ELEVATED INTRACRANIAL PRESSURE (ICP) DUE TO MICROGRAVITY-INDUCED CEPHALAD FLUID REDISTRIBUTION IS CURRENTLY THOUGHT TO BE THE MAJOR CONTRIBUTING FACTOR TO THE VISUAL IMPAIRMENT/INTRACRANIAL PRESSURE (VIIP) SYNDROME. CURRENTLY THE ONLY AVAILABLE MEASUREMENT OF ICP IS A POSTFLIGHT OPENING PRESSURE VIA LUMBAR PUNCTURE (LP). GIVEN THE INVASIVENESS OF LP AND THE RELUCTANCE TO UTILIZE IT IN THE ABSENCE OF CLINICAL INDICATIONS ICP ELEVATIONS ARE YET TO BE CONSISTENTLY DOCUMENTED IN CREWMEMBERS. IN ADDITION THE CAUSE FOR ICP ELEVATION IN-FLIGHT HAS NOT YET BEEN ESTABLISHED. CURRENT INVESTIGATIONS OF THE VIIP SYNDROME MAINLY FOCUS ON THE VASCULAR AND INTERSTITIAL COMPONENTS OF THE CEPHALAD FLUID REDISTRIBUTION. AN OVERLOOKED COMPONENT OF FLUID SHIFT THAT THIS STUDY WILL EVALUATED IS THE REDISTRIBUTION OF CEREBROSPINAL FLUID (CSF) IN THE CRANIOSPINAL SYSTEM AND ITS EFFECT ON ICP. AS THE CRANIUM CONTAINS MORE CSF THAN BLOOD THIS COMPONENT OF FLUID SHIFT MAY BE A LARGER CONTRIBUTOR TO ICP ELEVATIONS THAN THE VASCULAR/INTERSTITIAL COMPONENTS. THE POTENTIAL REDUCTION IN SPINAL CANAL COMPLIANCE BUFFERING DUE TO SPINAL ELONGATION MIGHT CONTRIBUTE TO ICP ELEVATIONS AS WELL.THE PROPOSED STUDY WILL UTILIZE SPECIALIZED MRI SEQUENCES COLLECTED ON 7 SHORT-DURATION AND 10 LONG-DURATION CREWMEMBERS TO ASSESS CSF HYDRODYNAMICS AND VASCULAR HEMODYNAMICS AND THEIR RELATIONSHIP TO VIIP. KEY PARAMETERS THAT WILL BE ANALYZED INCLUDE TOTAL CEREBRAL BLOOD FLOW VENOUS DRAINAGE INTRACRANIAL COMPLIANCE AND PRESSURE AS WELL AS CRANIO-SPINAL COMPLIANCE DISTRIBUTION. THESE VALUES WILL BE CORRELATED WITH CHANGES IN VISUAL/OCULAR FUNCTION AND MORPHOLOGY AND MEASURES OF SPINAL ELONGATION. EFFECTS OF MISSION DURATION WILL BE ELUCIDATED BY COMPARING SHORT AND LONG-DURATION CREWMEMBERS. THESE ANALYSES WILL ELUCIDATE THE ROLE OF CEPHALAD CSF SHIFT IN THE ETIOLOGY OF VIIP WILL DEFINE HYDRODYNAMIC MEASURES THAT MAY PREDICT SUSCEPTIBILITY TO VIIP AND MAY LEAD TO IDENTIFICATION OF NOVEL COUNTERMEASURES. THIS STUDY WILL BE CONSTRAINED BY THE NUMBER OF SUBJECT MRIS AVAILABLE FOR ANALYSIS COMPARED WITH AN OPTIMAL TERRESTRIAL STUDY WHERE MORE SUBJECTS WOULD BE AVAILABLE FOR STUDY.$300,000
· FY2014 · National Aeronautics and Space Administration