BMJ Neurobone

Question:
I have recently heard of a medical article reporting alarming long-term effects of Diving. Should I worry?

Answer:
Long-Term Effects of Diving - The latest news isn't exactly new.
As a result of a recent paper published in the British Medical Journal Lancet in early June, a number of subsequent articles have surfaced which question the long-term consequences of recreational diving. This has caused a considerable amount of inquiry among scuba divers - and many divers have looked to DAN for a response.
The paper, by Dr. Jurgen Reul and colleagues from the Technical University of Aachen, Germany, is titled "Central nervous system lesions and cervical disc hemiations in amateur divers." These scientists studied 102 subjects - 52 amateur divers and 50 from other sports - using magnetic resonance imaging (MRI) of the brain and cervical spinal cord.
Of the divers, one had a history of decompression sickness (DCS) and two others reported situations which almost caused DCS. In the MRI results, 27 of 52 divers had a total of 85 lesions; of the 50 nondivers, 14 lesions were found in 10 people.
In addition, 32 of the divers showed at least one abnormality of a cervical disc, compared to nine in the nondivers. What does this show? First, that all of this should be put in context - these findings are not new. Whether sport and commercial divers have changes in their brains as a result of diving has been a question for many years, but as yet there has been no substantive proof.
The supposition of any damage to the brain rests on the occurrence of so-called "silent bubbles" occurring in the blood or brain and spinal cord. That such bubbles do exist has been well demonstrated by Doppler technology in blood and tissue studies of animals' spinal cords. Whether these silent bubbles are the cause of changes in the brain remains as yet unproven.
In most cases, the lungs filter out bubbles - except when there is a hole in the heart, or patent foramen ovale, when bubbles can pass to the arterial side to reach the brain and spinal cord. Spontaneous growth of bubbles in tissue during ascent is another question and relies on an adequate tension of gas in the neurological tissues accompanied by too rapid an ascent. Hence, it is more likely in deeper dives and more rapid ascents.
On the commercial front in diving, the Norwegians have organized two workshops: the first in 1983 called "Long-Term Neurological Consequences of Deep Diving," and another two years ago whose proceedings and consensus opinions were published in 1994. The 1993 consensus by international physicians and scientists was: "There is evidence that changes in bone, the central nervous system and the lungs can be demonstrated in some divers who have not experienced a diving accident. The changes are, in most cases, minor and do not influence the diver's quality of life. However, the changes are of a nature that may influence the diver's future health. [There is no evidence to support this.] The scientific evidence is limited, and future research is required to obtain adequate answers to the questions of long-term health effects. "
More recent research by Dr. P.A. Rinck reported MRI studies in 70 professional divers and 47 nondiving controls. Focal areas of high-signal density (called unidentified bright objects, or UBOs) like the lesions reported by Dr. Reul were seen in 34 percent of the divers and 42 percent of the nondivers. These UBOs are often seen in all MRIs - and more often as we age. They do not indicate scarring of the brain, but, on the other hand, we do not know exactly what they mean.
The issue of brain lesions remains unproven; and if there are effects, they do not appear to materially affect the individual. As more sensitive tests become available, it is inevitable that unusual results will be found, not only in diving, but in many other unusual environments. We must, therefore, probably rely on the quality of life as the standard.
More research is needed, but the world is filled with divers - including diving medicine physicians and scientists like myself - who have been diving for over 40 years who show no unusual effects or early aging processes. Meanwhile, the research will continue.

Note from David Elliott: Most of the basic references for this subject are in Moon & Elliott in the 4th edition of B&E and, since then, there have been only two well publicised papers on 'healthy' divers, both with MRI findings worthy of criticism. One is Ruel et al LANCET, 3 June 1995 and the other Knauth et al BMJ 1997;314: 701-4.