Pseudocystic inflammatory demyelinating lesions in multiple sclerosis: A clinical, radiological, and pathological description.

BACKGROUND: Pseudocystic inflammatory demyelinating lesions (PIDLs) are poorly described in MS and might represent a diagnostic challenge. OBJECTIVES: We described the clinical, radiological, pathological, and follow-up characteristics of 13 PIDL in 9 MS patients. METHODS: We constituted a single-center retrospective case series of PIDLs in MS, defined on MRI as expansive cyst-like lesions, with a fluid-signal content, and a diameter of 1 cm or more. RESULTS: PIDL often occurred at first event (56%), were often asymptomatic (69%), and encircled by a hypo-T2 diffusion-restricted rim and a thin ring-like gadolinium enhancement (100%) on magnetic resonance imaging (MRI). Associated typical MS lesions were constant. Biopsies from two PIDLs displayed classical features of active MS, except for unusual edema. CONCLUSION: PIDLs are clinically unremarkable and associated with a good outcome. Their easily recognizable MRI features could help avoid biopsy.

White matter hyperintensities in Alzheimer's disease: Beyond vascular contribution.

White matter hyperintensities (WMH), frequently seen in older adults, are usually considered vascular lesions, and participate in the vascular contribution to cognitive impairment and dementia. However, emerging evidence highlights the heterogeneity of WMH pathophysiology, suggesting that non-vascular mechanisms could also be involved, notably in Alzheimer's disease (AD). This led to the alternative hypothesis that in AD, part of WMH may be secondary to AD-related processes. The current perspective brings together the arguments from different fields of research, including neuropathology, neuroimaging and fluid biomarkers, and genetics, in favor of this alternative hypothesis. Possible underlying mechanisms leading to AD-related WMH, such as AD-related neurodegeneration or neuroinflammation, are discussed, as well as implications for diagnostic criteria and management of AD. We finally discuss ways to test this hypothesis and remaining challenges. Acknowledging the heterogeneity of WMH and the existence of AD-related WMH may improve personalized diagnosis and care of patients.

Contribution of diffusion-weighted imaging to distinguish herpetic encephalitis from auto-immune encephalitis at an early stage.

OBJECTIVES: To determine whether diffusion-weighted imaging (DWI) can help to distinguish early stage autoimmune (AI) and herpes simplex virus (HSV) encephalitides. METHODS: This case-control study included patients from a multi-center cohort of AI encephalitides whose initial MRI including DWI was performed within ten days after symptoms onset. They were compared with patients with HSV encephalitis enrolled prospectively in a single-center from June, 2020 to December, 2020. The final diagnosis of AI encephalitis required a positive autoantibody assay, and that of HSV encephalitis required a positive HSV polymerase chain reaction based on cerebrospinal fluid. Brain MRI were evaluated for restricted diffusion, fluid-inversion recovery (FLAIR) abnormalities, lesion topography, hemorrhagic changes, and contrast enhancement. RESULTS: Forty-nine patients were included of which, 19 (38.8%) had AI encephalitis. Twenty-seven patients (55.1%) were males and the median age was 46.0 years (interquartile range (IQR):[22.0; 65.0]). Brain MRI were performed after a median of 4 days (IQR:[2.0; 7.0]) of symptom onset and time between symptom onset and MRI was not significantly different (p = 0.60). Twenty-six patients had restricted diffusion lesions in the medial temporal lobe, including 25/30 in the HSV encephalitis group (p < 0.001). FLAIR abnormalities were observed in 36 patients, including 29/30 in the HSV encephalitis group (p < 0.001). Lesion topography, hemorrhagic changes, and contrast enhancement did not differ significantly between the two groups. CONCLUSION: Our results suggest that restricted diffusion lesions in the medial temporal lobe are a hallmark of HSV encephalitis and may help distinguish it from early-stage AI encephalitis.

Cerebral perfusion using ASL in patients with COVID-19 and neurological manifestations: A retrospective multicenter observational study.

