Ferghal McVerry

Systematic Review of Methods for Assessing Leptomeningeal Collateral Flow

BACKGROUND AND PURPOSE: The importance of LMF in the outcome after acute ischemic stroke is increasingly recognized, but imaging presents a wide range of options for identification of collaterals and there is no single system for grading collateral flow. The aim of this study was to systematically review the literature on the available methods for measuring LMF adequacy. MATERIALS AND METHODS: We performed a systematic review of Ovid, MEDLINE, and Embase databases for studies in which flow in the leptomeningeal collateral vessels was evaluated. Imaging technique, grading scale, and reliability assessment for collateral flow measurement were recorded. RESULTS: We found 81 publications describing 63 methods for grading collateral flow on the basis of conventional angiography (n = 41), CT (n = 7), MR imaging (n = 9), and transcranial Doppler (n = 6). Inter- and/or intraobserver agreement was assessed in only 8 publications. CONCLUSIONS: There is inconsistency in how LMF is graded, with a variety of grading scales and imaging modalities being used. Consistency in evaluating collateral flow at baseline is required for the impact of collateral flow to be fully appreciated.

Clinical relevance and practical implications of trials of perfusion and angiographic imaging in patients with acute ischaemic stroke: a multicentre cohort imaging study

Background In randomised trials testing treatments for acute ischaemic stroke, imaging markers of tissue reperfusion and arterial recanalisation may provide early response indicators. Objective To determine the predictive value of structural, perfusion and angiographic imaging for early and late clinical outcomes and assess practicalities in three comprehensive stroke centres. Methods We recruited patients with potentially disabling stroke in three stroke centres, performed magnetic resonance (MR) or CT, including perfusion and angiography imaging, within 6 h, at 72 h and 1 month after stroke. We assessed the National Institutes of Health Stroke Scale (NIHSS) score serially and functional outcome at 3 months, tested associations between clinical variables and structural imaging, several perfusion parameters and angiography. Results Among 83 patients, median age 71 (maximum 89), median NIHSS 7 (range 1–30), 38 (46%) received alteplase, 41 (49%) had died or were dependent at 3 months. Most baseline imaging was CT (76%); follow-up was MR (79%) despite both being available acutely. At presentation, perfusion lesion size varied considerably between parameters (p<0.0001); 40 (48%) had arterial occlusion. Arterial occlusion and baseline perfusion lesion extent were both associated with baseline NIHSS (p<0.0001). Recanalisation by 72 h was associated with 1 month NIHSS (p=0.0007) and 3 month functional outcome (p=0.048), whereas tissue reperfusion, using even the best perfusion parameter, was not (p=0.11, p=0.08, respectively). Conclusion Early recanalisation on angiography appeared to predict clinical outcome more directly than did tissue reperfusion. Acute assessment with CT and follow-up with MR was practical and feasible, did not preclude image analysis, and would enhance trial recruitment and generalisability of results.

Iodinated Contrast Media and Cerebral Hemorrhage After Intravenous Thrombolysis

Background and Purpose— Iodinated contrast is increasingly used in CT perfusion or angiographic examinations in acute stroke. Increased risk of intracranial hemorrhage (ICH) complicating microcatheter contrast injections has recently been reported in the second Interventional Management of Stroke (IMS 2) trial with contrast toxicity potentially contributory. Methods— We reviewed clinical and radiological data on all patients treated with intravenous alteplase at a single center between May 2003 and November 2008. Results— Of 312 patients treated with intravenous alteplase, 69 (22.1%) received intravenous iodinated contrast in volumes between 50 and 150 mL. Incidence of symptomatic ICH defined as per European Cooperative Acute Stroke Study 2 was 16 of 312 (5.1%; 95% CI, 2.7% to 7.6%); among patients not given contrast, it was 12 of 243 (4.9%; 2.2% to 7.7%) compared with 4 of 69 (5.8%; 0.3% to 11.3%) in those given contrast. Incidence of symptomatic ICH defined as per Safe Implementation of Thrombolysis in Stroke-MOnitoring Study (SITS-MOST) criteria was 12 of 312 (3.9%; 1.7% to 6%), 9 of 243 (3.7%; 1.3% to 6%) among those not given contrast, and 3 of 69 (4.4%; 95% CI, −0.5% to 9.2%) among those given contrast. Patients with symptomatic ICH were older, had higher pretreatment National Institutes of Health Stroke Scale, and blood glucose than those without symptomatic ICH. In logistic regression analysis, pretreatment blood glucose was the only significant predictor of symptomatic ICH by either definition (OR, 1.23; 95% CI, 1.03 to 1.48 per mmol/L increment; P=0.024). Contrast administration or dose was not associated with symptomatic ICH. Conclusions— Intravenous iodinated contrast in doses typically required for CT angiography and perfusion imaging was not associated with symptomatic intracranial hemorrhage in patients treated with alteplase.

