A comparison of treating physician versus independent core lab assessments of post-aneurysm treatment imaging outcomes: an analysis of prospectively collected data from a randomized trial.

OBJECTIVE: Aneurysm occlusion has been used as surrogate marker of aneurysm treatment efficacy. Aneurysm occlusion scales are used to evaluate the outcome of endovascular aneurysm treatment and to monitor recurrence. These scales, however, require subjective interpretation of imaging data, which can reduce the utility and reliability of these scales and the validity of clinical studies regarding aneurysm occlusion rates. Use of a core lab with independent blinded reviewers has been implemented to enhance the validity of occlusion rate assessments in clinical trials. The degree of agreement between core labs and treating physicians has not been well studied with prospectively collected data. METHODS: In this study, the authors analyzed data from the Hydrogel Endovascular Aneurysm Treatment (HEAT) trial to assess the interrater agreement between the treating physician and the blinded core lab. The HEAT trial included 600 patients across 46 sites with intracranial aneurysms treated with coiling. The treating site and the core lab independently reviewed immediate postoperative and follow-up imaging (3-12 and 18-24 months, respectively) using the Raymond-Roy occlusion classification (RROC) scale, Meyer scale, and recanalization survey. A post hoc analysis was performed to calculate interrater reliability using Cohen's kappa. Further analysis was performed to assess whether degree of agreement varied on the basis of various factors, including scale used, timing of imaging, size of the aneurysm, imaging modality, location of the aneurysm, dome-to-neck ratio, and rupture status. RESULTS: Minimal interrater agreement was noted between the core lab reviewers and the treating physicians for assessing aneurysm occlusion using the RROC grading scale (k = 0.39, 95% CI 0.38-0.40) and Meyer scale (k = 0.23, 95% CI 0.14-0.38). The degree of agreement between groups was slightly better but still weak for assessing recanalization (k = 0.45, 95% CI 0.38-0.52). Factors that significantly improved degree of agreement were scales with fewer variables, greater time to follow-up, imaging modality (digital subtraction angiography), and wide-neck aneurysms. CONCLUSIONS: Assessment of aneurysm treatment outcome with commonly used aneurysm occlusion scales suffers from risk of poor interrater agreement. This supports the use of independent core labs for validation of outcome data to minimize reporting bias. Use of outcome tools with fewer point categories is likely to provide better interrater reliability. Therefore, the outcome assessment tools are ideal for clinical outcome assessment provided that they are sensitive enough to detect a clinically significant change.

Middle meningeal artery embolization for chronic subdural hematoma: a systematic review and meta-analysis.

Middle meningeal artery (MMA) embolization has been proposed as a minimally invasive treatment for chronic subdural hematoma (cSDH). The aim of this systematic review and meta-analysis is to compare outcomes after MMA embolization versus conventional management for cSDH. We performed a systematic review of PubMed, Embase, Oxford Journal, Cochrane, and Google Scholar databases from April 1987 to October 2020 in accordance with PRISMA guidelines. Studies reporting outcomes after MMA embolization for ≥3 patients with cSDH were included. A meta-analysis comparing MMA embolization with conventional management was performed. The analysis comprised 20 studies with 1416 patients, including 718 and 698 patients in the MMA embolization and conventional management cohorts, respectively. The pooled recurrence, surgical rescue, and in-hospital complication rates in the MMA embolization cohort were 4.8% (95% CI 3.2% to 6.5%), 4.4% (2.8% to 5.9%), and 1.7% (0.8% to 2.6%), respectively. The pooled recurrence, surgical rescue, and in-hospital complication rates in the conventional management cohort were 21.5% (0.6% to 42.4%), 16.4% (5.9% to 27.0%), and 4.9% (2.8% to 7.1%), respectively. Compared with conservative management, MMA embolization was associated with lower rates of cSDH recurrence (OR=0.15 (95% CI 0.03 to 0.75), p=0.02) and surgical rescue (OR=0.21 (0.07 to 0.58), p=0.003). In-hospital complication rates were comparable between the two cohorts (OR=0.78 (0.34 to 1.76), p=0.55). MMA embolization is a promising minimally invasive therapy that may reduce the need for surgical intervention in appropriately selected patients with cSDH. Additional prospective studies are warranted to determine the long-term durability of MMA embolization, refine eligibility criteria, and establish this endovascular approach as a viable definitive treatment for cSDH.

