Intraoperative neurophysiological monitoring in spine surgery: indications, efficacy, and role of the preoperative checklist.

Spine surgery carries an inherent risk of damage to critical neural structures. Intraoperative neurophysiological monitoring (IONM) is frequently used to improve the safety of spine surgery by providing real-time assessment of neural structures at risk. Evidence-based guidelines for safe and efficacious use of IONM are lacking and its use is largely driven by surgeon preference and medicolegal issues. Due to this lack of standardization, the preoperative sign-in serves as a critical opportunity for 3-way discussion between the neurosurgeon, anesthesiologist, and neuromonitoring team regarding the necessity for and goals of IONM in the ensuing case. This analysis contains a review of commonly used IONM modalities including somatosensory evoked potentials, motor evoked potentials, spontaneous or free-running electromyography, triggered electromyography, and combined multimodal IONM. For each modality the methodology, interpretation, and reported sensitivity and specificity for neurological injury are addressed. This is followed by a discussion of important IONM-related issues to include in the preoperative checklist, including anesthetic protocol, warning criteria for possible neurological injury, and consideration of what steps to take in response to a positive alarm. The authors conclude with a cost-effectiveness analysis of IONM, and offer recommendations for IONM use during various forms of spine surgery, including both complex spine and minimally invasive procedures, as well as lower-risk spinal operations.

Outcomes Following Penetrating Brain Injuries in Military Settings: A Systematic Review and Meta-Analysis.

OBJECTIVE: While neurosurgeons are experienced in treating penetrating brain injuries (PBIs) in civilian settings, much less is known about management and outcomes of PBIs in military settings. METHODS: A systematic review was performed according to Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Data extracted included surgical management, age, gender, location/type of injury, initial Glasgow Coma Scale (GCS) score, and outcomes. The primary outcomes were last reported Glasgow Outcome Score (GOS) and mortality. The secondary outcomes included central nervous system infections, seizures, and cerebrospinal fluid leak/fistula. Odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were used for outcome analysis. RESULTS: Twelve studies with 1738 patients treated for PBIs in military settings were included. The weighted mean age was 27.8 years, 86.7% were male, and 64.3% underwent neurosurgical intervention. Most patients (64.3%) presented with a GCS score >8, while 31.0% presented in a coma (GCS score <8). Over a median last follow-up time of 9 months, 68.6% achieved a favorable (GOS = 4-5) outcome and 34.2% achieved a poor (GCS score = 1-3) outcome. The overall mortality was 18.0%. A meta-analysis was performed using 5 of 12 studies to evaluate the effect of the presenting GCS score on primary outcomes. Patients with an initial GCS score <8 had statistically significant lower odds of a favorable (GOS = 4-5) outcome (OR: 0.03; 95% CI: 0.00-0.19; P: 0.000) and higher odds of mortality (OR: 28.46; 95% CI: 8.62-94; P: 0.000) than patients with an initial GCS score >8. The pooled rates of central nervous system infection, seizures, and cerebrospinal fluid leak/fistula were 13.8%, 13.2%, and 5.4%, respectively. CONCLUSIONS: In this first systematic review and meta-analysis of outcomes following combat-related PBIs, a GCS score >8 at presentation was found to be an important predictor of a favorable GOS and decreased mortality.

Comparing Short-term Complications of Inpatient Versus Outpatient Single-level Anterior Cervical Discectomy and Fusion: An Analysis of 6940 Patients Using the ACS-NSQIP Database.

STUDY DESIGN: Multicenter propensity score-adjusted retrospective cohort study. OBJECTIVE: To determine baseline 30-day complication rates for anterior cervical discectomy and fusion (ACDF) and compare clinical complications for patients undergoing single-level ACDFs between inpatient and outpatient settings. SUMMARY OF BACKGROUND DATA: ACDF remains the most common procedure in the treatment of a variety of cervical disc pathologies, making it a focus of quality improvement initiatives. Outpatient single-level ACDFs are becoming more common and offer advantages including reducing nosocomial infections and costs, as well as improved patient satisfaction. MATERIALS AND METHODS: The 2011-2013 NSQIP datasets were queried to identify all patients who underwent single-level ACDF procedures using current procedural terminology codes. Outpatient and inpatient cohorts were matched 1:1 using propensity score analysis to assess short-term outcomes. The outcomes assessed included 30-day medical and surgical complications, reoperation, readmission, and mortality. RESULTS: In total, 6940 patients underwent a single-level ACDF with an overall complication rate of 4.2%. A total of 5162 patients (74.4%) had an inpatient hospital stay after surgery, whereas 1778 patients (25.6%) had outpatient surgery. After matching based on preoperative and operative characteristics to account for potential confounders, the overall complication rate was higher in the inpatient arm compared with the outpatient arm (2.5% vs. 1.2%; P=0.003). The 30-day readmission rate was also higher but not significant in the inpatient group than the outpatient group (2.2% vs. 1.8%; P=0.355). Mortality was the same with 0.1% in both groups (P=0.564). CONCLUSIONS: Patients undergoing outpatient single-level ACDF had a lower 30-day complication rates than those undergoing it in the inpatient setting. Outpatient surgery for single-level ACDF is safe and a favorable option for suitable patients. LEVEL OF EVIDENCE: Level 3.

