Publications by authors named "Jeffrey R Balzer"

55 Publications

Triggered Electromyography is a Useful Intraoperative Adjunct to Predict Postoperative Neurological Deficit Following Lumbar Pedicle Screw Instrumentation.

Global Spine J 2021 May 20:21925682211018472. Epub 2021 May 20.

Department of Neurological Surgery, 6595University of Pittsburgh Medical Center, Pittsburgh, PA, USA.

Study Design: Systematic review and meta-analysis.

Objectives: Malposition of pedicle screws during instrumentation in the lumbar spine is associated with complications secondary to spinal cord or nerve root injury. Intraoperative triggered electromyographic monitoring (t-EMG) may be used during instrumentation for early detection of malposition. The association between lumbar pedicle screws stimulated at low EMG thresholds and postoperative neurological deficits, however, remains unknown. The purpose of this study is to assess whether a low threshold t-EMG response to lumbar pedicle screw stimulation can serve as a predictive tool for postoperative neurological deficit.

Methods: The present study is a meta-analysis of the literature from PubMed, Web of Science, and Embase identifying prospective/retrospective studies with outcomes of patients who underwent lumbar spinal fusion with t-EMG testing.

Results: The total study cohort consisted of 2,236 patients and the total postoperative neurological deficit rate was 3.04%. 10.78% of the patients incurred at least 1 pedicle screw that was stimulated below the respective EMG alarm threshold intraoperatively. The incidence of postoperative neurological deficits in patients with a lumbar pedicle screw stimulated below EMG alarm threshold during placement was 13.28%, while only 1.80% in the patients without. The pooled DOR was 10.14. Sensitivity was 49% while specificity was 88%.

Conclusions: Electrically activated lumbar pedicle screws resulting in low t-EMG alarm thresholds are highly specific but weakly sensitive for new postoperative neurological deficits. Patients with new postoperative neurological deficits after lumbar spine surgery were 10 times more likely to have had a lumbar pedicle screw stimulated at a low EMG threshold.
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http://dx.doi.org/10.1177/21925682211018472DOI Listing
May 2021

Diagnostic Accuracy of SSEP Changes during Lumbar Spine Surgery for Predicting Postoperative Neurological Deficit: A Systematic Review and Meta-Analysis.

Spine (Phila Pa 1976) 2021 May 6. Epub 2021 May 6.

Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA, USA Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA, USA Department of Neurology, University of Pittsburgh Medical Center, Pittsburgh, PA, USA Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA, USA.

Study Design: This study is a meta-analysis of prospective and retrospective studies identified in PubMed, Web of Science, and Embase with outcomes of patients who received intraoperative SSEP monitoring during lumbar spine surgery.

Objective: The objective of this study is to determine the diagnostic accuracy of intraoperative lower extremity (LE) SSEP changes for predicting postoperative neurological deficit. As a secondary analysis, we evaluated three subtypes of intraoperative SSEP changes: reversible, irreversible, and total signal loss.

Summary Of Background Data: Lumbar decompression and fusion surgery can treat lumbar spinal stenosis and spondylolisthesis but carry a risk for nerve root injury. Published neurophysiological monitoring guidelines provide no conclusive evidence for the clinical utility of intraoperative somatosensory evoked potential (SSEP) monitoring during lumbar spine surgery.

Methods: A systematic review was conducted to identify studies with outcomes of patients who underwent lumbar spine surgeries with intraoperative SSEP monitoring. The sensitivity, specificity, and diagnostic odds ratio (DOR) were calculated and presented with forest plots and a summary receiver operating characteristic (ROC) curve.

Results: The study cohort consisted of 5,607 patients. All significant intraoperative SSEP changes had a sensitivity of 44% and specificity of 97% with a DOR of 22.13 (95% CI, 11.30-43.34). Reversible and irreversible SSEP changes had sensitivities of 28% and 33% and specificities of 97% and 97%, respectively. The DORs for reversible and irreversible SSEP changes were 13.93 (95% CI, 4.60-40.44) and 57.84 (95% CI, 15.95-209.84), respectively. Total loss of SSEPs had a sensitivity of 9% and specificity of 99% with a DOR of 23.91 (95% CI, 7.18-79.65).

Conclusion: SSEP changes during lumbar spine surgery are highly specific but moderately sensitive for new postoperative neurological deficits. Patients who had postoperative neurological deficit were 22 times more likely to have exhibited intraoperative SSEP changes.Level of Evidence: 2.
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http://dx.doi.org/10.1097/BRS.0000000000004099DOI Listing
May 2021

Optimal "Low" Pedicle Screw Stimulation Threshold to Predict New Postoperative Lower-Extremity Neurologic Deficits During Lumbar Spinal Fusions.

World Neurosurg 2021 Apr 16. Epub 2021 Apr 16.

Departments of Neurological Surgery and Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA. Electronic address:

Objective: Previous studies have shown that pedicle screw stimulation thresholds ≤6-8 mA yield a high diagnostic accuracy of detecting misplaced screws. Our objective was to determine the optimal "low" stimulation threshold to predict new postoperative neurologic deficits and identify additional risk factors associated with deficits.

Methods: We included patients with complete pedicle screw stimulation testing who underwent posterior lumbar spinal fusion surgeries from 2010-2012. We calculated the diagnostic accuracy of pedicle screw responses of ≤4 mA, ≤6 mA, ≤8 mA, ≤10 mA, ≤12 mA, and ≤20 mA to predict new postoperative lower-extremity (LE) neurologic deficits. We used multivariate modeling to determine the best logistic regression model to predict LE deficits and identify additional risk factors. Statistics software packages used were Python3.8.5, NumPy 1.19.1, Pandas 1.1.1, and SPSS26.

Results: We studied 1179 patients who underwent 8584 pedicle screw stimulations with somatosensory evoked potential and free-run electromyographic monitoring for posterior lumbar spinal fusion. Twenty-five (2.1%) patients had new LE neurologic deficits. A stimulation threshold of ≤8 mA had a sensitivity/specificity of 32%/90% and a diagnostic odds ratio/area under the curve of 4.34 [95% confidence interval: 1.83, 10.27]/0.61 [0.49, 0.74] in predicting postoperative deficit. Multivariate analysis showed that patients who had pedicle screws with stimulation thresholds ≤8 mA are 3.15 [1.26, 7.83]× more likely to have postoperative LE deficits while patients who have undergone a revision lumbar spinal fusion surgery are 3.64 [1.38, 9.61]× more likely.

Conclusions: Our results show that low thresholds are indicative of not only screw proximity to the nerve but also an increased likelihood of postoperative neurologic deficit. Thresholds ≤8 mA prove to be the optimal "low" threshold to help guide a correctly positioned pedicle screw placement and detect postoperative deficits.
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http://dx.doi.org/10.1016/j.wneu.2021.04.022DOI Listing
April 2021

What is the predictive value of intraoperative somatosensory evoked potential monitoring for postoperative neurological deficit in cervical spine surgery?-a meta-analysis.

