Faculty Bibliography

OBJECTIVE:Machine learning algorithms excel at leveraging big data to identify complex patterns that can be used to aid in clinical decision-making. The objective of this study is to demonstrate the performance of machine learning models in predicting postoperative complications following anterior cervical discectomy and fusion (ACDF). METHODS:Artificial neural network (ANN), logistic regression (LR), support vector machine (SVM), and random forest decision tree (RF) models were trained on a multicenter data set of patients undergoing ACDF to predict surgical complications based on readily available patient data. Following training, these models were compared to the predictive capability of American Society of Anesthesiologists (ASA) physical status classification. RESULTS:A total of 20,879 patients were identified as having undergone ACDF. Following exclusion criteria, patients were divided into 14,615 patients for training and 6,264 for testing data sets. ANN and LR consistently outperformed ASA physical status classification in predicting every complication (p < 0.05). The ANN outperformed LR in predicting venous thromboembolism, wound complication, and mortality (p < 0.05). The SVM and RF models were no better than random chance at predicting any of the postoperative complications (p < 0.05). CONCLUSION/CONCLUSIONS:ANN and LR algorithms outperform ASA physical status classification for predicting individual postoperative complications. Additionally, neural networks have greater sensitivity than LR when predicting mortality and wound complications. With the growing size of medical data, the training of machine learning on these large datasets promises to improve risk prognostication, with the ability of continuously learning making them excellent tools in complex clinical scenarios.

BACKGROUND: Defining prognostic factors is a crucial initial step for determining the management of patients with brain metastases. Randomized trials assessing radiosurgery have commonly limited inclusion criteria to 1 to 4 brain metastases, in part due to multiple retrospective studies reporting on the number of brain metastases as a prognostic indicator. The present study reports on the survival of patients with 1 to 4 versus >/=5 brain metastases treated with radiosurgery. METHODS: We evaluated a retrospective multi-institutional database of 1523 brain metastases in 507 patients who were treated with radiosurgery (Gamma Knife or Cyberknife) between 2001 and 2014. A total of 243 patients were included in the analysis. Patients with 1 to 4 brain metastases were compared with patients with >/=5 brain metastases using a standard statistical analysis. Cox hazard regression was used to construct a multivariable model of overall survival (OS). To find covariates that best separate the data at each split, a machine learning technique Chi-squared Automated Interaction Detection tree was utilized. RESULTS: On Pearson correlation, systemic disease status, number of intracranial metastases, and overall burden of disease (number of major involved organ systems) were found to be highly correlated (P<0.001). Patients with 1 to 4 metastases had a median OS of 10.8 months (95% confidence interval, 6.1-15.6 mo), compared with a median OS of 8.5 months (95% confidence interval, 4.4-12.6 mo) for patients with >/=5 metastases (P=0.143). The actuarial 6 month local failure rate was 5% for patients with 1 to 4 metastases versus 3.2% for patients with >/=5 metastases (P=0.404). There was a significant difference in systemic disease status between the 2 groups; 30% of patients had controlled systemic disease in the <5 lesions group, versus 8% controlled systemic disease in the >/=5 lesions group (P=0.005). Patients with 1 to 4 metastases did not have significantly improved OS in a multivariable model adjusting for systemic disease status, systemic extracranial metastases, and other key variables. The Chi-squared Automated Interaction Detection tree (machine learning technique) algorithm consistently identified performance status and systemic disease status as key to disease classification, but not intracranial metastases. CONCLUSIONS: Although the number of brain metastases has previously been accepted as an independent prognostic indicator, our multicenter analysis demonstrates that the number of intracranial metastases is highly correlated with overall disease burden and clinical status. Proper matching and controlling for these other determinants of survival demonstrates that the number of intracranial metastases alone is not an independent predictive factor, but rather a surrogate for other clinical factors.