Predictors for Airway Complications Following Single- and Multilevel Anterior Cervical Discectomy and Fusion.

STUDY DESIGN: A retrospective, multivariate analyses of a prospectively collected multicenter database. OBJECTIVE: The aim of this study was to evaluate the risk factors for postoperative airway complications following single- and multilevel anterior cervical discectomy and fusion (ACDF). SUMMARY OF BACKGROUND DATA: Airway compromise following ACDF may result in catastrophic outcome. However, its predictors have not been identified by a multi-institutional study. METHODS: Patients who underwent ACDF between 2011 and 2013 were selected from the American College of Surgeons National Surgical Quality Improvement Program database. Multiple logistic regression analysis was performed to identify the risk factors for airway compromise following ACDF. RESULTS: Twelve thousand one hundred eighty-five patients were analyzed in this study. Our multivariate analysis identified older age, male gender, dependent functional status, chronic obstructive pulmonary disease, bleeding disorder, American Society of Anesthesiology class >2, Wound Class >2, and prolonged operative durations as significant predictors of postoperative airway compromise following ACDF. Surprisingly, multilevel and corpectomy procedures were not significant risk factors for airway complication following ACDF. CONCLUSION: We identified significant risk factors for airway compromise following ACDF procedures. While ACDF is considered a safe procedure, postoperative airway complication can lead to disastrous outcome. Continued efforts to elucidate preoperative risk factors and subsequent optimization are warranted to improve outcomes in ACDF. LEVEL OF EVIDENCE: 3.

Timing and risks of chemoprophylaxis after spinal surgery: a single-center experience with 6869 consecutive patients.

OBJECTIVE Venous thromboembolism (VTE) after spinal surgery is a major cause of morbidity, but chemoprophylactic anticoagulation can prevent it. However, there is variability in the timing and use of chemoprophylactic anticoagulation after spine surgery, particularly given surgeons' concerns for spinal epidural hematomas. The goal of this study was to provide insight into the safety, efficacy, and timing of anticoagulation therapy after spinal surgery. METHODS The authors retrospectively examined records from 6869 consecutive spinal surgeries performed in their departments at Northwestern University. Data on patient demographics, surgery, hospital course, timing of chemoprophylaxis, and complications, including deep venous thrombosis (DVT), pulmonary embolism (PE), and spinal epidural hematomas requiring evacuation, were collected. Data from the patients who received chemoprophylaxis (n = 1904) were compared with those of patients who did not (n = 4965). The timing of chemoprophylaxis, the rate of VTEs, and the incidence of spinal epidural hematomas were analyzed. RESULTS The chemoprophylaxis group had more risk factors, including greater age (59.70 vs 51.86 years, respectively; p < 0.001), longer surgery (278.59 vs 145.66 minutes, respectively; p < 0.001), higher estimated blood loss (995 vs 448 ml, respectively; p < 0.001), more comorbid diagnoses (2.69 vs 1.89, respectively; p < 0.001), history of VTE (5.8% vs 2.1%, respectively; p < 0.001), and a higher number were undergoing fusion surgery (46.1% vs 24.7%, respectively; p < 0.001). The prevalence of VTE was higher in the chemoprophylaxis group (3.62% vs 2.03%, respectively; p < 0.001). The median time to VTE occurrence was shorter in the nonchemoprophylaxis group (3.6 vs 6.8 days, respectively; p = 0.0003, log-rank test; hazard ratio 0.685 [0.505-0.926]), and the peak prevalence of VTE occurred in the first 3 postoperative days in the nonchemoprophylaxis group. The average time of initiation of chemoprophylaxis was 1.46 days after surgery. The rates of epidural hematoma were 0.20% (n = 4) in the chemoprophylaxis group and 0.18% (n = 9) in the nonchemoprophylaxis group (p = 0.622). CONCLUSIONS The risks of spinal epidural hematoma among patients who receive chemoprophylaxis and those who do not are low and equivalent. Administering anticoagulation therapy from 1 day before to 3 days after surgery is safe for patients at high risk for VTE.

Assessment of Paraspinal Muscle Cross-sectional Area After Lumbar Decompression: Minimally Invasive Versus Open Approaches.

