Sabareesh K. Natarajan

Hemodynamic–Morphologic Discriminants for Intracranial Aneurysm Rupture

Background and Purpose— The purpose of this study was to identify significant morphological and hemodynamic parameters that discriminate intracranial aneurysm rupture status using 3-dimensional angiography and computational fluid dynamics. Methods— One hundred nineteen intracranial aneurysms (38 ruptured, 81 unruptured) were analyzed from 3-dimensional angiographic images and computational fluid dynamics. Six morphological and 7 hemodynamic parameters were evaluated for significance with respect to rupture. Receiver operating characteristic analysis identified area under the curve (AUC) and optimal thresholds separating ruptured from unruptured aneurysms for each parameter. Significant parameters were examined by multivariate logistic regression analysis in 3 predictive models—morphology only, hemodynamics only, and combined—to identify independent discriminants, and the AUC receiver operating characteristic of the predicted probability of rupture status was compared among these models. Results— Morphological parameters (size ratio, undulation index, ellipticity index, and nonsphericity index) and hemodynamic parameters (average wall shear stress [WSS], maximum intra-aneurysmal WSS, low WSS area, average oscillatory shear index, number of vortices, and relative resident time) achieved statistical significance (P<0.01). Multivariate logistic regression analysis demonstrated size ratio to be the only independently significant factor in the morphology model (AUC, 0.83; 95% CI, 0.75 to 0.91), whereas WSS and oscillatory shear index were the only independently significant variables in the hemodynamics model (AUC, 0.85; 95% CI, 0.78 to 0.93). The combined model retained all 3 variables, size ratio, WSS, and oscillatory shear index (AUC, 0.89; 95% CI, 0.82 to 0.96). Conclusion— All 3 models—morphological (based on size ratio), hemodynamic (based on WSS and oscillatory shear index), and combined—discriminate intracranial aneurysm rupture status with high AUC values. Hemodynamics is as important as morphology in discriminating aneurysm rupture status.

Conscious Sedation Versus General Anesthesia During Endovascular Therapy for Acute Anterior Circulation Stroke: Preliminary Results From a Retrospective, Multicenter Study

Background and Purpose— Patients undergoing intra-arterial therapy (IAT) for acute ischemic stroke receive either general anesthesia (GA) or conscious sedation. GA may delay time to treatment, whereas conscious sedation may result in patient movement and compromise the safety of the procedure. We sought to determine whether there were differences in safety and outcomes in GA patients before initiation of IAT. Methods— A cohort of 980 patients at 12 stroke centers underwent IAT for acute stroke between 2005 and 2009. Only patients with anterior circulation strokes due to large-vessel occlusion were included in the study. A binary logistic-regression model was used to determine independent predictors of good outcome and death. Results— The mean age was 66±15 years and median National Institutes of Health Stroke Scale score was 17 (interquartile range, 13–20). The overall recanalization rate was 68% and the symptomatic hemorrhage rate was 9.2%. GA was used in 44% of patients with no differences in intracranial hemorrhage rates when compared with the conscious sedation group. The use of GA was associated with poorer neurologic outcome at 90 days (odds ratio=2.33; 95% CI, 1.63–3.44; P<0.0001) and higher mortality (odds ratio=1.68; 95% CI, 1.23–2.30; P<0.0001) compared with conscious sedation. Conclusions— Patients placed under GA during IAT for anterior circulation stroke appear to have a higher chance of poor neurologic outcome and mortality. There do not appear to be differences in hemorrhagic complications between the 2 groups. Future clinical trials with IAT can help elucidate the etiology of the differences in outcomes.

Patient Outcome at Long-term Follow-up after Aggressive Microsurgical Resection of Cranial Base Chondrosarcomas