Spine J 2021 04 16;21(4):555-570. Epub 2021 Jan 16.

Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA, USA; Department of Neurology, University of Pittsburgh Medical Center, Pittsburgh, PA, USA. Electronic address:

Background Context: Cervical decompression and fusion surgery remains a mainstay of treatment for a variety of cervical pathologies. Potential intraoperative injury to the spinal cord and nerve roots poses nontrivial risk for consequent postoperative neurologic deficits. Although neuromonitoring with intraoperative somatosensory evoked potentials (SSEPs) is often used in cervical spine surgery, its therapeutic value remains controversial.

Purpose: The purpose of the present study was to evaluate whether significant SSEP changes can predict postoperative neurologic complications in cervical spine surgery. A subgroup analysis was performed to compare the predictive power of SSEP changes in both anterior and posterior approaches.

Study Design: The present study was a meta-analysis of the literature from PubMed, Web of Science, and Embase to identify prospective/retrospective studies with outcomes of patients who underwent cervical spine surgeries with intraoperative SSEP monitoring.

Patient Sample: The total cohort consisted of 7,747 patients who underwent cervical spine surgery with intraoperative SSEP monitoring.

Methods: Inclusion criteria for study selection were as follows: (1) prospective or retrospective cohort studies, (2) studies conducted in patients undergoing elective cervical spine surgery not due to aneurysm, tumor, or trauma with intraoperative SSEP monitoring, (3) studies that reported postoperative neurologic outcomes, (4) studies conducted with a sample size ≥20 patients, (5) studies with only adult patients ≥18 years of age, (6) studies published in English, (7) studies inclusive of an abstract.

Outcome Measures: The sensitivity, specificity, diagnostic odds ratio (DOR), and likelihood ratios of overall SSEP changes, reversible SSEP changes, irreversible SSEP changes, and SSEP loss for predicting postoperative neurological deficit were calculated.

Results: The total rate of postoperative neurological deficits was 2.50% (194/7,747) and the total rate of SSEP changes was 7.36% (570/7,747). The incidence of postoperative neurological deficit in patients with intraoperative SSEP changes was 16.49% (94/570) while only 1.39% (100/7,177) in patients without. All significant intraoperative SSEP changes had a sensitivity of 46.0% and specificity of 96.7% with a DOR of 27.32. Reversible and irreversible SSEP changes had sensitivities of 17.7% and 37.1% and specificities of 97.5% and 99.5%, respectively. The DORs for reversible and irreversible SSEP changes were 9.01 and 167.90, respectively. SSEP loss had a DOR of 51.39, sensitivity of 17.3% and specificity 99.6%. In anterior procedures, SSEP changes had a DOR of 9.60, sensitivity of 34.2%, and specificity of 94.7%. In posterior procedures, SSEP changes had a DOR of 13.27, sensitivity of 42.6%, and specificity of 94.0%.

Conclusions: SSEP monitoring is highly specific but weakly sensitive for postoperative neurological deficit following cervical spine surgery. The analysis found that patients with new postoperative neurological deficits were nearly 27 times more likely to have had significant intraoperative SSEP change. Loss of SSEP signals and irreversible SSEP changes seem to indicate a much higher risk of injury than reversible SSEP changes.
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http://dx.doi.org/10.1016/j.spinee.2021.01.010DOI Listing
April 2021

Diagnostic Accuracy of Thresholds Less Than or Equal to 8 mA in Pedicle Screw Testing During Lumbar Spine Procedures to Predict New Postoperative Lower Extremity Neurological Deficits.

Spine (Phila Pa 1976) 2021 Jan;46(2):E139-E145

Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA.

Study Design: Retrospective observational study.

Objective: It has been shown that pedicle screw stimulation thresholds less than or equal to 8 mA yield a very high diagnostic accuracy of detecting misplaced screws in spinal surgery. In our study, we determined clinical implications of low stimulation thresholds.

Summary Of Background Data: Posterior lumbar spinal fusions (PSF), using pedicle screws, are performed to treat many spinal pathologies, but misplaced pedicle screws can result in new postoperative neurological deficits.

Methods: Patients with pedicle screw stimulation testing who underwent PSF between 2010 and 2012 at the University of Pittsburgh Medical Center (UPMC) were included in the study. We evaluated the sensitivity, specificity, and diagnostic odds ratio (DOR) to determine how effectively low pedicle screw responses predict new postoperative lower extremity neurological deficits.

Results: One thousand one hundred seventy nine eligible patients underwent 8584 pedicle screw stimulations with lower extremity somatosensory evoked potentials (LE SSEP) monitoring for lumbar fusion surgery. One hundred twenty one of these patients had 187 pedicle screws with a stimulation response at a threshold less than or equal to 8 mA. Smoking had a significant correlation to pedicle screw stimulation less than or equal to 8 mA (P = 0.012). A threshold of less than or equal to 8 mA had a sensitivity/specificity of 0.32/0.90 with DOR of 4.34 [1.83, 10.27] and an area under the ROC curve (AUC) of 0.61 [0.49, 0.74]. Patients with screw thresholds less than or equal to 8 mA and abnormal baselines had a DOR of 9.8 [95% CI: 2.13-45.17] and an AUC of 0.73 [95% CI: 0.50-0.95].

Conclusion: Patients with pedicle screw stimulation thresholds less than or equal to 8 mA are 4.34 times more likely to have neurological clinical manifestations. Smoking and LE deficits were shown to be significantly correlated with pedicle screw stimulation thresholds less than or equal to 8 mA. Low stimulation thresholds result in a high specificity of 90%. Pedicle screw stimulation less than or equal to 8 mA can serve as an accurate rule in test for postoperative neurological deficit, warranting reevaluation of screw placement and/or replacement intraoperatively.Level of Evidence: 3.
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http://dx.doi.org/10.1097/BRS.0000000000003727DOI Listing
January 2021

Role of Intraoperative Neurophysiologic Monitoring in Internal Carotid Artery Injury During Endoscopic Endonasal Skull Base Surgery.

World Neurosurg 2021 Apr 7;148:e43-e57. Epub 2020 Dec 7.

Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA; Department of Neurology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA. Electronic address:

Objective: In the present study, we investigated the role of intraoperative neuromonitoring (IONM) in internal carotid artery (ICA) injury during endoscopic endonasal skull base surgery (EESBS).

Methods: The study group included all 13 patients who had experienced an ICA injury during EESBS with IONM from 2004 to 2017. The medical records were reviewed for the perioperative data. The IONM reports were reviewed to evaluate the baseline somatosensory evoked potentials (SSEP), electroencephalography (EEG), and brainstem auditory evoked potentials (BAEP) and their significant changes related to ICA injury and/or the subsequent surgical/endovascular interventions.

