Toward an Intravoxel Incoherent Motion 2-in-1 Magnetic Resonance Imaging Sequence for Ischemic Stroke Diagnosis? An Initial Clinical Experience With 1.5T Magnetic Resonance.

OBJECTIVE: This initial study aimed to investigate the feasibility of simultaneously measuring perfusion and diffusion including kurtosis features in acute ischemic stroke with the combined intravoxel incoherent motion and non-Gaussian diffusional kurtosis imaging (DKI-IVIM). MATERIAL AND METHODS: Five ischemic stroke patients underwent a 4-minute diffusion weighted imaging (DWI) protocol, using 8 b values chosen with the Cramer-Rao-Lower-Bound optimization approach, in addition to conventional DWI and arterial spin labeling sequences. Regions of interest in pathological and control regions were analyzed with DKI-IVIM, and parametric maps were reconstructed. RESULTS: The IVIM diffusion coefficient (D) decreased (P < 0.0001) in the infarcted areas, whereas higher kurtosis coefficient values were found (P = 0.0002). Regarding the perfusion, the individual IVIM perfusion fraction f decreased in 3 matching cases with the cerebral blood flow estimated through arterial spin labeling and the fD* decreased only in 2 patients of those. CONCLUSIONS: When compared with conventional stroke imaging protocol, DKI-IVIM 4-minute 2-in-1 acquisition can provide diffusion results comparable with conventional DWI with complementary kurtosis estimations but a limited robustness regarding perfusion estimations for clinical purpose.

Impact of Head-Down Position on Cerebral Blood Flow in Healthy Subjects: An Arterial Spin-Labeling MR Perfusion Study.

BACKGROUND: A head-down (HD) position is used in some stroke centers to maintain cerebral perfusion (CP) in stroke patients. PURPOSE: To assess CP in healthy volunteers in the supine and HD (-15°) positions. STUDY TYPE: Prospective. POPULATION: Eighteen healthy subjects of 53 (±8) years old. FIELD STRENGTH/SEQUENCE: 1.5T / arterial spin-labeling (ASL) in the supine position and after 4 minutes of HD position. ASSESSMENT: Regions of interest from reconstructed cerebral blood-flow (CBF) maps: subcortical nuclear gray matter (accumbens, amygdala, caudate, hippocampus, pallidum, putamen, thalamus), cortical gray matter (cGM), and white matter (WM). We also monitored hemodynamic parameters. STATISTICAL TESTS: Shapiro-Wilk test, analysis of variance (ANOVA) tests, Student's t-tests, and Pearson correlation analysis. RESULTS: CBF was higher in women compared to men, whatever the position (mean difference of 17% in supine, and 13% in HD position). From supine to HD position, CBF was decreased in all regions (mean decrease of -7%). Simultaneously, mean arterial pressure and systolic blood pressure increased (respectively P = 0.004 and P < 0.001). DATA CONCLUSION: The CBF decrease, despite increased hemodynamic parameters, may indicate efficient cerebral autoregulation. Our results seem to reflect only early cerebral autoregulation stages but may open the way towards a more precise understanding of CP. LEVEL OF EVIDENCE: 1 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2020;51:218-224.

Predictive value of conventional MRI parameters in first spinal attacks of neuromyelitis optica spectrum disorder.

BACKGROUND: While spinal cord (SC) attacks of neuromyelitis optica spectrum disorder (NMOSD) are often devastating, signs predictive of their poor clinical outcome have been elusive until now, except for the delay in initiating plasma exchange (PE). OBJECTIVE: We studied the correlation between conventional non-standardized magnetic resonance imaging (MRI) parameters, PE treatment, and clinical data obtained at nadir and recovery. METHODS: Retrospective study of first SC attacks of NMOSD. RESULTS: Sixty-nine Afro-Caribbean NMOSD patients were included (aquaporin-4 (AQP4) antibodies positive in 65%). Median nadir and residual expanded disability status score (EDSS) were, respectively, 7.5 and 4.0. In bivariate analysis, all conventional MRI parameters were correlated with nadir and residual EDSS. In multivariate analysis, nadir EDSS correlated with lesion length (p = 0.022) and edema (p = 0.019), whereas residual EDSS correlated with T1w (T1-weighted) hypointense signal (p = 0.003). Gadolinium enhancement was not associated with outcome. CONCLUSION: A specific pattern of lesions in conventional MRI data is differentially associated with nadir and residual EDSS. Lesions associated with poor prognosis should prompt highly efficient treatment.