Endovascular Management of Distal Anterior Cerebral Artery Aneurysms: A Multicenter Retrospective Review.

INTRODUCTION: Distal anterior cerebral artery aneurysms (DACAA) are a rare and difficult entity to manage. Endovascular treatment has evolved for safe and durable treatment of these lesions. The objective of this study is to report the safety, efficacy, and outcomes of endovascular treatment of DACAA. METHODS: A retrospective review of DACAA endovascularly treated at 5 different institutions was performed. Data included demographics, rupture status, radiographic features, endovascular technique, complication rates, and long-term angiographic and clinical outcomes. A primary endpoint was a good clinical outcome (modified Rankin scale 0-2). Secondary endpoints included complications and radiographic occlusion at follow-up. RESULTS: A total of 84 patients were reviewed. The mean age was 56, and 64 (71.4%) were female. Fifty-two (61.9%) aneurysms were ruptured. A good functional outcome was achieved in 59 patients (85.5%). Sixty (71.4%) aneurysms were treated with primary coiling, and the remaining 24 were treated with flow diversion. Adequate occlusion was achieved in 41 (95.3%) aneurysms treated with coiling, and 17 (89.5%) with flow diversion. There were total 11 (13%) complications. In the flow diversion category, there were 2, both related to femoral access. In the coiling category, there were 9: 5 thromboembolic, 3 ruptures, and 1 related to femoral access. CONCLUSION: Endovascular treatment, and in particular, flow diversion for DACAA, is safe, feasible, and associated with good long-term angiographic and clinical outcomes.

Snare salvage technique for deformed WEB device after deployment.

The Woven EndoBridge (WEB) device is a new endovascular technology that allows safe and effective treatment of wide-neck bifurcation aneurysms without the need for dual antiplatelet therapy.1-4 The case is presented of a patient in their 50 s with a history of systemic lupus erythematosus and receiving warfarin for recurrent deep venous thrombosis and an unruptured right middle cerebral artery bifurcation aneurysm. The aneurysm was treated with a WEB SL aneurysm embolization device (MicroVention, Tustin, California, USA). After the final deployment, a technical error (inadvertent forward movement of the pusher) led to the deformation of the device along its longitudinal axis, leaving the aneurysm partially untreated. An Amplatz Goose Neck Microsnare was used to capture the proximal detachment marker and used gentle traction to restore the original shape of the device (video 1).5-7 A follow-up angiogram revealed a restoration of the device's shape with a similar result during the 4- month follow-up angiogram. neurintsurg;13/3/294/V1F1V1Video 1.

Woven Endobridge device for treatment of dissection-related PICA aneurysm.

Ruptured vertebrobasilar dissecting aneurysms require urgent, often challenging treatment as they have with a high re-hemorrhage rate within the first 24 hours. The patient is a 57-year-old woman who presented with severe-sudden onset headache. Further work up showed a ruptured dissecting aneurysm of the caudal loop of the posterior inferior cerebellar artery (PICA) with associated narrowing distally, in the ascending limb. The aneurysm was immediately occluded with a Woven Endobridge (WEB) device (MicroVention, Tustin, CA, USA) while flow diversion treatment of the diseased ascending limb was postponed. Follow-up angiography three months later showed complete occlusion of the aneurysm, as well as healing of the diseased distal vessel, obviating the need for further intervention. WEB embolization of a ruptured dissecting posterior circulation aneurysm provided an excellent outcome for this patient.

Minimally Invasive Endoscopy for Acute Subdural Hematomas: A Report of 3 Cases.