Results: All 13 patients had undergone SSEP and 7 patients had BAEP monitoring during surgery. EEG was added during emergent angiography following the surgery for 5 patients. Two patients showed significant SSEP changes, and one showed significant SSEP and EEG changes, indicating cerebral hypoperfusion. Of these 3 patients, patient 1 had experienced irreversible SSEP loss with postoperative stroke. Patients 2 and 3 had SSEP and/or EEG changes that had recovered to baseline after interventions without postoperative deficits. Despite ICA injury, 10 patients showed no significant SSEP and/or EEG changes, and all 7 patients with BAEP monitoring showed no significant BAEP changes, indicating adequate cerebral and brainstem perfusion, respectively. The injured ICA was sacrificed in 4 patients, of whom 3 showed stable SSEP and 1 had experienced irreversible SSEP loss. IONM correlated with the postoperative neurologic examination findings in all cases, adequately predicting the neurologic outcomes after ICA injury.

Conclusion: SSEP and EEG monitoring can accurately detect cerebral hypoperfusion and provide real-time feedback during surgery. SSEP and EEG changes predicted for neurologic outcomes and guide surgical decisions regarding the preservation or sacrifice of the ICA. Comprehensive multimodality monitoring according to the surgical risks can serve to detect and guide the management of ICA injury in EESBS.
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http://dx.doi.org/10.1016/j.wneu.2020.11.154DOI Listing
April 2021

Last Electrically Well: Intraoperative Neurophysiological Monitoring for Identification and Triage of Large Vessel Occlusions.

J Stroke Cerebrovasc Dis 2020 Oct 29;29(10):105158. Epub 2020 Jul 29.

The Departments of Neurology and Neurological Surgery, University of Pittsburgh Medical, Center, Pittsburgh, PA USA. Electronic address:

Introduction: Intra-operative stroke (IOS) is associated with poor clinical outcome as detection is often delayed and time of symptom onset or patient's last known well (LKW) is uncertain. Intra-operative neurophysiological monitoring (IONM) is uniquely capable of detecting onset of neurological dysfunction in anesthetized patients, thereby precisely defining time last electrically well (LEW). This novel parameter may aid in the detection of large vessel occlusion (LVO) and prompt treatment with endovascular thrombectomy (EVT).

Methods: We performed a retrospective analysis of a prospectively maintained AIS and LVO database from May 2018-August 2019. Inclusion criteria required any surgical procedure under general anesthesia (GA) utilizing EEG (electroencephalography) and/or SSEP (somatosensory evoked potentials) monitoring with development of intraoperative focal persistent changes using predefined alarm criteria and who were considered for EVT.

Result: Five cases were identified. LKW to closure time ranged from 66 to 321 minutes, while LEW to closure time ranged from 43 to 174 min. All LVOs were in the anterior circulation. Angiography was not pursued in two cases due to large established infarct (both patients expired in the hospital). EVT was pursued in two cases with successful recanalization and spontaneous recanalization was noted in one patient (mRS 0-3 at 90 days was achieved in all 3 cases).

Conclusions: This study demonstrates that significant IONM changes can accurately identify patients with an acute LVO in the operative setting. Given the challenges of recognizing peri-operative stroke, LEW may be an appropriate surrogate to quickly identify and treat IOS.
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http://dx.doi.org/10.1016/j.jstrokecerebrovasdis.2020.105158DOI Listing
October 2020

The Utility of Intraoperative Lateral Spread Recording in Microvascular Decompression for Hemifacial Spasm: A Systematic Review and Meta-Analysis.

Neurosurgery 2020 09;87(4):E473-E484

Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.

Background: Microvascular decompression (MVD) is the surgical treatment of choice for hemifacial spasm (HFS). During MVD, monitoring of the abnormal lateral spread response (LSR), an evoked response to facial nerve stimulation, has been traditionally used to monitor adequacy of cranial nerve (CN) VII decompression.

Objective: To assess the utility of LSR monitoring in predicting spasm-free status after MVD postoperatively.

Methods: We searched PubMed, Web of Science, and Embase for relevant publications. We included studies reporting on intraoperative LSR monitoring during MVD for HFS and spasm-free status following the procedure. Sensitivity of LSR, specificity, diagnostic odds ratio, and positive predictive value were calculated.

Results: From 148 studies, 26 studies with 7479 patients were ultimately included in this meta-analysis. The final intraoperative LSR status predicted the clinical outcome of MVD with the following specificities and sensitivities: 89% (0.83- 0.93) and 40% (0.30- 0.51) at discharge, 90% (0.84-0.94) and 41% (0.29-0.53) at 3 mo, 89% (0.83-0.93) and 40% (0.30-0.51) at 1 yr. When LSR persisted after MVD, the probability (95% CI) for HFS persistence was 47.8% (0.33-0.63) at discharge, 40.8% (0.23-0.61) at 3 mo, and 24.4% (0.13-0.41) at 1 yr. However, when LSR resolved, the probability for HFS persistence was 7.3% at discharge, 4.2% at 3 mo, and 4.0% at 1 yr.

Conclusion: Intraoperative LSR monitoring has high specificity but modest sensitivity in predicting the spasm-free status following MVD. Persistence of LSR carries high risk for immediate and long-term facial spasm persistence. Therefore, adequacy of decompression should be thoroughly investigated before closing in cases where intraoperative LSR persists.
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http://dx.doi.org/10.1093/neuros/nyaa069DOI Listing
September 2020

The efficacy of somatosensory evoked potentials in evaluating new neurological deficits after spinal thoracic fusion and decompression.

J Neurosurg Spine 2020 Mar 6:1-6. Epub 2020 Mar 6.

Departments of1Neurological Surgery and.

Objective: Posterior thoracic fusion (PTF) is used as a surgical treatment for a wide range of pathologies. The monitoring of somatosensory evoked potentials (SSEPs) is used to detect and prevent injury during many neurological surgeries. The authors conducted a study to evaluate the efficacy of SSEPs in predicting perioperative lower-extremity (LE) neurological deficits during spinal thoracic fusion surgery.

Methods: The authors included patients who underwent PTF with SSEP monitoring performed throughout the entire surgery from 2010 to 2015 at the University of Pittsburgh Medical Center (UPMC). The sensitivity, specificity, odds ratio, and receiver operating characteristic curve were calculated to evaluate the diagnostic accuracy of SSEP changes in predicting postoperative deficits. Univariate analysis was completed to determine the impact of age exceeding 65 years, sex, obesity, abnormal baseline testing, surgery type, and neurological deficits on the development of intraoperative changes.

Results: From 2010 to 2015, 771 eligible patients underwent SSEP monitoring during PTF at UPMC. Univariate and linear regression analyses showed that LE SSEP changes significantly predicted LE neurological deficits. Significant changes in LE SSEPs had a sensitivity and specificity of 19% and 96%, respectively, in predicting LE neurological deficits. The diagnostic odds ratio for patients with new LE neurological deficits who had significant changes in LE SSEPs was 5.86 (95% CI 2.74-12.5). However, the results showed that a loss of LE waveforms had a poor predictive value for perioperative LE deficits (diagnostic OR 1.58 [95% CI 0.19-12.83]).

