Acute MRI Research Articles

Age-Related Frontal Periventricular White Matter Hyperintensities and miR-92a-3p Are Associated with Early-Onset Post-Stroke Depression.

Objective: To explore the correlationship among white matter hyperintensities (WMHs), miR-92a-3p and early-onset post-stroke depression (PSD).Methods: We recruited consecutively 238 patients with acute cerebral infarction and MRI examination in the Department of neurology, Ruijin hospital, Shanghai Jiaotong University School of Medicine. The diagnosis of early-onset PSD was made in accordance with DSM-IV criteria for depression in 2 weeks after stroke. Clinical information and assessments of stroke severity were recorded on admission. The analysis of plasma miR-92a-3p was performed using quantitative PCR at the same time. WMHs were evaluated by the Fazekas and Scheltens visual rating scales. The relationship among WMHs, miR-92a-3p and PSD were analyzed by SPSS 22.0 software.Results: Logistic regression demonstrated that periventricular WMHs (PVWMHs) in frontal caps was an independent risk factor with early-onset PSD (OR = 1.579, 95% CI: 1.040–2.397, p = 0.032). The age and numbers of lacunes were related to frontal PVWMHs. Plasma miR-92a-3p in the PSD group was higher compared with the non-depressed group. Receiver operating curve analysis revealed that miR-92a-3p could predict early-onset PSD with 90% sensitivity and 90% specificity. The higher miR-92a-3p trended toward association with greater frontal PVWMHs.Conclusion: Acute ischemic stroke patients with frontal PVWMHs or a high plasma miR-92a-3p at baseline were more likely to develop early-onset PSD. MiR-92a-3p might be involved in the white matter impairment and post-stroke depression.

Design and rationale for examining neuroimaging genetics in ischemic stroke: The MRI-GENIE study.

Objective:To describe the design and rationale for the genetic analysis of acute and chronic cerebrovascular neuroimaging phenotypes detected on clinical MRI in patients with acute ischemic stroke (AIS) within the scope of the MRI–GENetics Interface Exploration (MRI-GENIE) study.Methods:MRI-GENIE capitalizes on the existing infrastructure of the Stroke Genetics Network (SiGN). In total, 12 international SiGN sites contributed MRIs of 3,301 patients with AIS. Detailed clinical phenotyping with the web-based Causative Classification of Stroke (CCS) system and genome-wide genotyping data were available for all participants. Neuroimaging analyses include the manual and automated assessments of established MRI markers. A high-throughput MRI analysis pipeline for the automated assessment of cerebrovascular lesions on clinical scans will be developed in a subset of scans for both acute and chronic lesions, validated against gold standard, and applied to all available scans. The extracted neuroimaging phenotypes will improve characterization of acute and chronic cerebrovascular lesions in ischemic stroke, including CCS subtypes, and their effect on functional outcomes after stroke. Moreover, genetic testing will uncover variants associated with acute and chronic MRI manifestations of cerebrovascular disease.Conclusions:The MRI-GENIE study aims to develop, validate, and distribute the MRI analysis platform for scans acquired as part of clinical care for patients with AIS, which will lead to (1) novel genetic discoveries in ischemic stroke, (2) strategies for personalized stroke risk assessment, and (3) personalized stroke outcome assessment.

P2-118. Clinical electroencephalographic study in ten cases with Posterior Reversible Encephalopathy Syndrome (PRES)

Posterior reversible encephalopathy syndrome (PRES) is firstly a reversible vasogenic edema derived from vascular endothelial dysfunction and elevation of blood pressure but is finally an irreversible cytotoxic edema. We retrospectively assessed medical charts and EEG and MRI studies of ten child patients with PRES treated between 2008 and 2015. Onset age are 4–9 (mean 6) year of age. The underlying disorders were hemato-oncologic disease in 5, nephrotic syndrome in 5, Henoch-schonlein purpura in 1 and chronic EBV infection in 1. EEG showed PLEDs (Periodic Lateralized Epileptic Discharges) in 6, diffuse irregular slow in1, normal in 3. MRI of PLEDs group revealed all cytotoxic edema as high signal on DWI and low signal on ADC map. MRI of others showed vasogenic edema as low signal on DWI and high signal on ADC map or only high signal on FLAIR image. All had recovered under regulation of blood pressure. We observed high frequently PLEDs on acute stage and MRI shows cytotoxic edema. By contrast, those who showed vasogenic edema on MRI had no PLEDs. It seemed that presence of PLEDs indicate severity of cell damages. PLEDs sign indicate as a marker of cytotoxic edema on PRES.

