Structural Brain Changes following Long-Term 6° Head-Down Tilt Bed Rest as an Analog for Spaceflight.

BACKGROUND AND PURPOSE: Following long-term spaceflight, a subset of the National Aeronautics and Space Administration astronauts present with visual impairment and increased intracranial pressure, known as visual impairment and intracranial pressure syndrome. We investigated structural brain changes following long-term head-down tilt bed rest as a spaceflight analog. MATERIALS AND METHODS: Volumetric analysis was performed on structural pre- and post-bed rest brain MR images. RESULTS: Comparing post-bed rest to pre-bed rest images, we found the following: 1) no significant group differences in GM, WM, CSF, or ventricular volumes; 2) shift of the center of mass of the brain upward and posterior rotation of the brain relative to the skull; 3) a significant correlation between posterior brain rotation and changes in ventricular volume; and 4) significant increases in brain tissue density in regions at the vertex, including the frontoparietal lobes, with contraction of adjacent extra-axial CSF spaces, and significant decreases in tissue density in areas along the base of the brain, including the orbitofrontal cortex. CONCLUSIONS: We observed widespread morphologic changes with brain tissue redistribution in response to gravity changes; possible associated functional changes are unknown. The observation that ventricular change is correlated to posterior brain rotation suggests an alteration in CSF homeostasis. Ultimately, to elucidate any structural changes that may play a role in visual impairment and intracranial pressure syndrome, volumetric analysis of pre- and postflight structural scans of astronauts is needed.

Effects of radiation on a model of malignant glioma invasion.

We sought to characterize the effects of radiation alone and in combination with BCNU and dexamethasone on malignant glioma invasion. A model of malignant glioma invasion into a gel matrix of collagen type I was used to characterize response to radiation treatment for four malignant glioma cell lines (C6, U251, U373, A172) and nine primary human glioblastoma explants. A radiation dose dependent inhibition of invasion was noted for the C6 astrocytoma cell line but not the other cell lines or explants. Addition of BCNU and dexamethasone to radiation produced additional inhibition of invasion among the cell lines and explants but could not suppress invasion entirely.

The clinical diagnosis of asphyxia responsible for brain damage in the human fetus.

OBJECTIVE: Our objective was to review the clinical findings in infants who died in the perinatal period with brain damage attributable to asphyxia. STUDY DESIGN: The neuropathologic findings in 208 perinatal deaths have been reviewed. Thirty cases (22 fetal, eight newborn) had evidence of white matter or neuronal necrosis due to asphyxia. The clinical course of the pregnancy in 22 cases with brain damage attributable to fetal asphyxia were examined. RESULTS: The diagnosis of asphyxia was confounded by several factors: (1) asphyxia may occur at any time in the last half of pregnancy, (2) 50% of the antepartum asphyxia occurred when the pregnancy had no risk factors, (3) periodic fetal assessment in the complicated preterm pregnancies failed to identify the asphyxial episodes in the remaining cases of antepartum asphyxia, and (4) indicators of fetal asphyxia in the cases of intrapartum fetal asphyxia were obtained after the central nervous system injury had occurred. CONCLUSION: These findings highlight the difficulty in the diagnosis of fetal asphyxia at a stage that could permit intervention to prevent brain damage.