OBJECTIVE:To evaluate patient clinical outcome and survival at long-term follow-up after aggressive microsurgical resection of chondrosarcomas of the cranial base. METHODS:Over a 20-year period, 47 patients underwent 72 operative procedures for resection of cranial base chondrosarcomas. Thirty-three patients were previously untreated, whereas 14 patients previously had undergone surgery or radiation. Twenty-three patients had a single operation and 24 underwent staged (more than one) operations because of extensive disease. Patients who underwent subtotal resection also underwent radiotherapy or radiosurgery. Patients were evaluated at follow-up clinically and by imaging studies. RESULTS:Gross total resection was accomplished in 29 (61.7%) patients, and subtotal resection was accomplished in 18 patients (38.3%). The resection was better in patients who underwent a primary operation (gross total resection, 68.8 versus 46.7%) rather than a reoperation. Patients who underwent incomplete resection underwent postoperative radiotherapy, which included proton beam radiotherapy (15.6%), radiosurgery (68%), and fractionated radiation (15.6%). There were no operative deaths. Postoperative complications (cerebrospinal fluid leakage, quadriparesis, infections, cranial nerve palsies, etc.) were observed in 10 patients (18%). The follow-up ranged from 2 to 255 months, with an average of 86 months. At the conclusion of study, 36 (76.6%) patients were alive, and 21 (44.7%) patients were alive without disease. Recurrence-free survival was 32% at 10 years in all patients, 42.3% in primary patients and 13.8% in those who underwent reoperation. The Karnofsky performance score was 82.4 ± 9.8 before surgery, 85 ± 12.5 at 1 year after surgery, and 85.3 ± 5.8 at the latest follow-up. Two patients died as a result of radiotherapy complications (malignancy, radiation necrosis). CONCLUSION:Cranial base chondrosarcomas can be managed well by complete surgical resection or by a combination of surgery and radiotherapy. The study cannot comment about the efficacy of radiotherapy. Approximately half of the patients survived without recurrence at long-term follow-up (>132 mo). The functional status of the surviving patients was excellent at follow-up.

Multimodality treatment of brain arteriovenous malformations with microsurgery after embolization with Onyx: Single-center experience and technical nuances

OBJECTIVETo report our experience with the treatment of brain arteriovenous malformations (AVM) with microsurgical resection after embolization with Onyx liquid embolic agent (eV3, Irvine, CA). METHODSBetween August 2005 and December 2006, 28 patients were treated by the same surgical-endovascular team. Twenty-eight AVMs were embolized preoperatively in 55 sessions (71 pedicles) with Onyx. We analyzed the AVM size, volume, number of embolization sessions, degree of preoperative obliteration, time to embolization and resection after the bleed, intraprocedural complications, intraoperative blood loss, other complications, and postoperative outcome at 6 months. Technical nuances of the embolization and surgical resection of the embolized AVMs are illustrated in illustrative cases. RESULTSThe average size and volume of AVMs treated with Onyx were 3.56 cm (largest, 7.6 cm), and 13.03 ml, respectively. The average Spetzler-Martin grade was 2.75. The average preoperative volumetric obliteration was 74.1%. The average blood loss during resection of embolized AVMs was 348 ml. Complications related to embolization were stuck microcatheter (two patients), proximal vessel perforation (one patient), and anterior choroidal territory stroke (one patient). Surgical complications included wound infection (one patient), residual AVM nidus (one patient), normal pressure perfusion breakthrough with worsening of neurological deficit caused by embolization (one patient), and new-onset motor deficits in five patients. At the time of the 6-month follow-up examination, four patients with new-onset motor deficits had recovered completely or nearly completely, and one patient was disabled. One patient died, never recovering from the initial poor condition due to the bleed. Pathological examination of resected AVMs showed angionecrosis in 42.9%, foreign body giant cells in 39.3%, and evidence of recanalization of Onyx-embolized vessels in 14.3% of specimens. CONCLUSIONMultimodality treatment with microsurgery is safe and effective after embolization with Onyx. High occlusion rates and low complication rates were observed after Onyx embolization and were comparable to those in previous reports. Superselective intranidal or perinidal catheter positions and slow, controlled injections that protect the draining veins make the therapy safe even in complex AVMs and critical locations. We recommend resection of the AVM despite apparently complete embolization with Onyx. Team work and coordination between the surgeon and the interventional neuroradiologist are important to achieve a good outcome.

Safety and Effectiveness of Endovascular Therapy After 8 Hours of Acute Ischemic Stroke Onset and Wake-Up Strokes

