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Prolonged space travel causes brain and eye abnormalities in astronauts (Forwarded)
Radiological Society of North America
Oak Brook, Illnois
Linda Brooks, 630-590-7762
Prolonged space travel causes brain and eye abnormalities in astronauts
Magnetic resonance imaging (MRI) of the eyes and brains of 27 astronauts who
have spent prolonged periods of time in space revealed optical abnormalities
similar to those that can occur in intracranial hypertension of unknown
cause, a potentially serious condition in which pressure builds within the
skull. A retrospective analysis of the MRI data appears online in the
A team of researchers performed MRIs and analyzed the data on the 27
astronauts, each of whom were exposed to microgravity, or zero gravity, for
an average of 108 days while on space shuttle missions and/or the
International Space Station (ISS), a habitable research facility that has
been orbiting the earth since 1998. Eight of the 27 astronauts underwent a
second MRI exam after a second space mission that lasted an average of 39
"The MRI findings revealed various combinations of abnormalities following
both short- and long-term cumulative exposure to microgravity also seen with
idiopathic intracranial hypertension," said Larry A. Kramer, M.D., professor
of diagnostic and interventional imaging at The University of Texas Medical
School at Houston. "These changes that occur during exposure to microgravity
may help scientists to better understand the mechanisms responsible for
intracranial hypertension in non-space traveling patients."
Among astronauts with more than 30 days of cumulative lifetime exposure to
microgravity, findings included expansion of the cerebral spinal fluid space
surrounding the optic nerve in nine of the 27 (33 percent) astronauts,
flattening of the rear of the eyeball in six (22 percent), bulging of the
optic nerve in four (15 percent) and changes in the pituitary gland and its
connection to the brain in three (11 percent) of the astronauts. The
pituitary gland secretes and stores hormones that regulate a variety of
important body functions.
The same types of abnormalities are observed in cases of intracranial
hypertension where no cause can be found for increased pressure around the
brain. The pressure causes swelling of the juncture between the optic nerve
and the eyeball which can result in visual impairment.
Bone mineral loss and muscle atrophy are some of the known effects of zero
gravity on astronauts. With the onset of longer excursions in space afforded
by the ISS, visual changes have also been observed and are now being
"Microgravity-induced intracranial hypertension represents a hypothetical
risk factor and a potential limitation to long-duration space travel," Dr.
William J. Tarver, M.D., M.P.H., chief of flight medicine clinic at
NASA/Johnson Space Center, said the agency has noted changes in vision in
some ISS astronauts, the origin of which is not yet fully understood. No
astronauts have been considered ineligible for space flight duties as a
result of the findings, which he said are suspicious but not conclusive of
"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," Dr. Tarver said.
"Orbital and Intracranial Effects of Microgravity: Findings at 3-T MR
Imaging." Collaborating with Dr. Kramer were Ashot Sargsyan, M.D., Khader M.
Hasan, Ph.D., James D. Polk, D.O., and Douglas R. Hamilton, M.D., Ph.D.
Radiology is edited by Herbert Y. Kressel, M.D., Harvard Medical School,
Boston, Mass., and owned and published by the Radiological Society of North
America, Inc. (http://radiology.rsna.org/)
RSNA is an association of more than 48,000 radiologists, radiation
oncologists, medical physicists and related scientists committed to
excellence in patient care through education and research. The Society is
based in Oak Brook, Ill.
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