Imaging Triage of Patients with Late-Window (6-24 Hours) Acute Ischemic Stroke: A Comparative Study Using Multiphase CT Angiography versus CT Perfusion.

BACKGROUND AND PURPOSE: The role of collateral imaging in selecting patients for endovascular thrombectomy beyond 6 hours from onset has not been established. To assess the comparative utility of collateral imaging using multiphase CTA in selecting late window patients for EVT. MATERIALS AND METHODS: We used data from a prospective multicenter observational study in which all patients underwent imaging with multiphase CT angiography as well as CTP. Two blinded reviewers evaluated patients' eligibility for endovascular thrombectomy using published collateral imaging (multiphase CTA) criteria compared with CTP using the selection criteria of the Clinical Mismatch in the Triage of Wake Up and Late Presenting Strokes Undergoing Neurointervention with Trevo (DAWN) and Endovascular Therapy Following Imaging Evaluation for Ischemic Stroke 3 (DEFUSE-3) trials. CTP images were processed using automated commercial software. The outcomes of patients eligible for endovascular thrombectomy according to multiphase CTA, DAWN, or DEFUSE-3 criteria were compared using multivariable logistic regression modeling. Model characteristics were compared using the C-statistic for the receiver operating characteristic curve, the Akaike information criterion, and the Bayesian information criterion. RESULTS: Eighty-six patients presented beyond 6 hours from onset/last known well (median, 9.6 hours; interquartile range, 4.1 hours). Thirty-five patients (40.7%) received endovascular thrombectomy, of whom good functional outcome (90-day mRS, 0-2) was achieved in 16/35 (47%). Collateral-based imaging paradigms significantly modified the treatment effect of endovascular thrombectomy on 90-day mRS 0-2 (P interaction = .007). The multiphase CTA-based regression model best fit the data for the 90-day outcome (C-statistic, 0.86; 95% CI, 0.77-0.94) and was associated with the least information loss (Akaike information criterion, 95.7; Bayesian information criterion, 114.9) compared with CTP-based models. CONCLUSIONS: The collateral-based imaging paradigm using multiphase CTA compares well with CTP in selecting patients for endovascular thrombectomy in the late time window.

Dismantling the ability of CT and MRI to identify the target mismatch profile in patients with anterior circulation large vessel occlusion beyond six hours from symptom onset.

PURPOSE: Patients with large vessel occlusion and target mismatch on imaging may be thrombectomy candidates in the extended time window. However, the ability of imaging modalities including non-contrast CT Alberta Stroke Program Early Computed Tomographic Scoring (CT ASPECTS), CT angiography collateral score (CTA-CS), diffusion-weighted MRI ASPECTS (DWI ASPECTS), DWI lesion volume, and DWI volume with clinical deficit (DWI + NIHSS), to identify mismatch is unknown. METHODS: We defined target mismatch as core infarct (DWI volume) of < 70 mL, mismatch volume (tissue with TMax > 6 s) of ≥ 15 mL, and mismatch ratio of ≥ 1.8. Using experimental dismantling design, ability to identify this profile was determined for each imaging modality independently (phase 1) and then with knowledge from preceding modalities (phase 2). We used a generalized mixed model assuming binary distribution with PROC GLIMMIX/SAS for analysis. RESULTS: We identified 32 patients with anterior circulation occlusions, presenting > 6 h from symptom onset, with National Institute of Health Stroke Scale of ≥ 6, who had CT and MR before thrombectomy. Sensitivities for identifying target mismatch increased modestly from 88% for NCCT to 91% with the addition of CTA-CS, and up to 100% for all MR-based modalities. Significant gains in specificity were observed from successive tests (29, 19, and 16% increase for DWI ASPECTS, DWI volume, and DWI + NIHSS, respectively). CONCLUSIONS: The combination of NCCT ASPECTS and CTA-CS has high sensitivity for identifying the target mismatch in the extended time window. However, there are gains in specificity with MRI-based imaging, potentially identifying treatment candidates who may have been excluded based on CT imaging alone.

Imaging of Patients with Suspected Large-Vessel Occlusion at Primary Stroke Centers: Available Modalities and a Suggested Approach.