Heroin-induced acute myelopathy with extreme high levels of CSF glial fibrillar acidic protein indicating a toxic effect on astrocytes

A man aged 33 years with previous heroin substance abuse was found unconscious lying in a bush. The patient had been without heroin for some time but had just started...

Acute Cardiac MRI Assessment of Radiofrequency Ablation Lesions for Pediatric Ventricular Arrhythmia: Feasibility and Clinical Correlation.

Arrhythmia ablation with current techniques is not universally successful. Inadequate ablation lesion formation may be responsible for some arrhythmia recurrences. Periprocedural visualization of ablation lesions may identify inadequate lesions and gaps to guide further ablation and reduce risk of arrhythmia recurrence. This feasibility study assessed acute postprocedure ablation lesions by MRI, and correlated these findings with clinical outcomes. Ten pediatric patients who underwent ventricular tachycardia ablation were transferred immediately postablation to a 1.5T MRI scanner and late gadolinium enhancement (LGE) imaging was performed to characterize ablation lesions. Immediate and mid-term arrhythmia recurrences were assessed. Patient characteristics include median age 14 years (1-18 years), median weight 52 kg (11-81 kg), normal cardiac anatomy (n = 6), d-transposition of great arteries post arterial switch repair (n = 2), anomalous coronary artery origin post repair (n = 1), and cardiac rhabdomyoma (n = 1). All patients underwent radiofrequency catheter ablation of ventricular arrhythmia with acute procedural success. LGE was identified at the reported ablation site in 9/10 patients, all arrhythmia-free at median 7 months follow-up. LGE was not visible in 1 patient who had recurrence of frequent premature ventricular contractions within 2 hours, confirmed on Holter at 1 and 21 months post procedure. Ventricular ablation lesion visibility by MRI in the acute post procedure setting is feasible. Lesions identifiable with MRI may correlate with clinical outcomes. Acute MRI identification of gaps or inadequate lesions may provide the unique temporal opportunity for additional ablation therapy to decrease arrhythmia recurrence.

Intra- and interrater reliability of three different MRI grading and classification systems after acute hamstring injuries

ObjectiveTo assess and compare the intra- and interrater reliability of three different MRI grading and classification systems after acute hamstring injury. MethodsMale athletes (n=40) with clinical diagnosis of acute hamstring injury and MRI ≤5days were selected from a prospective cohort. Two radiologists independently evaluated the MRIs using standardised scoring form including the modified Peetrons grading system, the Chan acute muscle strain injury classification and the British Athletics Muscle Injury Classification. Intra-and interrater reliability was assessed with linear weighted kappa (κ) or unweighted Cohen's κ and percentage agreement was calculated. ResultsWe observed ‘substantial’ to ‘almost perfect’ intra- (κ range 0.65–1.00) and interrater reliability (κ range 0.77–1.00) with percentage agreement 83–100% and 88–100%, respectively, for severity gradings, overall anatomical sites and overall classifications for the three MRI systems. We observed substantial variability (κ range −0.05 to 1.00) for subcategories within the Chan classification and the British Athletics Muscle Injury Classification, however, the prevalence of positive scorings was low for some subcategories. ConclusionsThe modified Peetrons grading system, overall Chan classification and overall British Athletics Muscle Injury Classification demonstrated ‘substantial' to ‘almost perfect' intra- and interrater reliability when scored by experienced radiologists. The intra- and interrater reliability for the anatomical subcategories within the classifications remains unclear.

