Price Transparency for Cervical Spinal Fusion Among High-Performing Spine Centers in the United States.

BACKGROUND AND OBJECTIVES: As of January 1, 2021, all US hospitals are required by the Hospital Price Transparency Final Rule (HPTFR) to publish standard charges for all items and services, yet the state of price transparency for cervical spinal fusion is unknown. Here, we assess the nationwide price transparency landscape for cervical spinal fusion among high-performing spine centers in the United States. METHODS: In this cross-sectional economic evaluation, we queried publicly available price transparency websites of 332 "high-performing" spine centers, as defined by the US News and World Report. We extracted variables including gross charges for cervical spinal fusion, payor options, price reporting methodology, and prices relevant to consumers including listed cash prices and minimum and maximum negotiated charges. RESULTS: While nearly all 332 high-performing spine surgery centers (99.4%) had an online cost estimation tool, the HPTFR compliance rate was only 8.4%. Gross charges for cervical spinal fusion were accessible for 68.1% of hospitals, discounted cash prices for 46.4% of hospitals, and minimum and maximum charges for 10.8% of hospitals. There were large IQRs for gross charges ($48 491.98-$99 293.37), discounted cash prices ($26 952.25-$66 806.63), minimum charges ($10 766.11-$21 248.36), and maximum charges ($39 280.49-$89 035.35). There was geographic variability in the gross charges of cervical spinal fusion among high-performing spine centers within and between states. There was a significant association between "excellent" discharge to home status and lower mean gross charges. CONCLUSION: Although online cost reporting has drastically increased since implementation of the HPTFR, data reported for cervical spinal fusion remain inadequate and difficult to interpret by both providers and patients.

Accuracy of the Veterans Health Administration COVID-19 (VACO) Index for predicting short-term mortality among 1307 US academic medical centre inpatients and 427 224 US Medicare patients.

BACKGROUND: The Veterans Health Administration COVID-19 (VACO) Index predicts 30-day all-cause mortality in patients with COVID-19 using age, sex and pre-existing comorbidity diagnoses. The VACO Index was initially developed and validated in a nationwide cohort of US veterans-we now assess its accuracy in an academic medical centre and a nationwide US Medicare cohort. METHODS: With measures and weights previously derived and validated in US national Veterans Health Administration (VA) inpatients and outpatients (n=13 323), we evaluated the accuracy of the VACO Index for estimating 30-day all-cause mortality using area under the receiver operating characteristic curve (AUC) and calibration plots of predicted versus observed mortality in inpatients at a single US academic medical centre (n=1307) and in Medicare inpatients and outpatients aged 65+ (n=427 224). RESULTS: 30-day mortality varied by data source: VA 8.5%, academic medical centre 17.5%, Medicare 16.0%. The VACO Index demonstrated similar discrimination in VA (AUC=0.82) and academic medical centre inpatient population (AUC=0.80), and when restricted to patients aged 65+ in VA (AUC=0.69) and Medicare inpatient and outpatient data (AUC=0.67). The Index modestly overestimated risk in VA and Medicare data and underestimated risk in Yale New Haven Hospital data. CONCLUSIONS: The VACO Index estimates risk of short-term mortality across a wide variety of patients with COVID-19 using data available prior to or at the time of diagnosis. The VACO Index could help inform primary and booster vaccination prioritisation, and indicate who among outpatients testing positive for SARS-CoV-2 should receive greater clinical attention or scarce treatments.

Endovascular therapy versus microsurgical clipping of unruptured wide-neck aneurysms: a prospective multicenter study with propensity score analysis.