Improved detection and characterization of arterial occlusion in acute ischemic stroke using contrast enhanced MRA.

BACKGROUND AND PURPOSE: To compare the accuracy and utility of contrast enhanced magnetic resonance angiography (MRA) (CEMRA) to Time of Flight MRA (TOF MRA) during detection and evaluation of occlusions on patients diagnosed with acute ischemic stroke (AIS). METHODS: This single-center study was approved by our local institutional research ethics board. From August 2014 to July 2016, 131 consecutive adult patients with confirmed AIS were included. Detection of an arterial occlusion and its characterization were evaluated independently with CEMRA or TOF MRA by two blinded neuroradiologists, then by consensus using all available MR sequences. A Cohen's Kappa coefficient (κ) and intra-class correlation coefficients (ICC) were used to compare the two techniques. RESULTS: There was substantial concordance in the detection of arterial occlusion between CEMRA and TOF MRA (κ = 0.75). TOF MRA was more likely to show an arterial occlusion than CEMRA (63 versus 52 patients respectively). There were 13 and 1 false positive arterial occlusion with TOF MRA and CEMRA respectively, and 1 false negative with TOF MRA. There was excellent concordance between the location of arterial occlusions and CEMRA and TOF MRA [κ = 0.89 (0.72-0.97)]. CEMRA was significantly more likely to allow measurement of the thrombus than was TOF MRA [38 (75%) versus 14 (22%)] (P < 0.0001). CONCLUSIONS: Our study showed that CEMRA imaging detected arterial occlusions better than TOF MRA in AIS patients and more precisely such that thrombus length and location could be known, which improves the patient's management and care.

Transoceanic Management and Treatment of Aneurysmal Subarachnoid Hemorrhage: A 10-Year Experience.

BACKGROUND AND PURPOSE: Because of the small number of yearly cases of ruptured cerebral aneurysms, endovascular treatment is not performed in Martinique. Therefore, patients from Martinique are sent 7000 km to Paris on commercial flights as soon as possible, where treatment is performed. Nontransportable patients are treated locally with either surgery or symptomatic care. The objective of our study was to assess patient outcomes and safety of this treatment strategy. METHODS: We retrospectively examined all cases of aneurysmal subarachnoid hemorrhage in Martinique diagnosed during 2004 to 2013. Medical case records were searched for the type and location of treatment, clinical status, and transfer duration. RESULTS: A total of 119 patients had an aneurysmal subarachnoid hemorrhage during the 10-year period. Of these, 91 were transferred to Paris, 12 were surgically treated locally, and 16 received symptomatic treatment. None of the transferred patients experienced any hemorrhagic recurrence, and none suffered a significant complication related to the air transportation. The median time between aneurysmal subarachnoid hemorrhage diagnosis and arrival at the referral center was 32 hours. The 30-day case fatality rate for treated cases was 14.6% (8.8% for those treated in Paris and 58.3% for those treated locally). CONCLUSIONS: Our treatment strategy for aneurysmal subarachnoid hemorrhage resulted in a 30-day case fatality rate similar to those observed elsewhere, despite an 8-hour flight and a median treatment delay of 32 hours. This strategy therefore seems to be safe and reliable for isolated regions with small populations.

Measuring Cerebral Hypoperfusion Induced by Hyperventilation Challenge With Intravoxel Incoherent Motion Magnetic Resonance Imaging in Healthy Volunteers.

