Comparison between postmortem computed tomography and autopsy in the detection of traumatic head injuries.

INTRODUCTION: The aim of this study was to assess the agreement between postmortem computed tomography (PMCT) and autopsy in detecting traumatic head injuries. MATERIALS AND METHODS: Consecutive cases of death that underwent both unenhanced PMCT and conventional autopsy were collected from our institution database during a period of 3 years and reviewed retrospectively. PMCT images were reviewed for the presence of fractures (cranial vault, skull base, facial bones and atlas/axis) and intracranial hemorrhage. Kappa values were calculated to determine the agreement between PMCT and autopsy reports. RESULTS: 73 cases were included, of which 44 (60%) had head trauma. Agreement between PMCT and autopsy was almost perfect (κ = 0.95) for fractures and substantial (κ = 0.75) for intracranial hemorrhage. PMCT was superior to autopsy in detecting facial bone and upper cervical spine fractures, and intraventricular hemorrhage. However, in some cases thin extra-axial blood collections were missed on PMCT. CONCLUSIONS: The agreement between PMCT and autopsy in detecting traumatic head injuries was good. Using a combination of both techniques increases the quality of postmortem evaluation because more lesions are detected.

Unruptured intracranial aneurysms: An updated review of current concepts for risk factors, detection and management.

The management of patients with unruptured intracranial aneurysms (UIAs) is a complex clinical challenge and constitutes an immense field of research. While a preponderant proportion of these aneurysms never rupture, the consequences of such an event are severe and represent an important healthcare problem. To date, however, the natural history of UIAs is not completely understood and there is no accurate means to discriminate the UIAs that will rupture from those that will not. Yet, a good understanding of the recent evidence and future perspectives is needed when advising a patient with IA to tailor any information to the given patient's level of risk and psychoaffective status. Thus, this review addresses the current concepts of epidemiology, risk factors, detection and management of UIAs.

Can a 15-sec FLAIR replace conventional FLAIR sequence in stroke MR protocols?

BACKGROUND AND PURPOSE: Triage imaging facilitates the timely recognition of acute stroke with prognostic implications. Improvement in MR acquisition speed is needed given the extreme time constraints before treatment. We compared an ultrafast Echo-Planar FLAIR sequence (EPI-FLAIR) and a conventional FLAIR sequence (cFLAIR) for their diagnostic performances and ability to estimate the age of infarction. MATERIAL AND METHODS: Between June and August 2014, 125 consecutive patients (age 69±18 years, 48% men) admitted for a suspicion of acute (≤48-hrs) stroke were explored by both FLAIR sequences at 1.5-Tesla. EPI-FLAIR (15-sec) and cFLAIR (2-min and 15-sec) were compared by two readers, blinded to clinical data. RESULTS: EPI-FLAIR was less prone to kinetic artefacts than cFLAIR (2-3% vs. 23-49% depending on the reader, P<0.001). Diagnostic concordance was excellent for both readers (к>0.9). Amongst 8 hemorrhages, one subarachnoid hemorrhage presenting as a sudden deficit was missed on EPI-FLAIR sequence. Amongst 60 infarctions, cFLAIR and EPI-FLAIR were concordant in 50 (83%), while signal changes were visible on cFLAIR only in the remaining 10 (17%) cases. Amongst the 43 patients with known onset time (n=17 within 4.5hrs), FLAIR-DWI mismatch identified<4.5-hrs infarction with the same sensitivity (65%) using cFLAIR and EPI-FLAIR, but the positive predictive value (PPV) was higher for cFLAIR than for EPI-FLAIR (73% vs. 50%, P=0.008). CONCLUSION: EPI-FLAIR allows a drastic reduction of acquisition time devoted to FLAIR sequence and minimizes motion artifacts. Compared with cFLAIR, it is however associated with increased risk of undiagnosed stroke mimics and lower PPV for identifying<4.5-hrs infarctions.

Susceptibility vessel sign on T2* magnetic resonance imaging and recanalization results of mechanical thrombectomy with stent retrievers: a multicentre cohort study.

