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Arvin R. Wali, David R. Santiago-Dieppa, Justin M. Brown and Ross Mandeville

OBJECTIVE

Pan–brachial plexus injury (PBPI), involving C5–T1, disproportionately affects young males, causing lifelong disability and decreased quality of life. The restoration of elbow flexion remains a surgical priority for these patients. Within the first 6 months of injury, transfer of spinal accessory nerve (SAN) fascicles via a sural nerve graft or intercostal nerve (ICN) fascicles to the musculocutaneous nerve can restore elbow flexion. Beyond 1 year, free-functioning muscle transplantation (FFMT) of the gracilis muscle can be used to restore elbow flexion. The authors present the first cost-effectiveness model to directly compare the different treatment strategies available to a patient with PBPI. This model assesses the quality of life impact, surgical costs, and possible income recovered through restoration of elbow flexion.

METHODS

A Markov model was constructed to simulate a 25-year-old man with PBPI without signs of recovery 4.5 months after injury. The management options available to the patient were SAN transfer, ICN transfer, delayed FFMT, or no treatment. Probabilities of surgical success rates, quality of life measurements, and disability were derived from the published literature. Cost-effectiveness was defined using incremental cost-effectiveness ratios (ICERs) defined by the ratio between costs of a treatment strategy and quality-adjusted life years (QALYs) gained. A strategy was considered cost-effective if it yielded an ICER less than a willingness-to-pay of $50,000/QALY gained. Probabilistic sensitivity analysis (PSA) was performed to address parameter uncertainty.

RESULTS

The base case model demonstrated a lifetime QALYs of 22.45 in the SAN group, 22.0 in the ICN group, 22.3 in the FFMT group, and 21.3 in the no-treatment group. The lifetime costs of income lost through disability and interventional/rehabilitation costs were $683,400 in the SAN group, $727,400 in the ICN group, $704,900 in the FFMT group, and $783,700 in the no-treatment group. Each of the interventional modalities was able to dramatically improve quality of life and decrease lifelong costs. A Monte Carlo PSA demonstrated that at a willingness-to-pay of $50,000/QALY gained, SAN transfer dominated in 88.5% of iterations, FFMT dominated in 7.5% of iterations, ICN dominated in 3.5% of iterations, and no treatment dominated in 0.5% of iterations.

CONCLUSIONS

This model demonstrates that nerve transfer surgery and muscle transplantation are cost-effective strategies in the management of PBPI. These reconstructive neurosurgical modalities can improve quality of life and lifelong earnings through decreasing disability.

Free access

Milli Desai, Arvin R. Wali, Harjus S. Birk, David R. Santiago-Dieppa and Alexander A. Khalessi

OBJECTIVE

Women have been shown to have a higher risk of cerebral aneurysm formation, growth, and rupture than men. The authors present a review of the recently published neurosurgical literature that studies the role of pregnancy and female sex steroids, to provide a conceptual framework with which to understand the various risk factors associated with cerebral aneurysms in women at different stages in their lives.

METHODS

The PubMed database was searched for “(“intracranial” OR “cerebral”) AND “aneurysm” AND (“pregnancy” OR “estrogen” OR “progesterone”)” between January 1980 and February 2019. A total of 392 articles were initially identified, and after applying inclusion and exclusion criteria, 20 papers were selected for review and analysis. These papers were then divided into two categories: 1) epidemiological studies about the formation, growth, rupture, and management of cerebral aneurysms in pregnancy; and 2) investigations on female sex steroids and cerebral aneurysms (animal studies and epidemiological studies).

RESULTS

The 20 articles presented in this study include 7 epidemiological articles on pregnancy and cerebral aneurysms, 3 articles reporting case series of cerebral aneurysms treated by endovascular therapies in pregnancy, 3 epidemiological articles reporting the relationship between female sex steroids and cerebral aneurysms through retrospective case-control studies, and 7 experimental studies using animal and/or cell models to understand the relationship between female sex steroids and cerebral aneurysms. The studies in this review report similar risk of aneurysm rupture in pregnant women compared to the general population. Most ruptured aneurysms in pregnancy occur during the 3rd trimester, and most pregnant women who present with cerebral aneurysm have caesarean section deliveries. Endovascular treatment of cerebral aneurysms in pregnancy is shown to provide a new and safe form of therapy for these cases. Epidemiological studies of postmenopausal women show that estrogen hormone therapy and later age at menopause are associated with a lower risk of cerebral aneurysm than in matched controls. Experimental studies in animal models corroborate this epidemiological finding; estrogen deficiency causes endothelial dysfunction and inflammation, which may predispose to the formation and rupture of cerebral aneurysms, while exogenous estrogen treatment in this population may lower this risk.