The overwhelming benefit of endovascular therapy in patients with large-vessel occlusions suggests that more patients will be screened than treated. Some of those patients will be evaluated first at primary stroke centers; this type of evaluation calls for standardizing the imaging approach to minimize delays in assessing, transferring, and treating these patients. Here, we propose that CT angiography (performed at the same time as head CT) should be the minimum imaging approach for all patients with stroke with suspected large-vessel occlusion presenting to primary stroke centers. We discuss some of the implications of this approach and how to facilitate them.

Endovascular treatment of acute carotid occlusion.

OBJECTIVES: Acute cervical carotid occlusion is one of the most challenging scenarios encountered in endovascular stroke treatment. PATIENTS AND METHODS: A retrospective analysis of 11 consecutive non-dissection stroke patients with concomitant cervical carotid and intracranial occlusion treated with intraarterial (IA) mechanical thrombectomy and/or pharmacologic thrombolysis over five years at two academic hospitals was performed. Data was analyzed using Fisher's exact test. RESULTS: Patients included 3 females and 8 males. Average age was 64.7 years (range 30-94 years). All patients had both cervical carotid and intracranial occlusions. Intracranial occlusion involved the internal carotid artery in 7 patients and the middle cerebral artery in 4 patients. All of the patients received intracranial IA Tissue Plasminogen Activator (tPA). Six patients received carotid stents for cervical occlusion as part of their treatment. Five patients received only IA tPA via collateral circulation. Of the patients receiving stents, 5 of 6 (83.3%) had successful recanalization (Thrombolysis in Cerebral Ischemia 2b or 3 flow). Only 1 of 5 (20%) patients who did not receive stents prior to intracranial treatment had successful recanalization. The difference in recanalization rates approached statistical significance (p=.08). There were 4 total in-hospital mortalities: 2 in the group that received stents prior to thrombolysis and 2 in the non-stent group. There were 2 clinically significant hemorrhages in the study, both in the stent group. CONCLUSIONS: Revascularization of the cervical carotid occlusion prior to treatment of the intracranial occlusion led to increased rates of recanalization in patients with tandem extracranial and intracranial occlusions. Whether a clinical benefit can be consistently derived likely relies on other factors, including the evaluation of cerebral perfusion.

The clinical and radiographic importance of distinguishing partial from near-complete reperfusion following intra-arterial stroke therapy.

BACKGROUND AND PURPOSE: Reperfusion following intra-arterial stroke therapy is associated with improved clinical outcomes. However, the degree of reperfusion needed to achieve successful outcomes is unknown. The purpose of this analysis was to determine whether the degree of reperfusion has an impact on final infarct volumes and clinical outcomes. MATERIALS AND METHODS: A retrospective analysis identified 88 consecutive patients who underwent intra-arterial therapy for acute anterior circulation stroke. Reperfusion was graded by using the TICI scale into none (TICI 0 or 1), partial (TICI 2a), or near-complete (TICI 2b/3). Baseline characteristics were compared. For each of these groups, we compared discharge disposition and final infarct volumes. RESULTS: Near-complete, partial, and no reperfusion occurred in 44.3%, 26.1%, and 29.6% of patients, respectively. Baseline characteristics were similar across all 3 groups. The median NIHSS score was 15. Significant differences in discharge disposition were seen, with 41.0% of the TICI 2b/3 group discharged home versus 17.4% of TICI 2a and 7.7% of TICI 0/1. In-hospital mortality was 12.8% for TICI 2b/3 compared with 39.1% for TICI 2a and 34.6% for TICI 0/1. Patients with near-complete reperfusion were significantly more likely to have infarct volumes ≤70 mL (OR = 12.1; 95% CI, 2.7-54.2), compared with patients with partial reperfusion (OR = 2.2; 95% CI, 0.5-9.6). CONCLUSIONS: Significant differences exist in outcomes and infarct volumes between partial (TICI 2a) and near-complete (TICI 2b/3) reperfusion following intra-arterial stroke therapy. Further trials should separately report these groups to facilitate comparison among treatment paradigms.

Clinical stroke penumbra: use of National Institutes of Health stroke scale as a surrogate for CT perfusion in patient triage for intra-arterial middle cerebral artery stroke therapy.