Derivation and Evaluation of Thresholds for Core and Tissue at Risk of Infarction Using CT Perfusion

Computed tomography perfusion provides information on tissue viability according to proposed thresholds. We evaluated thresholds for ischemic core and tissue at risk and subsequently tested their accuracy in independent datasets.

Collateral flow predicts outcome after basilar artery occlusion: The posterior circulation collateral score

Background and Aim Our aim was to assess the prognostic value of a semiquantitative computed tomography angiography-based grading system, for the prediction of outcome in patients with acute basilar artery occlusion, based on the presence of potential collateral pathways on computed tomography angiography: the posterior circulation collateral score (PC-CS). Methods One hundred forty-nine patients with acute basilar artery occlusion from the Basilar Artery International Cooperation Study were included. We related poor outcome at one month, defined as a modified Rankin scale score of 4 or 5, or death to collateral flow with Poisson regression. We used a 10 points grading system to quantify the potential for collateral flow in the posterior communicating arteries and the cerebellar arteries. Additionally, the relation between the presence and size of posterior communicating arteries and outcome was analyzed. Results Thirty-six patients had poor (PC-CS: 0–3), 59 patients intermediate (PC-CS: 4–5), and 54 patients good (PC-CS: 6–10) collaterals. Multivariable analyses showed a statistically significant lower risk of poor outcome in patients with a good PC-CS than in patients with a poor PC-CS (risk ratio (RR): 0.74, 95% confidence interval (CI): 0.58–0.96), but not for patients with an intermediate PC-CS compared with patients with a poor PC-CS (RR: 0.95, 95% CI: 0.78–1.15). Multivariable analyses showed a statistically significant lower risk of poor outcome for the presence of at least one posterior communicating artery and for larger caliber of posterior communicating arteries (RR: 0.79, 95% CI: 0.66–0.95 and 0.76, 95% CI: 0.61–0.96, respectively). Conclusions The PC-CS predicted poor outcome at one month. In a separate analysis, both the absence and smaller caliber of posterior communicating arteries predicted poor outcome.

How many stroke patients might be eligible for mechanical thrombectomy

Introduction Recent studies showed improved patient outcomes with endovascular treatment of acute stroke compared to medical care, including IV rtPA, alone. Seven trials have reported results, each using different clinical and imaging criteria for patient selection. We compared eligibility for different trial protocols to estimate the number of patients eligible for treatment. Patients and methods Patient data were extracted from a single centre database that combined patients recruited to three clinical studies, each of which obtained both CTA and CTP within 6 h of stroke onset. The published inclusion and exclusion criteria of seven intervention trials (MR CLEAN, EXTEND–IA, ESCAPE, SWIFT-PRIME, REVASCAT, THERAPY and THRACE) were applied to determine the proportion that would be eligible for each of these studies. Results A total of 263 patients was included. Eligibility for IAT in individual trials ranged from 53% to 3% of patients; 17% were eligible for four trials and under 10% for two trials. Only three patients (1%) were eligible for all studies. The most common cause of exclusion was absence of large artery occlusion (LAO) on CTA. When applying simplified criteria requiring an ASPECT score > 6, 16% were eligible for IAT, but potentially 40% of these patients were excluded by perfusion criteria and more than half by common NIHSS thresholds. Conclusion Around 15% of patients presenting within 6 h of stroke onset were potentially eligible for IAT, but clinical trial eligibility criteria have much more limited overlap than is commonly assumed and only 1% of patients fulfilled criteria for all recent trials.

What is the relationship among penumbra volume, collaterals, and time since onset in the first 6 h after acute ischemic stroke?:

Background The steep, time-dependent loss of benefit from reperfusion in clinical trials is consistent with loss of penumbra over the early hours of ischemia, as observed in animal models. Human imaging studies, however, show persistent penumbra for up to 48 h. We investigated core and penumbra volumes and collateral status in relation to time after stroke onset within the first 6 h. Methods Using data from three multimodal computer tomography-based studies in acute ischemic stroke patients <6 h after onset, we measured core and penumbra volumes, collateral status, and target mismatch (defined as core volume < 50 ml, perfusion lesion volume > 15 ml, mismatch ratio > 1.8). Patients were grouped by onset to imaging time (<3, 3–4.5, 4.5–6 h). We explored correlates of penumbra proportion by multivariable linear regression. Results Analysis included 144 subjects. Across time epochs, neither proportions of penumbra (59%, 64%, 75% at <3, 3–4.5, >4. 5 h, respectively, p = 0.4) nor poor collaterals (15/56 (27%), 14/47 (30%), 4/15 (27%) at <3, 3–4.5, >4.5 h, p = 0.9) differed significantly. Penumbra proportion was not clearly related to time to imaging (R2 = 0.003; p = 0.5) but a trend for divergent effects by collateral status was seen (slight increase in penumbra over time with good collaterals versus reduced with poor, interaction = 0.08). The proportion of patients with target mismatch did not vary by time (56%, 74%, and 67% at <3, 3–4.5, >4.5 h, p = 0.09). Conclusions In a cross-sectional sample imaged within 6 h, neither the proportions of penumbral tissue nor “target mismatch” varied by time from onset. A trend for reducing penumbra proportion only among those with poor collaterals may have pathophysiological and therapeutic importance.