Conclusions: Patients with new postoperative LE neurological deficits are 5.9 times more likely to have significant changes in LE SSEPs during PTF. Surgeon awareness of an LE SSEP loss may alter surgical strategy and positively impact rates of postoperative LE neurological deficit status. The relatively poor sensitivity of LE SSEP monitoring may indicate a need for multimodal neurophysiological monitoring, including motor evoked potentials, in thoracic fusion surgery.
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http://dx.doi.org/10.3171/2019.12.SPINE191157DOI Listing
March 2020

Effects of Alternating Standing and Sitting Compared to Prolonged Sitting on Cerebrovascular Hemodynamics.

Sport Sci Health 2019 Aug 23;15(2):375-383. Epub 2019 Jan 23.

Neurological Surgery, University of Pittsburgh, Pittsburgh, PA.

Purpose: Previous research suggests that prolonged sitting may acutely reduce cerebral blood flow velocity (CBFv). The purpose of this study was to evaluate the effects of alternating standing and sitting vs prolonged sitting on CBFv.

Methods: This randomized crossover study enrolled working adults (N=25) with pre-to-stage 1 hypertension not using antihypertensive medications, and a body mass index from 25 to < 40 kg/m. Subjects participated in two simulated workday conditions: 1) sitting continuously (SIT), and 2) alternating standing and sitting every 30 min (SS). Beat-to-beat systolic, mean and diastolic CBFv were recorded bilaterally for 1 min via insonation of the middle cerebral artery using transcranial Doppler ultrasonography before (morning), between (midday) and following (afternoon) two 3-hr 40 min work periods.

Results: Mean±SD age was 42±12 years, blood pressure (BP) was 132±9/83±8 mmHg, and BMI was 32±5 kg/m. Cerebrovascular hemodynamics did not differ across condition (P>0.05). There were, however, significant nonlinear effects of time (decrease from morning to midday; increase from midday to afternoon) on systolic CBFv (P=0.014), mean CBFv (P=0.001), diastolic CBFv (P=0.002), and pulsatility index (P=0.038). When overall time effects were evaluated during each time interval, mean and diastolic CBFv significantly decreased morning to midday and all CBFv increased from midday to afternoon. When separated by condition, significant time effects were observed for all CBFv during SIT (P<0.02) but not SS (P>0.05).

Conclusions: In individuals with elevated BP and BMI, CBFv significantly decreased by midday and increased by afternoon, especially during a workday of prolonged sitting. Future studies should evaluate the combination of frequent walks and a sit-stand desk to break up prolonged sitting.
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http://dx.doi.org/10.1007/s11332-019-00526-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6897374PMC
August 2019

Evoked potentials improve multimodal prognostication after cardiac arrest.

Resuscitation 2019 06 14;139:92-98. Epub 2019 Apr 14.

Department of Emergency Medicine, University of Pittsburgh Medical Center, Pittsburgh, PA, USA. Electronic address:

Aim: Predicting recovery in comatose post-cardiac arrest patients requires multiple modalities of prognostic assessment. In isolation, absent N20 cortical responses in somatosensory evoked potentials (SSEPs) are a specific predictor of poor outcome. It is unknown whether SSEP results, when assessed in the context of prior knowledge (demographic and clinical information), change the pretest predicted probability of recovery.

Methods: In a single center retrospective study, a cohort of 323 patients admitted to post-cardiac arrest service at a tertiary care center were classified into a group based on SSEP testing. We built adjusted logistic regression models including clinical examination findings on the day SSEPs were recorded to generate a pre-test outcome probability for awakening, withdrawal of life-sustaining therapy (WLST) and survival to discharge. We then added the upper extremity N20 cortical response results to the model to obtain updated outcome probabilities. ROC curve was used to determine the additive effect of using SSEPs to the model. Survival to discharge, awakening, and WLST due to neurological reasons were designated as primary, secondary and tertiary outcomes, respectively.

Results: Analyses showed that evoked potentials are ordered in sicker patients. Adding SSEP to the model increased the proportion of patients with less than 1% and 5% chance of survival, as well as the proportion of patients with over 95% chance of WLST. AUC for survival increased from 0.85 to 0.93 when SSEP was included (p = 0.006).

Conclusion: Adding the N20 SSEP response results to prior knowledge changed the predicted probability of WLST and survival to discharge in comatose post-arrest patients.
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http://dx.doi.org/10.1016/j.resuscitation.2019.04.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6555685PMC
June 2019

The diagnostic accuracy of somatosensory evoked potentials in evaluating neurological deficits during 1057 lumbar interbody fusions.

J Clin Neurosci 2019 Mar 4;61:78-83. Epub 2018 Dec 4.

Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, PA, USA; Department of Neurology, University of Pittsburgh, Pittsburgh, PA, USA. Electronic address:

Background: Lumbar interbody spinal fusion (LIF) surgeries are performed to treat or prevent back pain in patients with degenerated intervertebral discs and a variety of spinal diseases. However, post-operative neurological complications may ensue. Intraoperative monitoring techniques have been used to predict and potentially reduce the risk of complications.

Methods: This study examined the diagnostic accuracy of significant changes of somatosensory evoked potentials (SSEPs) to evaluate and predict post-operative neurological deficits after LIF. All patients underwent LIF at UPMC from 2010 to 2012. One thousand fifty-seven patients had pre-operative baseline and continuous intraoperative SSEP monitoring. Statistical analysis was completed using SPSS version 22. No relevant disclosure.

Results: Patient outcomes were not significantly affected by age over 65, gender, obesity, and abnormal baselines. Lower extremity (LE) significant changes in SSEPs and LE loss of responses resulted in a sensitivity/specificity of 0.03/0.99 and 0.03/0.99; they had an AUC of 0.54/0.73 with a 95% confidence interval (CI) of [0.34, 0.74]/[0.29, 1.00].

Conclusions: Significant SSEP changes during LIF are a very specific but poorly sensitive indicator of perioperative neurological deficits. The odds ratio for LE loss of responses was 29.14 with a 95% CI of 1.79-475.5, so LE SSEP loss of responses can serve as a biomarker of perioperative neurological deficits after LIF.
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http://dx.doi.org/10.1016/j.jocn.2018.10.140DOI Listing
March 2019

Practice guidelines for the supervising professional: intraoperative neurophysiological monitoring.

J Clin Monit Comput 2019 04 30;33(2):175-183. Epub 2018 Oct 30.

Golden Gate Neuromonitoring, San Francisco, CA, USA.