BACKGROUND AND PURPOSE: CTP may help triage acute stroke patients for IAT, but requires additional contrast agent, radiation, and imaging time. Our aim was to determine whether clinical examination (NIHSS) with NCCT and CTA can substitute for CTP without significantly affecting IAT triage of patients with acute MCA stroke. MATERIALS AND METHODS: We reviewed NCCT, CTA, and CTP imaging performed within 8 hours of symptom onset in 36 patients presenting with MCA territory stroke (September 2007-October 2009). Two neuroradiologists reviewed, independently and by consensus, NCCT, CTA, and CTP (CTP group), and 2 different neuroradiologists blinded to CTP reviewed NCCT, CTA, and NIHSS (stroke scale group) to determine IAT eligibility: M1 or proximal M2 occlusion; infarct core <1/3 MCA territory; and ischemic penumbra >20% infarct core. The stroke scale group estimated infarct core from NCCT and CTA source images and ischemic penumbra from core size relative to NIHSS score and re-evaluated patients after unblinding to CTP. We computed intragroup and intergroup κ scores for IAT treatment recommendation and used the McNemar test to determine whether CTP significantly affected the stroke scale group's decisions. RESULTS: IAT was recommended in 16/36 (44%) and 17/36 (47%) patients by the CTP and stroke scale groups, respectively, with intragroup κ scores of 0.78 ± 0.11 versus 0.83 ± 0.09. The intergroup κ score was 0.83 ± 0.09. When unblinded to CTP, the stroke scale group revised 2/36 (5.6%) decisions, which was insignificant (P = .48, McNemar test). CONCLUSIONS: NIHSS interpreted with NCCT and CTA may be an effective substitute for CTP-derived measures in the IAT triage of patients with acute MCA stroke. Replacing CTP may potentially reduce radiation and contrast dose and time to treatment.

Incidence of extrinsic compression of the internal jugular vein in unselected patients undergoing CT angiography.

BACKGROUND AND PURPOSE: Little is known about how commonly the internal jugular vein is compressed by extrinsic structures in the upper neck. The purpose of this paper was to identify the frequency and cause of external compression of the superior segment of the internal jugular vein. MATERIALS AND METHODS: Retrospective review of CT angiograms of the neck was performed in 108 consecutive patients. Axial source images were evaluated for moderate (>50%) or severe (>80%) stenosis of the internal jugular vein on the basis of external compression. The cause of extrinsic compression was also recorded. In cases with stenosis, the presence of ipsilateral isoattenuated collateral veins was recorded and considered representative of collateral flow. RESULTS: Moderate stenosis was seen in 33.3% of right and 25.9% of left internal jugular veins. Severe stenosis was seen in 24.1% of right and 18.5% of left internal jugular veins. The most common causes of extrinsic compression included the styloid process and the posterior belly of the digastric muscle. In patients with severe internal jugular vein stenosis, 53.8% of right sides and 55% of left sides had associated condylar collaterals. CONCLUSIONS: Extrinsic compression of the superior segment of the internal jugular vein is a common finding in unselected patients, often caused by the styloid process or the posterior belly of the digastric muscle. Presence of severe stenosis is not universally associated with collateral formation.

StarClose vascular closure device: safety and efficacy of deployment and reaccess in a neurointerventional radiology service.

BACKGROUND AND PURPOSE: Obtaining safe and effective closure of the femoral access site following neurointerventional procedures can sometimes be challenging, especially in patients on anti-coagulation or anti-platelet therapy. The purpose of this study was to evaluate the safety and efficacy of a novel percutaneous closure device that employs a nitinol clip-mediated extravascular closure strategy following neurointerventional procedures. MATERIALS AND METHODS: We performed a retrospective review of all patients who underwent neurointerventional procedures at our institution between January 1, 2006 and December 31, 2008. We evaluated the safety and efficacy of the StarClose device in patients undergoing first and repeat procedures. Groin complications were classified as self-limited hematoma, hematoma requiring transfusion, other/minor (pseudoaneurysm, infection), and other/major (vascular complication). RESULTS: StarClose device use was attempted in 281 of 352 cases (79.8%) with success reported in 269 cases (95.7%). Minor and major complications occurred in 0.7% and 0.4% of patients, respectively. There was one major vascular complication. Repeat use was performed in 84 patients with 100% success and a 2.3% minor complication rate. Time to reaccess ranged from 1 to 1036 days (mean, 105 days). CONCLUSIONS: The StarClose device achieves rapid and safe femoral arterial closure in patients, both for primary closure and after reaccess.