OBJECTIVE: Numerous techniques have been developed to treat wide-neck aneurysms (WNAs), each with different safety and efficacy profiles. Few studies have compared endovascular therapy (EVT) with microsurgery (MS). The authors' objective was to perform a prospective multicenter study of a WNA registry using rigorous outcome assessments and to compare EVT and MS using propensity score analysis (PSA). METHODS: Unruptured, saccular, not previously treated WNAs were included. WNA was defined as an aneurysm with a neck width ≥ 4 mm or a dome-to-neck ratio (DTNR) < 2. The primary outcome was modified Rankin Scale (mRS) score at 1 year after treatment (good outcome was defined as mRS score 0-2), as assessed by blinded research nurses and compared with PSA. Angiographic outcome was assessed using the Raymond scale with core laboratory review (adequate occlusion was defined as Raymond scale score 1-2). RESULTS: The analysis included 224 unruptured aneurysms in the EVT cohort (n = 140) and MS cohort (n = 84). There were no differences in baseline demographic characteristics, such as proportion of patients with good baseline mRS score (94.3% of the EVT cohort vs 94.0% of the MS cohort, p = 0.941). WNA inclusion criteria were similar between cohorts, with the most common being both neck width ≥ 4 mm and DTNR < 2 (50.7% of the EVT cohort vs 50.0% of the MS cohort, p = 0.228). More paraclinoid (32.1% vs 9.5%) and basilar tip (7.1% vs 3.6%) aneurysms were treated with EVT, whereas more middle cerebral artery (13.6% vs 42.9%) and pericallosal (1.4% vs 4.8%) aneurysms were treated with MS (p < 0.001). EVT aneurysms were slightly larger (p = 0.040), and MS aneurysms had a slightly lower mean DTNR (1.4 for the EVT cohort vs 1.3 for the MS cohort, p = 0.010). Within the EVT cohort, 9.3% of patients underwent stand-alone coiling, 17.1% balloon-assisted coiling, 34.3% stent-assisted coiling, 37.1% flow diversion, and 2.1% PulseRider-assisted coiling. Neurological morbidity secondary to a procedural complication was more common in the MS cohort (10.3% vs 1.4%, p = 0.003). One-year mRS scores were assessed for 218 patients (97.3%), and no significantly increased risk of poor clinical outcome was found for the MS cohort (OR 2.17, 95% CI 0.84-5.60, p = 0.110). In an unadjusted direct comparison, more patients in the EVT cohort achieved a good clinical outcome at 1 year (93.4% vs 84.1%, p = 0.048). Final adequate angiographic outcome was superior in the MS cohort (97.6% of the MS cohort vs 86.5% of the EVT cohort, p = 0.007). CONCLUSIONS: Although the treatments for unruptured WNA had similar clinical outcomes according to PSA, there were fewer complications and superior clinical outcome in the EVT cohort and superior angiographic outcomes in the MS cohort according to the unadjusted analysis. These results may be considered when selecting treatment modalities for patients with unruptured WNAs.

Endovascular Therapy Versus Microsurgical Clipping of Ruptured Wide Neck Aneurysms (EVERRUN Registry): a multicenter, prospective propensity score analysis.

OBJECTIVE: Randomized controlled trials have demonstrated the superiority of endovascular therapy (EVT) compared to microsurgery (MS) for ruptured aneurysms suitable for treatment or when therapy is broadly offered to all presenting aneurysms; however, wide neck aneurysms (WNAs) are a challenging subset that require more advanced techniques and warrant further investigation. Herein, the authors sought to investigate a prospective, multicenter WNA registry using rigorous outcome assessments and compare EVT and MS using propensity score analysis (PSA). METHODS: Untreated, ruptured, saccular WNAs were included in the analysis. A WNA was defined as having a neck ≥ 4 mm or a dome/neck ratio (DNR) < 2. The primary outcome was the modified Rankin Scale (mRS) score at 1 year posttreatment, as assessed by blinded research nurses (good outcome: mRS scores 0-2) and compared using PSA. RESULTS: The analysis included 87 ruptured aneurysms: 55 in the EVT cohort and 32 in the MS cohort. Demographics were similar in the two cohorts, including Hunt and Hess grade (p = 0.144) and modified Fisher grade (p = 0.475). WNA type inclusion criteria were similar in the two cohorts, with the most common type having a DNR < 2 (EVT 60.0% vs MS 62.5%). More anterior communicating artery aneurysms (27.3% vs 18.8%) and posterior circulation aneurysms (18.2% vs 0.0%) were treated with EVT, whereas more middle cerebral artery aneurysms were treated with MS (34.4% vs 18.2%, p = 0.025). Within the EVT cohort, 43.6% underwent stand-alone coiling, 50.9% balloon-assisted coiling, 3.6% stent-assisted coiling, and 1.8% flow diversion. The 1-year mRS score was assessed in 81 patients (93.1%), and the primary outcome demonstrated no increased risk for a poor outcome with MS compared to EVT (OR 0.43, 95% CI 0.13-1.45, p = 0.177). The durability of MS was higher, as evidenced by retreatment rates of 12.7% and 0% for EVT and MS, respectively (p = 0.04). CONCLUSIONS: EVT and MS had similar clinical outcomes at 1 year following ruptured WNA treatment. Because of their challenging anatomy, WNAs may represent a population in which EVT's previously demonstrated superiority for ruptured aneurysm treatment is less relevant. Further investigation into the treatment of ruptured WNAs is warranted.