BACKGROUND: Acute subdural hematomas (aSDHs) occur in approximately 10% to 20% of all closed head injury and represent a significant cause of morbidity and mortality in traumatic brain injury patients. Conventional craniotomy is an invasive intervention with the potential for excess blood loss and prolonged postoperative recovery time. OBJECTIVE: To evaluate the outcomes of minimally invasive endoscopy for evacuation of aSDHs in a pilot feasibility study. METHODS: We retrospectively reviewed the records of consecutive patients with aSDHs who underwent surgical treatment at our institution with minimally invasive endoscopy using the Apollo/Artemis Neuro Evacuation Device (Penumbra, Alameda, California) between April 2015 and July 2018. RESULTS: The study cohort comprised three patients. The Glasgow Coma Scale on admission was 15 for all 3 patients, median preoperative hematoma volume was 49.5 cm3 (range 44-67.8 cm3), median postoperative degree of hematoma evacuation was 88% (range 84%-89%), and median modified Rankin Scale at discharge was 1 (range 0-3). CONCLUSION: Endoscopic evacuation of aSDHs can be a safe and effective alternative to craniotomy in appropriately selected patients. Further studies are needed to refine the selection criteria for endoscopic aSDH evacuation and evaluate its long-term outcomes.

Low-Dose Intravenous Heparin Infusion After Aneurysmal Subarachnoid Hemorrhage is Associated With Decreased Risk of Delayed Neurological Deficit and Cerebral Infarction.

BACKGROUND: Patients who survive aneurysmal subarachnoid hemorrhage (aSAH) are at risk for delayed neurological deficits (DND) and cerebral infarction. In this exploratory cohort comparison analysis, we compared in-hospital outcomes of aSAH patients administered a low-dose intravenous heparin (LDIVH) infusion (12 U/kg/h) vs those administered standard subcutaneous heparin (SQH) prophylaxis for deep vein thrombosis (DVT; 5000 U, 3 × daily). OBJECTIVE: To assess the safety and efficacy of LDIVH in aSAH patients. METHODS: We retrospectively analyzed 556 consecutive cases of aSAH patients whose aneurysm was secured by clipping or coiling at a single institution over a 10-yr period, including 233 administered the LDIVH protocol and 323 administered the SQH protocol. Radiological and outcome data were compared between the 2 cohorts using multivariable logistic regression and propensity score-based inverse probability of treatment weighting (IPTW). RESULTS: The unadjusted rate of cerebral infarction in the LDIVH cohort was half that in SQH cohort (9 vs 18%; P = .004). Multivariable logistic regression showed that patients in the LDIVH cohort were significantly less likely than those in the SQH cohort to have DND (odds ratio (OR) 0.53 [95% CI: 0.33, 0.85]) or cerebral infarction (OR 0.40 [95% CI: 0.23, 0.71]). Analysis following IPTW showed similar results. Rates of hemorrhagic complications, heparin-induced thrombocytopenia and DVT were not different between cohorts. CONCLUSION: This cohort comparison analysis suggests that LDIVH infusion may favorably influence the outcome of patients after aSAH. Prospective studies are required to further assess the benefit of LDIVH infusion in patients with aSAH.

Delayed presentation of acute ischemic strokes during the COVID-19 crisis.

BACKGROUND: The COVID-19 pandemic has disrupted established care paths worldwide. Patient awareness of the pandemic and executive limitations imposed on public life have changed the perception of when to seek care for acute conditions in some cases. We sought to study whether there is a delay in presentation for acute ischemic stroke patients in the first month of the pandemic in the US. METHODS: The interval between last-known-well (LKW) time and presentation of 710 consecutive patients presenting with acute ischemic strokes to 12 stroke centers across the US were extracted from a prospectively maintained quality database. We analyzed the timing and severity of the presentation in the baseline period from February to March 2019 and compared results with the timeframe of February and March 2020. RESULTS: There were 320 patients in the 2-month baseline period in 2019, there was a marked decrease in patients from February to March of 2020 (227 patients in February, and 163 patients in March). There was no difference in the severity of the presentation between groups and no difference in age between the baseline and the COVID period. The mean interval from LKW to the presentation was significantly longer in the COVID period (603±1035 min) compared with the baseline period (442±435 min, P<0.02). CONCLUSION: We present data supporting an association between public awareness and limitations imposed on public life during the COVID-19 pandemic in the US and a delay in presentation for acute ischemic stroke patients to a stroke center.