STUDY DESIGN: A retrospective, blinded analysis of imaging studies. SUMMARY OF BACKGROUND DATA: To evaluate changes in paraspinal muscle cross-sectional area (CSA) after surgical treatment for lumbar stenosis and to compare these changes between minimally invasive and standard open approaches. The open approach to lumbar stenosis is effective, but it involves retraction and resection of muscle from the spinous process, which can result in ischemia and denervation of paraspinal musculature and may lead to muscle atrophy and pain. OBJECTIVE: It is hypothesized that the microendoscopic decompression of stenosis (MEDS) technique will better preserve the paraspinal muscles compared with the open procedure. MATERIALS AND METHODS: A total of 18 patients underwent a 1-level posterior decompression for lumbar stenosis, (9 open, 9 MEDS). Lumbar magnetic resonance imaging was obtained before surgery and after surgery (open approach average 16.3 mo; MEDS average 16.6 mo). CSA of paraspinal muscles were averaged over the distance of the surgical site. RESULTS: The mean age of patients treated with the open and MEDS approaches were 55.2 and 66.4 years, respectively (P=0.07). Paraspinal muscle CSA decreased by an average of 5.4% (SD=10.6%; range, -24.5% to +7.7%) in patients treated with the open approach and increased by an average of 9.9% (SD=14.4%; range, -9.8% to +33.1%) in patients treated with MEDS (P=0.02). For the open approach, changes in CSA did not differ significantly between the left and right sides for erector spinae (P=0.35) or multifidus muscles (P=0.90). After the MEDS approach there were no significant differences between the dilated and contralateral sides with regard to change in CSA for erector spinae (P=0.85) or multifidus muscles (P=0.95). CONCLUSIONS: Compared with the open approach for lumbar stenosis, MEDS had significantly less negative impact on the paraspinal muscle CSA. Previous reports have documented negative effects of paraspinal muscle injury, including weakness, disability, and pain. Collectively, these data suggest that the MEDS approach for lumbar decompression is less destructive to the paraspinous muscles than the open approach and may facilitate better clinical outcomes.

Predictors of unplanned readmission in patients undergoing lumbar decompression: multi-institutional analysis of 7016 patients.

OBJECT: Unplanned hospital readmission represents a large financial burden on the Centers for Medicare and Medicaid Services, commercial insurance payers, hospitals, and individual patients, and is a principal target for cost reduction. A large-scale, multi-institutional study that evaluates risk factors for readmission has not been previously performed in patients undergoing lumbar decompression procedures. The goal of this multicenter retrospective study was to find preoperative, intraoperative, and postoperative predictive factors that result in unplanned readmission (UR) after lumbar decompression surgery. METHODS: The National Surgical Quality Improvement Program (NSQIP) database was retrospectively reviewed to identify all patients who received lumbar decompression procedures in 2011. Risk-adjusted multivariate logistic regression analysis was performed to estimate independent predictors of UR. RESULTS: The overall rate of UR among patients undergoing lumbar decompression was 4.4%. After multivariate logistic regression analysis, anemia (odds ratio [OR] 1.48), dependent functional status (OR 3.03), total operative duration (OR 1.003), and American Society of Anesthesiologists Physical Status Class 4 (OR 3.61) remained as independent predictors of UR. Postoperative complications that were significantly associated with UR included overall complications (OR 5.18), pulmonary embolism (OR 3.72), and unplanned reoperation (OR 56.91). CONCLUSIONS: There were several risk factors for UR after lumbar spine decompression surgery. Identification of high-risk patients and appropriate allocation of resources to reduce postoperative incidence may reduce the readmission rate.

Sir Victor Horsley's contributions to the study and treatment of gunshot wounds of the head.

Sir Victor Horsley'S many contributions to neurological surgery include experimental and clinical studies of gunshot wounds (GSW) of the head. Horsley's publications from 1894 to 1897 and 1914 to 1915 on GSWs were reviewed. Horsley described GSWs in animal and clay models, illustrating characteristics of the primary missile tract and secondary cavitation. A transcranial GSW model in 67 dogs related intracranial damage to the projectile's velocity and sectional area, producing a marked sudden increase in intracranial pressure that presumably "tunneled" to the medullary respiratory and cardiac centers. If the resultant sudden apnea was treated with artificial respiration and prompt surgical decompression, the animal often survived. In these animal experiments, Horsley clearly described increased intracranial pressure, hypertension, and bradycardia-later recognized as the Cushing response or triad. With the onset of World War I, Horsley again reviewed the ballistics of military weaponry, emphasizing projectile spin and velocity as the main wounding mechanisms. He was outspoken against the "wicked tradition" of neglecting cranial GSWs and personally treated cases with aggressive respiratory support and prompt decompression of devitalized tissue. Horsley's contributions to the experimental and clinical aspects of GSWs to the head are consistent with his other important contributions to neurosurgery and have largely stood the test of time.