The American Society of Neurophysiological Monitoring (ASNM) was founded in 1989 as the American Society of Evoked Potential Monitoring. From the beginning, the Society has been made up of physicians, doctoral degree holders, Technologists, and all those interested in furthering the profession. The Society changed its name to the ASNM and held its first Annual Meeting in 1990. It remains the largest worldwide organization dedicated solely to the scientifically-based advancement of intraoperative neurophysiology. The primary goal of the ASNM is to assure the quality of patient care during procedures monitoring the nervous system. This goal is accomplished primarily through programs in education, advocacy of basic and clinical research, and publication of guidelines, among other endeavors. The ASNM is committed to the development of medically sound and clinically relevant guidelines for the performance of intraoperative neurophysiology. Guidelines are formulated based on exhaustive literature review, recruitment of expert opinion, and broad consensus among ASNM membership. Input is likewise sought from sister societies and related constituencies. Adherence to a literature-based, formalized process characterizes the construction of all ASNM guidelines. The guidelines covering the Professional Practice of intraoperative neurophysiological monitoring were initially published January 24th, 2013, and subsequently that document has undergone review and revision to accommodate broad inter- and intra-societal feedback. This current version of the ASNM Professional Practice Guideline was fully approved for publication according to ASNM bylaws on February 22nd, 2018, and thus overwrites and supersedes the initial guideline.
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http://dx.doi.org/10.1007/s10877-018-0201-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6420431PMC
April 2019

Effect of Using a Sit-Stand Desk on Ratings of Discomfort, Fatigue, and Sleepiness Across a Simulated Workday in Overweight and Obese Adults.

J Phys Act Health 2018 10 24;15(10):788-794. Epub 2018 Aug 24.

Background: Limited research examines the influence of sit-stand desks on ratings of discomfort, sleepiness, and fatigue. This study evaluated the time course of these outcomes over 1 day.

Methods: Adults (N = 25) completed a randomized cross-over study in a laboratory with two 8-hour workday conditions: (1) prolonged sitting (SIT) and (2) alternating sitting and standing every 30 minutes (SIT-STAND). Sleepiness was assessed hourly. Discomfort, physical fatigue, and mental fatigue were measured every other hour. Linear mixed models evaluated whether these measures differed across conditions and the workday. Effect sizes were calculated using Cohen's d.

Results: Participants were primarily white (84%) males (64%), with mean (SD) body mass index of 31.9 (5.0) kg/m and age 42 (12) years. SIT-STAND resulted in decreased odds of discomfort (OR = 0.37, P = .01) and lower overall discomfort (β = -0.19, P < .001, d = 0.42) versus SIT. Discomfort during SIT-STAND was lower in the lower and upper back, but higher in the legs (all Ps< .01, d = 0.26-0.42). Sleepiness (β = -0.09, P = .01, d = 0.15) and physical fatigue (β = -0.34, P = .002, d = 0.34) were significantly lower in SIT-STAND. Mental fatigue was similar across conditions.

Conclusions: Sit-stand desks may reduce acute levels of sleepiness, physical fatigue, and both overall and back discomfort. However, levels of lower extremity discomfort may be increased with acute exposure.
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http://dx.doi.org/10.1123/jpah.2017-0639DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6982465PMC
October 2018

Toward Improving Safety in Neurosurgery with an Active Handheld Instrument.

Ann Biomed Eng 2018 Oct 16;46(10):1450-1464. Epub 2018 Jul 16.

Robotics Institute, Carnegie Mellon University, Pittsburgh, USA.

Microsurgical procedures, such as petroclival meningioma resection, require careful surgical actions in order to remove tumor tissue, while avoiding brain and vessel damaging. Such procedures are currently performed under microscope magnification. Robotic tools are emerging in order to filter surgeons' unintended movements and prevent tools from entering forbidden regions such as vascular structures. The present work investigates the use of a handheld robotic tool (Micron) to automate vessel avoidance in microsurgery. In particular, we focused on vessel segmentation, implementing a deep-learning-based segmentation strategy in microscopy images, and its integration with a feature-based passive 3D reconstruction algorithm to obtain accurate and robust vessel position. We then implemented a virtual-fixture-based strategy to control the handheld robotic tool and perform vessel avoidance. Clay vascular phantoms, lying on a background obtained from microscopy images recorded during petroclival meningioma surgery, were used for testing the segmentation and control algorithms. When testing the segmentation algorithm on 100 different phantom images, a median Dice similarity coefficient equal to 0.96 was achieved. A set of 25 Micron trials of 80 s in duration, each involving the interaction of Micron with a different vascular phantom, were recorded, with a safety distance equal to 2 mm, which was comparable to the median vessel diameter. Micron's tip entered the forbidden region 24% of the time when the control algorithm was active. However, the median penetration depth was 16.9 μm, which was two orders of magnitude lower than median vessel diameter. Results suggest the system can assist surgeons in performing safe vessel avoidance during neurosurgical procedures.
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http://dx.doi.org/10.1007/s10439-018-2091-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6150797PMC
October 2018

Vasopressor Infusion After Subarachnoid Hemorrhage Does Not Increase Regional Cerebral Tissue Oxygenation.

J Neurosci Nurs 2018 Aug;50(4):225-230

Elizabeth Crago, PhD RN, School of Nursing, University of Pittsburgh, Pittsburgh, PA. Yuefang Chang, PhD, Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA. Theodore F. Lagattuta, RN, School of Nursing, University of Pittsburgh, Pittsburgh, PA. Khadejah Mahmoud, BSN RN, School of Nursing, University of Pittsburgh, Pittsburgh, PA. Lori Shutter, MD, University of Pittsburgh School of Medicine, and Department of Critical Care Medicine, University of Pittsburgh Medical Center, Pittsburgh, PA. Jeffrey R. Balzer, PhD, School of Nursing, University of Pittsburgh, and Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA. Michael R. Pinsky, MD CM DrHC, University of Pittsburgh School of Medicine, and Department of Critical Care Medicine, University of Pittsburgh Medical Center, Pittsburgh, PA. Robert M. Friedlander, MD, Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA. Marilyn Hravnak, PhD RN ACNP-BC FCCM FAAN, School of Nursing, University of Pittsburgh, Pittsburgh, PA.

Introduction: Vasopressors are commonly used after aneurysmal subarachnoid hemorrhage (aSAH) to sustain cerebral pressure gradients. Yet, the relationship between vasopressors and the degree of cerebral microcirculatory support achieved remains unclear. This study aimed to explore the changes in cerebral and peripheral regional tissue oxygen saturation (rSO2) as well as blood pressure (BP) before and after vasopressor infusion in patients with aSAH.

Methods: Continuous noninvasive cerebral and peripheral rSO2 was obtained using near-infrared spectroscopy for up to 14 days after aSAH. Within-subject differences in rSO2 before and after the commencement of vasopressor infusion were analyzed controlling for Hunt and Hess grade and vasospasm.

Results: Of 45 patients with continuous rSO2 monitoring, 19 (42%) received vasopressor infusion (all 19 on norepinephrine, plus epinephrine in 2 patients, phenylephrine in 4 patients, and vasopressin in 2 patients). In these 19 patients, their vasopressor infusion times were associated with higher BP (systolic [b = 15.1], diastolic [b = 7.3], and mean [b = 10.1]; P = .001) but lower cerebral rSO2 (left cerebral rSO2 decreased by 4.4% [b = -4.4, P < .0001]; right cerebral rSO2 decreased by 5.5% [b = -5.5, P = .0002]).