Abstract TP37: Negative Diffusion-Weighted Imaging in Mild Ischemic Stroke Patients: An Exploratory Analysis of a Single-Center Six-Year Cohort

Background: DWI-negativity was observed in nearly one third of patients with non-disabling ischemic stroke in a recent study and complete reversal of DWI-positivity was reported in 2% of mild-moderate strokes after IV rtPA treatment. We sought to identify acute DWI-negativity and DWI reversal rates in an independent cohort treated with IV rtPA because of mild stroke symptoms (defined as NIHSS 0-5). Methods: We reviewed a prospective single-center registry of consecutive, IV rtPA-treated patients at Aarhus University Hospital from 2004 to 2010 with a substantial number of strokes with low (0-5) NIHSS scores and reviewed their acute (<4.5 hours) and 24-hour MRI characteristics. Acute MRI is standard stroke work-up imaging at our center (except for patients with MRI contraindications). The local practice was to prefer IV rtPA treatment in mild stroke patients if clinical suspicion was supported by either MRI DWI positivity or other imaging data (MRI-perfusion lesions or visualized arterial occlusions on MRA). Only patients with final diagnoses of ischemic stroke upon hospital discharge were included in this analysis. Results: Among 694 patients treated with IV rtPA from 2004-2010, 266 (38.3%) had NIHSS 0-5. Among these mild stroke patients, 238 received acute MRI and 107 had 24-hour follow-up MRI. Acute DWI-negativity was observed in 32/238 (13.5%; 95% CI 9.4-18.4) patients prior to IV rtPA treatment. Among the cohort with both acute and 24-hour MRIs, acute DWI-negativity was present in 15/107 (14.0%) patients and persisted in 8/15 (53.3%; 95% CI 26.6-78.7). Of 92 DWI-positive patients, only 2/92 (2.1%) became DWI-negative at 24 hours. An association of acute DWI-negativity with younger age (OR 0.98; 95% CI 0.96-1.01) or lower NIHSS (OR 0.90; 95% CI 0.69-1.18) was not found in this cohort. Conclusions: Acute DWI-negativity was observed in ~14% of ischemic strokes with NIHSS 0-5, and half remained negative at 24 hours following IV rtPA. DWI reversal from positive to negative, possibly representing an averted infarction, occurred in 2% of patients. These rates may be lower than the true rate of DWI-negativity and reversal in mild stroke, given limitations of this analysis, including DWI-positivity influencing the initial IV rtPA decision.

Abstract TMP121: Gender Differences in Functional Outcomes After Acute Ischemic Stroke: The Role of White Matter Structural Integrity

Background: Women are known to have worse post-stroke outcomes; however, the underlying mechanisms remain unclear. We evaluated sex-specific clinical and neuroimaging characteristics linked to cerebrovascular brain health in association with functional recovery after acute ischemic stroke (AIS). Methods: We reviewed 316 AIS patients with acute MRI (<48 hours from symptom onset) and modified Rankin scale score (mRS) assessed at 3-6 months post-stroke. Acute infarct volume on diffusion-weighted imaging (DWIv) and white matter hyperintensity volume (WMHv) on FLAIR sequences were determined using a validated semi-automated method. Mean diffusivity (MD) and fractional anisotropy (FA) of normal appearing white matter (NAWM) were derived from the contralesional hemisphere. Wilcoxon rank sum, Spearman correlation, and Fisher’s exact tests were used at p-value <0.05, as appropriate. Results: Women comprised 41.1% of this AIS cohort, and as compared to men, they were older (68 vs. 62.8 years, p = 0.002), had higher prevalence of atrial fibrillation (21.5% vs. 12.4%, p = 0.04), and less tobacco use (21.1% vs. 36.3%, p = 0.03). There was no statistically significant difference between men and women in admission stroke severity, TOAST stroke subtype distribution, DWIv or WMHv. However, women were significantly less likely to have a favorable outcome (mRS <2), as compared to men (53.7% vs. 68.5%, p = 0.01). Both FA (ρ -0.18, p=0.04) and MD (ρ 0.28, p=0.002) values in NAWM correlated with follow-up mRS in women, but only MD (ρ 0.26, p=0.0004) in men. Conclusion: Despite no differences in admission NIHSS, acute infarct size, WMH burden or stroke subtype, women with AIS had significantly worse post-stroke outcomes in our cohort. Our findings suggest that microstructural integrity, as assessed by NAWM diffusivity anisotropy measurements, may represent a neuroimaging correlate of worse outcomes in women. The correlation between markers of white matter microstructural integrity and long-term mRS provides insight into the underlying mechanisms of disease that may influence functional recovery after stroke.

