The risk has been underestimated

Editor—Using magnetic resonance imaging Michael Knauth and colleagues reinforce the message that scuba diving is a dangerous sport1; they show images of some small areas of brain damage found in apparently normal participants. I think that they have greatly underestimated the amount of damage and are wrong to criticise the findings of Reul et al, whose study included greatly enlarged perivascular spaces as lesions.2 Knauth and colleagues cite a paper by Jungreis et al which suggested that such fluid filled spaces may be of no pathological significance3; however, these findings applied to people of stroke age in whom such spaces are indeed significant but should not be confused with lacunar infarcts. Healthy people with a mean age of 35.7 years whom Knauth and colleagues studied do not show large widely scattered perivascular spaces.

In his editorial in the same issue Peter Wilmshurst4 refers to a paper by my colleagues and me, in which we reported the histological study of many small lesions in scuba and young professional divers.5 Distension of the perivascular space was always associated with local destruction of the arterial muscle coat and elastic lamina, leaving a length of vessel of hyaline and collagen. Sometimes the artery or arteriole was itself dilated at that point. …