Inverse National Trends in Decompressive Craniectomy versus Endovascular Thrombectomy for Stroke.

OBJECTIVE: Endovascular thrombectomy (ET) for acute large vessel occlusion reduces infarct size, and it should hypothetically decrease the incidence of major ischemic strokes requiring decompressive craniectomy (DC). The aim of this retrospective cohort study is to determine trends in the utilization of ET versus DC for stroke in the United States over a 10-year span. METHODS: We extracted data from the Nationwide Inpatient Sample using International Classification of Diseases-9/10 codes from 2006-2016. Patients with a primary diagnosis of stroke were included. Baseline demographics, outcomes, and hospital charges were analyzed. RESULTS: The study cohort comprised 14,578,654 patients diagnosed with stroke. During the study period, DC and ET were performed in 124,718 and 62,637 patients, respectively. The number of stroke patients who underwent either ET or DC increased by 266% from 2006 to 2016. During that time period, the ET utilization rate increased (0.19% in 2006 to 14.07% in 2016, P < 0.0004), whereas the DC utilization rate decreased (7.07% in 2006 to 6.43% in 2016, P < 0.0001). In 2015, the utilization rate of ET (9.73%) exceeded that of DC (9.67%). ET-treated patients had shorter hospitalization durations (mean 8.8 vs. 16.8 days, P < 0.0001), lower mortality (16.2% vs. 19.3%), higher likelihood of discharge home (27.1% vs. 24.1%, P < 0.0001), and reduced hospital charges (mean $189,724 vs. $261,314, P < 0.0001). CONCLUSIONS: We identified an inverse relationship between national trends in rising ET and diminishing DC utilization for stroke treatment over a recent decade. Although direct causation cannot be inferred, our findings suggest that ET curtails the necessity for DC.

Heparin Treatment in Aneurysmal Subarachnoid Hemorrhage: A Review of Human Studies.

Aneurysmal subarachnoid hemorrhage (aSAH) remains a significant cause of stroke disability despite gradual reductions in physical morbidity and mortality. Heparin is an effective anti-inflammatory agent and may potentially prevent delayed neurological injury in the days to weeks after the hemorrhage. Various human studies have shown the safety of a continuous infusion of low-dose unfractionated heparin in the setting of subarachnoid hemorrhage as well as its efficacy in minimizing delayed neurological deficits including symptomatic cerebral vasospasm, vasospasm-related infarction, and cognitive dysfunction. Studies have also shown mixed results with low-molecular-weight heparin usage in this patient population. Heparin treatment is not associated with significant hemorrhagic complications; however, vigilance is essential for early detection of heparin-induced thrombocytopenia in order to prevent devastating sequelae. Multicenter randomized controlled trials are necessary for objective characterization of the effects of heparin.

Statins for neuroprotection in spontaneous intracerebral hemorrhage.

Statins, a common drug class for treatment of dyslipidemia, may be neuroprotective for spontaneous intracerebral hemorrhage (ICH) by targeting secondary brain injury pathways in the surrounding brain parenchyma. Statin-mediated neuroprotection may stem from downregulation of mevalonate and its derivatives, targeting key cell signaling pathways that control proliferation, adhesion, migration, cytokine production, and reactive oxygen species generation. Preclinical studies have consistently demonstrated the neuroprotective and recovery enhancement effects of statins, including improved neurologic function, reduced cerebral edema, increased angiogenesis and neurogenesis, accelerated hematoma clearance, and decreased inflammatory cell infiltration. Retrospective clinical studies have reported reduced perihematomal edema, lower mortality rates, and improved functional outcomes in patients who were taking statins before ICH. Several clinical studies have also observed lower mortality rates and improved functional outcomes in patients who were continued or initiated on statins after ICH. Subgroup analysis of a previous randomized trial has raised concerns of a potentially elevated risk of recurrent ICH in patients with previous hemorrhagic stroke who are administered statins. However, most statin trials failed to show an association between statin use and increased hemorrhagic stroke risk. Variable statin dosing, statin use in the pre-ICH setting, and selection biases have limited rigorous investigation of the effects of statins on post-ICH outcomes. Future prospective trials are needed to investigate the association between statin use and outcomes in ICH.