Abstract WP35: Penumbra Saved in Acute Stroke Patients Treated with IV Thrombolysis Predicts Minimal Infarct Growth Independent of Onset to Treatment

Purpose and Hypothesis: The ability to measure the immediate tissue effects in patients treated with thrombolysis ultra-early relative to their known onset has increased. We hypothesized that shorter onset to treatment times (OTT) would lead to more penumbra saved, calculated using multimodal MRI. Methods: Patients were included in this study if they met the following criteria: (1) were admitted between January 2010 and June 1, 2014 at one of two regional stroke centers, (2) had known last seen normal, acute MRI and IV tPA start times, (3) received an admit diagnosis of ischemic stroke, and (4) were treated with standard IV tPA. Penumbral volumes were calculated using the baseline MRI-defined mismatch regions minus the infarcted regions defined by the co-registered DWI at 24 hours. Patients were categorized to the “early” IV tPA cohort if their OTT was ≤ 120 minutes. Infarct growth was quantitatively defined as lesion volume increase > 5 mL from baseline DWI to 5-day FLAIR. Favorable clinical outcome was defined as discharge or later mRS < 2. Results: Sixty-three patients, 23 early- and 40 late-treated, were included in the study with mean age 75 (±15) years, 48% female, median [IQR]: admit NIHSS 10 [5-19], OTT 139 [109-185] minutes, baseline DWI volume 11.2mL [3.5-39.6], baseline MTT volume 120.9mL [37.8-220.7], and baseline mismatch volume 119.3mL [34.6-200.7]. Aside from time-based variables, only the amount of penumbra infarcted at 24 hours (p=0.015) was significantly different between the early- (9mL [1.7-19.7] and late-treated (2.4mL [0.7-7]) cohorts. The patients with favorable outcome were younger (p=0.012) with less severe admit NIHSS (p=0.026), smaller baseline DWI volume (p=0.017), smaller 24 hour DWI volume (p=0.041), and greater percentage of penumbra saved at 24 hours (p=0.010) but no difference in OTT (p=0.267). Using binomial logistic regression, percentage of penumbra saved at 24 hours (95%CI:0.000-0.011, p=0.010) was the only independent predictor of no infarct growth. Conclusions: This study establishes that significantly larger penumbral tissue saved at 24 hours, not early OTT, is predictive of both favorable clinical outcome and no infarct growth.

Abstract TP302: Improvement of Endovascular Stroke Care Performance After Transition From MRI/A to an CTP-based Imaging Protocol

