TUESDAY, March 13 (HealthDay News) -- Extended space travel can cause eye and brain abnormalities in astronauts, researchers have found.
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For the study, published online March 13 in the journal Radiology, investigators used MRI scans to examine the eyes and brains of 27 astronauts who spent an average of 108 days in space aboard the space shuttle and/or the International Space Station.
Eight of the 27 astronauts underwent a second MRI exam after a second space mission that lasted an average of 39 days.
The study authors found that among those who experienced a lifetime total of more than 30 days of exposure to microgravity, 33 percent of the astronauts had expansion of the cerebral spinal fluid space surrounding the optic nerve, 22 percent had flattening of the rear of the eyeball, 15 percent had bulging of the optic nerve, and 11 percent had changes in the pituitary gland and its connection to the brain.
These types of abnormalities are seen in cases of intracranial hypertension for which no cause can be found for the increased pressure around the brain. The pressure causes swelling of the juncture between the optic nerve and the eyeball, which can lead to vision problems.
"Microgravity-induced intracranial hypertension represents a hypothetical risk factor and a potential limitation to long-duration space travel," study author Dr. Larry Kramer, a professor of diagnostic and interventional imaging at the University of Texas Medical School at Houston, said in a news release from the Radiological Society of North America.
The microgravity-related changes seen in astronauts may help improve understanding of the causes of intracranial pressure in earthbound patients, he added.
Vision changes in some International Space Station astronauts have been noted but the cause is not fully understood, according to Dr. William Tarver, chief of the flight medicine clinic at NASA/Johnson Space Center.
No astronauts have been listed as ineligible for space flight duties as a result of the study findings, which Tarver described as suspicious but not conclusive of intracranial hypertension.
"NASA has placed this problem high on its list of human risks, has initiated a comprehensive program to study its mechanisms and implications, and will continue to closely monitor the situation," he said in the news release.
-- Robert Preidt
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SOURCE: Radiological Society of North America, news release, March 8, 2012