The Impact of Interhospital Competition on Treatment Strategy and Outcomes for Unruptured Intracranial Aneurysms.

BACKGROUND: Interhospital competition has been shown to affect surgical outcomes and expenditures. However, interhospital competition's impact on neurosurgery is poorly characterized. OBJECTIVE: To assess how interhospital competition is associated with treatment strategy and outcomes for unruptured intracranial aneurysms (UIAs). METHODS: We identified all elective UIA admissions in the National Inpatient Sample from 2002 to 2011. Competitive intensity of each hospital market was quantified using the validated Herfindahl-Hirschman Index (HHI), with lower values denoting higher competition. We then obtained nationwide HHI values for 2012 to 2016 from the Health Care Cost Project. Outcomes included treatment modality (clipping, coiling, or nonoperative management), inpatient mortality, disposition, complications, length of stay (LOS), and costs. Multivariate regression assessed the association between HHI and outcomes, controlling for patient demographics, severity metrics, hospital characteristics, and treatment. RESULTS: We studied 157 979 elective UIA admissions at 1435 hospitals from 2002 to 2011, with an increase in coiling admissions (13.4% to 33.7%) and decrease in clipping admissions (30.9% to 17.6%). Mean hospital HHI was 0.11 (range = 0.001-0.97). Competition decreased for 61.8% of hospitals from 2002 to 2011 and 68.1% of metropolitan localities from 2012 to 2016. Admissions in more competitive hospital markets exhibited increased odds of undergoing surgery (odds ratio [OR] = 1.37, P < .001), with preference toward coiling over clipping (OR = 1.27, P < .001). HHI was not associated with mortality, disposition, or LOS. However, increased interhospital competition was associated with more complications (OR = 1.09, P = .001) and greater hospital costs (ß-coefficient = 1.06, P < .001). CONCLUSION: For UIA patients, admission to hospitals in more competitive geographies was associated with increased rates of surgical intervention, coiling utilization, complications, and hospitalization costs.

Development and validation of a 30-day mortality index based on pre-existing medical administrative data from 13,323 COVID-19 patients: The Veterans Health Administration COVID-19 (VACO) Index.

BACKGROUND: Available COVID-19 mortality indices are limited to acute inpatient data. Using nationwide medical administrative data available prior to SARS-CoV-2 infection from the US Veterans Health Administration (VA), we developed the VA COVID-19 (VACO) 30-day mortality index and validated the index in two independent, prospective samples. METHODS AND FINDINGS: We reviewed SARS-CoV-2 testing results within the VA between February 8 and August 18, 2020. The sample was split into a development cohort (test positive between March 2 and April 15, 2020), an early validation cohort (test positive between April 16 and May 18, 2020), and a late validation cohort (test positive between May 19 and July 19, 2020). Our logistic regression model in the development cohort considered demographics (age, sex, race/ethnicity), and pre-existing medical conditions and the Charlson Comorbidity Index (CCI) derived from ICD-10 diagnosis codes. Weights were fixed to create the VACO Index that was then validated by comparing area under receiver operating characteristic curves (AUC) in the early and late validation cohorts and among important validation cohort subgroups defined by sex, race/ethnicity, and geographic region. We also evaluated calibration curves and the range of predictions generated within age categories. 13,323 individuals tested positive for SARS-CoV-2 (median age: 63 years; 91% male; 42% non-Hispanic Black). We observed 480/3,681 (13%) deaths in development, 253/2,151 (12%) deaths in the early validation cohort, and 403/7,491 (5%) deaths in the late validation cohort. Age, multimorbidity described with CCI, and a history of myocardial infarction or peripheral vascular disease were independently associated with mortality-no other individual comorbid diagnosis provided additional information. The VACO Index discriminated mortality in development (AUC = 0.79, 95% CI: 0.77-0.81), and in early (AUC = 0.81 95% CI: 0.78-0.83) and late (AUC = 0.84, 95% CI: 0.78-0.86) validation. The VACO Index allows personalized estimates of 30-day mortality after COVID-19 infection. For example, among those aged 60-64 years, overall mortality was estimated at 9% (95% CI: 6-11%). The Index further discriminated risk in this age stratum from 4% (95% CI: 3-7%) to 21% (95% CI: 12-31%), depending on sex and comorbid disease. CONCLUSION: Prior to infection, demographics and comorbid conditions can discriminate COVID-19 mortality risk overall and within age strata. The VACO Index reproducibly identified individuals at substantial risk of COVID-19 mortality who might consider continuing social distancing, despite relaxed state and local guidelines.

