review of 177 intracranial aneurysm surgeries at our institution in which TAO was performed before placement of a permanent clip under monitoring with somatosensory evoked potentials (SSEPs) and electroencephalography. Perioperative stroke was defined as a new-onset neurologic deficit that developed within 24 hours postoperatively that was correlated with hypodensity on postoperative computed tomography. Ten (6%) patients developed perioperative stroke in the vascular territory of TAO. SSEP changes were observed in 50% (5/10) of patients with perioperative stroke and in 14% (24/167) of patients without stroke (P= 0.003). Mean maximum single-episode TAO duration for patients who developed perioperative stroke was 12.6 minutes (95%confidence interval 8.1-17.1) and TAO duration for patients without stroke was 8.0 minutes (95% confidence interval 7.3-8.7; P= 0.026). In patients with SSEP changes, risk of stroke was particularly elevated with unruptured aneurysms (P= 0.013) compared with patients with ruptured aneurysms. Temporary clip location, number of occlusive episodes, onset and duration of intraoperative neurophysiologic monitoring changes, and rupture status were not predictive of perioperative stroke. SSEP changes and increased single-episode TAO duration are independently associated with increased perioperative stroke risk. SSEP changes are most predictive for perioperative stroke in unruptured cases.

Monitoring rate and predictability of intraoperative monitoring in patients with intradural extramedullary and epidural metastatic spinal tumors.

Single-center retrospective study. To evaluate the monitoring rate, sensitivity and specificity of intraoperative monitoring (IOM) during removal of intradural extramedullary (IDEM) or epidural metastatic spinal tumors. Also, to assess the efficacy of monitoring somatosensory-evoked potentials (SSEP) when motor-evoked potentials (MEP) are not measurable. The Neuro-Oncology Clinic, National Cancer Center, Korea. Patients (n=101) with IDEM or epidural metastatic spinal tumors at the cord level underwent surgeries monitored with SSEP and/or MEP. The monitoring rate was defined as negative when MEP or SSEP could not be measured after reversal of the neuromuscular block under general anesthesia. Positive IOM changes included more than a 50% change in the MEP or SSEP amplitude and more than a 10% delay in SSEP latency. MEP was measurable in 73% of patients. The MEP monitoring rate in patients with motor power grades of 3 or less was 39%, which was lower than that of SSEP (83%). The sensitivity, specificity and predictability of MEP for motor changes were 93, 90 and 91%, respectively. Conversely, the sensitivity, specificity and predictability of SSEP were 62, 97 and 89%, respectively. In patients in whom MEP was not measurable (n=24), SSEP was monitored with a predictability of 83%. In cases of extramedullary spinal tumors, MEP shows a higher sensitivity than SSEP does. However, the monitoring rate of MEP in non-ambulatory patients was lower than that of SSEP. In those cases, SSEP can be useful to monitor for postoperative neurological deficits.

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

BackgroundIntraoperative 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. MethodsAll 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. ResultsEighty-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. ConclusionsIntraoperative 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.

The influence of anaesthesia on intraoperative neuromonitoring changes in high-risk spinal surgery

Background: The use of intraoperative neuromonitoring is a well-established method of detecting neurologic injuries during spine surgery. Anaesthesia, especially inhalational agents, influence motor evoked potential (MEP) monitoring. The aim of our study was to compare the effect of balanced anaesthesia (BA) (intravenous plus inhalational anaesthesia) and total intravenous anaesthesia (TIVA) on the incidence of intraoperative neuromonitoring changes, interventions performed and neurological outcomes of patients following high-risk spinal surgery. Methods: After Research and Ethics Board approval, a retrospective review of 155 patients who underwent spinal surgery with MEP was performed. Data were collected on changes in MEP and/or somatosensory evoked potential, interventions performed and neurological outcomes. Patients were divided into BA and TIVA groups and data were analysed. Results: A total of 152 patients were eligible for the study (mean age 54 ± 17, male: female 45:55). A BA technique was used in 62% and TIVA in 38%. Desflurane ( P = 0.197). Anaesthetic or surgical interventions were performed in 12 patients, with a resolution of changes in 50% ( P = 0.455). All 5 patients with persistent MEP changes had worsening of existing neurological deficits postoperatively; 8 had transient MEP changes, and 2 experienced worsening of existing neurological deficits. Conclusions: We found that intraoperative neurophysiological monitoring can be performed with both BA (MAC <0.5) and TIVA in high-risk spinal surgery with no statistical difference in the incidence of intraoperative monitoring changes.