OBJECTIVES: The aim of this study was to demonstrate the feasibility to assess cerebral hypoperfusion with a hyperventilation (HV) challenge protocol using intravoxel incoherent motion (IVIM) magnetic resonance imaging. MATERIALS AND METHODS: Magnetic resonance imaging experiments were performed on 10 healthy volunteers at 1.5 T, with a diffusion IVIM magnetic resonance imaging protocol using a set of b-values optimized by Cramer-Rao Lower Bound analysis. Hypoperfusion was induced by an HV maneuver. Measurements were performed in normoventilation and HV conditions. Biexponential curve fitting was used to obtain the perfusion fraction (f), pseudodiffusion coefficient (D*), and the product fD* in gray matter (GM) regions of interest (ROIs). Regional cerebral blood flow in the same ROIs was also assessed with arterial spin labeling. RESULTS: The HV challenge led to a diminution of IVIM perfusion-related parameters, with a decrease of f and fD* in the cerebellum (P = 0.03 for f; P = 0.01 for fD*), thalamus GM (P = 0.09 for f; P = 0.01 for fD*), and lenticular nuclei (P = 0.03 for f; P = 0.02 for fD*). Mean GM cerebral blood flow (in mL/100 g tissue/min) measured with arterial spin labeling averaged over all ROIs also decreased (normoventilation: 42.7 ± 4.1 vs HV: 33.2 ± 2.2, P = 0.004) during the HV challenge. CONCLUSIONS: The optimized IVIM protocol proposed in the current study allows for measurements of cerebral hypoperfusion that might be of great interest for pathologies diagnosis such as ischemic stroke.

Can MRI water apparent diffusion coefficient (ADC) value discriminate between idiopathic normal pressure hydrocephalus, Alzheimer's disease and subcortical vascular dementia?

Numerous similarities in MRI and clinical symptoms exist between Alzheimer's disease (AD), subcortical vascular dementia (sVD) and possible idiopathic normal pressure hydrocephalus (iHPN). The aim of this study is to explore mean apparent coefficient diffusion (ADC) difference between theses diseases in different periventricular and deep white matter areas, as compared to healthy controls. This retrospective study analyzed mean ADC values of 120 patients in normal appearing deep white matter and lenticular nuclei, frontal, caudate nuclei corpus and parietal periventricular and deep white matter areas INPH group showed significantly lower ADC than sVD group in frontal periventricular region (1567.10-6mm2/s vs 1755.10-6mm2/s; P=0.0009) and in parietal deep region (1087.10-6mm2/s vs 1271.10-6mm2/s; P=0.0052), but showed significantly higher ADC in lenticular nuclei ROI (834.10-6mm2/s vs 753.10-6mm2/s; P=0.002). The comparison between iNPH and sVD showed a cut-off value of 1676.10-6mm2/s (sensitivity 0.70, specificity 0.77) in periventricular frontal area. INPH group, in comparison with NA group, showed significantly higher ADC in all ROIs. The iNPH group also showed significantly higher ADC than AD group in all ROIs. AD group showed significantly lower ADC than sVD group in all regions, except in normal appearing lenticular nuclei and caudate nuclei corpus deep ROI. SVD group showed significantly higher ADC than NA in all ROIs, except in normal appearing lenticular nucleus ROI. Different patterns of ADC values can differentiate between AD, sVD and iNPH, even when other MRI sequences appear morphologically similar.

Diffusional kurtosis imaging (DKI) incorporation into an intravoxel incoherent motion (IVIM) MR model to measure cerebral hypoperfusion induced by hyperventilation challenge in healthy subjects.

OBJECTIVES: The objectives were to investigate the diffusional kurtosis imaging (DKI) incorporation into the intravoxel incoherent motion (IVIM) model for measurements of cerebral hypoperfusion in healthy subjects. MATERIALS AND METHODS: Eight healthy subjects underwent a hyperventilation challenge with a 4-min diffusion weighted imaging protocol, using 8 b values chosen with the Cramer-Rao Lower Bound optimization approach. Four regions of interest in gray matter (GM) were analyzed with the DKI-IVIM model and the bi-exponential IVIM model, for normoventilation and hyperventilation conditions. RESULTS: A significant reduction in the perfusion fraction (f) and in the product fD* of the perfusion fraction with the pseudodiffusion coefficient (D*) was found with the DKI-IVIM model, during the hyperventilation challenge. In the cerebellum GM, the percentage changes were f: -43.7 ± 40.1, p = 0.011 and fD*: -50.6 ± 32.1, p = 0.011; in thalamus GM, f: -47.7 ± 34.7, p = 0.012 and fD*: -47.2 ± 48.7, p = 0.040. In comparison, using the bi-exponential IVIM model, only a significant decrease in the parameter fD* was observed for the same regions of interest. In frontal-GM and posterior-GM, the reduction in f and fD* did not reach statistical significance, either with DKI-IVIM or the bi-exponential IVIM model. CONCLUSION: When compared to the bi-exponential IVIM model, the DKI-IVIM model displays a higher sensitivity to detect changes in perfusion induced by the hyperventilation condition.