Background and Purpose: The 2015 Focused Update for the Acute Ischemic Stroke Guidelines emphasized the importance of rapid patient selection, optimization of endovascular procedures and organizations of systems of care. Our institution, which has been performing endovascular procedures using a rapid MRI/MRA imaging protocol, transitioned in 2015 to a CT/CTA/CTP imaging protocol. The goal of the study is to evaluate the impact of the transition to CTP on endovascular performance, as measured by door to imaging time and door to skin puncture, and the improvement of the neurological deficit measured by NIHSS difference at admission and discharge. Methods: All endovascular procedures performed from January 2014 to May 2016 were reviewed from our prospective database. CT perfusion was performed with injection of 40 cc iodinated contrast and 40 seconds acquisition time. The CTA images were generated from the CT perfusion. Demographics, endovascular performance and discharged status were obtained. Continuous variables were assessed for normality by the Kolmogorov-Smirnov test. Non-parametric data were reported as median and analysed using the Kruskal-Wallis test or Wilcoxon Ranks test. Results: A total of 91 thrombectomies were initially identified. The median age was 65 (IQR:53-77) with 52% males. 78% were anterior circulation strokes (ACS). Although the overall number of stroke admission remained relatively stable, the proportion of thrombectomies duplicated every year (23/1003 in 2014 vs. 38/1159 in 2015 vs. 32/632 until May 2016). Door to advance imaging median time (52 mins vs 24 mins vs.25 minutes; p=0.023) and door to skin puncture median time (130 mins vs. 100 mins vs. 81 mins; p=0.007) demonstrated significant differences in the ACS. A significant improvement in NIHSS at discharge was noted after implementation of the protocol (18 to 8; p=0.001 in 2015 and 17.5 to 8 in 2016; p=0.006 vs. 14 to 9 in 2014; p=0.777). Conclusion: Transition to CT-based imaging protocols was associated with improvement in the delivery of endovascular acute care in a Comprehensive Center used to acute MRI imaging despite the logistic challenges and lack of familiarity with the new technique. Transition to CT-based imaging is a reasonable approach to improve endovascular care.

Occurrence of Asymptomatic Acute Neuromyelitis Optica Spectrum Disorder-Typical Brain Lesions during an Attack of Optic Neuritis or Myelitis.

We aimed to investigate the frequency of asymptomatic acute brain MRI abnormalities accompanying optic neuritis (ON) or myelitis in neuromyelitis optica spectrum disorder (NMOSD) patients with aquaporin-4 antibodies (AQP4-Ab). We reviewed 324 brain MRI scans that were obtained during acute attacks of ON or myelitis, in 165 NMOSD patients with AQP4-Ab. We observed that acute asymptomatic NMOSD-typical brain lesions accompanied 27 (8%) acute attacks of ON or myelitis in 24 (15%) patients. The most common asymptomatic brain abnormalities included edematous corpus callosum lesions (n = 17), followed by lesions on the internal capsule and/or cerebral peduncle lesions (n = 9), periependymal surfaces of the fourth ventricle (n = 5), large deep white matter lesions (n = 4), periependymal cerebral lesions surrounding the lateral ventricles (n = 3), and hypothalamic lesions (n = 1). If asymptomatic NMOSD-typical brain abnormalities were considered as evidence for DIS, while also assuming that the AQP4-IgG status was unknown, the median time to diagnosis using the 2015 diagnosis criteria for NMOSD was shortened from 28 months to 6 months (p = 0.008). Asymptomatic acute NMOSD-typical brain lesions can be accompanied by an acute attack of ON or myelitis. Identifying these asymptomatic brain lesions may help facilitate earlier diagnosis of NMOSD.

No evidence of ischemia in stroke-like lesions of mitochondrial POLG encephalopathy

Stroke-like lesions are characteristically associated with mitochondrial encephalopathies such as those caused by mutations of polymerase gamma (POLG) and the m.3243A>G mitochondrial DNA (mtDNA) mutation. The combination of acute clinical onset, MRI and pathological abnormalities, have led to the suggestion that these lesions are ischemic. Here, we sought to determine the role of ischemia in the pathogenesis of mitochondrial stroke-like lesions. We performed a systematic study of cerebral blood vessel morphology, density and distribution in post mortem brain tissue from nine patients with POLG-encephalopathy and seven neurologically healthy controls. We found that patients had significantly higher cerebral vascular density than controls: this was more pronounced in areas of chronic neurodegeneration, where vascular density correlated with the severity of neuronal loss, but was also seen in acute lesions. Further, blood vessels were patent and, in acute lesions, dilated suggesting increased perfusion. In contrast to what would be expected in ischemia, stroke-like lesions were not pan-necrotic and were highly vascularized. Our results suggest that ischemia does not contribute to the pathogenesis of either the chronic neurodegeneration or acute lesions in POLG encephalopathy. Neovascularization and vascular dilatation does occur and suggests a compensatory response. We suggested the acute lesions are more likely to reflect energy insufficiency and our earlier studies suggest that this is driven in large part by seizure activity.