CONCLUSIONS

The aim of this work is to equip the neurosurgical and obstetrical/gynecological readership with the tools to better understand, critique, and apply findings from research on sex differences in cerebral aneurysms.

Free access

Arvin R. Wali, Charlie C. Park, David R. Santiago-Dieppa, Florin Vaida, James D. Murphy and Alexander A. Khalessi

OBJECTIVE

Rupture of large or giant intracranial aneurysms leads to significant morbidity, mortality, and health care costs. Both coiling and the Pipeline embolization device (PED) have been shown to be safe and clinically effective for the treatment of unruptured large and giant intracranial aneurysms; however, the relative cost-to-outcome ratio is unknown. The authors present the first cost-effectiveness analysis to compare the economic impact of the PED compared with coiling or no treatment for the endovascular management of large or giant intracranial aneurysms.

METHODS

A Markov model was constructed to simulate a 60-year-old woman with a large or giant intracranial aneurysm considering a PED, endovascular coiling, or no treatment in terms of neurological outcome, angiographic outcome, retreatment rates, procedural and rehabilitation costs, and rupture rates. Transition probabilities were derived from prior literature reporting outcomes and costs of PED, coiling, and no treatment for the management of aneurysms. Cost-effectiveness was defined, with the incremental cost-effectiveness ratios (ICERs) defined as difference in costs divided by the difference in quality-adjusted life years (QALYs). The ICERs < $50,000/QALY gained were considered cost-effective. To study parameter uncertainty, 1-way, 2-way, and probabilistic sensitivity analyses were performed.

RESULTS

The base-case model demonstrated lifetime QALYs of 12.72 for patients in the PED cohort, 12.89 for the endovascular coiling cohort, and 9.7 for patients in the no-treatment cohort. Lifetime rehabilitation and treatment costs were $59,837.52 for PED; $79,025.42 for endovascular coiling; and $193,531.29 in the no-treatment cohort. Patients who did not undergo elective treatment were subject to increased rates of aneurysm rupture and high treatment and rehabilitation costs. One-way sensitivity analysis demonstrated that the model was most sensitive to assumptions about the costs and mortality risks for PED and coiling. Probabilistic sampling demonstrated that PED was the cost-effective strategy in 58.4% of iterations, coiling was the cost-effective strategy in 41.4% of iterations, and the no-treatment option was the cost-effective strategy in only 0.2% of iterations.

CONCLUSIONS

The authors’ cost-effective model demonstrated that elective endovascular techniques such as PED and endovascular coiling are cost-effective strategies for improving health outcomes and lifetime quality of life measures in patients with large or giant unruptured intracranial aneurysm.

Free access

Michael G. Brandel, Robert C. Rennert, Arvin R. Wali, David R. Santiago-Dieppa, Jeffrey A. Steinberg, Christian Lopez Ramos, Peter Abraham, J. Scott Pannell and Alexander A. Khalessi

OBJECTIVE

Preoperative embolization of meningiomas can facilitate their resection when they are difficult to remove. The optimal use and timing of such a procedure remains controversial given the risk of embolization-linked morbidity in select clinical settings. In this work, the authors used a large national database to study the impact of immediate preoperative embolization on the immediate outcomes of meningioma resection.

METHODS

Meningioma patients who had undergone elective resection were identified in the National (Nationwide) Inpatient Sample (NIS) for the period 2002–2014. Patients who had undergone preoperative embolization were propensity score matched to those who had not, adjusting for patient and hospital characteristics. Associations between preoperative embolization and morbidity, mortality, and nonroutine discharge were investigated.