Absolute and regional cerebral perfusion assessment feasibility in head-down position with arterial spin-labeling magnetic resonance. A preliminary report on healthy subjects.

PURPOSE: Head-down (HD)-positioning, used in some stroke centers during early ischemic stroke management, is empirical but supported by some physiological findings. It has been shown by nonmagnetic resonance methods that this position can increase cerebral perfusion. This study aimed to investigate magnetic resonance imaging (MRI) ability to measure the response to head-down tilt (HDT) challenge in healthy volunteers. Cerebral blood flow (CBF) was assessed with arterial spin labeling (ASL) in supine and HD (-15°) positions. METHODS: Cerebral perfusion was measured in supine and HD positions in seven healthy subjects at 1.5T with a large magnet bore (70cm) MRI device. 3D pseudocontinuous arterial spin-labeling (pCASL) sequences were acquired in both positions and cerebral blood flow (CBF) maps were reconstructed. Regions of interest were subcortical gray matter structures (accumbens nuclei, amygdala, caudate nucleus, hippocampus, pallidum, putamen and thalamus), whole cortical gray matter and whole white matter. RESULTS: White matter and subcortical gray matter structures' CBF, averaged over the volunteers' sample, remained stable from supine to HD position. Accumbens nuclei and cortical gray matter CBF decreased by 11.5% (P=0.013) and 11.4% (P=0.018) when head position was changed from flat to -15°. CONCLUSIONS: Regional CBF assessment, especially in HDT, is challenging with most perfusion techniques because of ionizing radiations, inherent limitations and logistical considerations. This preliminary report presents a noninvasive technique assessing regional and absolute cerebral blood flow changes in response to posture change. It can lead to further clinical investigations for a better understanding of cerebral perfusion.

MRI characteristics of carotid bulb atypical fibromuscular dysplasia in black stroke patients.

BACKGROUND AND PURPOSE: In black stroke patients, a particular form of fibromuscular dysplasia (FMD), called atypical FMD (aFMD), is involved in stroke mechanism. The high rate of stroke recurrence under medical treatment leads to propose surgery in such patients. Regarding its location level on the carotid bulb, aFMD is often confused with atherosclerosis or free-floating thrombus. Nowadays, only histology can confirm the diagnosis. MRI of aFMD has never been assessed. MATERIALS AND METHODS: The constitution of a black patient's cohort with aFMD-related ischemic stroke is currently in progress in the French West Indies, Martinique. In patients scheduled for surgery, MRI of the carotid bifurcation was analyzed preoperatively, with subsequent histological examination of the excised specimen. The first four black stroke patients with MRI and histological findings are described. RESULTS: On imaging, aFMD lesion was homogeneous with isosignal on T2-weighted sequences and slight hypersignal on T1-weighted sequences with mild gadolinium enhancement of the inner layer. Histological findings confirmed the aFMD mainly located in the intima. CONCLUSIONS: aFMD generates a particular MRI pattern in our four patients, which could increase the diagnosis accuracy. Carotid bulb lesion in black stroke patients should suggest aFMD and MRI analysis may contribute to rule out differential diagnoses.

Carotid-bulb atypical fibromuscular dysplasia in young Afro-Caribbean patients with stroke.