BACKGROUND AND PURPOSE: Cerebral hypoperfusion has been reported in patients with COVID-19 and neurological manifestations in small cohorts. We aimed to systematically assess changes in cerebral perfusion in a cohort of 59 of these patients, with or without abnormalities on morphological MRI sequences. METHODS: Patients with biologically-confirmed COVID-19 and neurological manifestations undergoing a brain MRI with technically adequate arterial spin labeling (ASL) perfusion were included in this retrospective multicenter study. ASL maps were jointly reviewed by two readers blinded to clinical data. They assessed abnormal perfusion in four regions of interest in each brain hemisphere: frontal lobe, parietal lobe, posterior temporal lobe, and temporal pole extended to the amygdalo-hippocampal complex. RESULTS: Fifty-nine patients (44 men (75%), mean age 61.2 years) were included. Most patients had a severe COVID-19, 57 (97%) needed oxygen therapy and 43 (73%) were hospitalized in intensive care unit at the time of MRI. Morphological brain MRI was abnormal in 44 (75%) patients. ASL perfusion was abnormal in 53 (90%) patients, and particularly in all patients with normal morphological MRI. Hypoperfusion occurred in 48 (81%) patients, mostly in temporal poles (52 (44%)) and frontal lobes (40 (34%)). Hyperperfusion occurred in 9 (15%) patients and was closely associated with post-contrast FLAIR leptomeningeal enhancement (100% [66.4%-100%] of hyperperfusion with enhancement versus 28.6% [16.6%-43.2%] without, p = 0.002). Studied clinical parameters (especially sedation) and other morphological MRI anomalies had no significant impact on perfusion anomalies. CONCLUSION: Brain ASL perfusion showed hypoperfusion in more than 80% of patients with severe COVID-19, with or without visible lesion on conventional MRI abnormalities.

Leptomeningeal enhancement on post-contrast FLAIR images for early diagnosis of Susac syndrome.

BACKGROUND: Leptomeningeal enhancement (LME) is a key feature of Susac syndrome (SuS) but is only occasionally depicted on post-contrast T1-weighted images (T1-WI). OBJECTIVE: As post-contrast fluid-attenuated inversion recovery (FLAIR) may be more sensitive, our aim was to assess LME in SuS on this sequence. METHODS: From 2010 to 2020, 20 patients with definite SuS diagnosis were retrospectively enrolled in this multicentre study. Two radiologists independently assessed the number of LME on post-contrast FLAIR and T1-WI acquisitions performed before any treatment. A chi-square test was used to compare both sequences and the interrater agreement was calculated. RESULTS: Thirty-five magnetic resonance imagings (MRIs) were performed before treatment, including 19 post-contrast FLAIR images in 17 patients and 25 post-contrast T1-WI in 19 patients. In terms of patients, LME was observed on all post-contrast FLAIR, contrary to post-contrast T1-WI (17/17 (100%) vs. 15/19 (79%), p < 0.05). In terms of sequences, LME was observed on all post-contrast FLAIR, contrary to post-contrast T1-WI (19/19 (100%) vs. 16/25 (64%), p < 0.005). LME was disseminated at both supratentorial (19/19) and infratentorial (18/19) levels on post-contrast FLAIR, contrary to post-contrast T1-WI (3/25 and 9/25, respectively). Interrater agreement was excellent for post-contrast FLAIR (κ = 0.95) but only moderate for post-contrast T1-WI (κ = 0.61). CONCLUSION: LME was always observed and easily visible on post-contrast FLAIR images prior to SuS treatment. In association with other MRI features, it is highly indicative of SuS.

Validation of an automatic tool for the rapid measurement of brain atrophy and white matter hyperintensity: QyScore®.

