Brain Lesions in Scuba Divers

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The summary below is from the full report titled "Relation between Directly Detected Patent Foramen Ovale and Ischemic Brain Lesions in Sport Divers." It is in the 2 January 2001 issue of Annals of Internal Medicine (volume 134, pages 21-24). The authors are M Schwerzmann, C Seiler, E Lipp, R Guzman, KO Lövblad, M Kraus, and N Kucher.

What is the problem and what is known about it so far?

A known risk of scuba diving is decompression illness, commonly known as "the bends." The brain can be injured in decompression illness because small gas bubbles that form in the blood as a diver rises to the surface can block circulation to the brain. The symptoms of decompression illness include skin changes, joint pain, confusion, and other transient or lasting neurologic symptoms. Brain imaging tests in divers who have previously had decompression illness show areas that have been injured as a result of getting too little oxygen (ischemic brain lesions). A recent study suggested that these brain lesions also occur in divers who have never had symptoms of decompression illness. It is believed that these lesions may be more common in divers who have an abnormality of the heart called a patent foramen ovale. A patent foramen ovale is an abnormal hole in the wall between chambers of the heart, which could allow more bubbles to get into the brain circulation.

Why did the researchers do this particular study?

To find out whether ischemic brain lesions in scuba divers are associated with symptomatic decompression illness and patent foramen ovale.

Who was studied?

The study included 52 divers who had completed at least 200 scuba dives and 52 healthy adults who had never dived (controls).

How was the study done?

The researchers asked the divers detailed questions about previous symptoms of decompression illness. The divers and nondiving controls all had ultrasound tests of the heart (echocardiograms) to look for patent foramen ovale and magnetic resonance imaging (MRI) tests of the brain to look for ischemic lesions.

What did the researchers find?

Divers with patent foramen ovale were at least four times more likely to report decompression illness and had more brain lesions than divers without patent foramen ovale. However, divers had more ischemic brain lesions than nondivers, regardless of whether they had experienced decompression illness or had a patent foramen ovale.

What were the limitations of the study?

This study was small and relied on divers' reports on whether they had ever had decompression illness, rather on than actual examination at the time of the illness. Divers who felt ill after a dive may have been more likely to participate in the study than divers who had not felt ill. The study does not tell us whether the presence of ischemic brain lesions is associated with any health consequences.

What are the implications of the study?

Scuba diving is associated with ischemic brain lesions, regardless of whether a diver has a patent foramen ovale. Divers with a patent foramen ovale have an increased number of ischemic brain lesions.