BACKGROUND AND PURPOSE: An atypical form of fibromuscular dysplasia located in the internal carotid-bulb (CaFMD) is thought to be uncommon and is poorly described as a cause of ischemic stroke in the young. This study aimed to obtain a better description of CaFMD in Afro-Caribbean population, who could be particularly affected by it. METHODS: This study included consecutive patients <55 years consulting at Fort-de-France University Hospital Stroke Center (Martinique, FWI) found to have CaFMD as the only cause after a comprehensive work-up. CaFMD was diagnosed when computed tomographic angiography showed a bulbar spur without calcification. RESULTS: Twenty-five patients with stroke and CaFMD were identified. Computed tomographic angiography showed 2 CaFMD patterns: a thin (n=15) or thick (n=10) spur. Three patients initial computed tomographic angiography images showed a mural thrombus overlying the CaFMD. CaFMD was surgically removed from 7 of 25 and 20 of 25 patients who received antiplatelet therapy; after mean follow-up of 25.3±19.5 months, their respective recurrence rates were 0% and 30%. CONCLUSIONS: CaFMD could be a common condition in young Afro-Caribbeans with carotid-territory ischemic stroke. Recurrences were frequent under antiplatelet treatment, while surgical CaFMD removal seemed more effective.

Trends in incidence and early outcomes in a Black Afro-Caribbean population from 1999 to 2012: Etude Réalisée en Martinique et Centrée sur l'Incidence des Accidents Vasculaires Cérébraux II Study.

BACKGROUND AND PURPOSE: Seldom studies are available on trends in stroke incidence in blacks. We aimed to evaluate whether stroke risk prevention policies modified first-ever stroke incidence and outcomes in the black Afro-Caribbean population of Martinique. METHODS: Etude Réalisée en Martinique et Centrée sur l'Incidence des Accidents Vasculaires Cérébraux (ERMANCIA) I and II are 2 sequential prospective population-based epidemiological studies. There have assessed temporal trends in first-ever stroke incidence, risk factors, pathological types, and early outcomes in the black Afro-Caribbean population of Martinique comparing two 12-month periods (1998-1999 and 2011-2012). Crude and age-standardized incidence and 30-day outcomes for stroke in the 2 study periods were compared using Poisson regression. RESULTS: We identified 580 and 544 first-ever strokes in the 2 studies. World age-standardized incidence rates decreased by 30.6% in overall (111 [95% confidence interval, 102-120] versus 77 [95% confidence interval, 70-84]). Rate decline was greater in women than in men (34% versus 26%) particularly in women aged 65 to 74 years (-69%) and 75 to 84 years (-43%). Frequencies of hypertension and diabetes mellitus were unchanged, whereas dyslipidemia, smoking, and atrial fibrillation significantly increased. Only ischemic stroke types showed significant rate reduction in overall and in women, incidence rate ratio (95% confidence intervals) of 0.69 (0.50-0.97) and 0.61 (0.42-0.88), respectively. The overall 30-day case-fatality ratio remained stable (19.3%/17.6%), whereas a better 30-day outcome was found (modified Rankin Score, ≤2 in 47%/37.6%; P=0.03). CONCLUSIONS: Over 13 years, there has been a significant decrease (30.6%) in the age-specific first-ever stroke incidence in our Afro-Carribean population. Although prevention policies seem effective, we need to focus on new risk factors limitation and on male population adherence to prevention program.

Clinical, imaging, and management features of symptomatic carotid web: Insight from CAROWEB registry.

BACKGROUND: Although carotid web (CaW) is increasingly diagnosed as a cause of cryptogenic stroke, data are still limited to monocentric small sample cohort. To broaden knowledge on symptomatic CaW, CAROWEB registry has been recently implemented. AIMS: In a large cohort of symptomatic CaW patients, we described epidemiologic characteristics, admission clinical and imaging features, and the current management including the secondary preventive strategy choice made in comprehensive French Stroke Units. METHODS: CAROWEB is an ongoing French observational multicenter registry enrolling consecutive CaW patients diagnosed after an ipsilateral ischemic stroke (IS) or transient ischemic attack (TIA). Submitted cases were validated by two experienced neurologist and neuroradiologist. Clinical, imaging, and management features were collected for this study. RESULTS: Between June 2019 and December 2021, 244 cases were submitted by 14 centers, 42 rejected, and 202 included (IS, 91.6%; TIA, 7.9%; retinal infarction, 0.5%; mean age, 50.8 ± 12.2 years; female, 62.9%; Caucasian, 47.5%; Afro-Caribbean, 20.3%). IS patients showed median (interquartile range (IQR)) admission National Institutes of Health Stroke Scale (NIHSS) score, 8 (2-15); intracranial artery occlusion, 71.8%; ipsilateral chronic cerebral infarction (CCI), 16.3%; and reperfusion treatment, 57.3%. CaW was not identified during the mechanical thrombectomy procedure in 30 of 85 (35.3%) patients. Secondary prevention was invasive in 55.6% (stenting, n = 80; surgery, n = 30). In multivariable analysis, the invasive therapeutic option was associated with ipsilateral CCI (odds ratio (OR): 4.24 (1.27-14.2), p = 0.019) and inversely associated with risk factors (OR: 0.47 (0.24-0.91), p = 0.025) and admission NIHSS score (OR: 0.93 (0.89-0.97), p = 0.001). CONCLUSION: CaW must be considered in all ethnic groups including Caucasians. Secondary prevention is heterogeneous in large French Stroke Centers. The absence of risk factors, milder severity strokes, and ipsilateral CCI were predictive variables of secondary invasive treatment. The high rate of invasive treatment suggests that medical treatment alone is deemed ineffective to avoid recurrence and emphasize the need of randomized trials.