Perioperative stroke after carotid endarterectomy: etiology and implications.

Carotid endarterectomy (CEA) is the procedure of choice for reducing the risk of stroke in both symptomatic and asymptomatic carotid artery stenoses. Stroke is associated with significant morbidity and mortality peri-operatively (2-3%). Our primary aim is to evaluate the etiology of these strokes after CEA and their impact on morbidity by comparing the length of stay in the hospital. A total of 584 patients with documented neurological status evaluations who underwent CEAs were included in the study. Neurophysiological monitoring data was obtained during CEA for carotid stenosis included eight-channel electroencephalography (EEG) and upper extremity somatosensory evoked potentials (SSEPs). Twenty-one (3.595%) patients had strokes in the perioperative period and they were more likely to have left-sided surgery (p = 0.008), intraoperative monitoring (IOM) changes (p < 0.001), an intraoperative shunt placed (p = 0.0002) or a hospital stay longer than 5days (p = 0.0042). Unilateral anterior circulation ischemic stroke were the most common in our series. In a logistic regression model, left-sided surgery was shown to be 4.78 times more likely to be associated with perioperative stroke (1.50-15.27; p = 0.008) while intraoperative shunts were 11.85 times more likely to have strokes (3.97-35.34; p < 0.0001). Patients with stenosis greater than 70% were 6.67 times less likely to have a stroke (0.04-0.59; p = 0.007). Ischemic anterior circulation strokes are the most common type of post-operative neurological changes in patients undergoing CEA. Intraoperative shunt placement was a strong predictor of perioperative strokes. Since shunts are only placed following intraoperative monitoring changes, SSEPs and EEG can therefore function as a biomarker of cerebral hypo-perfusion.

Somatosensory Evoked Potentials and Electroencephalography during Carotid Endarterectomy Predict Late Stroke but not Death

Late stroke and death rates are anticipated to be higher in patients undergoing carotid endarterectomy (CEA) compared with healthy counterparts. However, little is known regarding predictors other than the baseline comorbidities. We have recently shown that dual intraoperative somatosensory evoked potentials (SSEPs) and electroencephalography (EEG) monitoring improves the ability to predict perioperative strokes. We seek to determine if dual intraoperative monitoring (IOM) can further predict long-term strokes and death. Consecutive patients who underwent CEA under dual SSEP and EEG IOM between January 1, 2000 and December 31, 2010 were analyzed. Patients were divided in 2 groups, those with and those without IOM changes. IOM changes were classified as either occurring during carotid cross-clamp placement or at any time during the operation. End points were time to stroke and death. Log-rank tests and Cox regression analysis were used to identify predictors of postoperative stroke and death. A total of 853 CEAs (mean age 70.6±9.5years, 58.7% male, 38.9% symptomatic) were performed during the study period with a mean clinical follow-up of 48±38months. One hundred seven patients (13.6%) had significant SSEP or EEG changes at the time of clamping, while considerably more patients (217, 25.4%) had SSEP and/or EEG changes recorded at any point during the procedure, including clamping. Baseline characteristics including rates of bilateral disease, statin use, and antiplatelet use were similar between groups. Female gender, symptomatic disease, and significant contralateral carotid stenosis were more frequent in the group with IOM changes. The overall stroke-free survival rate at 5years was significantly higher in patients without IOM changes (94.7% vs. 88.2%, P<0.05) and at 10years (86.1% vs. 78.0%, P<0.05). Despite differences in stroke-free survival, overall survival at 10years was not different between groups (44.0% in patients with IOM changes vs. 42.8% in patients without, P=0.7). Renal insufficiency (hazards ratio [HR] 2.13, P=0.03), diabetes (HR 1.84, P=005), and age > 80 at the time of operation (HR 3.24, P=0.001) were significant predictors of late stroke, while statins were significantly protective (HR 0.55, P=0.05). Controlling for these factors, IOM changes (HR 2.5, P=0.004) were a strong predictor of long-term risk of stroke after CEA. Intraoperative SSEP and/or EEG changes are predictive of late stroke but not death following CEA indicating a need for further elucidation and management of the underlying risk factors driving the elevated stroke risk in this subset of CEA patients.