RESULTS

Overall, 27,008 admissions met the inclusion criteria, and 633 patients (2.34%) had undergone preoperative embolization and 26,375 (97.66%) had not. The embolization group was younger (55.17 vs 57.69 years, p < 0.001) with a lower proportion of females (63.5% vs 69.1%, p = 0.003), higher Charlson Comorbidity Index (p = 0.002), and higher disease severity (p < 0.001). Propensity score matching retained 413 embolization and 413 nonembolization patients. In the matched cohort, preoperative embolization was associated with increased rates of cerebral edema (25.2% vs 17.7%, p = 0.009), posthemorrhagic anemia or transfusion (21.8% vs 13.8%, p = 0.003), and nonroutine discharge (42.8% vs 35.7%, p = 0.039). There was no difference in mortality (≤ 2.4% vs ≤ 2.4%, p = 0.82). Among the embolization patients, the mean interval from embolization to resection was 1.49 days. On multivariate analysis, a longer interval was significantly associated with nonroutine discharge (OR 1.33, p = 0.004) but not with complications or mortality.

CONCLUSIONS

Relative to meningioma patients who do not undergo preoperative embolization in the same admission, those who do have higher rates of cerebral edema and nonroutine discharge but not higher rates of stroke or death. Thus, meningiomas requiring preoperative embolization represent a distinct clinical entity that requires prolonged, more complex care. Further, among embolization patients, the timing of resection did not affect the risk of in-hospital complications, suggesting that the timing of surgery can be determined according to surgeon discretion.

Free access

Peter Abraham, J. Scott Pannell, David R. Santiago-Dieppa, Vincent Cheung, Jeffrey Steinberg, Arvin Wali, Mihir Gupta, Robert C. Rennert, Roland R. Lee and Alexander A. Khalessi

OBJECTIVE

In vivo and in vitro studies have demonstrated histological evidence of iatrogenic endothelial injury after stent retriever thrombectomy. However, noncontrast vessel wall (VW)–MRI is insufficient to demonstrate vessel injury. Authors of this study prospectively evaluated iatrogenic endothelial damage after stent retriever thrombectomy in humans by utilizing high-resolution contrast-enhanced VW-MRI. Characterization of VW-MRI changes in vessels subject to mechanical injury from thrombectomy may allow better understanding of the biological effects of this intervention.

METHODS

The authors prospectively recruited 11 patients for this study. The treatment group included 6 postthrombectomy patients and the control group included 5 subjects undergoing MRI for nonvascular indications. All subjects were evaluated on a Signa HD× 3.0-T MRI scanner with an 8-channel head coil. Both pre- and postcontrast T1-weighted Cube VW images as well as MR angiograms were acquired. Sequences obtained for evaluation of the brain parenchyma included diffusion-weighted, gradient echo, and T2-FLAIR imaging. Two independent neuroradiologists, who were blinded to the treatment status of each patient, determined the presence of VW enhancement. Patient age, National Institutes of Health Stroke Scale score on presentation, location of occlusion, stroke etiology, type of device used, number of device deployments, Thrombolysis in Cerebral Infarction (TICI) reperfusion score, stroke volume, and 90-day modified Rankin Scale score were also noted.

RESULTS

Postcontrast T1-weighted VW enhancement was detected in the M2 segment in 100% of the thrombectomy patients, in the M1 segment in 83%, and in the internal carotid artery in 50%. One patient also demonstrated A1 segment enhancement, which was attributable to thrombectomy treatment of that vessel segment during the same procedure. None of the control patients demonstrated VW enhancement of their intracranial vasculature on T1-weighted images.

CONCLUSIONS

The study findings suggest that VW injury incurred during stent retriever thrombectomy can be reliably detected utilizing contrast-enhanced 3-T VW-MRI. The results further demonstrate that endothelial injury is associated with oversizing of stent retrievers relative to the treated vessel. Further studies are needed to evaluate the clinical significance of endothelial injury and to characterize the differential effects of various devices.

Free access

David R. Santiago-Dieppa, Brian R. Hirshman, Arvin Wali, J. Scott Pannell, Yasaman Alam, Scott Olson, Vincent J. Cheung, Jeffrey A. Steinberg, Mihir Gupta and Alexander A. Khalessi

OBJECTIVE

Carotid artery stenting (CAS) has antihypertensive effects, but the durability and degree of this response remain variable. The authors propose that this clinical variability is a function of the presence or absence of a complete circle of Willis (COW). Incomplete COWs perfuse through a higher-resistance pial collateral pathway, and therefore patients may require a higher mean arterial pressure (MAP). Carotid artery revascularization in these patients would reduce the end-organ collateral demand that has been hypothesized to drive the MAP response.