Cognitive outcomes after unruptured intracranial aneurysm treatment with flow diversion.

OBJECTIVE: Flow diversion is increasingly used to treat a variety of intracranial aneurysms with good safety and efficacy; however, there is some evidence that this treatment is associated with a larger postoperative ischemic burden on imaging than that with other traditional endovascular modalities. These findings typically do not manifest as neurological deficits, but any subtle effects on cognition remain unknown. In this study, the authors describe the neurocognitive performance of a cohort of patients with unruptured intracranial aneurysms (UIAs) before and after treatment with flow diversion. This is the first report of cognitive outcomes following aneurysm treatment with flow diversion. METHODS: The authors prospectively collected data on cognitive function using the Montreal Cognitive Assessment (MoCA) tool in patients with UIAs who were undergoing endovascular aneurysm treatment with flow diversion between June 2017 and July 2019. Patients completed the MoCA prior to intervention, at the 1-month follow-up after treatment, and again at 6 months after the procedure. All patients with UIAs treated with flow diversion were included regardless of age, aneurysm location, or morphology, unless their functional status precluded completion of the MoCA instrument. A repeated-measures linear mixed-effects model was used to compare preintervention and postintervention cognitive status at the time intervals outlined. RESULTS: Fifty-one patients with 61 aneurysms underwent endovascular aneurysm treatment with flow diversion (mean age 52.5 years, 90.2% females). There was no difference between baseline and postprocedure MoCA scores at any time interval (p > 0.05). The MoCA scores at baseline, 1 month postprocedure, and 6 months postprocedure were 26.1, 26.2, and 26.6, respectively. There was also no difference between pre- and postprocedure scores on any individual domain of the instrument (visuospatial, naming, attention, language, abstraction, delayed recall, and orientation) at any time interval (p > 0.05). Thirty-four patients had follow-up MRI or CT imaging, 5 of whom showed radiographic changes or ischemia. All patients with follow-up clinical evaluation had a 6-month modified Rankin Scale score ≤ 2. CONCLUSIONS: Flow diversion is increasingly used in the treatment of intracranial aneurysms. This study suggests that this treatment may not alter neurocognitive function. Larger patient samples and longer follow-ups with other tests of cognitive functions are needed to confirm these findings.

Blood Pressure after Endovascular Therapy for Ischemic Stroke (BEST): A Multicenter Prospective Cohort Study.

Background and Purpose- To identify the specific post-endovascular stroke therapy (EVT) peak systolic blood pressure (SBP) threshold that best discriminates good from bad functional outcomes (a priori hypothesized to be 160 mm Hg), we conducted a prospective, multicenter, cohort study with a prespecified analysis plan. Methods- Consecutive adult patients treated with EVT for an anterior ischemic stroke were enrolled from November 2017 to July 2018 at 12 comprehensive stroke centers accross the United States. All SBP values within 24 hours post-EVT were recorded. Using Youden index, the threshold of peak SBP that best discriminated primary outcome of dichotomized 90-day modified Rankin Scale score (0-2 versus 3-6) was identified. Association of this SBP threshold with the outcomes was quantified using multiple logistic regression. Results- Among 485 enrolled patients (median age, 69 [interquartile range, 57-79] years; 51% females), a peak SBP of 158 mm Hg was associated with the largest difference in the dichotomous modified Rankin Scale score (absolute risk reduction of 19%). Having a peak SBP >158 mm Hg resulted in an increased likelihood of modified Rankin Scale score 3 to 6 (odds ratio, 2.24 [1.52-3.29], P<0.01; adjusted odds ratio, 1.29 [0.81-2.06], P=0.28, after adjustment for prespecified variables). Conclusions- A peak post-EVT SBP of 158 mm Hg was prospectively identified to best discriminate good from bad functional outcome. Those with a peak SBP >158 had an increased likelihood of having a bad outcome in unadjusted, but not in adjusted analysis. The observed effect size was similar to prior studies. This finding should undergo further testing in a future randomized trial of goal-targeted post-EVT antihypertensive treatment.