Interhospital competition and hospital charges and costs for patients undergoing cranial neurosurgery.

OBJECTIVE: Research has documented significant growth in neurosurgical expenditures and practice consolidation. The authors evaluated the relationship between interhospital competition and inpatient charges or costs in patients undergoing cranial neurosurgery. METHODS: The authors identified all admissions in 2006 and 2009 from the National Inpatient Sample. Admissions were classified into 5 subspecialties: cerebrovascular, tumor, CSF diversion, neurotrauma, or functional. Hospital-specific interhospital competition levels were quantified using the Herfindahl-Hirschman Index (HHI), an economic metric ranging continuously from 0 (significant competition) to 1 (monopoly). Inpatient charges (hospital billing) were multiplied with reported cost-to-charge ratios to calculate costs (actual resource use). Multivariate regressions were used to assess the association between HHI and inpatient charges or costs separately, controlling for 17 patient, hospital, severity, and economic factors. The reported ß-coefficients reflect percentage changes in charges or costs (e.g., ß-coefficient = 1.06 denotes a +6% change). All results correspond to a standardized -0.1 change in HHI (increase in competition). RESULTS: In total, 472,938 nationwide admissions for cranial neurosurgery treated at 896 unique hospitals met inclusion criteria. Hospital HHIs ranged from 0.099 to 0.724 (mean 0.298 ± 0.105). Hospitals in more competitive markets had greater charge/cost markups (ß-coefficient = 1.10, p < 0.001) and area wage indices (ß-coefficient = 1.04, p < 0.001). Between 2006 and 2009, average neurosurgical charges and costs rose significantly ($62,098 to $77,812, p < 0.001; $21,385 to $22,389, p < 0.001, respectively). Increased interhospital competition was associated with greater charges for all admissions (ß-coefficient = 1.07, p < 0.001) as well as cerebrovascular (ß-coefficient = 1.08, p < 0.001), tumor (ß-coefficient = 1.05, p = 0.039), CSF diversion (ß-coefficient = 1.08, p < 0.001), neurotrauma (ß-coefficient = 1.07, p < 0.001), and functional neurosurgery (ß-coefficient = 1.11, p = 0.037) admissions. However, no significant associations were observed between HHI and costs, except for CSF diversion surgery (ß-coefficient = 1.03, p = 0.021). Increased competition was not associated with important clinical outcomes, such as inpatient mortality, favorable discharge disposition, or complication rates, except for lower mortality for brain tumors (OR 0.78, p = 0.026), but was related to greater length of stay for all admissions (ß-coefficient = 1.06, p < 0.001). For a sensitivity analysis adjusting for outcomes, all findings for charges and costs remained the same. CONCLUSIONS: Hospitals in more competitive markets exhibited higher charges for admissions of patients undergoing an in-hospital cranial procedure. Despite this, interhospital competition was not associated with increased inpatient costs except for CSF diversion surgery. There was no corresponding improvement in outcomes with increased competition, with the exception of a potential survival benefit for brain tumor surgery.

Preoperative Urinary Tract Infection Increases Postoperative Morbidity in Spine Patients.