The value of neuroimaging team meetings for patients in a district general hospital

ABSTRACT Neuroradiologists provide quality-assured neuroimaging reports. We developed the use of a neuroimaging team meeting to provide second-opinion reporting by neuroradiologists on neuroimaging that had previously been reported by general radiologists. Neuroimaging from selected patients was reviewed at the meeting. Where there were discrepancies between an original report from a general radiologist and the report obtained from the meeting involving a neuroradiologist, we classified the discrepancies, recorded the scan modality involved and used the data to assess temporal trends in discrepancy rates. Over 4 years, 562 patients (312 women, 250 men, mean age 50.6 [SD 17.3] years) were studied. Agreement occurred for 396 (70.5%) patients. Discrepancies that were not clinically important occurred for 60 (10.7%) patients. Clinically important discrepancies were found for 106 (18.9%) patients: missed lesions for 47 (8.3%) patients and misinterpretations for 59 (10.5%) patients. Cerebrovascular disease was the most common reason for a recommendation of neuroimaging review at a meeting. Scan modality did not influence the frequency of discrepancies. Discrepancy rates decreased with time (chi-squared test for linear trend p=0.015), while the frequency of neuroradiologists’ recommendations for new investigations was stable at one in seven patients. Neuroimaging team meetings can facilitate improvements in neurology diagnoses.

Diagnostic test results in primary CNS vasculitis A systematic review of published cases

Background: Primary CNS vasculitis (PCNSV) can be diagnosed using cerebral angiography or histopathology combined with clinical features. The original diagnostic criteria, which weigh each test equally, have not been validated. Limited sensitivity and specificity for biopsy and angiography are recognized. We systematically reviewed results of diagnostic tests performed in patients with an ultimate diagnosis of PCNSV. Methods: We searched the OVID Medline database and bibliographies for original cases of PCNSV. We recorded demographics, diagnostic tests used, and assessed agreement between angiography and biopsy when both tests were performed. We also recorded MRI and CSF results. Results: We found 701 original cases with PCNSV diagnosed with angiography or pathology. A total of 269 patients (38.4%) had both cerebral angiography and histopathologic testing (biopsy/postmortem). Classic angiographic features of vasculitis were associated with pathologic confirmation in just 32 patients (4.6%). Seventy-four patients (10.6%) with any abnormality on angiography had a normal biopsy, and 99 patients (14.1%) with abnormal biopsies had normal angiography. Brain MRI was abnormal in 505/541 patients (93.3%) and CSF was abnormal in 360/484 patients (74.4%). Increasing use of angiography and decreasing histopathologic testing were found over time. Conclusions: Cerebral angiography and pathologic tissue examination were undertaken in a minority of published cases with a diagnosis of PCNSV. When both diagnostic tests were performed, disagreement between them was more than 5 times more likely than agreement. Diagnostic criteria for PCNSV may require revision to classify the clinical, pathologic, and radiologic features of this condition more accurately.

WHAT DO DIAGNOSTIC TESTS TELL US IN CENTRAL NERVOUS SYSTEM VASCULITIS

Introduction Primary Central Nervous System Vasculitis (PCNSV) can be diagnosed using cerebral angiography and/or biopsy as gold-standard tests. Diagnostic criteria weight each equally but are unvalidated and limited sensitivity and specificity for both tests is recognised. A systematic literature review was undertaken to investigate the performance of diagnostic tests in cases of PCNSV. Methods We searched the OVID Medline database for original cases of PCNSV. We recorded information on diagnostic tests used and assessed agreement between angiography and biopsy as well as ancillary tests. Results 701 original cases of PCNSV were found. Only 248 cases (34%) had both angiography and brain biopsy performed in the same patient. Both tests showed classical vasculitis features in just 32 individual cases (5%). 74 cases with abnormal angiography had normal brain biopsy, while 99 patients with abnormal biopsies had normal cerebral angiography. Brain MRI and CSF were usually abnormal. Conclusion Cerebral angiography and biopsy were performed together in only a minority of published cases of PCNSV. When both were performed, conflicting results from each gold-standard test were much more likely than agreement. The diagnostic criteria for PCNSV require revision in order to classify it correctly and to exclude mimics.