OBJECTIVES: QyScore® is an imaging analysis tool certified in Europe (CE marked) and the US (FDA cleared) for the automatic volumetry of grey and white matter (GM and WM respectively), hippocampus (HP), amygdala (AM), and white matter hyperintensity (WMH). Here we compare QyScore® performances with the consensus of expert neuroradiologists. METHODS: Dice similarity coefficient (DSC) and the relative volume difference (RVD) for GM, WM volumes were calculated on 50 3DT1 images. DSC and the F1 metrics were calculated for WMH on 130 3DT1 and FLAIR images. For each index, we identified thresholds of reliability based on current literature review results. We hypothesized that DSC/F1 scores obtained using QyScore® markers would be higher than the threshold. In contrast, RVD scores would be lower. Regression analysis and Bland-Altman plots were obtained to evaluate QyScore® performance in comparison to the consensus of three expert neuroradiologists. RESULTS: The lower bound of the DSC/F1 confidence intervals was higher than the threshold for the GM, WM, HP, AM, and WMH, and the higher bounds of the RVD confidence interval were below the threshold for the WM, GM, HP, and AM. QyScore®, compared with the consensus of three expert neuroradiologists, provides reliable performance for the automatic segmentation of the GM and WM volumes, and HP and AM volumes, as well as WMH volumes. CONCLUSIONS: QyScore® represents a reliable medical device in comparison with the consensus of expert neuroradiologists. Therefore, QyScore® could be implemented in clinical trials and clinical routine to support the diagnosis and longitudinal monitoring of neurological diseases. KEY POINTS: • QyScore® provides reliable automatic segmentation of brain structures in comparison with the consensus of three expert neuroradiologists. • QyScore® automatic segmentation could be performed on MRI images using different vendors and protocols of acquisition. In addition, the fast segmentation process saves time over manual and semi-automatic methods. • QyScore® could be implemented in clinical trials and clinical routine to support the diagnosis and longitudinal monitoring of neurological diseases.

Quantitative Assessment of Motor Neglect.

Background and Purpose: We used differential actigraphy as a novel, objective method to quantify motor neglect (a clinical condition whereby patients mimic hemiplegia even in the absence of sensorimotor deficits), whose diagnosis is at present highly subjective, based on the clinical observation of patients' spontaneous motor behavior. Methods: Patients wear wristwatch-like accelerometers, which record spontaneous motor activity of their upper limbs during 24 hours. Asymmetries of motor behavior are then automatically computed offline. On the basis of normal participants' performance, we calculated cutoff scores of left/right motor asymmetry. Results: Differential actigraphy showed contralesional motor neglect in 9 of 35 patients with unilateral strokes, consistent with clinical assessment. An additional patient with clinical signs of motor neglect obtained a borderline asymmetry score. Lesion location in a subgroup of 25 patients was highly variable, suggesting that motor neglect is a heterogenous condition. Conclusions: Differential actigraphy provides an ecological measure of spontaneous motor behavior, and can assess upper limb motricity in an objective and quantitative manner. It thus offers a convenient, cost-effective, and relatively automatized procedure for following-up motor behavior in neurological patients and to assess the effects of rehabilitation.

Multiple sclerosis lesions segmentation from multiple experts: The MICCAI 2016 challenge dataset.

MRI plays a crucial role in multiple sclerosis diagnostic and patient follow-up. In particular, the delineation of T2-FLAIR hyperintense lesions is crucial although mostly performed manually - a tedious task. Many methods have thus been proposed to automate this task. However, sufficiently large datasets with a thorough expert manual segmentation are still lacking to evaluate these methods. We present a unique dataset for MS lesions segmentation evaluation. It consists of 53 patients acquired on 4 different scanners with a harmonized protocol. Hyperintense lesions on FLAIR were manually delineated on each patient by 7 experts with control on T2 sequence, and gathered in a consensus segmentation for evaluation. We provide raw and preprocessed data and a split of the dataset into training and testing data, the latter including data from a scanner not present in the training dataset. We strongly believe that this dataset will become a reference in MS lesions segmentation evaluation, allowing to evaluate many aspects: evaluation of performance on unseen scanner, comparison to individual experts performance, comparison to other challengers who already used this dataset, etc.

Ocular MRI Findings in Patients with Severe COVID-19: A Retrospective Multicenter Observational Study.

Coronavirus disease 2019 (COVID-19) may affect various organs. This case series reports nine patients (one of nine [11%] women and eight of nine [89%] men; mean age ± standard deviation, 56 years ± 13) with globe MRI abnormalities obtained from a multicenter cohort of 129 patients presenting with severe COVID-19 from March 4, 2020, to May 1, 2020. Nine of 129 (7%) patients had one or several nodules of the posterior pole that were hyperintense at fluid-attenuated inversion-recovery imaging. All patients had nodules in the macular region, eight of nine (89%) had bilateral nodules, and two of nine (22%) had nodules outside the macular region. Screening of these patients might improve the management of potentially severe ophthalmologic manifestations of the virus. See also the editorial by Kirsch in this issue. © RSNA, 2021 Online supplemental material is available for this article.