STUDY DESIGN: Retrospective review. OBJECTIVE: Compare postoperative infection rates and 30-day outcomes in spine surgery patients with and without a preoperative urinary tract infection (UTI). SUMMARY OF BACKGROUND DATA: There is mixed evidence regarding safety and risks when operating on spine patients with a preoperative UTI. METHODS: Using data from the American College of Surgeons National Surgical Quality Improvement Program, we identified all adult patients undergoing spine surgery between 2012 and 2017 with a preoperative UTI. Patients with other preoperative infections were excluded. Our primary outcome was any postoperative infection (pneumonia, sepsis, surgical site infection, and organ space infection). Our secondary outcomes included surgical site infections, non-infectious complications, return to operating room, and 30-day readmission and mortality. We used univariate, then multivariate Poisson regression models adjusted for demographics, comorbidities, laboratory values, and case details to investigate the association between preoperative UTI status and postoperative outcomes. RESULTS: A total of 270,371 patients who underwent spine surgery were analyzed. The most common procedure was laminectomy (41.9%), followed by spinal fusion (31.7%) and laminectomy/fusion (25.6%). Three hundred fourty one patients had a preoperative UTI (0.14%). Patients with a preoperative UTI were more likely to be older, female, inpatients, emergency cases, with a higher American Society of Anesthesiologists score, and a longer operating time (for all, P < 0.001). Patients with a preoperative UTI had higher rates of infectious and non-infectious complications, return to operating room, and unplanned readmissions (for all, P < 0.001). However, there was no significant difference in mortality (0.6% vs. 0.2%, P = 0.108). Even after controlling for demographics, comorbidities, labs, and case details, preoperative UTI status was significantly associated with more postoperative infectious complications (incidence rate ratio [IRR]: 2.88, 95% confidence interval [CI]: 2.25-3.70, P < 0.001). CONCLUSION: Preoperative UTI status is significantly associated with postoperative infections and worse 30-day outcomes. Spine surgeons should consider delaying or cancelling surgery in patients with a UTI until the infection has cleared to reduce adverse outcomes. LEVEL OF EVIDENCE: 3.

Neurosurgery Resident Wellness and Recovery from Burnout: A 39-Year Single-Institution Experience.

OBJECTIVE: Physician burnout in neurosurgery is highly prevalent and occurs most severely during residency. Although earlier assessments have identified stressors contributing to neurosurgery resident burnout, recovery interventions have not been studied extensively. We aimed to characterize burnout patterns and factors contributing to recovery through a single-institution assessment of neurosurgery residents across 4 decades. METHODS: We administered a 59-item questionnaire to all living current and former residents of a large neurosurgical training institution (n = 96). Respondents indicated the timeline of burnout or hardship during residency and evaluated burnout stressors and recovery factors through a 5-point Likert scale and free-text response. RESULTS: The survey response rate was 67% (64 of 96). The overall self-reported burnout rate was 30% (19 of 64). Recent trainees were significantly more likely to report burnout (P < 0.05). Postgraduate year 2 was cited by 66% of respondents as the onset of burnout or hardship. The most common stressors included work-life imbalance (55%) and imbalance of resident duties (33%). The highest-impact recovery factors were end of a rotation or postgraduate year (80%), increased sleep (48%), and meaningful relationships with colleagues (42%). Institution-specific factors, such as outdoor activities (52%) and intraprogram social events (34%), were also influential in recovery. In free-text responses, respondents identified a strong sense of mission in neurosurgical training as a central driver of recovery to wellness. CONCLUSIONS: Institutional support structures promoting mentorship and camaraderie are actionable methods to encourage resident burnout recovery. This study serves as a model for other programs to identify their "critical periods" of burnout and effective wellness interventions.

Volume-outcome relationship in pediatric neurotrauma care: analysis of two national databases.

OBJECTIVE: Previous research has demonstrated the association between increased hospital volume and improved outcomes for a wide range of neurosurgical conditions, including adult neurotrauma. The authors aimed to determine if such a relationship was also present in the care of pediatric neurotrauma patients. METHODS: The authors identified 106,146 pediatric admissions for traumatic intracranial hemorrhage (tICH) in the National Inpatient Sample (NIS) for the period 2002-2014 and 34,017 admissions in the National Trauma Data Bank (NTDB) for 2012-2015. Hospitals were stratified as high volume (top 20%) or low volume (bottom 80%) according to their pediatric tICH volume. Then the association between high-volume status and favorable discharge disposition, inpatient mortality, complications, and length of stay (LOS) was assessed. Multivariate regression modeling was used to control for patient demographics, severity metrics, hospital characteristics, and performance of neurosurgical procedures. RESULTS: In each database, high-volume hospitals treated over 60% of pediatric tICH admissions. In the NIS, patients at high-volume hospitals presented with worse severity metrics and more frequently underwent neurosurgical intervention over medical management (all p < 0.001). After multivariate adjustment, admission to a high-volume hospital was associated with increased odds of a favorable discharge (home or short-term facility) in both databases (both p < 0.001). However, there were no significant differences in inpatient mortality (p = 0.208). Moreover, high-volume hospital patients had lower total complications in the NIS and lower respiratory complications in both databases (all p < 0.001). Although patients at high-volume hospitals in the NTDB had longer hospital stays (ß-coefficient = 1.17, p < 0.001), they had shorter stays in the intensive care unit (ß-coefficient = 0.96, p = 0.024). To determine if these findings were attributable to the trauma center level rather than case volume, an analysis was conducted with only level I pediatric trauma centers (PTCs) in the NTDB. Similarly, treatment at a high-volume level I PTC was associated with increased odds of a favorable discharge (OR 1.28, p = 0.009), lower odds of pneumonia (OR 0.60, p = 0.007), and a shorter total LOS (ß-coefficient = 0.92, p = 0.024). CONCLUSIONS: Pediatric tICH patients admitted to high-volume hospitals exhibited better outcomes, particularly in terms of discharge disposition and complications, in two independent national databases. This trend persisted when examining level I PTCs exclusively, suggesting that volume alone may have an impact on pediatric neurotrauma outcomes. These findings highlight the potential merits of centralizing neurosurgery and pursuing regionalization policies, such as interfacility transport networks and destination protocols, to optimize the care of children affected by traumatic brain injury.

