Length of optic nerve double inversion recovery hypersignal is associated with retinal axonal loss.

OBJECTIVES: To assess the association between optic nerve double inversion recovery (DIR) hypersignal length and retinal axonal loss in neuroinflammatory diseases affecting optic nerves. METHODS: We recruited patients previously affected (> 6 months) by a clinical episode of optic neuritis (ON). We had 25 multiple sclerosis (MS) patients, eight neuromyelitis optica spectrum disorder (NMOSD) patients and two patients suffering from idiopathic caused ON undergo brain magnetic resonance imaging (MRI); including a 3-dimensional (3D) DIR sequence, optical coherence tomography (OCT) examination and visual disability evaluation. Evaluation criteria were retinal thickness/volume, optic nerve DIR hypersignal length and high/low contrast vision acuity. RESULTS: In the whole cohort, we found good associations (< 0.0001) between optic nerve DIR hypersignal length, peripapillary retinal nerve fiber layer thickness, inner macular layers volumes, and visual disability. We found subclinical radiological optic nerve involvement in 38.5% of non-ON MS eyes. CONCLUSIONS: Optic nerve DIR hypersignal length may be a biomarker for retinal axonal loss, easily applicable in routine and research on new anti-inflammatory or neuroprotective drug evaluation. Detection of subclinical ON with 3D-DIR in a non-negligible proportion of MS patients argues in favor of optic nerve imaging in future OCT MS studies, in order to achieve a better understanding of retinal axonal loss in non-ON eyes.

[Susceptibility weighted magnetic resonance sequences "SWAN, SWI and VenoBOLD": technical aspects and clinical applications]. / Séquences IRM « SWAN, SWI et VenoBOLD ¼ exploitant le phénomène de susceptibilité magnétique : principes techniques et applications cliniques.

Susceptibility-weighted MR sequences, T2 star weighted angiography (SWAN, General Electric), Susceptibility weighted imaging (SWI, Siemens) and venous blood oxygen level dependant (VenoBOLD, Philips) are 3D spoiled gradient-echo sequence that provide a high sensitivity for the detection of blood degradation products, calcifications, and iron deposits. For all these sequences, an appropriate echo time allows for the visualization of susceptibility differences between adjacent tissues. However, each of these sequences presents a specific technical background. The purpose of this review was to describe 1/the technical aspects of SWAN, VenoBOLD and SWI sequences, 2/the differences observed in term of contrast within the images, 3/the key imaging findings in neuroimaging using susceptibility-weighted MR sequences.

Delayed Contrast-Enhanced MR Angiography for the Assessment of Internal Carotid Bulb Patency in the Context of Acute Ischemic Stroke: An Accuracy, Interrater, and Intrarater Agreement Study.

BACKGROUND AND PURPOSE: CTA has shown limited accuracy and reliability in distinguishing tandem occlusions and pseudo-occlusions on initial acute stroke imaging. The utility of early and delayed contrast-enhanced MRA in this setting is unknown. We aimed to assess the accuracy and reliability of early and delayed contrast-enhanced MRA for carotid bulb patency in patients with acute ischemic stroke. MATERIALS AND METHODS: We retrospectively reviewed patients who had ICA occlusion and underwent thrombectomy with preprocedural early and delayed contrast-enhanced MRA in a single comprehensive stroke center. During 2 sessions, 10 raters independently assessed 32 cases with early contrast-enhanced MRA (with an additional delayed contrast-enhanced MRA sequence during the second reading session). Their judgments were compared with DSA as a reference standard. Accuracy and interrater agreement were measured. Five raters undertook a third reading session to assess intrarater agreement. RESULTS: Accuracy for the assessment of carotid bulb patency with early contrast-enhanced MRA was limited (69%; 95% CI, 59%-79%), with moderate interrater agreement (κ = 0.42; 95% CI, 0.27-0.55). The second reading with an additional delayed contrast-enhanced MRA sequence improved both accuracy (82%; 95% CI, 73%-91%; P < .001) (raters corrected 43%-77% of incorrect diagnoses with early contrast-enhanced MRA alone; mean = 59%) and interrater agreement (κ = 0.56; 95% CI, 0.41-0.73; P = .07). Intrarater agreement was almost perfect, substantial, and moderate for 3, 1, and 1 raters. CONCLUSIONS: Early contrast-enhanced MRA has limited accuracy and repeatability for the evaluation of carotid bulb patency in acute ischemic stroke. The additional delayed contrast-enhanced MRA sequence may improve accuracy and reliability.

[Gait disturbances and normal pressure hydrocephalus]. / Troubles de la marche et hydrocéphalie à pression normale.