Background and Purpose— This is a retrospective review of patients who underwent endovascular recanalization ≥8 hours after acute ischemic stroke symptom onset, including wake-up strokes, between June 2005 and June 2008. Methods— Thirty patients with a premorbid modified Rankin score ≤1 and NIHSS between 5 and 22 were included. All had admission CT, CTA, and CT perfusion scans to evaluate for salvageable brain tissue. Recanalization effectiveness was assessed by angiograms obtained within 30 hours after intervention. Patient, treatment characteristics, and immediate and 3-month outcomes were analyzed. Results— Mean NIHSS at presentation was 13 (median=12). Mean interval between time last-seen well and angiogram was 12.75 hours (median=10). Twenty-six patients (86.7%) presented with complete-to-near-complete vessel occlusion (thrombolysis in myocardial infarction [TIMI] 0/1); 4 had partial vessel occlusion (TIMI 2). Interventions included intra-arterial pharmacological thrombolysis (n=10), mechanical thrombectomy(n=21; Merci, 16; intracranial stent, 9; extracranial stent, 3), angioplasty (n=14; intracranial, 11; extracranial, 3). Nine patients received GPIIb/IIIa inhibitors (eptifibatide); all received heparin. Partial-to-complete recanalization (TIMI 2/3) was achieved in 20 patients (66.7%). Procedure-related complications included vascular perforations (n=3) and femoral access site complication (n=1). One patient had an embolic anterior cerebral artery infarct during intervention; another had progression of brain stem infarct. Symptomatic intracerebral hemorrhage occurred in 3 patients (10%), with 2 being primarily subarachnoid in location. Total in-hospital mortality including procedural mortality, disease progression, or other comorbidities was 23.3% (n=7). Mean discharge NIHSS was 9.5, representing an overall NIHSS 3.5-point improvement. Overall, mean modified Rankin score at death or last follow-up (mean=10.6 months) was 4.2. At 3 months, total mortality was 33.3% (n=10), 20% had modified Rankin score ≤2, and 33% had modified Rankin score ≤3. Among survivors, mean modified Rankin score at 3-month follow-up was 3. Conclusion— Our data show that delayed endovascular revascularization of carefully selected patients is safe, effective, and improves clinical outcome.

Cerebral revascularization for ischemia, aneurysms, and cranial base tumors.

This article extensively reviews the history, indications for bypass, choice of grafts, techniques, complications, and results after cerebral revascularization. The current role and future perspectives of cerebral revascularization are discussed. The results of 295 direct revascularization procedures in 285 patients (130 tumors and 115 aneurysms from 1988 to 2006; 40 cases of ischemia from 1994 to 2006) and 26 pial synangiosis procedures (for moyamoya syndrome in children from 1997 to 2007) have been summarized. Current operative techniques are illustrated with drawings and video clips.

Characterization of Critical Hemodynamics Contributing to Aneurysmal Remodeling at the Basilar Terminus in a Rabbit Model

Background and Purpose— Hemodynamic insult by bilateral common carotid artery ligation has been shown to induce aneurysmal remodeling at the basilar terminus in a rabbit model. To characterize critical hemodynamics that initiate this remodeling, we applied a novel hemodynamics–histology comapping technique. Methods— Eight rabbits received bilateral common carotid artery ligation to increase basilar artery flow. Three underwent sham operations. Hemodynamic insult at the basilar terminus was assessed by computational fluid dynamics. Bifurcation tissue was harvested on day 5; histology was comapped with initial postligation hemodynamic fields of wall shear stress (WSS) and WSS gradient. Results— All bifurcations showed internal elastic lamina loss in periapical regions exposed to accelerating flow with high WSS and positive WSS gradient. Internal elastic lamina damage happened 100% of the time at locations where WSS was >122 Pa and WSS gradient was >530 Pa/mm. The degree of destructive remodeling accounting for internal elastic lamina loss, medial thinning, and luminal bulging correlated with the magnitude of the hemodynamic insult. Conclusions— Aneurysmal remodeling initiates when local hemodynamic forces exceed specific limits at the rabbit basilar terminus. A combination of high WSS and positive WSS gradient represents dangerous hemodynamics likely to induce aneurysmal remodeling.

Delayed thrombosis or stenosis following enterprise-assisted stent-coiling: Is it safe? Midterm results of the interstate collaboration of enterprise stent coiling