Conclusions: Despite elevation in systemic BP during vasopressor infusion times, cerebral rSO2 was concurrently diminished. These findings warrant further investigation for the effect of induced hypertension on cerebral microcirculation.
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http://dx.doi.org/10.1097/JNN.0000000000000382DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6044455PMC
August 2018

Diagnostic value of somatosensory evoked potential changes during carotid endarterectomy for 30-day perioperative stroke.

Clin Neurophysiol 2018 09 14;129(9):1819-1831. Epub 2018 Jun 14.

Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA, USA; Department of Neurology, University of Pittsburgh Medical Center, Pittsburgh, PA, USA. Electronic address:

Objectives: Somatosensory evoked potentials (SSEPs) have proven useful as an intraoperative modality to predict perioperative stroke during carotid endarterectomy (CEA). However, the predictive value of SSEPs for predicting stroke 30 days postoperatively remains unclear. The primary objective is to evaluate the efficacy of intraoperative SSEP change in predicting the risk of stroke in the postoperative period beyond 24 h but within 30 days. Our secondary aim is to evaluate the predictive value of each subcategory of SSEP change.

Methods: We performed a meta-analysis of 25 prospective/retrospective studies from PubMed, Web of Science, and Embase regarding SSEP monitoring for postoperative outcomes in symptomatic and asymptomatic CEA patients.

Results: A 8307-patient cohort composed the total sample population, of which 54.17% had symptomatic CS. For SSEP change and stroke greater than 24 h but within 30 days, the diagnostic odds ratio was 8.68. The diagnostic odds ratio was 3.88 for transient SSEP change and stroke; 49.29 for persistent SSEP change and stroke; 36.45 for transient SSEP loss and stroke; and 281.35 for persistent SSEP loss and stroke.

Conclusions: Patients with SSEP changes are at increased risk of perioperative stroke within the entire 30-day period. There is a noticeable step-wise increase in the predicted risk of stroke with the severity of SSEP changes.

Significance: SSEP changes can serve as a predictor for 30-day perioperative stroke during CEA.
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http://dx.doi.org/10.1016/j.clinph.2018.05.018DOI Listing
September 2018

Risk factors for positioning-related somatosensory evoked potential changes in 3946 spinal surgeries.

J Clin Monit Comput 2019 Apr 31;33(2):333-339. Epub 2018 May 31.

Center for Clinical Neurophysiology, Department of Neurological Surgery, University of Pittsburgh, UPMC Presbyterian-Suite B-400, 200 Lothrop Street, Pittsburgh, PA, 15213, USA.

The goal of this study was to evaluate the risk factors associated with positioning-related SSEP changes (PRSC). The study investigated the association between 18 plausible risk factors and the occurrence of intraoperative PRSC. Risk factors investigated included demographic variables, comorbidities, and procedure related variables. All patients were treated by the University of Pittsburgh Medical Center from 2010 to 2012. We used univariate and multivariate statistical methods. 69 out of the 3946 (1.75%) spinal surgeries resulted in PRSC changes. The risk of PRSC was increased for women (p < 0.001), patients older than 65 years of age (p = 0.01), higher BMI (p < 0.001) patients, smokers (p < 0.001), and patients with hypertension (p < 0.001). No associations were found between PRSC and age greater than 80 years, diabetes mellitus, cardiovascular disease, and peripheral vascular disease. Three surgical situations were associated with PRSC including abnormal baselines (p < 0.001), patients in the "superman" position (p < 0.001), and patients in surgical procedures that extended over 200 min (p = 0.03). Patients with higher BMIs and who are undergoing spinal surgery longer than 200 min, with abnormal baselines, must be positioned with meticulous attention. Gender, hypertension, and smoking were also found to be risk factors from their odds ratios.
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http://dx.doi.org/10.1007/s10877-018-0148-xDOI Listing
April 2019

The diagnostic accuracy of somatosensory evoked potentials in evaluating neurological deficits during 1036 posterior spinal fusions.

Neurol Res 2017 Dec 19;39(12):1073-1079. Epub 2017 Sep 19.

a Department of Neurological Surgery , University of Pittsburgh , Pittsburgh , PA , USA.

Background: The goal of this study is to assess the sensitivity and specificity of somatosensory evoked potentials (SSEPs) in predicting perioperative neurological deficits during posterior spinal fusions (PSF).

Methods: This study examined the diagnostic accuracy of significant changes of SSEPs and multimodal monitoring to evaluate and predict post-operative neurological deficits after PSF. All 1036 patients underwent PSF at the University of Pittsburgh Medical Center from 2010 to 2012. Statistical analysis was completed using SPSS version 22.

Results: Of the 1036 patients included in the study, 35 (3.38%) patients had significant SSEP changes. Out of the 35 patients with significant SSEP changes, 22 (62.86%) patients had significant lower extremity (LE) SSEP changes. Ten (45.5%) of LE SSEP changes were loss of responses. Gender, obesity, and abnormal baselines did not significantly affect patient outcomes. Significant LE changes had an odds ratio of 13.18, 95% CI [3.44, 50.56], and LE loss of waveforms had an odds ratio of 19.48, 95% CI [3.76, 100.75].

Conclusions: Patients with perioperative neurological deficits are 13 times more likely to have LE significant changes, and 19 times more likely to have a LE loss of SSEP responses. Our study results indicate that LE significant changes or LE loss of waveforms in SSEPs can serve as a marker of perioperative neurological deficits.
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http://dx.doi.org/10.1080/01616412.2017.1378413DOI Listing
December 2017

Effect of alternating standing and sitting on blood pressure and pulse wave velocity during a simulated workday in adults with overweight/obesity.

J Hypertens 2017 12;35(12):2411-2418

aDepartment of Health and Physical Activity bDepartment of Neurological Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.

Objective: Reducing prolonged sitting at work has been recommended by an expert panel, but whether intermittent standing improves vascular health is unclear. We aimed to test whether using a sit-stand desk could reduce blood pressure (BP) and pulse wave velocity (PWV) during a simulated workday.

Methods: Overweight/obese adults with pre-to-Stage 1 hypertension completed a randomized crossover study with two simulated workday conditions: STAND-SIT (alternating standing and sitting condition every 30 min) and SIT (continuous sitting condition). Oscillometric BP was measured hourly. Carotid-femoral, carotid-radial, and carotid-ankle PWV were measured in the morning, mid-day, and late afternoon using tonometry.

