Introduction

Diving involves risk of neurological injuries. These may arise from decompression illness (a label which recognises the difficulty in distinguishing clinically decompression sickness due to gas nucleation from gas invasion caused by pulmonary barotrauma), anoxia (caused by near drowning), and the toxic effects of high partial pressures of breathing gases. The possibility that divers and others working in hyperbaric conditions may acquire neuropsychological damage without a clear history of a precipitating event is worrying. Since 1978 five international meetings have discussed this possibility, but no consensus exists whether diving per se causes brain damage.

Much of the evidence of functional abnormalities in divers with no history of decompression illness is anecdotal. Many reports describe findings in mixed groups of divers, some with and some without prior decompression illness.1 2 The most quoted study involved a snapshot assessment of intellectual function in Australian abalone divers,3 with no assessment of change over time and no controls. The psychological assessment probably failed to reflect the characteristics of these particular individuals, and their dive practices.

Nevertheless, degeneration and vasculopathy are seen after death in the brains and spinal cords of unaffected divers which resemble the abnormalities found after decompression illness.4 5 Retinal fluorescein angiography in …