Effect of distortion corrections on the tractography quality in spinal cord diffusion-weighted imaging.

PURPOSE: To assess the impact of a different distortion correction (DC) method and patient geometry (sagittal balance) on the quality of spinal cord tractography rendering according to different tractography approaches. METHODS: Forty-four adults free of spinal cord diseases underwent cervical diffusion-weighted imaging. The phase-encoding direction was head→foot. Sequence with opposed polarities (foot→head) was acquired to perform DC. Eddy-current, motion effects, and susceptibility artifact correction methods were used for DC, and two deterministic and one probabilistic tractography approaches were evaluated using MRtrix and DSI Studio tractography software. Fiber length and number of fibers were extracted to evaluate the quality of the tractography rendering. For each subject, cervical lordosis was measured to assess patient geometry. The angle between the main direction of the spinal cord and the orientation of the acquisition box were computed at each spine level to assess acquisition geometry and define an angle threshold for which a tractography of good quality is no longer possible. RESULTS: There was a significant improvement in tractography quality after performing DC with susceptibility artifact correction using a deterministic approach based on tensor. Before DC, the angle threshold was defined at C6 (15.2°) compared with C7 (21.9°) after corrections, demonstrating the importance of spinal cord angulation for DC. CONCLUSION: The impact of DC on tractography quality is greatly impacted by acquisition geometry. To obtain a good-quality tractography, we propose as a future perspective to adapt the acquisition geometry to that of the patient by automatically adjusting the acquisition box.

Oral nomegestrol acetate and transdermal 17-beta-estradiol for preventing post-partum relapses in multiple sclerosis: The POPARTMUS study.

BACKGROUND: Sex steroids could explain the course of multiple sclerosis (MS) in pregnancy. OBJECTIVE: To compare the annualized relapse rate (ARR) 12 weeks post-partum in women treated with nomegestrol acetate (NOMAc) and 17-beta-estradiol (E2) versus placebo. METHODS: POPARTMUS is a randomized, proof-of-concept trial in women with MS, receiving oral NOMAc 10 mg/day and transdermal estradiol 75 µg/week, or placebo. RESULTS: Recruitment was stopped prematurely due to slow inclusions (n = 202). No treatment effect was observed on ARR after 12 weeks (sex steroids = 0.90 (0.58-1.39), placebo = 0.97 (0.63-1.50) (p = 0.79)). CONCLUSION: POPARTMUS failed showing efficacy of a NOMAc-E2 combination in preventing post-partum relapses.

Chest CT for rapid triage of patients in multiple emergency departments during COVID-19 epidemic: experience report from a large French university hospital.

OBJECTIVES: To assess the diagnostic performances of chest CT for triage of patients in multiple emergency departments during COVID-19 epidemic, in comparison with reverse transcription polymerase chain reaction (RT-PCR) test. METHOD: From March 3 to April 4, 2020, 694 consecutive patients from three emergency departments of a large university hospital, for which a hospitalization was planned whatever the reasons, i.e., COVID- or non-COVID-related, underwent a chest CT and one or several RT-PCR tests. Chest CTs were rated as "Surely COVID+," "Possible COVID+," or "COVID-" by experienced radiologists. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated using the final RT-PCR test as standard of reference. The delays for CT reports and RT-PCR results were recorded and compared. RESULTS: Among the 694 patients, 287 were positive on the final RT-PCR exam. Concerning the 694 chest CT, 308 were rated as "Surely COVID+", 34 as "Possible COVID+," and 352 as "COVID-." When considering only the "Surely COVID+" CT as positive, accuracy, sensitivity, specificity, PPV, and NPV reached 88.9%, 90.2%, 88%, 84.1%, and 92.7%, respectively, with respect to final RT-PCR test. The mean delay for CT reports was three times shorter than for RT-PCR results (187 ± 148 min versus 573 ± 327 min, p < 0.0001). CONCLUSION: During COVID-19 epidemic phase, chest CT is a rapid and most probably an adequately reliable tool to refer patients requiring hospitalization to the COVID+ or COVID- hospital units, when response times for virological tests are too long. KEY POINTS: • In a large university hospital in Lyon, France, the accuracy, sensitivity, specificity, PPV, and NPV of chest CT for COVID-19 reached 88.9%, 90.2%, 88%, 84.1%, and 92.7%, respectively, using RT-PCR as standard of reference. • The mean delay for CT reports was three times shorter than for RT-PCR results (187 ± 148 min versus 573 ± 327 min, p < 0.0001). • Due to high accuracy of chest CT for COVID-19 and shorter time for CT reports than RT-PCR results, chest CT can be used to orient patients suspected to be positive towards the COVID+ unit to decrease congestion in the emergency departments.

