[Show abstract][Hide abstract] ABSTRACT: This pictorial essay highlights the role of the radiologist as a member of the adult epilepsy multidisciplinary team, and gives an overview of MRI-evident epileptogenic lesions.
Journal of Medical Imaging and Radiation Oncology 01/2014; 58(3). DOI:10.1111/1754-9485.12150 · 1.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Changes in collateral blood flow, which sustains brain viability distal to arterial occlusion, may impact infarct evolution but have not previously been demonstrated in humans. We correlated leptomeningeal collateral flow, assessed using novel perfusion magnetic resonance imaging (MRI) processing at baseline and 3 to 5 days, with simultaneous assessment of perfusion parameters. Perfusion raw data were averaged across three consecutive slices to increase leptomeningeal collateral vessel continuity after subtraction of baseline signal analogous to digital subtraction angiography. Changes in collateral quality, Tmax hypoperfusion severity, and infarct growth were assessed between baseline and days 3 to 5 perfusion-diffusion MRI. Acute MRI was analysed for 88 patients imaged 3 to 6 hours after ischemic stroke onset. Better collateral flow at baseline was associated with larger perfusion-diffusion mismatch (Spearman's Rho 0.51, P<0.001) and smaller baseline diffusion lesion volume (Rho -0.70, P<0.001). In 30 patients without reperfusion at day 3 to 5, deterioration in collateral quality between baseline and subacute imaging was strongly associated with absolute (P=0.02) and relative (P<0.001) infarct growth. The deterioration in collateral grade correlated with increased mean Tmax hypoperfusion severity (Rho -0.68, P<0.001). Deterioration in Tmax hypoperfusion severity was also significantly associated with absolute (P=0.003) and relative (P=0.002) infarct growth. Collateral flow is dynamic and failure is associated with infarct growth.Journal of Cerebral Blood Flow & Metabolism advance online publication, 8 May 2013; doi:10.1038/jcbfm.2013.77.
Journal of cerebral blood flow and metabolism: official journal of the International Society of Cerebral Blood Flow and Metabolism 05/2013; 33(8). DOI:10.1038/jcbfm.2013.77 · 5.41 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background and purpose:
Intracerebral hemorrhage growth independently predicts disability and death. We hypothesized that noncontrast quantitative CT densitometry reflects active bleeding and improves predictive models of growth.
Materials and methods:
We analyzed 81 of the 96 available baseline CT scans obtained <3 hours post-ICH from the placebo arm of the phase IIb trial of recombinant factor VIIa. Fifteen scans could not be analyzed for technical reasons, but baseline characteristics were not statistically significantly different. Hounsfield unit histograms for each ICH were generated. Analyzed qCTD parameters included the following: mean, SD, coefficient of variation, skewness (distribution asymmetry), and kurtosis ("peakedness" versus "flatness"). These densitometry parameters were examined in statistical models accounting for baseline volume and time-to-scan.
The coefficient of variation of the ICH attenuation was the most significant individual predictor of hematoma growth (adjusted R(2) = 0.107, P = .002), superior to BV (adjusted R(2) = 0.08, P = .006) or TTS (adjusted R(2) = 0.03, P = .05). The most significant combined model incorporated coefficient of variation, BV, and TTS (adjusted R(2) = 0.202, P = .009 for coefficient of variation) compared with BV and TTS alone (adjusted R(2) = 0.115, P < .05). qCTD increased the number of growth predictions within ±1 mL of actual 24-hour growth by up to 47%.
Heterogeneous ICH attenuation on hyperacute (<3 hours) CT imaging is predictive of subsequent hematoma expansion and may reflect an active bleeding process. Further studies are required to determine whether qCTD can be incorporated into standard imaging protocols for predicting ICH growth.
American Journal of Neuroradiology 01/2013; 34(6). DOI:10.3174/ajnr.A3375 · 3.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Protoplasmic astrocytomas are a poorly recognized and uncommon subtype of astrocytoma. While usually categorized with other low-grade gliomas, there is literature to suggest that protoplasmic astrocytomas have differences in biology compared to other gliomas in this group. This paper presents the MR imaging characteristics of a series of eight protoplasmic astrocytomas.