115 - Can the Acute MRI Features Reflect Neurological Prognosis in Patients with Cervical Spinal Cord Injury?

PURPOSE: The purpose of the present study was to investigate the relationship between the acute MRI features and neurological prognosis, especially walking ability of patients with cervical spinal cord injury (CSCI). Moreover, at any point, MRI was clearly correlated with the patient's prognosis.

Multi-site laser Doppler flowmetry for assessing collateral flow in experimental ischemic stroke: Validation of outcome prediction with acute MRI

High variability in infarct size is common in experimental stroke models and affects statistical power and validity of neuroprotection trials. The aim of this study was to explore cerebral collateral flow as a stratification factor for the prediction of ischemic outcome. Transient intraluminal occlusion of the middle cerebral artery was induced for 90 min in 18 Wistar rats. Cerebral collateral flow was assessed intra-procedurally using multi-site laser Doppler flowmetry monitoring in both the lateral middle cerebral artery territory and the borderzone territory between middle cerebral artery and anterior cerebral artery. Multi-modal magnetic resonance imaging was used to assess acute ischemic lesion (diffusion-weighted imaging, DWI), acute perfusion deficit (time-to-peak, TTP), and final ischemic lesion at 24 h. Infarct volumes and typology at 24 h (large hemispheric versus basal ganglia infarcts) were predicted by both intra-ischemic collateral perfusion and acute DWI lesion volume. Collateral flow assessed by multi-site laser Doppler flowmetry correlated with the corresponding acute perfusion deficit using TTP maps. Multi-site laser Doppler flowmetry monitoring was able to predict ischemic outcome and perfusion deficit in good agreement with acute MRI. Our results support the additional value of cerebral collateral flow monitoring for outcome prediction in experimental ischemic stroke, especially when acute MRI facilities are not available.

ACR Appropriateness Criteria Head Trauma

Neuroimaging plays an important role in the management of head trauma. Several guidelines have been published for identifying which patients can avoid neuroimaging. Noncontrast head CT is the most appropriate initial examination in patients with minor or mild acute closed head injury who require neuroimaging as well as patients with moderate to severe acute closed head injury. In short-term follow-up neuroimaging of acute traumatic brain injury, CT and MRI may have complementary roles. In subacute to chronic traumatic brain injury, MRI is the most appropriate initial examination, though CT may have a complementary role in select circumstances. Advanced neuroimaging techniques are areas of active research but are not considered routine clinical practice at this time. In suspected intracranial vascular injury, CT angiography or venography or MR angiography or venography is the most appropriate imaging study. In suspected posttraumatic cerebrospinal fluid leak, high-resolution noncontrast skull base CT is the most appropriate initial imaging study to identify the source, with cisternography reserved for problem solving.The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every three years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

Neurogenic Thoracic Outlet Syndrome Presenting as Chronic Elbow Pain After Obstacle Course