Progressive multifocal leukoencephalopathy: MRI findings in HIV-infected patients are closer to rituximab- than natalizumab-associated PML.

OBJECTIVES: To compare brain MRI findings in progressive multifocal leukoencephalopathy (PML) associated to rituximab and natalizumab treatments and HIV infection. MATERIALS AND METHODS: In this retrospective, multicentric study, we analyzed brain MRI exams from 72 patients diagnosed with definite PML: 32 after natalizumab treatment, 20 after rituximab treatment, and 20 HIV patients. We compared T2- or FLAIR-weighted images, diffusion-weighted images, T2*-weighted images, and contrast enhancement features, as well as lesion distribution, especially gray matter involvement. RESULTS: The three PML entities affect U-fibers associated with low signal intensities on T2*-weighted sequences. Natalizumab-associated PML showed a punctuate microcystic appearance in or in the vicinity of the main PML lesions, a potential involvement of the cortex, and contrast enhancement. HIV and rituximab-associated PML showed only mild contrast enhancement, punctuate appearance, and cortical involvement. The CD4/CD8 ratio showed a trend to be higher in the natalizumab group, possibly mirroring a more efficient immune response. CONCLUSION: Imaging features of rituximab-associated PML are different from those of natalizumab-associated PML and are closer to those observed in HIV-associated PML. KEY POINTS: • Nowadays, PML is emerging as a complication of new effective therapies based on monoclonal antibodies. • Natalizumab-associated PML shows more inflammatory signs, a perivascular distribution "the milky way," and more cortex involvement than rituximab- and HIV-associated PML. • MRI differences are probably related to higher levels of immunosuppression in HIV patients and those under rituximab therapy.

Abnormal MRI findings of the orbital or visual pathways in patients with severe COVID-19: Observations from the French multicenter COVID-19 cohort.

OBJECTIVES: COVID-19 is a multisystemic disease. Ophthalmological abnormalities are relatively rare among COVID-19-infected patients. The aim of our study was to report orbital and visual pathways MRI findings in a nationwide multicenter cohort of patients with severe COVID-19. METHODS: This IRB-approved retrospective multi-center study included participants presenting with severe COVID-19, who underwent brain MRI from March 4th to May 1st 2020. Two neuroradiologists ("blinded"), blinded to all data, individually analyzed morphological MRIs focusing on the orbits and the visual pathways. A second consensus reading session was performed in the case of disagreement between both readers. Clinical and ophthalmological data were compared to MRI findings. Descriptive statistical analysis and interobserver agreement for MRI reading using non-weighted Cohen kappa statistics were performed. RESULTS: 129 participants (43 [33%] women and 86 [67%] men, mean age 63 ± 14 years) were included in the study. 17/129 (13%) patients had abnormal MRI findings of the orbit or visual pathways. 11/17 (65%) patients had a FLAIR-WI hyperintense optic disc. 6/17 (35%) patients had abnormal signal of at least one of the visual pathway structures: 6/6 (100%) of the optic nerve, 1/6 (17%) of the optic chiasm, 2/6 (33%) of the optic tract and 1/6 (17%) of the optic radiations. CONCLUSIONS: Our study showed that a substantial number of patients with severe COVID-19 presented with abnormal MRI findings of the orbit or visual pathways, which might lead to potentially severe visual impairment.

Diagnostic value of bright spotty lesions on MRI after a first episode of acute myelopathy.