Cerebral Venous Thrombosis at High Altitude: A Retrospective Cohort of Twenty-one Consecutive Patients.

Background  Cerebral venous thrombosis (CVT) is a rare cerebrovascular disorder, comprising <1% of all strokes. The incidence of CVT is higher in females but a small number of cases suggest that men have a higher risk for CVT in high elevation. The aim of this retrospective cohort study is to investigate this gender-related relationship and to describe the baseline characteristics and treatment outcomes of patients who suffered CVT at high altitude in eastern Nepal. Methods  We conducted a retrospective analysis of 21 consecutive patients with CVT at a tertiary care center in Nepal from July 2017 to January 2018. Clinical data, radiologic characteristics, therapeutic strategies, and outcomes were analyzed. The Glasgow Outcome Scale (GOS) at discharge was reported for each patient.  Result The study cohort comprised 21 patients (76% males) with a mean of 56 years. Medical comorbidities included hypertension (76%) and diabetes mellitus (57%). All patients received low-molecular-weight heparin therapy (LMWH). Eight patients (38%) underwent decompressive craniectomy while the remaining 13 (62%) were treated with medical therapy alone. The GOS at discharge was 5 in 57%, 2-4 in 33%, and 1 in 10%. Conclusion  In our series, men were found to have a higher risk for CVT at high altitude. The reversal in the gender ratio could be related to elevation, but could also be confounded by alcoholism. Increasingly sophisticated imaging techniques, such as computed tomography venography (CTV) and magnetic resonance venography (MRV), have facilitated the diagnosis of CVT. LMWH is a safe and easily accessible treatment option, especially in developing countries. Further studies are needed to assess the incidence and prevalence of CVT in the developing world, to establish the gender-related trends.

Medical Management Versus Surgical Bypass for Symptomatic Intracranial Atherosclerotic Disease: A Systematic Review.

INTRODUCTION: Intracranial atherosclerotic disease (ICAD) is a major cause of stroke worldwide. The optimal management of patients with symptomatic ICAD is controversial. Therefore, the aim of this systematic review is to compare medical management versus surgical bypass for the treatment of symptomatic ICAD. METHODS: A literature review was performed to identify studies reporting outcomes of patients with ICAD who were managed medically or surgically with either direct or indirect bypass. Baseline, treatment, and outcomes data were analyzed. Complications included ischemic stroke, intracranial hemorrhage, and cerebrovascular death. Secondary analyses of the surgically treated cohort were performed to compare the outcomes of direct versus indirect bypass. RESULTS: The pooled analysis was derived from 18 studies, comprising a total of 2160 patients with ICAD, including 1790 managed medically and 370 treated with surgical bypass. The rates of ischemic stroke, intracranial hemorrhage, and cerebrovascular death were 16%, 1%, and 4.5% in the medical cohort, respectively, versus 8%, 0.6%, and 1.9% in the surgical cohort, respectively. Among patients with ICAD who underwent bypass surgery, the rates of ischemic stroke and cerebrovascular death were 7% and 1.9% in the direct bypass group, respectively, versus 19% and 2.1% in the indirect bypass group, respectively. CONCLUSIONS: Direct or indirect bypass surgery is a reasonable treatment option for appropriately selected patients with ICAD. Careful preoperative evaluation of hemodynamic parameters and the relevant donor and recipient vessels is crucial to maximizing the success of bypass for ICAD. Further studies remain necessary to clarify the roles of medical versus surgical management for ICAD.