BACKGROUND AND PURPOSE: The susceptibility vessel sign (SVS) on T2*-weighted magnetic resonance imaging has been reported in several studies as a negative predictor of early recanalization after intravenous thrombolysis. The meaning of SVS regarding the results of mechanical thrombectomy with stent retrievers was investigated. METHODS: Susceptibility vessel sign presence and length were studied in 153 acute ischaemic stroke patients (82 men; mean ± SD age 59 ± 17 years, baseline National Institutes of Health Stroke Scale score 17.2 ± 6.5) from three stroke centres, treated with either mechanical thrombectomy alone (n = 84) or bridging therapy (n = 69). Variables were compared between recanalizers, defined as thrombolysis in cerebral infarction (TICI) scores ≥2b, and non-recanalizers (TICI<2b). RESULTS: The SVS was present in 113 (73.8%) patients. There was no association between the presence of SVS and recanalization, obtained in 86 (56.2%) patients, in the whole population [odds ratio (OR) 1.24, 95% confidence interval (CI) 0.53-2.92, P = 0.84) and in treatment subgroups (bridging: OR = 0.91, 95% CI 0.29-2.87, P = 1.0; thrombectomy alone: OR = 1.85, 95% CI 0.48-7.16, P = 0.54). However, in SVS+ patients, recanalization decreased with SVS length (OR 0.94 for each additional mm, 95% CI 0.89-0.99; P = 0.02). CONCLUSIONS: The success of recanalization in acute stroke patients treated with stent retrievers was related to thrombus length but not to the presence of SVS.

[Imaging Moya-Moya disease]. / Imagerie du Moya-Moya.

Moya-Moya disease is a rare arterial occlusive disease affecting the internal carotid artery and its branches. It is found in both pediatric and adult populations, and it may lead to severe clinical presentations such as stroke and intracranial hemorrhage. Several surgical procedures have been developed to improve its clinical outcome. Imaging techniques have a key role in management of Moya-Moya disease, as they are necessary for diagnosis, choice of treatment and follow-up. Although catheter angiography remains the diagnostic gold standard, and nuclear-medicine techniques best perform hemodynamic studies, less invasive imaging techniques have become efficient in serving these purposes. Conventional MRI and MR angiography, as well as MR functional and metabolic studies, are now widely used in each stage of disease management, from diagnosis to follow-up. CT scan and Doppler sonography may also help assess severity of disease and effects of treatment. The aim of this review is to clarify the utility, efficiency and latest developments of each imaging modality in management of Moya-Moya disease.

An update on brain imaging in transient ischemic attack.

Neuroimaging is critical in the evaluation of patients with transient ischemic attack (TIA) and MRI is the recommended modality to image an ischemic lesion. The presence of a diffusion (DWI) lesion in a patient with transient neurological symptoms confirms the vascular origin of the deficit and is predictive of a high risk of stroke. Refinement of MR studies including high resolution DWI and perfusion imaging using either MRI or CT further improve the detection of ischemic lesions. Rapid etiological work-up includes non-invasive imaging of cervical and intracranial arteries to search for symptomatic stenosis/occlusion associated with an increased risk of stroke.

MR screening of candidates for thrombolysis: How to identify stroke mimics?

Stroke mimics account for up to a third of suspected strokes. The main causes are epileptic deficit, migraine aura, hypoglycemia, and functional disorders. Accurate recognition of stroke mimics is important for adequate identification of candidates for thrombolysis. This decreases the number of unnecessary treatments and invasive vascular investigations. Correctly identifying the cause of symptoms also avoids delaying proper care. Therefore, this pictorial review focuses on what the radiologist should know about the most common MRI patterns of stroke mimics in the first hours after onset of symptoms. The issues linked to the accurate diagnosis of stroke mimics in the management of candidates for thrombolysis will be discussed.

Does anticoagulation promote mural hematoma growth or delayed occlusion in spontaneous cervical artery dissections?.