We retrospectively reviewed MR images and histopathology of eight consecutive cases of histologically proven protoplasmic astrocytomas.
Patients ranged from 17 to 51 years of age with a 5:3 male to female ratio. The tumors were located in the frontal or temporal lobes and tended to be large, well defined, and had a very high signal on T2 (close to cerebrospinal fluid). Generally, a large proportion of the tumor showed substantial signal suppression on T2 fluid-attenuated inversion recovery (FLAIR). Six of the eight lesions also demonstrated a partial or complete rim of reduced apparent diffusion coefficient (ADC) around the T2 FLAIR suppressing portion.
The possibility that a primary cerebral neoplasm represents a protoplasmic astrocytoma should be considered in a patient with a large frontal or temporal tumor that has a very high signal on T2 with a large proportion of the tumor showing substantial T2 FLAIR suppression. A further clue is a partial or complete rim of reduced ADC.
[Show abstract][Hide abstract] ABSTRACT: the Echoplanar Imaging Thrombolytic Evaluation Trial (EPITHET) was a prospective, randomized, double-blinded, placebo-controlled, phase II trial of alteplase between 3 and 6 hours after stroke onset. The primary outcome of infarct growth attenuation on MRI with alteplase in mismatch patients was negative when mismatch volumes were assessed volumetrically, without coregistration, which underestimates mismatch volumes. We hypothesized that assessing the extent of mismatch by coregistration of perfusion and diffusion MRI maps may more accurately allow the effects of alteplase vs placebo to be evaluated.
patients were classified as having mismatch if perfusion-weighted imaging divided by coregistered diffusion-weighted imaging volume ratio was >1.2 and total coregistered mismatch volume was ≥ 10 mL. The primary outcome was a comparison of infarct growth in alteplase vs placebo patients with coregistered mismatch.
of 99 patients with baseline diffusion-weighted imaging and perfusion-weighted imaging, coregistration of both images was possible in 95 patients. Coregistered mismatch was present in 93% (88/95) compared to 85% (81/95) with standard volumetric mismatch. In the coregistered mismatch patients, of whom 45 received alteplase and 43 received placebo, the primary outcome measure of geometric mean infarct growth was significantly attenuated by a ratio of 0.58 with alteplase compared to placebo (1.02 vs 1.77; 95% CI, 0.33-0.99; P=0.0459).
when using coregistration techniques to determine the presence of mismatch at study entry, alteplase significantly attenuated infarct growth. This highlights the necessity for a randomized, placebo-controlled, phase III clinical trial of alteplase using penumbral selection beyond 3 hours.
[Show abstract][Hide abstract] ABSTRACT: Transient ischemic attack (TIA) has recently been redefined to incorporate the latest clinical and neuroimaging information that has shed new light on TIA pathophysiology. Patients suffering from TIA are at a substantial risk of subsequent stroke, but quantifying this risk is difficult as TIA patients are a heterogeneous population and there are multiple TIA mimics. Clinical scores for prediction of stroke risk are principally based on patient history and potentially understate actual risk. Magnetic resonance imaging (MRI), in particular diffusion-weighted imaging (DWI) performed in the first days following TIA, reveals relevant focal ischemic abnormalities in 21-68% of patients. These lesions predict stroke recurrence, functional dependence and subsequent vascular events. Adding imaging information to clinical scores improves prediction of stroke risk following TIA. Alongside clinical judgement, use of MRI has the potential to change the management of TIA patients and is the imaging modality of choice for this condition.