Results: Participants [n = 25, 64% male, 84% white, mean (SD) age: 42 (12) years] had average resting SBP of 132 (9) mmHg and DBP of 83 (8) mmHg. In linear mixed models, STAND-SIT resulted in a significantly lower DBP (mean ± SE: -1.0 ± 0.4 mmHg, P = 0.020) and mean arterial pressure (MAP) (-1.0 ± 0.4 mmHg, P = 0.029) compared with SIT. SBP (-0.9 ± 0.7 mmHg, P = 0.176) was not different across conditions. Carotid-ankle PWV was significantly lower during the STAND-SIT vs. SIT condition (-0.27 ± 0.13 m/s, P = 0.047), whereas carotid-femoral PWV (-0.03 ± 0.13 m/s, P = 0.831) and carotid-radial PWV (-0.30 ± 0.18 m/s, P = 0.098) were not. Changes in MAP partially explained changes in PWV.

Conclusion: Interrupting prolonged sitting during deskwork with intermittent standing was a sufficient stimulus to slightly, but statistically significantly, decrease DBP, MAP, and carotid-ankle PWV. Though the clinical significance of the observed effects is modest, regular use of a sit-stand desk may be a practical way to lower BP and PWV while performing deskwork.
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http://dx.doi.org/10.1097/HJH.0000000000001463DOI Listing
December 2017

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

World Neurosurg 2017 Aug 17;104:442-451. Epub 2017 May 17.

Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA; Department of Neurology, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA. Electronic address:

Background: 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.

Methods: 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.

Results: 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.

Conclusions: 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.
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http://dx.doi.org/10.1016/j.wneu.2017.05.036DOI Listing
August 2017

Brainstem Auditory Evoked Potentials' Diagnostic Accuracy for Hearing Loss: Systematic Review and Meta-Analysis.

J Neurol Surg B Skull Base 2017 Feb 20;78(1):43-51. Epub 2016 Jun 20.

Department of Neurological Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, United States.

 Microvascular decompression (MVD) utilizes brainstem auditory evoked potential (BAEP) intraoperative monitoring to reduce the risk of iatrogenic hearing loss. Studies report varying efficacy and hearing loss rates during MVD with intraoperative monitoring.  This study aims to perform a comprehensive review and study of diagnostic accuracy of BAEPs during MVD to predict hearing loss in studies published from January 1984 to December 2013.  The PubMed/MEDLINE and World Science databases were searched. Studies performed MVD for trigeminal neuralgia, hemifacial spasm, glossopharyngeal neuralgia or geniculate neuralgia and monitored intraoperative BAEPs to prevent hearing loss. Retrospectively, BAEP parameters were compared with postoperative hearing. The diagnostic accuracy of significant change in BAEPs, which includes loss of response, was tested using summary receiver operative curve and diagnostic odds ratio (DOR).  A total of 13 studies were included in the analysis with a total of 2,540 cases. Loss of response pooled sensitivity, specificity, and DOR with 95% confidence interval being 74% (60-84%), 98% (88-100%), and 69.3 (18.2-263%), respectively. The similar significant change results were 88% (77-94%), 63% (40-81%), and 9.1 (3.9-21.6%).  Patients with hearing loss after MVD are more likely to have shown loss of BAEP responses intraoperatively. Loss of responses has high specificity in evaluating hearing loss. Patients undergoing MVD should have BAEP monitoring to prevent hearing loss.
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http://dx.doi.org/10.1055/s-0036-1584557DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5288122PMC
February 2017

Transcranial Doppler Monitoring in Carotid Endarterectomy: A Systematic Review and Meta-analysis.

J Ultrasound Med 2017 Mar 27;36(3):621-630. Epub 2017 Jan 27.

Department of Neurologic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.

Objectives: To evaluate the efficacy of intraoperative transcranial Doppler monitoring in predicting perioperative strokes after carotid endarterectomy (CEA).

Methods: An electronic search of PubMed, Embase, and Web of Science databases was conducted for studies on transcranial Doppler monitoring in CEA published from January 1970 through September 2015. All titles and abstracts were independently screened on the basis of predetermined inclusion criteria, which included randomized clinical trials and prospective or retrospective cohort reviews, patients who underwent CEA with intraoperative transcranial Doppler monitoring (either middle cerebral artery velocity [MCAV] or cerebral microembolic signals [MES]) and postoperative neurologic assessments up to 30 days after the surgery, and studies including an abstract, published in English on adult humans 18 years and older with a sample size of 50 or greater.

Results: A total of 25articles with a sample population of 4705 patients were analyzed. Among the study patients, 189 developed perioperative strokes. Transcranial Doppler monitoring (either MCAV or MES) showed specificity of 72.7% (95% confidence interval [CI], 61.2%-81.8%) and sensitivity of 56.1% (95% CI, 46.8%-65.0%) for predicting perioperative strokes. Intraoperative MCAV changes during CEA showed strong specificity of 84.1% (95% CI, 74.4%-90.6) and sensitivity of 49.7% (95% CI, 40.6%-58.8) for predicting perioperative strokes.

Conclusions: Patients with perioperative strokes are 4 times more likely to have had transcranial Doppler changes (either MCAV or MES) during CEA compared to patients without strokes. Simultaneous MCAV and MES monitoring by transcranial Doppler sonography and combined intraoperative monitoring of transcranial Doppler sonography with somatosensory evoked potentials and electroencephalography during CEA to predict perioperative stroke could not be evaluated because of a lack of clinical studies combining these measures.
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http://dx.doi.org/10.7863/ultra.16.02077DOI Listing
March 2017

Diagnostic accuracy of motor evoked potentials to detect neurological deficit during idiopathic scoliosis correction: a systematic review.

J Neurosurg Spine 2017 Mar 9;26(3):374-383. Epub 2016 Dec 9.

Departments of 1 Neurological Surgery and.

OBJECTIVE The goal of this study was to evaluate the efficacy of intraoperative transcranial motor evoked potential (TcMEP) monitoring in predicting an impending neurological deficit during corrective spinal surgery for patients with idiopathic scoliosis (IS). METHODS The authors searched the PubMed and Web of Science database for relevant lists of retrieved reports and/or experiments published from January 1950 through October 2014 for studies on TcMEP monitoring use during IS surgery. The primary analysis of this review fit the operating characteristic into a hierarchical summary receiver operating characteristic curve model to determine the efficacy of intraoperative TcMEP-predicted change. RESULTS Twelve studies, with a total of 2102 patients with IS were included. Analysis found an observed incidence of neurological deficits of 1.38% (29/2102) in the sample population. Of the patients who sustained a neurological deficit, 82.8% (24/29) also had irreversible TcMEP change, whereas 17.2% (5/29) did not. The pooled analysis using the bivariate model showed TcMEP change with sensitivity (mean 91% [95% CI 34%-100%]) and specificity (mean 96% [95% CI 92-98%]). The diagnostic odds ratio indicated that it is 250 times more likely to observe significant TcMEP changes in patients who experience a new-onset motor deficit immediately after IS correction surgery (95% CI 11-5767). TcMEP monitoring showed high discriminant ability with an area under the curve of 0.98. CONCLUSIONS A patient with a new neurological deficit resulting from IS surgery was 250 times more likely to have changes in TcMEPs than a patient without new deficit. The authors' findings from 2102 operations in patients with IS show that TcMEP monitoring is a highly sensitive and specific test for detecting new spinal cord injuries in patients undergoing corrective spinal surgery for IS. They could not assess the value of TcMEP monitoring as a therapeutic adjunct owing to the limited data available and their study design.
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http://dx.doi.org/10.3171/2015.7.SPINE15466DOI Listing
March 2017

Perioperative stroke after carotid endarterectomy: etiology and implications.