METHODS

Using a retrospective, nonrandomized within-subject case-control design, the authors compared the postoperative effects of CAS in patients with and without a complete COW by using changes in MAP and antihypertensive medication as end points. They recorded MAP and antihypertensive medications 3 months prior to surgery, preoperatively, immediately postoperatively, and at the 3-month follow-up.

RESULTS

Data were collected from 64 consecutive patients undergoing CAS. Patients without a complete COW (25%) were more likely to demonstrate a decrease in BP response to stenting (i.e., a drop in MAP of 10 mm Hg and/or a reduction or cessation of BP medications at 3 months postoperatively). Of the patients in the incomplete COW cohort, 75% had this outcome, whereas of those in the complete COW cohort, only 41% had it (p < 0.041). These findings remained statistically significant in a logistic regression analysis for possible confounders (p < 0.024). A receiver operating curve analysis of preoperative data indicated that a MAP > 96.3 mm Hg was 55.5% sensitive and 57.4% specific for predicting a complete COW and that patients with a MAP > 96.3 mm Hg were more likely to demonstrate a good MAP decrease following CAS (p < 0.0092).

CONCLUSIONS

CAS is associated with a significant decrease in MAP and/or a reduction/cessation in BP medications in patients in whom a complete COW is absent.

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Corey T. Walker, Chiazo S. Amene, Jeffrey S. Pannell, David R. Santiago-Dieppa, Robert C. Rennert, Lawrence A. Hansen and Alexander A. Khalessi

The differential diagnosis of spinal tumors is guided by anatomical location and imaging characteristics. Diagnosis of rare tumors is made challenging by abnormal features. The authors present the case of a 47-year-old woman who presented with progressive subacute right lower-extremity weakness and numbness of the right thigh. Physical examination further revealed an extensor response to plantar reflex on the right and hyporeflexia of the right Achilles and patellar reflexes. Magnetic resonance imaging of the lumbar spine demonstrated an 8-mm intramedullary exophytic nodule protruding into a hematoma within the conus medullaris. Spinal angiography was performed to rule out an arteriovenous malformation, and resection with hematoma evacuation was completed. Pathological examination of the resected mass demonstrated a spindle cell neoplasm with dense bundles of collagen. Special immunostaining was performed and a diagnosis of solitary fibrous tumor (SFT) was made. SFTs are mesenchymally derived pleural neoplasms, which rarely present at other locations of the body, but have been increasingly described to occur as primary neoplasms of the spine and CNS. The authors believe that this case is unique in its rare location at the level of the conus, and also that this is the first report of a hemorrhagic SFT in the spine. Therefore, with this report the authors add to the literature the fact that this variant of an increasingly understood but heterogeneous tumor can occur, and therefore should be considered in the differential of clinically similar tumors.

Free access

Arvin R. Wali, Michael G. Brandel, David R. Santiago-Dieppa, Robert C. Rennert, Jeffrey A. Steinberg, Brian R. Hirshman, James D. Murphy and Alexander A. Khalessi

OBJECTIVE

Markov modeling is a clinical research technique that allows competing medical strategies to be mathematically assessed in order to identify the optimal allocation of health care resources. The authors present a review of the recently published neurosurgical literature that employs Markov modeling and provide a conceptual framework with which to evaluate, critique, and apply the findings generated from health economics research.

METHODS

The PubMed online database was searched to identify neurosurgical literature published from January 2010 to December 2017 that had utilized Markov modeling for neurosurgical cost-effectiveness studies. Included articles were then assessed with regard to year of publication, subspecialty of neurosurgery, decision analytical techniques utilized, and source information for model inputs.

RESULTS

A total of 55 articles utilizing Markov models were identified across a broad range of neurosurgical subspecialties. Sixty-five percent of the papers were published within the past 3 years alone. The majority of models derived health transition probabilities, health utilities, and cost information from previously published studies or publicly available information. Only 62% of the studies incorporated indirect costs. Ninety-three percent of the studies performed a 1-way or 2-way sensitivity analysis, and 67% performed a probabilistic sensitivity analysis. A review of the conceptual framework of Markov modeling and an explanation of the different terminology and methodology are provided.

CONCLUSIONS

As neurosurgeons continue to innovate and identify novel treatment strategies for patients, Markov modeling will allow for better characterization of the impact of these interventions on a patient and societal level. The aim of this work is to equip the neurosurgical readership with the tools to better understand, critique, and apply findings produced from cost-effectiveness research.