BACKGROUND AND PURPOSE: To determine the diagnostic value of bright spotty lesions (BSLs) for aquaporin-4 antibody-positive neuromyelitis optica spectrum disorder (NMOSDAQP4+), the predictive value of axial-BSLs for AQP4-IgG seropositivity, and the radio-clinical differences in NMOSDAQP4+ patients with and without axial-BSLs. MATERIALS AND METHODS: Retrospective study that included patients aged≥16 years, with a first acute spinal cord syndrome between 2005 and 2018 and abnormal spinal cord MRI with axial and sagittal T2 sequences. Patients with MRI findings consistent with compressive myelopathy were excluded. All spinal cord MRI were retrospectively evaluated for the presence of BSLs by 2 radiologists blinded to the diagnosis of acute myelopathy. RESULTS: A total of 82 patients were included; 15 aquaporin-4 antibody-positive neuromyelitis optica spectrum disorder patients (NMOSDAQP4+), and 67 other patients, considered as the other causes of myelopathy (OM) group. The specificity of axial-BSLs for NMOSDAQP4+ patients was 94.0% (95% CI [85.6 to 97.7]). The sensitivity was 40.0% (95% CI [19.8 to 64.3]). In the multivariable analysis, the only MRI characteristic associated with AQP4-IgG positivity was the presence of axial-BSLs (OR: 9.2, 95% CI [1.2 to 72.9]; P=0.022). In NMOSDAQP4+ patients, the median of cord expansion ratio was higher with axial-BSL (1.2, IQR [1.1-1.3]) than without axial-BSL (1.1, IQR [1.0-1.2]; P=0.046). CONCLUSION: After a first acute spinal cord syndrome, the presence of axial-BSLs on spinal cord MRI seems very specific for NMOSDAQP4+ and seems to be a predictor radiological marker of AQP4-IgG positivity.

Cerebral vasculitis of medium-sized vessels as a possible mechanism of brain damage in COVID-19 patients.

BACKGROUND AND PURPOSE: Cerebral complications related to COVID-19 were recently reported, and the underlying mechanisms of brain damage remain uncertain, probably multifactorial. Among various hypotheses suggested, a possible vasculitis was issued but never confirmed. Herein, we aimed to describe brain MRIs focused on the intracranial vessel wall in a population of COVID-19 patients with neurologic manifestations. MATERIALS AND METHODS: Between March 1 and May 31, 2020, 69 consecutive COVID-19 patients with neurologic manifestations underwent a brain MRI allowing the study of the intracranial vessel wall at Strasbourg University hospitals and were retrospectively included. During the same period, 25 consecutive patients, without suspicion of SARS-CoV-2 infection, underwent a brain MRI urgently, with the same imaging protocols. A vasculitis seemed likely when imaging demonstrated vessel wall thickening with homogeneous and concentric enhancement. RESULTS: Among the 69 COVID-19 patients included, 11 (16%) presented arterial vessel wall thickening with homogeneous and concentric enhancement, compatible with cerebral vasculitis. These neuroimaging findings were not found among the 25 patients without SARS-CoV-2 infection, and the difference was statistically significant (p = 0.03). Middle cerebral arteries, basilar artery, and posterior cerebral arteries were the most frequent vessels involved. For nine of them, imaging demonstrated ischemic or hemorrhagic complications. CONCLUSION: Cerebral vasculitis of medium-sized vessels seems to be one of the mechanisms at the origin of brain damage related to COVID-19.

Signal changes in enhanced T1-weighted images related to gadolinium retention: A three-time-point imaging study.

BACKGROUND AND PURPOSE: Concern has grown about the finding of gadolinium deposits in the brain after administering gadolinium-based contrast agents (GBCAs). The mechanism is unclear, and related questions remain unanswered, including the stability over time. Therefore, we conducted a three-time-point study to explore T1-weighted (W) signal changes in the dentate nucleus (DN) and globus pallidus (GP), after the first, fifth, and tenth injections of either a macrocyclic agent (gadoterate meglumine) or a linear agent (gadobenate dimeglumine). MATERIALS AND METHODS: For this retrospective, multicenter, longitudinal study, two groups of 18 (gadoterate meglumine) and 19 (gadobenate dimeglumine) patients were identified. The evolution of the signal over time was analyzed using DN/pons (DN/P) and GP/thalamus (GP/T) ratios. RESULTS: DN/P and GP/T ratios tended to increase after the fifth administration of gadobenate dimeglumine, following by a downward trend. A trend in a decrease in DN/P and GP/T ratios were found after the fifth and tenth administrations of gadoterate meglumine. CONCLUSION: After exposure to gadobenate dimeglumine, the signal intensity (SI) tended to increase after the fifth injection owing to gadolinium accumulation, however, a SI increase was not found after the tenth administration supporting the hypothesis of a slow elimination of the previously retained gadolinium (wash-out effect) from the brain or of a change in form (by dechelation), causing the signal to fade. No increasing SI was found in the DN and GP after exclusive exposure to gadoterate meglumine, thus confirming its stability. We found, instead, a trend for a significative gadolinium elimination over time.