[Show abstract][Hide abstract] ABSTRACT: Background Stents are an alternative treatment to carotid endarterectomy for symptomatic carotid stenosis, but previous trials have not established equivalent safety and efficacy. We compared the safety of carotid artery stenting with that of carotid endarterectomy. Methods The International Carotid Stenting Study (ICSS) is a multicentre, international, randomised controlled trial with blinded adjudication of outcomes. Patients with recently symptomatic carotid artery stenosis were randomly assigned in a 1:1 ratio to receive carotid artery stenting or carotid endarterectomy. Randomisation was by telephone call or fax to a central computerised service and was stratified by centre with minimisation for sex, age, contralateral occlusion, and side of the randomised artery. Patients and investigators were not masked to treatment assignment. Patients were followed up by independent clinicians not directly involved in delivering the randomised treatment. The primary outcome measure of the trial is the 3-year rate of fatal or disabling stroke in any territory, which has not been analysed yet. The main outcome measure for the interim safety analysis was the 120-day rate of stroke, death, or procedural myocardial infarction. Analysis was by intention to treat (ITT). This study is registered, number ISRCTN25337470. Findings The trial enrolled 1713 patients (stenting group, n=855; endarterectomy group, n=858). Two patients in the stenting group and one in the endarterectomy group withdrew immediately after randomisation, and were not included in the ITT analysis. Between randomisation and 120 days, there were 34 (Kaplan-Meier estimate 4.0%) events of disabling stroke or death in the stenting group compared with 27 (3.2%) events in the endarterectomy group (hazard ratio [HR] 1.28, 95% CI 0.77-2.11). The incidence of stroke, death, or procedural myocardial infarction was 8.5% in the stenting group compared with 5.2% in the endarterectomy group (72 vs 44 events; HR 1.69, 1.16-2.45, p=0.006), Risks of any stroke (65 vs 35 events; HR 1.92, 1.27-2.89) and all-cause death (19 vs seven events; HR 2.76, 1.16-6.56) were higher in the stenting group than in the endarterectomy group. Three procedural myocardial infarctions were recorded in the stenting group, all of which were fatal, compared with four, all non-fatal, in the endarterectomy group. There was one event of cranial nerve palsy in the stenting group compared with 45 in the endarterectomy group. There were also fewer haematomas of any severity in the stenting group than in the endarterectomy group (31 vs 50 events; p=0.0197). Interpretation Completion of long-term follow-up is needed to establish the efficacy of carotid artery stenting compared with endarterectomy. In the meantime, carotid endarterectomy should remain the treatment of choice for patients suitable for surgery
The Lancet 01/2010; 375:985. · 45.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Reliable predictors of hemorrhagic transformation (HT) after stroke thrombolysis have not been identified. We analyzed hemorrhage in a randomized trial of tissue plasminogen activator (t-PA) vs placebo in ischemic stroke patients. We hypothesized that acute diffusion-weighted imaging (DWI) lesion volumes would be larger and blood pressures would be higher in patients with HT.
HT was assessed 2 to 5 days after treatment in 97 patients. Hemorrhage was assessed by using susceptibility-weighted imaging sequences and was classified as petechial hemorrhagic infarction (HI) or parenchymal hematoma (PH).
PH was more frequent in t-PA- (11/49) than in placebo- (4/48) treated patients (P=0.049). Patients with PH had larger DWI lesion volumes (63.1+/-56.1 mL) than did those without HT (27.6+/-39.0 mL, P=0.033). There were no differences in baseline systolic blood pressure (SBP) between patients with and without hemorrhage. Weighted average SBP 24 hours after treatment was higher in patients with PH (159.4+/-18.8 mL, P<0.011) relative to those without HT (143.1+/-20.0 mL). Multinomial logistic regression indicated that PH was predicted by DWI lesion volume (odds ratio=1.16 per 10 mL; 95% CI, 1.03 to 1.30), atrial fibrillation (odds ratio=9.33; 95% CI, 2.30 to 37.94), and 24-hour weighted average SBP (odds ratio=1.59 per 10 mm Hg; 95% CI, 1.14 to 2.23).
Pretreatment DWI lesion volume and postthrombolysis BP are both predictive of HT. Consideration should be given to excluding patients with very large baseline DWI volumes from t-PA therapy and to more stringent BP control after stroke thrombolysis.
[Show abstract][Hide abstract] ABSTRACT: Intracerebral hemorrhage (ICH) growth predicts mortality and functional outcome. We hypothesized that irregular hematoma shape and density heterogeneity, reflecting active, multifocal bleeding or a variable bleeding time course, would predict ICH growth.