BACKGROUND: In case of spontaneous cervical artery dissection (CAD), a medical treatment with anticoagulant or antiplatelet (AP) drugs would avoid the occurrence of an ischemic stroke. Although immediate anticoagulation (AC) is advocated, evidence from randomized trials is lacking. Since CAD is characterized by a mural accumulation of blood, the dissecting hematoma may enlarge under AC, with subsequent lumen narrowing. Although direct evidence of mural hematoma enlargement is lacking in the literature, such a complication may not only be theoretical. Magnetic resonance imaging (MRI) of the mural hematoma on transverse sections through the neck is the current diagnostic gold standard. Our aim was to compare the evolution of the mural hematoma in CAD during the first week after treatment initiation (AP agent: groupAP, AC: groupAC), using dedicated cervical MRI of the arterial wall. METHODS: The study was -approved by the Ethics Committee of Ile de France III. Informed consent was waived. The manuscript was prepared in accordance with the STROBE statement. Fast spin-echo T1-weighted fat-suppressed axial sequences were performed at admission (MRI1) and during the first week after initiation of the treatment (MRI2). Two readers measured volumes, craniocaudal length of the mural hematoma and lumen patency, and searched for early recurrent CAD. They also searched for extension or recurrence of ischemic brain lesions and for hemorrhagic transformation on diffusion-weighted imaging (DWI) and gradient echo T2 (T2*) sequences, respectively. RESULTS: The population included 44 patients (31 in groupAC, 13 in groupAP) with 49 CAD (35 carotid, 14 vertebral). Recurrent CAD and reduction of the lumen did not occur in either group. We did not observe recurrent DWI lesions or occurrence of hemorrhagic transformation. Interobserver agreement [intraclass correlation coefficient (95% CI)] was excellent for volume measurement [0.98 (0.97-0.99) and 0.99 (0.98-1.0) for volume1 and volume2, respectively]. While mean volumes and length of the mural hematoma decreased after treatment in both groups (volume: groupAC -13 ± 22%, groupAP -12 ± 24%, p = 0.33; length: groupAC -10 ± 27%, groupAP -10 ± 20%, p = 0.18), approximately one third of patients in each group had some growth of the mural hematoma as well as an increase in length. CONCLUSION: Limited growth of the mural hematoma was seen with both treatments in approximately one third of patients during the first week after treatment initiation. However, neither AC nor AP agents promote reduction of the lumen or recurrent dissection.

Correlations of cerebello-thalamo-prefrontal structure and neurological soft signs in patients with first-episode psychosis.

OBJECTIVE: This study aimed at determining brain structural imaging correlates of neurological soft signs (NSS) in patients suffering from a first-episode psychosis. METHOD: Fifty-two patients with a DSMIV diagnosis of first-episode psychosis (schizophrenia or schizophrenia spectrum disorder) were consecutively included. Subjects were assessed using a standardized neurological examination for motor coordination, motor integration and sensory integration. Anatomical magnetic resonance images (MRI) were analysed in the whole brain using optimized voxel-based morphometry. RESULTS: Neurological soft signs (NSS) total score (P-corrected = 0.013) and motor integration subscore (P-corrected = 0.035) were found to negatively correlate with grey matter structure of the dorsolateral prefrontal cortices. Motor coordination subscore was positively correlated with grey matter structure of the thalami (P-corrected = 0.002) and negatively with white matter structure of the cerebellum (P-corrected = 0.034). The addition of age and gender as covariate yielded similar results. We did not find any correlation between neither sensory integration subscore and grey matter structure nor NSS total score, motor integration subscore and voxel-based morphometry (VBM) white matter structure. CONCLUSION: Structural alteration in the cerebello-thalamo-prefrontal network is associated with neurological soft signs in schizophrenia, a candidate network for 'cognitive dysmetria'.

DTI-MR tractography of white matter damage in stroke patients with neglect.

Left visual neglect is a dramatic neurological condition that impairs awareness of left-sided events. Neglect has been classically reported after strokes in the territory of the right middle cerebral artery. However, the precise lesional correlates of neglect within this territory remain discussed. Recent evidence strongly suggests an implication of dysfunction of large-scale perisylvian networks in chronic neglect, but the quantitative relationships between neglect signs and damage to white matter (WM) tracts have never been explored. In this prospective study, we used diffusion tensor imaging (DTI) tractography in twelve patients with a vascular stroke in the right hemisphere. Six of these patients showed signs of neglect. Nonparametric voxel-based comparisons between neglect and controls on fractional anisotropy maps revealed clusters in the perisylvian WM and in the external capsule. Individual DTI tractography identified specific disconnections of the fronto-parietal and fronto-occipital pathways in the neglect group. Voxel-based correlation statistics highlighted correlations between patients' performance on two visual search tasks and damage to WM clusters. These clusters were located in the anterior limb of the internal capsule and in the WM underlying the inferior frontal gyrus, along the trajectory of the anterior segment of the arcuate fasciculus (asAF). These results indicate that chronic visual neglect can result from, and correlate with, damage to fronto-parietal connections in the right hemisphere, within large-scale cortical networks important for orienting of spatial attention, arousal and spatial working memory.

[Grading of adults primitive glial neoplasms using arterial spin-labeled perfusion MR imaging]. / Évaluation du degré de malignité des tumeurs gliales primitives de l'adulte en IRM de perfusion par marquage des spins.