BACKGROUND:Stent-assisted coiling of intracranial aneurysms with self-expanding stents has widened the applicability of neuroendovascular therapies to those aneurysms previously considered “uncoilable” because of poor morphology. The Enterprise Vascular Reconstruction Device and Delivery System (Cordis) has demonstrated promising initial short-term results. However, the rates of delayed in-stent stenosis or thrombosis are not known. OBJECTIVE:To report midterm results of the Enterprise stent system. METHODS:A 10-center registry was created to provide a large volume of data on the safety and efficacy of the Enterprise stent system. Pooled data were compiled for consecutive patients undergoing Enterprise stent-assisted coiling at each institution. Available follow-up data were evaluated for the incidence of in-stent stenosis, thrombosis, and aneurysm occlusion. RESULTS:In total, 213 patients (176 females) with 219 aneurysms were treated with the Enterprise stent. One hundred ten patients had undergone delayed angiography (≥30 days from stent placement, mean follow-up 174.6 days). Forty percent of patients demonstrated total occlusion with 88% having ≥90% aneurysm occlusion. Six percent of patients had delayed (>30 days) angiographic findings, of which 3% demonstrated significant (≥50%) in-stent stenosis or occlusion. Seven delayed thrombotic events occurred (3%), along with 2 additional immediate periprocedural events. All 7 delayed events were concomitant to cessation of double-antiplatelet therapy. CONCLUSION:Midterm occlusion rates are excellent, and stenosis and thrombosis rates are comparable to other available neurovascular stents. Interruption of antiplatelet therapy appears to be a factor in those developing delayed stenosis or thrombosis.

Multimodality treatment of intracranial dural arteriovenous fistulas in the Onyx era: a single center experience.

BACKGROUND The results of treatment of intracranial dural arteriovenous fistulas (DAVFs) since Onyx became available as an embolic agent at our institution is reported. An algorithm is presented for treatment of DAVFs with Onyx, and the role of endovascular transvenous, surgical, and radiosurgical approaches are presented. METHODS Thirty-two patients with DAVFs treated between November 2005 and November 2008 by endovascular embolization, surgery, or radiosurgery were identified by a retrospective chart review. Treatment strategies were based on the location or complexity of the fistula and the patients clinical status. Data collected included DAVF characteristics, obliteration rates, complications, and outcomes. The results were analyzed and correlated with the treatment modality. RESULTS Presenting symptoms were as follows: hemorrhage (n = 12 patients), headaches (n = 12), tinnitus (n = 5), orbital symptoms (n = 7), and seizures (n = 1). Thirty patients were treated by endovascular embolization (transarterial only with Onyx-21, transvenous only with platinum coils-6, transarterial [Onyx] and transvenous [coils]-3). Five patients (4 after incomplete/failed embolization) had surgical excision of the fistula. Three patients were treated with Gamma Knife radiosurgery (primary-1, 2 after incomplete/failed embolization). The locations of the fistulas were transverse sigmoid (10 patients), petrotentorial (7 patients), indirect carotid cavernous fistula (7 patients), parasagittal/falcine (3 patients), middle fossa dura (3 patients), torcula (1 patient), and anterior fossa dura (1 patient). The distribution of patients according to Borden classification was I-6, II-13, and III-13. Complete obliteration of the fistula was achieved in 26/32 (81%) patients after multimodal treatment. All surgical cases had complete obliteration. In the high-risk group with cortical venous reflux, 23/26 (89%) patients were cured. Endovascular complications included a stuck microcatheter tip with fracture of the tip in two patients and cranial nerves V and VII palsies in one patient. At last follow-up (range 1-36 months), 24 patients had modified Rankin score of 0-2, 5 patients had modified Rankin score of 3-5, and 3 patients were dead. Two patients died during admission due to the insult of the hemorrhage, and one died after an accidental fall with subsequent traumatic subdural hematoma. CONCLUSIONS Multimodality treatment of DAVFs has high success rates for cure at our center. Transarterial embolization with Onyx has become the primary treatment for intracranial DAVFs at our center and is associated with high safety profile and efficacy. Transvenous coil embolization is still preferred in DAVFs with supply from arterial branches supplying cranial nerves, predominant internal carotid artery feeders and potential extracranial-intracranial collateral anastomosis. In our series, patients with incompletely treated DAVFs were treated with surgery and those with partially treated type I fistulas had radiosurgery for palliation.

High-flow bypass grafts in the management of complex intracranial aneurysms.

The majority of intracranial aneurysms can be treated by either endovascular coiling or microsurgical clipping. A small group of aneurysms may require vascular bypass or reconstruction for their management. A variety of vascular reconstruction techniques are available, including direct suture, patch grafting, local reimplantations, side to side anastomosis, and bypass grafts. Bypass grafts may include low-flow (superficial temporal to middle cerebral) and high-flow bypass grafts using either the radial artery or saphenous vein. In this article, the indications and techniques of high-flow bypasses and concurrent aneurysm management are discussed. Troubleshooting of these bypasses is also illustrated. Seven intraoperative videos have been provided to demonstrate the various techniques of radial artery graft harvesting, cervical exposure of carotid vessels, bypasses, and concurrent aneurysm management.