HISTORY: A 20-year-old female US Naval Academy freshman sustained a left elbow injury after repetitive shoulder abduction movements while completing a required obstacle course. She denied specific trauma, including a fall. There was no numbness, tingling, or radiation of pain. Five days later, she reported her left elbow pain to her physician. Originally diagnosed with an elbow contusion versus epicondylosis, the patient’s progressive left elbow pain lasted for more than 6 months when she developed ulnar dysesthesias in her hand. PHYSICAL EXAMINATION: Examination revealed diffuse elbow tenderness with swelling. Normal neurovascular examination was demonstrated. Elbow strength and range of motion were normal. Neck and shoulder exams demonstrated no abnormalities. Swelling resolved in one week. Exam remained unchanged for several months before she developed ulnar distribution pain. Then, an Allen test reproduced and worsened her elbow pain and neurologic symptoms. DIFFERENTIAL DIAGNOSIS: 1. Elbow Contusion 2. Chronic Regional Pain Syndrome 3. Intraarticular Body, Elbow Fracture 4. Brachial Plexopathy 5. Thoracic Outlet Syndrome TEST AND RESULTS: Left elbow anterior-posterior, lateral radiographs: — no acute osseous abnormality Left elbow MRI: — likely resolving bony contusion of radial head without evidence of fracture CT Left Elbow: —normal evaluation of the left elbow EMG left upper extremity: —normal electrodiagnostic study Left brachial plexus MRI: —normal left brachial plexus Chest MRI, with contrast: —findings consistent with thoracic outlet syndrome localized to costoclavicular space Left upper extremity venogram: —no evidence of venous occlusion or compression FINAL/WORKING DIAGNOSIS: Neurogenic Thoracic Outlet Syndrome TREATMENT AND OUTCOMES: 1. Relative rest, ice, compression and NSAIDs for 4 weeks without improvement. 2. Activity modification and trial of acupuncture demonstrated minimal improvement in presenting elbow pain. 3. Left scalene block with complete relief of symptoms, indicating neurogenic thoracic outlet syndrome. 4. Partial left first rib resection with resolution of chronic left elbow pain and ulnar nerve dysesthesias. 5. Range of motion, shoulder, and neck strengthening exercises started gradually 6 weeks post-surgery.

Abstract 63: Novel Imaging of Protein Integrity to Better Define Ischemic Injury After Stroke

Introduction: Ischemic injury on MRI is defined acutely by measuring the diffusion of water alone. Chemical exchange saturation transfer imaging (CEST) allows measurement of intracellular pH, and changes in protein structure and mobility using Nuclear Overhauser Enhancement (NOE). When identifying treatment targets, changes to protein integrity have the potential to complement diffusion-weighted imaging (DWI) in distinguishing irreversible from reversible intracellular processes that are amenable to therapeutic intervention. Methods: Patients with non-lacunar ischemic stroke underwent serial MRI over 1 month. The imaging protocol included single slice CEST imaging. NOE was quantified using a 3-pool exchange model relative to the contralateral hemisphere (rNOE*). DWI, ASL perfusion imaging, T1-weighted and FLAIR imaging were used to define the tissue outcome: ischemic core, infarct growth, and oligemic tissue that survived. Infarct growth was classified as early or late (before or after 24 hours). Images and masks were registered to CEST native image space for voxelwise and patient-level serial analyses. Results: 30 patients were included in the analysis. Within 6 hours rNOE* in early infarct growth was significantly lower than ischemic core and late infarct growth (p<0.001 and p<0.001, see Figure). In patient-level analyses, rNOE* dropped over the initial 24 hours in the ischemic core and early infarct growth regions, but not in regions of late infarct growth or oligemia. Conclusion: rNOE* showed a discrete temporal profile in tissue that infarcted by 24 hours in contrast to that which survived or infarcted later. This is additive information to that provided by routine acute stroke MRI at presentation, and demonstrates that the imaging of intracellular protein structure and mobility may have a role alongside DWI in helping to predict tissue fate. Further work is required to understand the potential of NOE as a modifiable imaging biomarker.

Abstract WP43: Advanced White Matter Disease is Associated With Increased Blood-Brain Barrier Permeability and Early Diffuse Microstructural Changes in Patients With Acute Ischemic Stroke