Minimally Invasive Surgery for Spontaneous Cerebellar Hemorrhage: A Multicenter Study.

BACKGROUND: Spontaneous intracranial hemorrhage (ICH) of the cerebellum can be life threatening because of mass effect on the brainstem and fourth ventricle. Suboccipital craniectomy is currently the treatment of choice for cerebellar ICH evacuation. Minimally invasive surgery (MIS) is currently being investigated for the treatment of supratentorial ICH. However, its utility for cerebellar ICH is unknown. The aim of this multicenter, retrospective cohort study is to evaluate the outcomes of MIS for cerebellar ICH. METHODS: We retrospectively reviewed the records of all patients with cerebellar ICH who underwent MIS using either the Apollo or Artemis Neuro Evacuation Device (Penumbra Inc., Alameda, California, USA) at 3 institutions from May 2015 to July 2018. Data from each contributing center were deidentified and pooled for analysis. RESULTS: The study cohort comprised 6 patients with a median age of 62.5 years. The median pre- and postoperative Glasgow Coma Scale scores were 10.5 and 15, respectively. The median degree of hematoma evacuation was 97.5% (range, 79%-100%). There were no procedural complications, but 1 patient required subsequent craniectomy (retreatment rate 17%). The median discharge modified Rankin scale score was 4, including 3 patients who improved to functional independence at follow-up durations of 3 months. Two patients died from medical complications (mortality rate 33%). CONCLUSIONS: MIS could represent a reasonable alternative to conventional surgery for the treatment of appropriately selected patients with cerebellar ICH. However, further studies are needed to clarify the perioperative and long-term risk to benefit profiles of this technique.

National trends in cerebral bypass for unruptured intracranial aneurysms: a National (Nationwide) Inpatient Sample analysis of 1998-2015.

OBJECTIVEThe development and recent widespread dissemination of flow diverters may have reduced the utilization of surgical bypass procedures to treat complex or giant unruptured intracranial aneurysms (UIAs). The aim of this retrospective cohort study was to observe trends in cerebral revascularization procedures for UIAs in the United States before and after the introduction of flow diverters by using the National (Nationwide) Inpatient Sample (NIS).METHODSThe authors extracted data from the NIS database for the years 1998-2015 using the ICD-9/10 diagnostic and procedure codes. Patients with a primary diagnosis of UIA with a concurrent bypass procedure were included in the study. Outcomes and hospital charges were analyzed.RESULTSA total of 216,212 patients had a primary diagnosis of UIA during the study period. The number of patients diagnosed with a UIA increased by 128% from 1998 (n = 7718) to 2015 (n = 17,600). Only 1328 of the UIA patients (0.6%) underwent cerebral bypass. The percentage of patients who underwent bypass in the flow diverter era (2010-2015) remained stable at 0.4%. Most patients who underwent bypass were white (51%), were female (62%), had a median household income in the 3rd or 4th quartiles (57%), and had private insurance (51%). The West (33%) and Midwest/North Central regions (30%) had the highest volume of bypasses, whereas the Northeast region had the lowest (15%). Compared to the period 1998-2011, bypass procedures for UIAs in 2012-2015 shifted entirely to urban teaching hospitals (100%) and to an elective basis (77%). The median hospital stay (9 vs 3 days, p < 0.0001), median hospital charges ($186,746 vs $66,361, p < 0.0001), and rate of any complication (51% vs 17%, p < 0.0001) were approximately threefold higher for the UIA patients with bypass than for those without bypass.CONCLUSIONSDespite a significant increase in the diagnosis of UIAs over the 17-year study period, the proportion of bypass procedures performed as part of their treatment has remained stable. Therefore, advances in endovascular aneurysm therapy do not appear to have affected the volume of bypass procedures performed in the UIA population. The authors' findings suggest a potentially ongoing niche for bypass procedures in the contemporary treatment of UIAs.