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EMBARGOED FOR RELEASE UNTIL 3:45 PM CST, FRIDAY, MAY 1, 1998
Test Can Determine Risk of Brain Injury for Scuba Divers A new test can help scuba divers determine their risk of developing brain injury from diving, according to a study released at the American Academy of NeurologyÃs 50th Anniversary Annual Meeting.
Scuba divers have been concerned since a 1995 study showed that recreational divers have a higher incidence of brain injury than the general population, according to neurologist Stefan Ries, MD, of the University of Heidelberg.
The test identifies divers with a patent foramen ovale, or an opening between two chambers in the heart. The opening is present in almost one-third of the general population and is a known risk factor for the uncommon strokes that occur in young people. In divers, the opening allows gas bubbles that form during the diversà ascent and decompression to enter arteries in the brain and block the blood flow. Blocked blood flow causes brain lesions, or areas where the brain cells stop functioning or die.
The study involved 87 recreational divers in Germany who had each performed at least 160 dives with self-contained underwater breathing apparatus (scuba). The divers were tested for the patent foramen ovale by injecting a solution containing harmless microbubbles into a vein in the arm, then using a type of ultrasound to see if the bubbles appeared in an artery in the brain. The divers were also tested for brain lesions with magnetic resonance imaging (MRI).
This process was demonstrated in a real-life situation for the first time by the researchers, who followed the pathway of gas bubbles in divers after simulated dives in a compression chamber. Bubbles formed after decompression in the veins of divers known to have the opening were then detected in arteries in the brain by ultrasound.
All divers with patent forament ovales did not have brain injury; 21 divers had patent foramen ovales and no lesions. The size of the opening affects the risk of brain injury, Ries said. Four divers with large openings had multiple brain lesions. In addition, seven divers who did not have the opening each had a single brain lesion.
Recreational divers should be tested for patent foramen ovales, Ries said. If one is present, they can adapt their diving behavior to the increased risk of accumulating brain lesions, he said. If the opening is large, it can be closed by interventional or surgical procedures.
The test, which uses echocontrast transcranial Doppler sonography, is minimally invasive, easy to perform and sensitive in detecting and estimating the size of a patent foramen ovale, Ries said.
There are approximately three million scuba divers in the United States, and diving is increasing in popularity worldwide, he said.
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