Aquaporin 4 distribution in the brain and its relevance for the radiological appearance of neuromyelitis optica spectrum disease.

BACKGROUND AND PURPOSE: To determine the precise incidence of lesions at sites of high Aquaporin-4 expression (hAQP4) and their possible association with known neuromyelitis optica spectrum disease (NMOSD) lesions patterns. MATERIALS AND METHODS: A retrospective analysis of brain and, when available, spinal cord MRI scans of 54 NMOSD patients recruited among the French NMOSD cohort was performed. Brain lesions were annotated as MS-like, non-specific, or evocative of NMOSD. The topography of hAQP4 was reassessed by human brain atlas. The incidence of lesions in hAQP4 and their association with lesions evocative of NMOSD was estimated. RESULTS: Among those included (41/54 female, mean age: 45 years) 47/54 (87%) presented brain lesions. Twenty-six/47 (55%) had lesions in hAQP4. Thirty-two/54 patients (60%) had lesions considered evocative of NMOSD. The majority of them also presented lesions in hAQP4 (65%, 21/32). Patients with lesions in hAQP4 and lesions evocative of NMOSD demonstrated more extensive myelitis compared to the other patients (7 [6-10] versus 4 [3-5] vertebral segments, P=0.009). CONCLUSION: The coexistence of lesions evocative of NMOSD and in hAQP4 is associated with significantly more extensive myelitis, and might have pathophysiological and clinical significance.

Observatoire Français de la Sclérose en Plaques (OFSEP): A unique multimodal nationwide MS registry in France.

The care of multiple sclerosis (MS) in France is based on two complementary interlinked networks: MS expert centers in university hospitals and regional networks of neurologists. The routine use of European database for multiple sclerosis (EDMUS) in all those centers has paved the way for the constitution of a national registry, designated as Observatoire Français de la Sclérose En Plaques (OFSEP). It promotes a prospective, standardized, high-quality, and multimodal collection of data. On June 2018, there were 68.097 files, with 71.1% females, representing 761,185 person-years. This huge database is open to the scientific community and might contribute exploring unresolved issues and unmet needs in MS.

Overcoming challenges of the human spinal cord tractography for routine clinical use: a review.

The spinal cord (SC) is a dense network of billions of fibers in a small volume surrounded by bones that makes tractography difficult to perform. We aim to provide a review collecting all technical settings of SC tractography and propose the optimal set of parameters to perform a good SC tractography rendering. The MEDLINE database was searched for articles reporting "spinal cord" "tractography" in "humans". Studies were selected only when tractography rendering was displayed and MRI acquisition and tracking parameters detailed. From each study, clinical context, imaging acquisition settings, fiber tracking parameters, region of interest (ROI) design, and quality of the tractography rendering were extracted. Quality of tractography rendering was evaluated by several objective criteria proposed herein. According to the reported studies, to obtain a good tractography rendering, diffusion tensor imaging acquisition should be performed with 1.5 or 3 Tesla MRI, in the axial plane, with > 20 directions; b value: 1000 s mm-2; right-left phase-encoding direction for cervical SC; isotropic voxel size; and no slice gap. Concerning the tracking process, it should be performed with determinist approach, fractional anisotropy threshold between 0.15 and 0.2, and curvature threshold of 40°. ROI design is an essential step for providing good tractography rendering, and their placement has to consider partial volume effects, magnetic susceptibility effects, and motion artifacts. The review reported herein highlights that successful SC tractography depends on many factors (imaging acquisition settings, fiber tracking parameters, and ROI design) to obtain a good SC tractography rendering.