Magnetic resonance imaging shows effect of prolonged space travel on vision.
Magnetic resonance imaging shows evidence of changes in the orbital and ventricular fluid volumes among astronauts who participated in prolonged missions on the International Space Station (ISS), according to a study published in the journal Radiology. Researchers from the University of Miami in Florida performed a retrospective study to determine the respective roles of vascular and cerebrospinal fluids in spaceflight-induced vision impairment in astronauts, known as the visual impairment and intracranial pressure (VIIP) syndrome. Sixteen astronauts participated in the study, nine who flew on the space shuttle for a mean of 14.1 days and seven who flew on the ISS for a mean of 188 days. Their mean age during their mission was 46.1 years. All participants underwent MR imaging before flight and again after their return to quantify pre- to post-flight changes in globe flattening and optic nerve protrusion. Automated quantitation was also used to measure pre- to post-flight changes in orbital and ventricular cerebrospinal fluid volumes and in brain tissue volumes. Relationships between individual measures and differences between cohorts were assessed by using correlation and unpaired t test, respectively. The results showed the pre- to post-flight increases in globe flattening and nerve protrusion were significant only in the long-duration cohort (0.031 ± 0.019 versus −0.001 ± 0.006 and 0.025 ± 0.013 vs 0.001 ± 0.006, respectively). The increases in globe flattening and nerve protrusion were associated with significant increases in orbital and ventricular cerebrospinal fluid volumes. In contrast, brain tissue volumes do not change or correlate with globe flattening and optic nerve protrusion. The researchers concluded these findings were evidence for a primary role for cerebrospinal fluid and a lesser role for brain volume changes in the formation of VIIP.