Engagement in research and academic productivity are crucial components in the training of a neurosurgeon. This process typically begins in residency training. In this study, we analyzed individual resident productivity as it correlated to publications across all Accreditation Council for Graduate Medical Education (ACGME)-accredited neurosurgery training programs in an attempt to identify how programs have developed and fostered a research culture and environment. We obtained a list of current neurosurgery residents in ACGME-accredited programs from the American Association of Neurological Surgeons database. An expanded PubMed and Scopus search was conducted for each resident through the present time. We tabulated all articles attributed to each resident. We then categorized the publications based on each neurosurgical subspecialty while in residency. A spreadsheet-based statistical analysis was performed. This formulated the average number of resident articles, h-indices, and most common subspecialty categories by training program. We analyzed 1352 current neurosurgery residents in 105 programs. There were a total of 10 645 publications, of which 3985 were resident first-author publications during the period of study. The most common subspecialties among all resident publications were vascular (24.9%), spine (16.9%), oncology (16.1%), pediatric (5.6%), functional (4.9%), and trauma (3.8%). The average resident published 2.9 first-author papers with average of 38.0 first-author publications by total residents at each program (range 0-241). The average h-index per resident is 2.47 ± 3.25. When comparing previously published faculty h-index program rankings against our resident h-index rankings, there is a strong correlation between the 2 datasets with a clear delineation between Top-20 productivity and that of other programs (average h-index 4.2 vs 1.7, respectively, P < .001). Increasing program size leads to a clear increase in academic productivity on both the resident and faculty level (average h-index 1.6, 1.9, 3.9 for 1, 2, and 3 resident per year programs, respectively, P < .001). Resident first-author publications correlated with recently described academic departmental productivity. Subspecialty resident publications are highest in cerebrovascular surgery. Resident research and publication is a key metric for assessing the productivity of academic neurosurgery programs and is consistent with one of the core foci of neurosurgical training.

INTRODUCTION/BACKGROUND:ADAPT (a direct aspiration first pass technique) has been shown to be fast, cost-effective, and associated with excellent angiographic and clinical outcomes in the treatment of acute ischemic stroke (AIS). OBJECTIVE:To identify any and all preoperative factors that are associated with successful revascularization using aspiration alone. METHODS:A retrospective review of 76 patients with AIS treated with thrombectomy was carried out. Cohort 1 included cases in which aspiration alone was successful (Thrombolysis in Cerebral Infarction 2b or 3). Cohort 2 included cases in which aspiration was unsuccessful or could not be performed despite an attempt. RESULTS:There was no difference between cohorts in gender, race, medications, National Institute of Health Stroke Scale score, IV tissue plasminogen activator, site or side of the occlusion, dense vessel sign, aortic arch type, severe stenosis, clot length, operator years of experience, and guide/aspiration catheters used. Patients in cohort 1 were on average younger (66.5 vs 74.1 years, p=0.025). There was a trend for more patients in cohort 2 to have atrial fibrillation/arrhythmias (62.5% vs 45.5%, p=0.168) and have a cardiogenic stroke etiology (78.1% vs 56.8%, p=0.086). There was also a trend for more reverse curves (2.3 vs 1.7, p=0.107), larger vessel diameter (3.26 mm vs 2.88 mm, p=0.184), larger vessel-to-catheter ratio (2.09 vs 1.87, p=0.192), and worse clot burden score (5.38 vs 6.68, p=0.104) in cohort 2. CONCLUSIONS:Aspiration success was associated with younger age. Our findings suggest that ADAPT can be used for the vast majority of patients but it may be beneficial to use a different method first in the elderly.

BACKGROUND:There is no facile quantitative method for monitoring hydrocephalus (HCP). We propose quantitative computed tomography (CT) ventriculography (qCTV) as a novel computer vision tool for empirically assessing HCP in patients with subarachnoid hemorrhage (SAH). METHODS:Twenty patients with SAH who were evaluated for ventriculoperitoneal shunt (VPS) placement were selected for inclusion. Ten patients with normal head computed tomography (CTH) findings were analyzed as negative controls. CTH scans were segmented both manually and automatically (by qCTV) to generate measures of ventricular volume. RESULTS:identified all patients who went on to require VPS placement (10 of 10; P = 0.011). CONCLUSIONS:qCTV is a reliable means of quantifying ventricular volume and hydrocephalus. This technique offers a new tool for monitoring neurosurgical patients for hydrocephalus, and may be beneficial for use in future research studies, as well as in the routine care of patients with hydrocephalus.