Three raters examined baseline sub-3-hour CT brain scans of 90 patients in the placebo arm of a Phase IIb trial of recombinant activated Factor VII in ICH. Each rater, blinded to growth data, independently applied novel 5-point categorical scales of density and shape to randomly presented baseline CT images of ICH. Density and shape were defined as either homogeneous/regular (Category 1 to 2) or heterogeneous/irregular (Category 3 to 5). Within- and between-rater reliability was determined for these scales. Growth was assessed as a continuous variable and using 3 binary definitions: (1) any ICH growth; (2) >or=33% or >or=12.5 mL ICH growth; and (3) radial growth >1 mm between baseline and 24-hour CT scan. Patients were divided into tertiles of baseline ICH volume: "small" (0 to 10 mL), "medium" (10 to 25 mL), and "large" (25 to 106 mL).
Inter- and intrarater agreements for the novel scales exceeded 85% (+/-1 category). Median growth was significantly higher in the large-volume group compared with the small group (P<0.001) and in heterogeneous compared with homogeneous ICH (P=0.008). Median growth trended higher in irregular ICHs compared with regular ICHs (P=0.084). Small ICHs were more regularly shaped (43%) than medium (17%) and large (3%) ICHs (P<0.001). Small ICHs were more homogeneous (73%) compared with medium (37%) and large (17%) ICHs (P<0.001). Adjusting for baseline ICH volume and time to scan, density heterogeneity, but not shape irregularity, independently predicted ICH growth (P=0.046) on a continuous growth scale.
Large ICHs were significantly more irregular in shape, heterogeneous in density, and had greater growth. Density heterogeneity independently predicted ICH growth using some definitions.
[Show abstract][Hide abstract] ABSTRACT: Background
Huntington's disease (HD) is an autosomal dominant progressive neurodegenerative disorder characterized by motor, psychiatric, and cognitive dysfunction. One of the main focuses of clinical research now is to define valid and reliable biomarkers of disease onset and progression that can be of use in future treatment trials. Various neuropathological and neuroimaging studies have indicated early involvement of various components of the basal ganglia.
In this study, we examined the sensitivity of three magnetic resonance techniques in detecting basal ganglia pathology. Diffusion tensor imaging (DTI) is an MRI technique that measures indices of passive water diffusion, which is believed to reflect the tissue fiber density, fiber architecture, and uniformity of nerve fiber direction. Proton MRS (1H-MRS) is a non-invasive technique that allows the detection of brain chemicals that contain hydrogen, such as N-Acetyl-aspartate (NAA), choline-containing compounds (CHO), creatine/phosphocreatine (CRE), glutamine, glutamate, myoinositol (mI), and lactate (LAC). Volumetric measures of caudate and putamen can be obtained from structural MRI scans.
We examined 25 HD gene carriers (13 preclinical and 12 early symptomatic) and 20 matched gene negative controls. The three imaging modalities were performed on each subject using a GE Signa 1.5T scanner during one scan session. Six HD gene carriers and two control subjects were scanned twice, two years apart. Clinical measures were also collected.
The H-MRS revealed increased choline/creatine and myoinositol/creatine ratios in the basal ganglia in the symptomatic group and decreased glutamate+glutamine/creatine ratios in the preclinical group. Preliminary DTI analyses suggest reduced anisotropy, measured as fractional anisotropy in the basal ganglia. More detailed DTI results and volumetric data will be presented at the meeting. The sensitivity, limitations of, and relationship between the three MRI imaging modalities in detecting basal ganglia pathology in HD will be discussed. The combination of all three techniques may provide a more powerful tool to predict aspects of the clinical presentation.
[Show abstract][Hide abstract] ABSTRACT: We report the case of a 74-year-old woman who presented with deterioration in gait, short-term memory loss and urinary incontinence. She had a past history of excision of a cervical dermal sinus tract at the age of 5 years. CT scan in 2004 revealed ventriculomegaly and an extremely hypodense ovoid structure lying in the midline low posterior fossa with calcification anteriorly. On MRI, the lesion was hypointense on T1-eighted and hyperintense on T2-weighted images, with incomplete suppression on fluid-attenuated inversion-recovery images and marked restriction on diffusion weighted images. Cerebrospinal fluid isotope study revealed non-communicating hydrocephalus. Posterior fossa crainectomy and removal of the lesion was undertaken. Pathological study revealed a dermoid cyst. Post-operatively, her hydrocephalus persisted and a ventriculo-atrial shunt was inserted with excellent functional recovery.