PURPOSE: We investigated the relationship between tumor blood-flow measurement based on perfusion-imaging by arterial spin-labeling (ASL) and histopathologic findings in adults' primitive glial tumours. PATIENTS AND METHODS: Thus, 40 primitive brain tumors (8 low-grade and 32 high-grade gliomas according to the Sainte-Anne classification) were imaged using pulsed (n=19) or continuous (n=21) ASL. Relative cerebral blood flow (rCBF=tumoral blood flow/normal cerebral blood flow) between high- and low-grade gliomas were compared. RESULTS: Using pulsed ASL, differences in mean rCBF were observed in high- and low-grade gliomas although no significant (respectively 1.95 and 1.5). Using continuous ASL, mean rCBF were significantly higher for high-grade than for low-grade gliomas (P<0.05). High-grade gliomas could be discriminated using a CBF threshold of 1.18, with a sensitivity of 88%, specificity of 60%, predictive positive value of 88%, and predictive negative value of 60%. CONCLUSION: ASL-based perfusion provides a quantitative, non-invasive alternative to dynamic susceptibility contrast perfusion MR methods for evaluating CBF. ASL is a suitable method for gliomas initial staging and could be useful to identify intermediate tumoral evolution.

[Diffusion-weighted MR imaging of the brain]. / IRM de diffusion et encéphale.

Imaging of water diffusion or diffusion-weighted MR imaging provides physiological information about brain diseases that cannot be obtained from conventional sequences. This technique is very sensitive for the detection of cerebral ischemia from arterial origin and can distinguish cerebral ischemia from other non-vascular brain pathologies in patients presenting with abrupt onset of focal neurological deficit. Diffusion-weighted imaging is used for the evaluation of non-vascular diseases as well. Combined with conventional sequences, it is helpful to differentiate brain abscesses from necrotic tumors. Quantitative diffusion-weighted imaging provides additional information in the characterization of tumors or inflammatory, degenerative and metabolic lesions. Finally, diffusion-weighted imaging data also has prognostic value.

Anatomical and functional MR imaging to define tumoral boundaries and characterize lesions in neuro-oncology.

Neuroimaging and especially MRI has emerged as a necessary imaging modality to detect, measure, characterize and monitor brain tumours. Advanced MRI sequences such as perfusion MRI, diffusion MRI and spectroscopy as well as new post-processing techniques such as automatic segmentation of tumours and radiomics play a crucial role in characterization and follow up of brain tumours. The purpose of this review is to provide an overview on anatomical and functional MRI use for brain tumours boundaries determination and tumour characterization in the specific context of radiotherapy. The usefulness of anatomical and functional MRI on particular challenges posed by radiotherapy such as pseudo progression and pseudo esponse and new treatment strategies such as dose painting is also described.

Three artificial intelligence data challenges based on CT and MRI.

PURPOSE: The second edition of the artificial intelligence (AI) data challenge was organized by the French Society of Radiology with the aim to: (i), work on relevant public health issues; (ii), build large, multicentre, high quality databases; and (iii), include three-dimensional (3D) information and prognostic questions. MATERIALS AND METHODS: Relevant clinical questions were proposed by French subspecialty colleges of radiology. Their feasibility was assessed by experts in the field of AI. A dedicated platform was set up for inclusion centers to safely upload their anonymized examinations in compliance with general data protection regulation. The quality of the database was checked by experts weekly with annotations performed by radiologists. Multidisciplinary teams competed between September 11th and October 13th 2019. RESULTS: Three questions were selected using different imaging and evaluation modalities, including: pulmonary nodule detection and classification from 3D computed tomography (CT), prediction of expanded disability status scale in multiple sclerosis using 3D magnetic resonance imaging (MRI) and segmentation of muscular surface for sarcopenia estimation from two-dimensional CT. A total of 4347 examinations were gathered of which only 6% were excluded. Three independent databases from 24 individual centers were created. A total of 143 participants were split into 20 multidisciplinary teams. CONCLUSION: Three data challenges with over 1200 general data protection regulation compliant CT or MRI examinations each were organized. Future challenges should be made with more complex situations combining histopathological or genetic information to resemble real life situations faced by radiologists in routine practice.

[Clinical and imaging features of diffuse cerebral vasoconstriction]. / Aspects radio cliniques de l'angiopathie cérébrale aiguë réversible.

PURPOSE: To report clinical and imaging features of diffuse cerebral vasoconstriction and to discuss the role of non-invasive imaging modalities for the diagnosis and the follow-up. PATIENTS AND METHODS: Retrospective study including 13 consecutive patients with a diffuse cerebral vasoconstriction. Evaluation of the sensitivity of Doppler US and magnetic resonance angiography for the diagnosis. RESULTS: The diagnosis is based on the association of a thunderclap headache, declenching factors found in 50% of cases and of stenosis involving middle and small cerebra arteries. In some cases cerebral hemorrhage may be present. DISCUSSION: Diffuse cerebral vasoconstriction is a rare cause of thunder clap headhache, which needs to exclude other causes such as subarchnoid hemorrhage from aneurysm rupture. Non contrast CT of the head, frequently normal, may be falsely reassuring. It is therefore necessary to further assess the cerebral arteries to exclude an aneurysm but also to detect the presence of stenoses that would suggest the diagnosis. Non-invasive imaging modalities (MRA and Doppler US) are favored for detection and follow-up of proximal lesions.