Assessment of a combined musculoskeletal and chest deep learning-based detection solution in an emergency setting.

Rationale and objectives: Triage and diagnostic deep learning-based support solutions have started to take hold in everyday emergency radiology practice with the hope of alleviating workflows. Although previous works had proven that artificial intelligence (AI) may increase radiologist and/or emergency physician reading performances, they were restricted to finding, bodypart and/or age subgroups, without evaluating a routine emergency workflow composed of chest and musculoskeletal adult and pediatric cases. We aimed at evaluating a multiple musculoskeletal and chest radiographic findings deep learning-based commercial solution on an adult and pediatric emergency workflow, focusing on discrepancies between emergency and radiology physicians. Material and methods: This retrospective, monocentric and observational study included 1772 patients who underwent an emergency radiograph between July and October 2020, excluding spine, skull and plain abdomen procedures. Emergency and radiology reports, obtained without AI as part of the clinical workflow, were collected and discordant cases were reviewed to obtain the radiology reference standard. Case-level AI outputs and emergency reports were compared to the reference standard. DeLong and Wald tests were used to compare ROC-AUC and Sensitivity/Specificity, respectively. Results: Results showed an overall AI ROC-AUC of 0.954 with no difference across age or body part subgroups. Real-life emergency physicians' sensitivity was 93.7 %, not significantly different to the AI model (P = 0.105), however in 172/1772 (9.7 %) cases misdiagnosed by emergency physicians. In this subset, AI accuracy was 90.1 %. Conclusion: This study highlighted that multiple findings AI solution for emergency radiographs is efficient and complementary to emergency physicians, and could help reduce misdiagnosis in the absence of immediate radiological expertize.

Intravoxel incoherent motion and diffusion kurtosis imaging at 3T MRI: Application to ischemic stroke.

BACKGROUND AND PURPOSE: The DKI-IVIM model that incorporates DKI (diffusional kurtosis imaging) into the IVIM (Intravoxel Incoherent Motion) concept was investigated to assess its utility for both enhanced diffusion characterization and perfusion measurements in ischemic stroke at 3 T. METHODS: Fifteen stroke patients (71 ± 11 years old) were enrolled and DKI-IVIM analysis was performed using 9 b-values from 0 to 1500 s/mm2 chosen with the Cramer-Rao-Lower-Bound optimization approach. Pseudo-diffusion coefficient D*, perfusion fraction f, blood flow-related parameter fD*, the diffusion coefficient D and an additional parameter, the kurtosis, K were determined in the ischemic lesion and controlateral normal tissue based on a region of interest approach. The apparent diffusion coefficient (ADC) and arterial spin labelling (ASL) cerebral blood flow (CBF) parameters were also assessed and parametric maps were obtained for all parameters. RESULTS: Significant differences were observed for all diffusion parameters with a significant decrease for D (p < 0.0001), ADC (p < 0.0001), and a significant increase for K (p < 0.0001) in the ischemic lesions of all patients. f decreased significantly in these regions (p = 0.0002). The fD* increase was not significant (p = 0.56). The same significant differences were found with a motion correction except for fD* (p = 0.47). CBF significantly decreased in the lesions. ADC was significantly positively correlated with D (p < 0.0001) and negatively with K (p = 0.0002); K was also negatively significantly correlated with D (p = 0.01). CONCLUSIONS: DKI-IVIM model enables for simultaneous cerebral perfusion and enhanced diffusion characterization in an acceptable clinically acquisition time for the ischemic stroke diagnosis with the additional kurtosis factor estimation, that may better reflect the microstructure heterogeneity.