Acta Neurochir (Wien) 2016 12 30;158(12):2377-2383. Epub 2016 Sep 30.

Department of Neurological Surgery, University of Pittsburgh School of Medicine, UPMC Presbyterian Hospital Suite B-400, 200 Lothrop Street, Pittsburgh, PA, 15213, USA.

Background: 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.

Methods: 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).

Results: 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 5 days (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).

Conclusions: 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.
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http://dx.doi.org/10.1007/s00701-016-2966-2DOI Listing
December 2016

Diagnostic Accuracy of Somatosensory Evoked Potentials in Evaluating New Neurological Deficits After Posterior Cervical Fusions.

Spine (Phila Pa 1976) 2017 Apr;42(7):490-496

Department of Neurological Surgery, Pittsburgh, PA.

Study Design: This study examined the diagnostic accuracy of significant changes of somatosensory evoked potentials (SSEPs) to evaluate and predict postoperative neurological deficits after posterior cervical fusions (PCF). Eight hundred forty six eligible patients underwent PCF at the University of Pittsburgh Medical Center (UPMC), from 2010 to 2012.

Objective: To assess the specificity and sensitivity of intraoperative monitoring in predicting postoperative neurological deficits during PCF.

Summary Of Background Data: We calculated the predictive value, including sensitivity and specificity, of changes in SSEPs to identify neurological deficits postoperatively. We used a receiver operating characteristic (ROC) curve with SSEP categories as cutoff values to further evaluate the diagnostic accuracy of change in SSEPs and postoperative neurological deficit.

Methods: All patients had preposition baselines and continuous SSEP monitoring throughout the surgery. Statistical analysis was completed using SPSS version 22 (IBM Corp., Armonk, NY).

Results: Age and sex did not influence outcomes. Obesity affected patient outcome. The SSEP categories of significant changes and loss of responses resulted in a sensitivity/specificity of 0.30/0.96 and 0.16/0.98, respectively. The receiver operating characteristic curve has an area under the curve for significant change in/loss of SSEPs of 0.62/0.65 with a 95% confidence interval of 0.525 to 0.714/0.509 to 0.797.

Conclusion: Significant SSEP changes during PCF are a very specific but poorly sensitive indicator of postoperative neurological deficits. The odds ratio for significant changes in SSEPs and loss of waveforms was 9.80 and 11.82, respectively, with a 95% confidence interval of 4.695 to 20.46 and 4.45 to 31.41, respectively.

Level Of Evidence: 1.
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http://dx.doi.org/10.1097/BRS.0000000000001882DOI Listing
April 2017

Diagnostic accuracy of somatosensory evoked potential and electroencephalography during carotid endarterectomy.

Neurol Res 2016 Aug 24;38(8):698-705. Epub 2016 Jun 24.

a Department of Neurological Surgery , Universityof Pittsburgh Medical Center , Pittsburgh , PA , USA.

Background And Purpose: Perioperative stroke risk following carotid endarterectomy (CEA) is reported to be approximately 2-3%. The diagnostic accuracies of intraoperative EEG and SSEP monitoring during CEA have been studied separately. However, to date, the effectiveness of simultaneous EEG and SSEP monitoring during CEA has only been evaluated in small study populations. This study examined the diagnostic accuracy of combined EEG and SSEP monitoring in a large (N = 1165) patient population.

Methods: This study included 1165 patients who underwent CEA from 2000 to 2012 at the University of Pittsburgh Medical Center. The sensitivities, specificities, and diagnostic odds ratio of EEG and SSEP monitoring methods were examined separately and together. Receiver operating characteristic curves were plotted to assess sensitivity and specificity of single and combined Intraoperative monitoring (IONM) methods.

Results: Maximum sensitivity was obtained with multimodality monitoring with an IONM change in either EEG or SSEP of 50.00 (95% CI, 30.66-69.34). The specificity of simultaneous EEG and SSEP changes was 93.95 (95% CI, 92.28-95.35%). Maximum area under ROC curve obtained for IONM change in either EEG or SSEP was 0.660 (95% CI, 0.547-0.773, p-value 0.004).

Conclusion: The diagnostic accuracy of multimodality IONM during CEA is higher than an approach using single modality IONM. Simultaneous EEG and SSEP monitoring improves the likelihood of detecting periprocedural strokes after CEA. Neuro protective therapies to prevent periprocedural strokes can be based on changes in SSEP and EEG during CEA.
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http://dx.doi.org/10.1080/01616412.2016.1200707DOI Listing
August 2016

Diagnostic Value of Somatosensory-Evoked Potential Monitoring During Cerebral Aneurysm Clipping: A Systematic Review.

World Neurosurg 2016 May 18;89:672-80. Epub 2015 Dec 18.

Department of Neurological Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.

Background: Perioperative stroke is a known complication in patients undergoing surgical clipping of cerebral aneurysms.

Objective: To evaluate whether intraoperative changes in somatosensory-evoked potential (SSEP) monitoring during cerebral aneurysm clipping is diagnostic of perioperative stroke.

Methods: An electronic search of PubMed, Embase, and Web of Science databases was done for studies published through May 2015 on SSEP monitoring in cerebral aneurysm clipping for predicting postoperative outcomes. All titles and abstracts were screened independently on the basis of predetermined criteria. Inclusion criteria included randomized clinical trials and prospective or retrospective cohort reviews; patients with intracranial aneurysms who underwent surgical clipping with intra-operative SSEP monitoring and postoperative neurologic assessment; studies published in English on adult humans ≥18 years with sample size of ≥50; and studies inclusive of an abstract with adequate details on outcomes.

Results: A total of 14 articles with a sample population of 2015 patients were analyzed. SSEP monitoring demonstrated a strong mean specificity of 84.5% (95% confidence interval [95% CI] -76.3 to 90.3) but weaker sensitivity of 56.8% (95% CI 44.1-68.6) for predicting stroke. A diagnostic odds ratio of 7.772 (95% CI 5.133-11.767) suggested that the odds of observing an SSEP change among those with a postoperative neurologic deficit were 7 times greater than those without a neurologic deficit.

Conclusion: Intraoperative SSEP monitoring is highly specific for predicting neurologic outcome after cerebral aneurysm clipping. Patients with postoperative neurologic deficits are 7 times more likely to have had intraoperative SSEP changes. SSEP monitoring may help design prevention strategies to reduce stroke rates after cerebral aneurysm clipping.
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http://dx.doi.org/10.1016/j.wneu.2015.12.008DOI Listing
May 2016