[Show abstract][Hide abstract] ABSTRACT: Whether intravenous tissue plasminogen activator (alteplase) is effective beyond 3 h after onset of acute ischaemic stroke is unclear. We aimed to test whether alteplase given 3-6 h after stroke onset promotes reperfusion and attenuates infarct growth in patients who have a mismatch in perfusion-weighted MRI (PWI) and diffusion-weighted MRI (DWI).
We prospectively and randomly assigned 101 patients to receive alteplase or placebo 3-6 h after onset of ischaemic stroke. PWI and DWI were done before and 3-5 days after therapy, with T2-weighted MRI at around day 90. The primary endpoint was infarct growth between baseline DWI and the day 90 T2 lesion in mismatch patients. Major secondary endpoints were reperfusion, good neurological outcome, and good functional outcome. Patients, caregivers, and investigators were unaware of treatment allocations. Primary analysis was per protocol. This study is registered with ClinicalTrials.gov, number NCT00238537.
We randomly assigned 52 patients to alteplase and 49 patients to placebo. Mean age was 71.6 years, and median score on the National Institutes of Health stroke scale was 13. 85 of 99 (86%) patients had mismatch of PWI and DWI. The geometric mean infarct growth (exponential of the mean log of relative growth) was 1.24 with alteplase and 1.78 with placebo (ratio 0.69, 95% CI 0.38-1.28; Student's t test p=0.239); the median relative infarct growth was 1.18 with alteplase and 1.79 with placebo (ratio 0.66, 0.36-0.92; Wilcoxon's test p=0.054). Reperfusion was more common with alteplase than with placebo and was associated with less infarct growth (p=0.001), better neurological outcome (p<0.0001), and better functional outcome (p=0.010) than was no reperfusion.
Alteplase was non-significantly associated with lower infarct growth and significantly associated with increased reperfusion in patients who had mismatch. Because reperfusion was associated with improved clinical outcomes, phase III trials beyond 3 h after treatment are warranted.
The Lancet Neurology 04/2008; 7(4):299-309. DOI:10.1016/S1474-4422(08)70044-9 · 21.90 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: For MR perfusion-diffusion (PWI-DWI) mismatch to become routine in thrombolysis patient selection, rapid and reliable assessment tools are required. We examined interrater variability in PWI/DWI volume measurements and developed a rapid assessment tool based on the Alberta Stroke Program Early CT Scores (ASPECTS) system.
DWI and PWI were performed in 35 patients with stroke <6 hours after symptom onset. DWI lesion and PWI (time to peak) volumes were measured with planimetric techniques by 4 raters and the 95% limits of agreement calculated. ASPECT scores were assessed separately by 4 investigators (2 experienced and 2 inexperienced) for DWI (MR DWI scores) and PWI (MR time to peak scores). MR mismatch scores were calculated as MR DWI-MR time to peak scores.
Interobserver variability was much greater for PWI (95% limit of agreement=+/-72.3 mL) than for DWI (95% limit of agreement=+/-12.6 mL). A semiautomated PWI volume (time to peak+2 s) was therefore used to calculate mismatch volume. MR mismatch scores >or=2 predicted 20% PWI-DWI mismatch by volume with mean 78% sensitivity (range, 72% to 84%) and 88% specificity (range, 83% to 90%). There was excellent agreement on mismatch classification using MR mismatch scores between experienced raters (weighted kappa scores of 0.94) with agreement in 34 of 35 cases. Agreement was less consistent between inexperienced raters (weighted kappa=0.49, 28 of 35 cases).
Variability in planimetric mismatch measurements arises primarily from differences in PWI volume assessment. High specificity and interrater reliability may make MR mismatch scores an ideal rapid screening tool for potential thrombolysis patients.