Link between COVID-19-related in-hospital mortality in continental France administrative areas and weather: an ecological study.

OBJECTIVE: To assess the effect of a weather index on in-hospital COVID-19-linked deaths. DESIGN: Ecological study. SETTING: Continental France administrative areas (départements; henceforth counties). The study period, from 18 March to 30 May 2020, corresponds to the main first outbreak period in France. POPULATION: COVID-19-linked in-hospital deaths. MAIN OUTCOME MEASURES: In-hospital deaths and demographics (population, human density, male sex and population percentage >59 years old) were obtained from national and centralised public databases. County weather indexes were calculated by the French National Meteorological Agency. METHODS: In this observational ecological study, the relationship between in-hospital COVID-19-related mortality and climate zones in continental French counties were analysed, by comparing the cumulative in-hospital death tolls in France by county to other factors (population density, climate, age and sex). The study period lasted from 18 March to 30 May 2020. A multivariate linear-regression analysis of in-hospital mortality included climate zones, population density, population >59 years old and percentages of males as potential predictors. The significance level was set at 5%. RESULTS: Weather indicators and population density were factors independently associated with the COVID-19 death toll. Colder counties had significantly higher mortality rates (p<0.00001). Percentages of males and population >59 years old in counties did not affect COVID-19 in-hospital mortality. CONCLUSIONS: Many parameters influence COVID-19 outbreak-severity indicators. Population density is a strong factor but its exact importance is difficult to discern. Weather (mainly cold winter temperatures) was independently associated with mortality and could help explain outbreak dynamics, which began and were initially more severe in the coldest counties of continental France. Weather partly explains fatality-rate discrepancies observed worldwide.

Arterial hypertension and cerebral hemodynamics: impact of head-down tilt on cerebral blood flow (arterial spin-labeling-MRI) in healthy and hypertensive patients.

OBJECTIVE: Hypertension affects cerebrovascular autoregulation and increases the risk of cerebrovascular events and dementia. Notably, it is associated with cerebrovascular remodeling and lower resting cerebral blood flow (CBF). We wanted to determine, using arterial spin-labeling-MRI, the impact of a head-down tilt (HDT) dynamic maneuver on CBF in hypertensive patients. METHODS: The current prospective study measured 36 patients' CBFs (18 normotensive individuals; 18 hypertensive patients) on 1.5T arterial spin-labeling-MRI in the supine position and after 4 min at -15° HDT. We reconstructed CBF maps of left and right subcortical nuclear gray matter, cortical gray matter and white matter (16 structures) to explore cerebrovascular autoregulation modification under dynamic conditions. RESULTS: Normotensive and hypertensive participants had no significant CBF differences in the supine position. After HDT, CBF mean variations (CBF-mVs) across all structures declined (mean -5.8%) for the whole population (n = 36), with -6.6 and -7.6% decreases, respectively, in white matter and gray matter (P < 0.001). Left and right accumbens nuclei had the largest changes (-9.6 and -9.2%, respectively; P < 0.001). No CBF-mV difference (0/16) was found in hypertensive patients after HDT, whereas normotensive participants' CBF-mVs changed significantly in four structures (left and right accumbens, putamen and left caudate nucleus) and gray matter. Hypertensive patients exhibited fewer CBF-mVs in left caudate nuclei (P = 0.039) and cortical gray matter (P = 0.013). Among hypertensive patients, people with diabetes had smaller CBF-mVs than people without diabetes. CONCLUSION: Our results highlight the significantly different CBF reactions to HDT of normotensive and hypertensive participants. They support the hypothesis that hypertension is responsible for deficient cerebrovascular autoregulation.