Narrowing of the central sulcus, upward shift of the brain, and narrowing of CSF spaces at the vertex occurred frequently and predominantly in astronauts after long-duration flights. Further investigation, including repeated postflight imaging conducted after some time on Earth, is required to determine the duration and clinical significance of these changes. (Funded by the National Aeronautics and Space Administration.).

The cuprizone mouse model is well-established for studying the processes of both demyelination and remyelination in the corpus callosum, and it has been utilized together with diffusion tensor imaging (DTI) to investigate myelin and axonal pathology. Although some underlying morphological mechanisms contributing to the changes in diffusion tensor (DT) metrics have been identified, the understanding of specific associations between histology and diffusion measures remains limited. Diffusional kurtosis imaging (DKI) is an extension of DTI that provides metrics of diffusional non-Gaussianity, for which an associated white matter modeling (WMM) method has been developed. The main goal of the present study was to quantitatively assess the relationships between diffusion measures and histological measures in the mouse model of cuprizone-induced corpus callosum demyelination. The diffusional kurtosis (DK) and WMM metrics were found to provide additional information that enhances the sensitivity to detect the morphological heterogeneity in the chronic phase of the disease process in the rostral segment of the corpus callosum. Specifically, in the rostral segment axonal water fraction (d = 2.6; p<0.0001), radial kurtosis (d = 2.0; p=0.001) and mean kurtosis (d = 1.5; p=0.005) showed the most sensitivity between groups with respect to yielding statistically significant p-values and high Cohen’s d values. These results demonstrate the ability of DK and WMM metrics to detect white mater changes and inflammatory processes associated with cuprizone-induced demyelination. They also validate, in part, the application of these new WMM metrics for studying neurological diseases, as well as help to elucidate their biophysical meaning.

The present study sought to determine if volumes of specific brain structures could discriminate cognitively normal seniors destined to develop mild cognitive impairment (MCI) within a few years from those who will remain normal. Brain scans were collected from seventy-one cognitively normal seniors. Seventeen individuals later developed MCI (the presymptomatic MCI; pMCI group), while fifty-four remained normal. Whole brain volume (WBV) and volumes of the entorhinal cortex (ERC), hippocampus, and three subregions of the hippocampus (head; HH, body; HB and tail; HT) were compared. Results indicated that the pMCI group had smaller volumes than the normal group in the ERC, HH and HB, but not the HT or WBV. When HH/HB volumes and baseline memory test scores were included in a single logistic regression model, classification accuracy was very high (area under the curve = 0.93). These results show that smaller normalized volumes of anterior medial temporal lobe structures contribute to the development of MCI, a finding which may have implications for identifying seniors at risk for cognitive decline.

Long-duration spaceflight induces changes to the brain and cerebrospinal fluid compartments and visual acuity problems known as spaceflight-associated neuro-ocular syndrome (SANS). The clinical relevance of these changes and whether they equally affect crews of different space agencies remain unknown. We used MRI to analyze the alterations occurring in the perivascular spaces (PVS) in NASA and European Space Agency astronauts and Roscosmos cosmonauts after a 6-mo spaceflight on the International Space Station (ISS). We found increased volume of basal ganglia PVS and white matter PVS (WM-PVS) after spaceflight, which was more prominent in the NASA crew than the Roscosmos crew. Moreover, both crews demonstrated a similar degree of lateral ventricle enlargement and decreased subarachnoid space at the vertex, which was correlated with WM-PVS enlargement. As all crews experienced the same environment aboard the ISS, the differences in WM-PVS enlargement may have been due to, among other factors, differences in the use of countermeasures and high-resistive exercise regimes, which can influence brain fluid redistribution. Moreover, NASA astronauts who developed SANS had greater pre- and postflight WM-PVS volumes than those unaffected. These results provide evidence for a potential link between WM-PVS fluid and SANS.

Background and Purpose While there have been recent reports of brain retention of gadolinium following gadolinium-based contrast agent (GBCA) administration in adults, a retrospective series of pediatric patients has not previously been reported. We investigated the relationship between the number of prior GBCA doses and increasing T1 signal in the dentate nucleus on unenhanced T1-weighted MR imaging. We hypothesized that, despite differences in pediatric physiology and the smaller GBCA doses pediatric patients are typically administered based on weighted-adjusted dosing, the pediatric brain would also demonstrate dose dependent increasing T1 signal in the dentate nucleus. Materials and methods We included children with multiple GBCA administrations at our institution. A blinded-reader placed regions of interest (ROIs) within the dentate nucleus and adjacent cerebellar white matter. To eliminate reader bias, automated ROI delineation of the dentate nucleus, cerebellar white matter, and pons was also performed. Dentate to cerebellar white matter (DN/C) and dentate to pons (DN/P) ratios were compared to the number of GBCA administrations. Results Over 20 years at our institution, 280 patients received at least 5 GBCA doses with one patient receiving 38 doses. Sixteen patients met inclusion/exclusion criteria for ROI analysis. Blinded-reader DN/C ratios were significantly associated with GBCA doses (rs=0.77, p=0.001). DN/P and DN/C ratios based on automated ROI placement were also significantly correlated with GBCA doses (t=4.98, p<0.0001 and t=2.73, p<0.02 respectively). Conclusion In pediatric patients, the number of prior GBCA doses is significantly correlated with progressive T1-weighted dentate hyperintensity. Definitive confirmation of gadolinium deposition requires tissue analysis. Any potential clinical sequelae of gadolinium retention in the developing brain are unknown. Given this uncertainty, we suggest taking a cautious stance including the use in pediatric patients of higher stability, macrocyclic agents, which in both human and animal studies have been shown to be associated with lower levels of gadolinium deposition, and detailed documentation of dosing. Most importantly, a patient should not be deprived of a well-indicated contrasted MR exam.