STUDY DESIGN/METHODS:A retrospective cohort study. OBJECTIVE:The aim of this study was to identify associations between abnormal coagulation profile and postoperative morbidity and mortality in patients undergoing posterior lumbar fusion (PLF). SUMMARY OF BACKGROUND DATA/BACKGROUND:The literature suggests that abnormal coagulation profile is associated with postoperative complications, notably the need for blood transfusion. However, there is little research that directly addresses the influence of coagulation profile on postoperative complications following PLF. METHODS:The American College of Surgeons National Surgical Quality Improvement Program database (ACS-NSQIP) was utilized to identify patients undergoing PLF between 2006 and 2013. Nine thousand two hundred ninety-five patients met inclusion criteria. Multivariate analysis was utilized to identify associations between abnormal coagulation profile and postoperative complications. RESULTS:Low platelet count was an independent risk factor for organ space surgical site infections (SSIs) [odds ratio (OR) = 6.0, P < 0.001], ventilation >48 hours (OR = 4.5, P = 0.002), Acute renal failure (OR = 5.8, P = 0.007), transfusion (OR = 1.6, P < 0.001), sepsis (OR = 2.2, P = 0.037), reoperation (OR = 2.5, P = 0.001), and death (OR = 3.7, P = 0.049). High partial thromboplastin time (PTT) was an independent risk factor for ventilation >48 hours (OR = 5.6, P = 0.002), cerebrovascular accident (CVA)/stroke with neurological deficit (OR = 5.1, P = 0.011), cardiac arrest (OR = 5.4, P = 0.030), transfusion (OR = 1.5, P = 0.020), and death (OR = 4.5, P = 0.050). High International Normalized Ration (INR) was an independent risk factor for pneumonia (OR = 8.7, P = 0.001), pulmonary embolism (OR = 5.6, P = 0.021), deep venous thrombosis/Thrombophlebitis (OR = 4.8, P = 0.011), septic shock (OR = 8.4, P = 0.048), and death (OR = 9.8, P = 0.034). Bleeding disorder was an independent risk factor for organ space SSI (OR = 5.4, P = 0.01), pneumonia (OR = 3.0, P = 0.023), and sepsis (OR = 4.4, P < 0.001). CONCLUSION/CONCLUSIONS:Abnormal coagulation profile was an independent predictor of morbidity and mortality in patients undergoing PLF. As such, it should be considered in preoperative optimization and risk stratification.

BACKGROUND: Melanoma has high propensity to metastasize to the brain. With recent gains in improving patient survival, stereotactic radiosurgery may offer an effective and less neurotoxic alternative to whole brain radiation. In the study, we report on the safety and efficacy of stereotactic radiosurgery (SRS) in treating melanoma brain metastases in 87 patients. METHODS: This retrospective, multicenter study examined 87 patients with 309 metastases underwent single-dose or multifractionated SRS for treatment of intracranial metastases from malignant melanoma. RESULTS: A total of eighty-seven patients with a median age of 62 years (26 to 85) were treated from 2007 to 2014. Eighty patients (92%) also had extracranial metastases at time of treatment, and sixty-nine patients (79%) had uncontrolled systemic disease. 79 patients (91%) underwent single-dose, 7 (8%) underwent 3 fractions, and 1 (1%) were treated in 5 fractions. Mean tumor volume (GTV) treated was 1.92 cc. Five patients developed symptoms of acute phase toxicity, and four developed late phase toxicity. None had radionecrosis. The median survival was 6 months. The Kaplan-Meier 1-year survival rate was 31%, and 1-year local control rate was 91%. 1-year survival rate for BRAF positive patients was 42%, and BRAF negative patients was 27%. Forty-two patients (48%) had distant intracranial recurrences, and 1-year distant control rate was 32%. CONCLUSIONS: SRS is a safe and effective treatment option for intracranial metastases from malignant melanoma. This paper serves as a reference for what is achievable in the absence of highly effective systemic therapy.