Background: In acute ischemic stroke (AIS), cerebral tissue damage and clinical outcomes are linked to pre-existing microvascular dysfunction, manifesting as white matter hyperintensity (WMH). Elevated blood-brain barrier permeability (BBB-P) has been implicated in advanced WMH. We tested the microstructural integrity of BBB as measured by dynamic susceptibility contrast (DSC) MRI K 2 coefficient values in AIS patients with advanced WMH. Methods: Twenty patients enrolled in a prospective acute MRI study underwent diffusion tensor (DTI) and DSC MRI on admission for AIS. BBB-P estimates were derived from DSC MRI using the K 2 coefficients. Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD) maps were calculated. Mean K 2 , MD, AD, RD and FA values were measured in regions of WMH and normally appearing white matter (NAWM) in the hemisphere contralateral to AIS and compared (two-tailed Student t-Test). WMH volume (WMHv) was assessed on acute FLAIR using a validated semi-automated volumetric protocol. Linear regression was performed to evaluate significant predictors of K 2 , MD, AD, RD, and FA. Correlation analysis was performed (Pearson product-moment). Results: Mean age of subjects was 66 (±10) years, 30% were women, median WMHv 3.5cm 3 [IQR 1.6-7.4]. K 2 values differed significantly between WMH and NAWM (0.32 x10 -3 vs. 1.1 x10 -3 , p<0.03), as did the diffusivity metrics for WMH and NAWM (FA: 0.25 vs 0.38; MD: 1.3 x10 -3 vs 0.84 x10 -3 ; AD: 1.6 x10 -3 vs 1.2 x10 -3 ; RD: 1.14 x10 -3 vs 0.66 x10 -3 ; all p<0.0001). K 2 and RD values were correlated within WMH (R=-0.45, P=0.046) but not in NAWM (R=0.06, P=0.81). Multivariate analysis found systolic BP (SBP) and lnWMHv to be significant predictors of MD (P=0.0009), AD (P=0.002), and RD (P=0.002) in NAWM. Discussion: BBB-P and diffusivity values in patients with AIS and advanced leukoaraiosis differed significantly between WMH and NAWM in the hemisphere contralateral to acute infarct. Association between the RD and K 2 coefficients in WMH suggests the role of BBB-P in pathophysiology of WMH and the loss of microstructural white matter integrity associated with it. Further, the influence of SBP and lnWMHv on NAWM diffusivity values suggests ongoing risk for developing future WMH.

Medulloblastoma of the Cerebellopontine Angle in a Child: A Case Report and Review of the Literature

Cerebellopontine angle medulloblastoma is a very uncommon presentation of medulloblastoma, especially in children. We report such a case in a 14-year-old boy. Clinical onset by acute hearing loss and MRI features were, furthermore, unusual findings. The tumour had an homogeneous signal on T1 and FLAIR sequences a high-signal intensity on diffusion-weighted images with slightly restricted ADC value (0.85 × 10³ mm²/s) and enhanced slightly and homogeneously after contrast. A subtotal removal of the tumour, followed by entire neuroaxis irradiation and chemotherapy were achieved. MRI data of the literature reported cases were reviewed. Features on conventional MRI sequences do not allow differentiating CPA medulloblastoma from other rare tumour of this location. We point out that ADC value and Spectroscopy might be useful differentiating CPA tumours, especially from ependymoma in children.

Prediction of hemorrhagic transformation after experimental ischemic stroke using MRI-based algorithms

Estimation of hemorrhagic transformation (HT) risk is crucial for treatment decision–making after acute ischemic stroke. We aimed to determine the accuracy of multiparametric MRI-based predictive algorithms in calculating probability of HT after stroke. Spontaneously, hypertensive rats were subjected to embolic stroke and, after 3 h treated with tissue plasminogen activator (Group I: n = 6) or vehicle (Group II: n = 7). Brain MRI measurements of T2, T2*, diffusion, perfusion, and blood–brain barrier permeability were obtained at 2, 24, and 168 h post-stroke. Generalized linear model and random forest (RF) predictive algorithms were developed to calculate the probability of HT and infarction from acute MRI data. Validation against seven-day outcome on MRI and histology revealed that highest accuracy of hemorrhage prediction was achieved with a RF-based model that included spatial brain features (Group I: area under the receiver-operating characteristic curve (AUC) = 0.85 ± 0.14; Group II: AUC = 0.89 ± 0.09), with significant improvement over perfusion- or permeability-based thresholding methods. However, overlap between predicted and actual tissue outcome was significantly lower for hemorrhage prediction models (maximum Dice’s Similarity Index (DSI) = 0.20 ± 0.06) than for infarct prediction models (maximum DSI = 0.81 ± 0.06). Multiparametric MRI-based predictive algorithms enable early identification of post-ischemic tissue at risk of HT and may contribute to improved treatment decision-making after acute ischemic stroke.