Brain networks of spatial awareness: evidence from diffusion tensor imaging tractography.

Left unilateral neglect, a dramatic condition which impairs awareness of left-sided events, has been classically reported after right hemisphere cortical lesions involving the inferior parietal region. More recently, the involvement of long range white matter tracts has been highlighted, consistent with the idea that awareness of events occurring in space depends on the coordinated activity of anatomically distributed brain regions. Damage to the superior longitudinal fasciculus (SLF), linking parietal to frontal cortical regions, or to the inferior longitudinal fasciculus (ILF), connecting occipital and temporal lobes, has been described in neglect patients. In this study, four right-handed patients with right hemisphere strokes underwent a high definition anatomical MRI with diffusion tensor imaging (DTI) sequences and a pencil and paper neglect battery of tests. We used DTI tractography to visualise the SLF, ILF and the inferior fronto-occipital fasciculus (IFOF), a pathway running the depth of the temporal lobe, not hitherto associated with neglect. Two patients with cortical involvement of the inferior parietal and superior temporal regions, but intact and symmetrical fasciculi, showed no signs of neglect. The other two patients with signs of left neglect had superficial damage to the inferior parietal cortex and white matter damage involving the IFOF. These findings suggest that superficial damage to the inferior parietal cortex per se may not be sufficient to produce visual neglect. In some cases, a lesion to the direct connections between ventral occipital and frontal regions (ie, IFOF) may contribute to the manifestation of neglect by impairing the top down modulation of visual areas from the frontal cortex.

Pulsed arterial spin labeling applications in brain tumors: practical review.

Few institutions use MRI perfusion without contrast injection called arterial spins labeling (ASL) routinely in clinical setting. After general considerations concerning the different ASL techniques and quantitative issues, we will detail a pulsed sequence that can be used on a clinical 1.5-T MR unit. We will discuss and illustrate the use of ASL in tumoral diseases for diagnosis, gliomas grading, stereotactic biopsy guidance and for follow-up after treatment.

Unruptured intracranial aneurysms: their illusive natural history and why subgroup statistics cannot provide normative criteria for clinical decisions or selection criteria for a randomized trial.

There is currently no evidence that treatment of unruptured aneurysms is beneficial. Confronted with the uncertainty, many clinicians are attracted by an individual calculus of risks using numbers extracted from subgroup statistics of observational studies or natural history data. The so-called natural history of unruptured aneurysms refers to a purely man-made ratio of events divided by the number of untreated patients identified by imaging, a ratio heavily influenced by referral patterns and arbitrary clinical decisions. Available studies lacked prespecified hypotheses, exposing all analyses to sampling error and bias, and sample sizes were too small to provide reliable subgroup statistics. Far from being "natural kinds" of aneurysms, subgroups were post-hoc creations. Resulting data-driven statistics can only be exploratory, the error too uncontrollable to serve for clinical decisions. A randomized trial is in order, but selection according to fixed size criteria is ill-advised, given the imprecision of imaging, the influence of other factors such as location, previous history, multiplicity of lesions, risks of treatment, age and the danger of arbitrarily excluding from a long trial a large segment of the population with aneurysms for whom the research question is most pertinent.

[High resolution MRI of carotid atherosclerosis: looking beyond the arterial lumen]. / IRM haute résolution de l'athérosclérose carotidienne: au-delà de la lumière artérielle.

Despite advances in diagnosis and treatment, atherosclerosis remains the second cause of death in the world. Due to technical advances, high resolution MRI (HR-MRI) allows depiction of the wall of cervical arteries, especially carotid atherosclerosis. HR-MRI allows visualization of the different components of atherosclerosis: necrotic lipid core, intraplaque hemorrhage, calcifications and fibrous cap. Global plaque volume as well as the volumes of individual plaque components can be calculated. Atherosclerotic plaque structure analysis, along with stenosis measurement, contribute to the stratification of the stroke risk. HR-MRI may also be used to assess treatment efficacy aimed at stabilizing or reducing plaque progression. Beyond the arterial lumen, direct evaluation of vessel wall should modify the management of atherosclerosis in the years to come.