Meningiomas are common intracranial tumors that can have a complex arterial supply. In a patient with a recurrent large left clinoid aypical grade 2 meningioma, diagnostic angiography revealed left proximal middle cerebral artery (MCA) occlusion and reconstitution of the MCA circulation from the left middle meningeal artery. Consequently, the planned surgical approach was adjusted to preserve the left external carotid artery circulation in a difficult meningioma resection. This case illustrates a role for preoperative angiography in surgical planning of patients with complex skull base tumors involving intracranial vascular structures and highlights the unique neovascularization that often occurs as meningiomas parasitize the exracranial blood supply.

BACKGROUND:Recent decades have seen a rapid expansion of involvement of medical students in biomedical research during medical school training. Research within medical school has been shown to influence medical students with regard to medical knowledge, career development, and residency specialty choice. The objective of this study was to evaluate the impact of neurosurgery medical student research grants on neurosurgery residency choice and provide an insight on the demographics of grant awardees. METHODS:In this retrospective study, a search of award recipients was performed using data available on the American Association of Neurological Surgeons, Congress of Neurological Surgeons, and Neurosurgery Research and Education Foundation websites. Searched years included the first cycle of American Association of Neurological Surgeons/Neurosurgery Research and Education Foundation (2007) and Council of State Neurosurgical Societies/Congress of Neurological Surgeons (2008-2009) grant awards until the 2015-2016 cycle, which is the latest award cycle to date. RESULTS:The initial search yielded 163 research grants that were awarded to 158 students between the years of 2007 and 2016. Among the 163 grant recipients, 126 (77.3%) were men. Among the 88 recipients who entered postgraduate residency programs, 51% (45 of 88) matched into neurosurgery residency. When considering both neurosurgery and neurology residency programs, the percentage increased to 59.1% (52 of 88). CONCLUSIONS:Neurosurgery grants for medical students are highly successful in producing future neurosurgeons with >50% of grant recipients matched into neurosurgery. Women are underrepresented in neurosurgery grants and neurosurgery residency programs. This situation can be improved by providing insight about the field early in medical school, perhaps through increased use of neurosurgery medical student grants.

BACKGROUND:With a recent surge of clinical trials, the treatment of ischemic stroke has undergone dramatic changes. OBJECTIVE:To evaluate the impact of evidence and a revamped stroke protocol on a large healthcare system. METHODS:A retrospective review of 69 patients with ischemic stroke treated with intra-arterial therapy was carried out. Cohort 1 included patients treated before implementation of a new stroke protocol, and cohort 2 after implementation. Angiographic outcome was graded using the Thrombolysis in Cerebral Infarction (TICI) score. Clinical outcomes were assessed using the National Institute of Health Stroke Scale (NIHSS) and modified Rankin Scale (mRS). RESULTS:Primary outcomes comparing cohorts demonstrated decreased arrival-to-puncture time (cohort 2: 104 vs cohort 1: 181 min, p<0.001), similar TICI 2b/3 rates (86.5% vs 81.3%, p=0.5530), and similar percentage of patients with discharge mRS 0-2 (18.9% vs 21.9%, p=0.7740). Notable secondary outcomes for cohort 2 included decreased puncture-to-first pass time (34 vs 53 min, p <0.001), increased TICI 3 rates (37.8% vs 18.8%, p=0.0290), a trend toward greater improvements in NIHSS on postoperative day 1 (6.8 vs 2.6, p=0.0980) and discharge (9.5 vs 6.7, p=0.1130), and a trend toward increased percentage of patients discharged with mRS 0-3 (48.6% vs 34.4%, p=0.3280 NS). There were similar rates of symptomatic intracerebral hemorrhage (10.8% vs 9.4%, p=0.9570) and death (10.8% vs 15.6%, p=0.5530). CONCLUSIONS:An interdisciplinary and rapid response to the emergence of strong clinical evidence can result in dramatic changes in a large healthcare system.