319 Predictive Value of Intraoperative Neurophysiological Monitoring During Spine Surgery

INTRODUCTION: A single-center study to define the sensitivity and specificity of intraoperative neurophysiological monitoring in detecting new neurological deficits. METHODS: A cohort of 4989 consecutive (2962 male and 2027 female) patients operated on over 3 years was evaluated. Subgroup analysis was performed for patients undergoing posterior cervical intervention (n = 1373) and posterior lumbar fusion surgery (n = 2420). Sensitivity and specificity were determined using Bayesian techniques. Impact of length of surgery and of variables, including age, sex, body mass index, diabetes mellitus, hypertension, coronary artery disease, cerebrovascular disease, and history of smoking, on the development of a new neurodeficit was defined. RESULTS: Of 4489 patients, 426 patients (9.4%) had significant intraoperative somatosensory evoked potential (SSEP) changes. New postoperative neurological deficits occurred in 121 (2.7%) patients. Twenty-five of 426 patients (5.8%) with neuromonitoring changes developed a new neurodeficit. Ninety-six of 4063 patients (2.3%) with no changes developed a new neurodeficit. In posterior cervical interventions, 98 of 1373 (7.1%) developed SSEP changes and 13 of 98 (13.2%) patients developed a new neurodeficit, whereas 49 (3.8%) developed a new neurodeficit without any changes in intraoperative monitoring (IOM). In posterior lumbar fusion SSEPs, electromyographs (EMGs), and pedicle screw stimulation was utilized. Two hundred forty-nine of 2420 (10.2%) patients developed IOM changes and 8 of 249 (3.2%) patients developed a new neurodeficit, while 37 (1.7%) developed a new neurodeficit without changes in IOM. In the entire cohort SSEPs had sensitivity 20.7% and specificity of 90.8%. In the posterior cervical cohort, SSEPs had s sensitivity of 20.9% and a specificity of 93.7%. In the lumbar fusion cohort, multimodality monitoring including SSEPs, EMGs, and pedicle screw stimulation had a sensitivity of 17.8% and a specificity of 88.6%. Neither the length of surgery nor did any analyzed patient-related variable have a statistically significant impact on the development of a new neurodeficit. CONCLUSION: The strength of SSEPs is their negative predictive value. A cost-utility analysis for IOM in spine surgery should be undertaken.

Is intraoperative neurophysiological monitoring valuable predicting postoperative neurological recovery?

We investigated the ability of intraoperative neurophysiological monitoring to predict postoperative neurological recovery in intradural-extramedullary spinal cord tumors. From 2010 to 2014, we operated on 173 intradural-extramedullary spinal cord tumor patients with intraoperative neurophysiological monitoring. We retrospectively compared preoperative and postoperative clinical status using a modified McCormick grading scale and correlated with intraoperative neurophysiological monitoring. We followed patients for at least 1 year and correlated neurological outcomes with intraoperative changes in intraoperative neurophysiological monitoring. We then compared the degree of intraoperative neurophysiological monitoring change with the duration of the neurological deficit. Monitorability was 92% and 57% with transcranial motor-evoked potential and somatosensory-evoked potential modalities, respectively. Waveform attenuation on transcranial motor-evoked potentials was detected in 8.17% of cases. For somatosensory-evoked potentials, waveform attenuation was detected in 7% of the patients. A multimodality approach incorporating any transcranial motor-evoked potential changes had a sensitivity of 0.91 and a specificity of 0.98. The McCormick grade scale increased until 1 month in patients with alarm criteria on transcranial motor-evoked potentials (P<0.05). Patients suffered neurological deterioration in case of abolishment or >50% irreversible attenuation of the waveform in transcranial motor-evoked potentials. All patients gradually recovered after 1 postoperative month with alarm criteria from 50% to 80% irreversible amplitude drop on transcranial motor-evoked potentials.

Persistent Intraoperative Neurophysiologic Monitoring Changes in Scoliosis Surgery Correlate with Postoperative Deficits (P5.017)

Persistent Intraoperative Neurophysiologic Monitoring Changes in Scoliosis Surgery Correlate with Postoperative Deficits (P5.017)