Cerebellar pial arteriovenous malformations presenting with medullary venous hypertension: imaging and endovascular treatment.

A patient in their 60s presented with headache and progressive lower extremity weakness over 1 week. Initial MRI was thought to represent venous hypertension secondary to a dural arteriovenous fistula. However, angiography revealed a cerebellar pial arteriovenous malformation with medullary venous hypertension. The imaging and endovascular treatment of this unusual case of a pial cerebellar arteriovenous malformation presenting in that manner is presented.

Flow instability and wall shear stress variation in intracranial aneurysms.

We investigate the flow dynamics and oscillatory behaviour of wall shear stress (WSS) vectors in intracranial aneurysms using high resolution numerical simulations. We analyse three representative patient-specific internal carotid arteries laden with aneurysms of different characteristics: (i) a wide-necked saccular aneurysm, (ii) a narrower-necked saccular aneurysm, and (iii) a case with two adjacent saccular aneurysms. Our simulations show that the pulsatile flow in aneurysms can be subject to a hydrodynamic instability during the decelerating systolic phase resulting in a high-frequency oscillation in the range of 20-50 Hz, even when the blood flow rate in the parent vessel is as low as 150 and 250 ml min(-1) for cases (iii) and (i), respectively. The flow returns to its original laminar pulsatile state near the end of diastole. When the aneurysmal flow becomes unstable, both the magnitude and the directions of WSS vectors fluctuate at the aforementioned high frequencies. In particular, the WSS vectors around the flow impingement region exhibit significant spatio-temporal changes in direction as well as in magnitude.

An easily identifiable anatomic landmark for fluoroscopically guided sacroplasty: anatomic description and validation with treatment in 13 patients.

BACKGROUND AND PURPOSE: Percutaneous sacroplasty has recently gained attention as a potential treatment for sacral insufficiency fractures. We describe a readily identifiable fluoroscopic landmark that facilitates needle placement and validate this with virtual needle placement by using CT data and fluoroscopically guided treatment in 13 patients. MATERIALS AND METHODS: From CTs of 100 consecutive patients, the optimal target zone for needle placement in the sacral ala was defined at the intersection of lines from each of the corners of the first sacral segment, which is readily identifiable on lateral fluoroscopy. We then measured the distance from that virtual target point to the anterior sacral cortex by using the CT data for 3 specific trajectories: 1) parallel to the L5-S1 disk, 2) axial with respect to the patient, and 3) along the long axis of the sacrum. Case records of 13 consecutive patients treated by using this technique were also reviewed. RESULTS: The mean distances for the 3 trajectories were 11.3 mm, 11.2 mm, and 12.8 mm, respectively. Needle placement would have been outside the anterior sacral cortex in 3 patients. Review of preprocedure imaging easily identified this potential breach. During treatment, needle placement by using the landmark was successful in all patients, and there were no complications. CONCLUSIONS: A safe target for sacroplasty needle placement in the superolateral sacral ala can be defined by using the intersection of lines drawn from the corners of the first sacral segment. We validated this landmark by using it for treatment in 13 patients. Further studies evaluating clinical outcomes following sacroplasty will be necessary.

Safety of intravenous heparin administration after endovascular treatment for ruptured intracranial aneurysms.