Normal pressure hydrocephalus must be considered when gait disturbance, cognitive impairment and sphincter disorders are associated. Symptoms of normal pressure hydrocephalus, especially gait disturbance, are potentially curable by surgery. Our paper provides a summary review of gait disorders associated with normal pressure hydrocephalus detailing their characteristics and the best assessment methods. Although the pathogenic mechanisms underlying normal pressure hydrocephalus remain poorly understood, advances in imaging have enabled considerable progress in our fundamental knowledge of the condition. Tapping the cerebrospinal fluid by lumbar puncture or external lumbar drainage remains the diagnostic test and is predictive of a favorable response to surgical treatment. Clinical severity scores validated for walking and for sphincter dysfunction and cognitive disorders provide the best means of assessing each patient's response to treatment.

Unusual Brain MRI Pattern in 2 Patients with COVID-19 Acute Respiratory Distress Syndrome.

We report the cases of 2 patients hospitalized in our intensive care unit with confirmed coronavirus disease 2019 infection in whom brain MR imaging showed an unusual DWI pattern with nodular and ring-shaped lesions involving the periventricular and deep white matter. We discuss the possible reasons for these findings and their relationship to the infection.

Follow-Up MRI for Small Brain AVMs Treated by Radiosurgery: Is Gadolinium Really Necessary?

BACKGROUND AND PURPOSE: Follow-up MR imaging of brain AVMs currently relies on contrast-enhanced sequences. Noncontrast techniques, including arterial spin-labeling and TOF, may have value in detecting a residual nidus after radiosurgery. The aim of this study was to compare noncontrast with contrast-enhanced MR imaging for the differentiation of residual-versus-obliterated brain AVMs in radiosurgically treated patients. MATERIALS AND METHODS: Twenty-eight consecutive patients with small brain AVMs (<20 mm) treated by radiosurgery were followed with the same MR imaging protocol. Three neuroradiologists, blinded to the results, independently reviewed the following: 1) postcontrast images alone (4D contrast-enhanced MRA and postcontrast 3D T1 gradient recalled-echo), 2) arterial spin-labeling and TOF images alone, and 3) all MR images combined. The primary end point was the detection of residual brain AVMs using a 5-point scale, with DSA as the reference standard. RESULTS: The highest interobserver agreement was for arterial spin-labeling/TOF (κ = 0.81; 95% confidence interval, 0.66-0.93). Regarding brain AVM detection, arterial spin-labeling/TOF had higher sensitivity (sensitivity, 85%; specificity, 100%; 95% CI, 62-97) than contrast-enhanced MR imaging (sensitivity, 55%; specificity, 100%; 95% CI, 27-73) and all MR images combined (sensitivity, 75%; specificity, 100%; 95% CI, 51-91) (P = .008). All nidus obliterations on DSA were detected on MR imaging. In 6 patients, a residual brain AVM present on DSA was only detected with arterial spin-labeling/TOF, including 3 based solely on arterial spin-labeling images. CONCLUSIONS: In this study of radiosurgically treated patients with small brain AVMs, arterial spin-labeling/TOF was found to be superior to gadolinium-enhanced MR imaging in detecting residual AVMs.

Structural Connectivity and Cortical Thickness Alterations in Transient Global Amnesia.

BACKGROUND AND PURPOSE: Transient global amnesia (TGA) is a sudden onset of anterograde and retrograde amnesia. We aimed to assess differences in terms of cortical thickness and structural brain connectome between patients with TGA (at acute and delayed postrecovery stages) and matched controls. MATERIALS AND METHODS: We report on 18 consecutive patients with TGA who underwent 3T MR imaging, including DTI and MPRAGE sequences, at the acute (mean delay postonset: 44 hours) and delayed post-recovery (mean delay: 35 days) stages. Structural connectome was assessed in patients with TGA and in 18 age- and sex-matched controls by using probabilistic fiber- tracking and segmentation of 164 cortical/subcortical structures ("nodes"). Connectivity graphs were computed and global network metrics were calculated. Network-based statistical analysis (NBS) was applied to compare patients with TGA at each stage with controls. We also compared cortical thickness between patients with TGA and healthy controls. RESULTS: Global network metrics were not altered in patients with TGA. NBS-analysis showed structural connectome alterations in patients with TGA compared with controls, in core regions involving the limbic network, with 113 nodes and 114 connections (33 left intrahemispheric, 31 right intrahemispheric, and 50 interhemispheric connections) showing significantly decreased structural connectivity (P < .05 NBS corrected, t-values ranging from 3.03 to 8.73). Lower cortical thickness compared with controls was associated with these structural alterations in patients with TGA, involving the orbitofrontal, cingulate, and inferior temporal cortices. All the abnormalities were visible at both acute and delayed postrecovery stages. CONCLUSIONS: Our preliminary study suggests there are structural abnormalities of the limbic network in patients with TGA compared with controls, including decreased structural connectivity and cortical thickness.