Restricted access

Christian Lopez Ramos, Robert C. Rennert, Michael G. Brandel, Peter Abraham, Brian R. Hirshman, Jeffrey A. Steinberg, David R. Santiago-Dieppa, Arvin R. Wali, Kevin Porras, Yazeed Almosa, Jeffrey S. Pannell and Alexander A. Khalessi

OBJECTIVE

Safety-net hospitals deliver care to a substantial share of vulnerable patient populations and are disproportionately impacted by hospital payment reform policies. Complex elective procedures performed at safety-net facilities are associated with worse outcomes and higher costs. The effects of hospital safety-net burden on highly specialized, emergent, and resource-intensive conditions are poorly understood. The authors examined the effects of hospital safety-net burden on outcomes and costs after emergent neurosurgical intervention for ruptured cerebral aneurysms.

METHODS

The authors conducted a retrospective analysis of the Nationwide Inpatient Sample (NIS) from 2002 to 2011. Patients ≥ 18 years old who underwent emergent surgical clipping and endovascular coiling for aneurysmal subarachnoid hemorrhage (SAH) were included. Safety-net burden was defined as the proportion of Medicaid and uninsured patients treated at each hospital included in the NIS database. Hospitals that performed clipping and coiling were stratified as low-burden (LBH), medium-burden (MBH), and high-burden (HBH) hospitals.

RESULTS

A total of 34,647 patients with ruptured cerebral aneurysms underwent clipping and 23,687 underwent coiling. Compared to LBHs, HBHs were more likely to treat black, Hispanic, Medicaid, and uninsured patients (p < 0.001). HBHs were also more likely to be associated with teaching hospitals (p < 0.001). No significant differences were observed among the burden groups in the severity of subarachnoid hemorrhage. After adjusting for patient demographics and hospital characteristics, treatment at an HBH did not predict in-hospital mortality, poor outcome, length of stay, costs, or likelihood of a hospital-acquired condition.

CONCLUSIONS

Despite their financial burden, safety-net hospitals provide equitable care after surgical clipping and endovascular coiling for ruptured cerebral aneurysms and do not incur higher hospital costs. Safety-net hospitals may have the capacity to provide equitable surgical care for highly specialized emergent neurosurgical conditions.

Free access

Kaisorn L. Chaichana, Mohamad Bydon, David R. Santiago-Dieppa, Lee Hwang, Gregory McLoughlin, Daniel M. Sciubba, Jean-Paul Wolinsky, Ali Bydon, Ziya L. Gokaslan and Timothy Witham

Object

Posterior lumbar spinal fusion for degenerative spine disease is a common procedure, and its use is increasing annually. The rate of infection, as well as the factors associated with an increased risk of infection, remains unclear for this patient population. A better understanding of these features may help guide treatment strategies aimed at minimizing infection for this relatively common procedure. The authors' goals were therefore to ascertain the incidence of postoperative spinal infections and identify factors associated with postoperative spinal infections.

Methods

Data obtained in adult patients who underwent instrumented posterior lumbar fusion for degenerative spine disease between 1993 and 2010 were retrospectively reviewed. Stepwise multivariate proportional hazards regression analysis was used to identify factors associated with infection. Variables with p < 0.05 were considered statistically significant.

Results

During the study period, 817 consecutive patients underwent lumbar fusion for degenerative spine disease, and 37 patients (4.5%) developed postoperative spine infection at a median of 0.6 months (IQR 0.3–0.9). The factors independently associated with an increased risk of infection were increasing age (RR 1.004 [95% CI 1.001–1.009], p = 0.049), diabetes (RR 5.583 [95% CI 1.322–19.737], p = 0.02), obesity (RR 6.216 [95% CI 1.832–9.338], p = 0.005), previous spine surgery (RR 2.994 [95% CI 1.263–9.346], p = 0.009), and increasing duration of hospital stay (RR 1.155 [95% CI 1.076–1.230], p = 0.003). Of the 37 patients in whom infection developed, 21 (57%) required operative intervention but only 3 (8%) required instrumentation removal as part of their infection management.

Conclusions

This study identifies that several factors—older age, diabetes, obesity, prior spine surgery, and length of hospital stay—were each independently associated with an increased risk of developing infection among patients undergoing instrumented lumbar fusion for degenerative spine disease. The overwhelming majority of these patients were treated effectively without hardware removal.