INTRODUCTION: Thromboembolic events are the primary complications encountered during endovascular treatment (EVT) of intracranial aneurysms. Intraprocedural heparinization is common during EVT but is less common post-procedure. The safety of heparinization following EVT is unknown, especially for ruptured aneurysms. MATERIALS AND METHODS: The records of 138 consecutive patients at our institution from 1 January 2000 to 30 June 2007 who were treated with EVT for 140 ruptured intracranial aneurysms were reviewed. All patients were treated with low dose intravenous heparin post-procedure for 24 h as per the departmental protocol. Cases of worsening hemorrhage requiring surgical evacuation were considered significant hemorrhages. Prior surgical exploration and external ventricular drain (EVD) placement were also noted. RESULTS: There were two cases (1.4%) of significant worsening hemorrhage during post-procedure heparin administration. Among 13 patients who underwent craniotomy (for hematoma evacuation or attempted surgical clipping) prior to EVT, there was one (7.7%) case of significant hemorrhage. Among the 60 patients who underwent EVD placement prior to EVT, there was one (1.7%) case of significant hemorrhage. CONCLUSION: Administration of systemic heparinization may be safe during the first 24 h post-EVT of a ruptured intracranial aneurysm in patients without recent craniotomy. Further study in determining the benefit of this protocol in reducing post-embolization thromboembolic complications may be warranted.

Neurologic complications of arteriovenous malformation embolization using liquid embolic agents.

BACKGROUND AND PURPOSE: Embolization of arteriovenous malformations (AVMs) is commonly used to achieve nidal volume reduction before microsurgical resection or stereotactic radiosurgery. The purpose of this study was to examine the overall neurologic complication rate in patients undergoing AVM embolization and analyze the factors that may determine increased risk. MATERIALS AND METHODS: We performed a retrospective review of all patients with brain AVMs embolized at 1 center from 1995 through 2005. Demographics, including age, sex, presenting symptoms, and clinical condition, were recorded. Angiographic factors including maximal nidal size, presence of deep venous drainage, and involvement of eloquent cortex were also recorded. For each embolization session, the agent used, number of pedicles embolized, the percentage of nidal obliteration, and any complications were recorded. Complications were classified as the following: none, non-neurologic (mild), transient neurologic deficit, and permanent nondisabling and permanent disabling deficits. The permanent complications were also classified as ischemic or hemorrhagic. Modified Rankin Scale (mRS) scores were collected pre- and postembolization on all patients. Univariate regression analysis of factors associated with the development of any neurologic complication was performed. RESULTS: Four hundred eighty-nine embolization procedures were performed in 192 patients. There were 6 Spetzler-Martin grade I (3.1%), 26 grade II (13.5%), 71 grade III (37.0%), 57 grade IV (29.7%), and 32 grade V (16.7%) AVMs. Permanent nondisabling complications occurred in 5 patients (2.6%) and permanent disabling complications or deaths occurred in 3 (1.6%). In addition, there were non-neurologic complications in 4 patients (2.1%) and transient neurologic deficits in 22 (11.5%). Five of the 8 permanent complications (2.6% overall) were ischemic, and 3 of 8 (1.6% overall) were hemorrhagic. Of the 178 patients who were mRS 0-2 pre-embolization, 4 (2.3%) were dependent or dead (mRS >2) at follow-up. Univariate analysis of risk factors for permanent neurologic deficits following embolization showed that basal ganglia location was weakly associated with a new postembolization neurologic deficit. CONCLUSION: Embolization of brain AVMs can be performed with a high degree of technical success and a low rate of permanent neurologic complications.

Treatment of traumatic cervical arteriovenous fistulas with N-butyl-2-cyanoacrylate.

We report 2 cases of traumatic arteriovenous fistulas in the neck treated with transarterial embolization with n-butyl-2-cyanoacrylate (n-BCA). In both cases, covered stent placement across the fistula to preserve the artery was not possible. Detachable coil placement was attempted in one case but was not successful. Both fistulas were successfully treated with n-BCA embolization. To our knowledge, these are the first 2 such cases reported of high-flow cervical arteriovenous fistulas treated with n-BCA embolization.

Multi-detector CT angiography of the intra-cranial circulation: normal anatomy and pathology with angiographic correlation.

Multidetector computed tomography angiography (MD-CTA) of the intra-cranial circulation shows great potential in the evaluation of intra-cranial vascular disease. Interpreting these studies requires a detailed knowledge of the technique, its advantages and disadvantages, as well as a strong understanding of normal intra-cranial vascular anatomy. The purpose of this review is to describe the technique for MD-CTA, demonstrate normal anatomy, anatomic variants and vascular pathology with an emphasis on aneurysms.