Volume-Cost Relationship in Neurosurgery: Analysis of 12,129,029 Admissions from the National Inpatient Sample.

BACKGROUND/OBJECTIVE: Several studies have documented improved outcomes at high-volume hospitals for neurosurgery. However, the relationship between neurosurgical volume and costs remains poorly understood. METHODS: Using neurosurgery-specific Diagnosis-Related Groups (DRG) codes, we identified adult neurosurgical admissions in the National Inpatient Sample from 2002 to 2014. We stratified hospitals by annual neurosurgical volume as high-volume (top 20%) or low-volume centers (bottom 80%). We performed survey-weighted regression analyses to examine the impact of case volume on inpatient costs. RESULTS: A total of 12,129,029 admissions underwent neurosurgery from 2002 to 2014, with 59.6% treated at high-volume hospitals. Patients at high-volume centers were more likely to have private insurance, higher risk of mortality scores, and higher DRG weight procedures than those at low-volume centers (P < 0.001). High-volume hospital admissions were on average 9% or $1791 more expensive than their low-volume counterparts. However, after adjustment for patient, hospital, and case-mix differences, high-volume hospitals were 4.3% less expensive than low-volume centers ($21,825 vs. $22,924; P < 0.01). The southern United States, which had the biggest volume, showed the highest savings (6.5%). CONCLUSIONS: High-volume hospitals provide more cost-effective neurosurgical care. Centralization of care at high-volume neurosurgical institutions may be a promising strategy to delivering higher-value care, achieving better outcomes at lower costs.

Wide-neck aneurysms: systematic review of the neurosurgical literature with a focus on definition and clinical implications.

OBJECTIVE: Wide-necked aneurysms (WNAs) are a variably defined subset of cerebral aneurysms that require more advanced endovascular and microsurgical techniques than those required for narrow-necked aneurysms. The neurosurgical literature includes many definitions of WNAs, and a systematic review has not been performed to identify the most commonly used or optimal definition. The purpose of this systematic review was to highlight the most commonly used definition of WNAs. METHODS: The authors searched PubMed for the years 1998-2017, using the terms "wide neck aneurysm" and "broad neck aneurysm" to identify relevant articles. All results were screened for having a minimum of 30 patients and for clearly stating a definition of WNA. Reference lists for all articles meeting the inclusion criteria were also screened for eligibility. RESULTS: The search of the neurosurgical literature identified 809 records, of which 686 were excluded (626 with < 30 patients; 60 for lack of a WNA definition), leaving 123 articles for analysis. Twenty-seven unique definitions were identified and condensed into 14 definitions. The most common definition was neck size ≥ 4 mm or dome-to-neck ratio < 2, which was used in 49 articles (39.8%). The second most commonly used definition was neck size ≥ 4 mm, which was used in 26 articles (21.1%). The rest of the definitions included similar parameters with variable thresholds. There was inconsistent reporting of the precise dome measurements used to determine the dome-to-neck ratio. Digital subtraction angiography was the only imaging modality used to study the aneurysm morphology in 87 of 122 articles (71.3%). CONCLUSIONS: The literature has great variability regarding the definition of a WNA. The most prevalent definition is a neck diameter of ≥ 4 mm or a dome-to-neck ratio of < 2. Whether this is the most appropriate and clinically useful definition is an area for future study.