Purpose: The ELTHI diving study has shown that professional divers are three times more likely to report 'forgetfullness or loss of concentration' than age matched, non-diving off-shore workers (1). This finding has been replicated in objective neuropsychological testing. We hypothesised that this may be due to gas microemboli generated during decompression and that 'forgetful' divers would have a greater number and/or severity of white matter lesions (WML) on brain magnetic resonance images (MRI). The aim of this study was to compare MRI in a group of 'forgetful' professional divers with MRI in 'non-forgetful' divers and other 'non-forgetful' off-shore workers
Methods and Materials: 291 subjects, with no history of head injury, matched for age and IQ (98 'forgetful' divers, 98 'non-forgetful' divers and 95 'non-forgetful' off-shore workers) were imaged on a 1.5T NVi system (General Electric) using fluid attenuation inversion recovery (FLAIR), T2W axial and 3D T1W sequences. FLAIR images were scored using a semiquantitative, modified Scheltens scale (2) by two experienced, blinded observers. Subcortical and deep WML in the frontal, parietal, temporal and occipital lobes and the internal capsule were scored on a 6 point scale for each region, giving a maximum possible white matter score of 30.
Results: 128 subjects had no WML. Scores for WML ranged from 1-18 with 102 subjects scoring between 1 and 3. The commonest location for WML was frontal. There was no significant difference in the number of 'forgetful' divers versus 'non-forgetful' divers or 'non-forgetful' off-shore workers with WML. Because many subjects had minor WML scores, thresholds of >6 for total WML score and >4 for frontal WML score were applied. Comparison of groups again showed no significant difference between 'forgetful' divers (7% had total WML score >6 and 6% had frontal WML score >4) 'non-forgetful' divers (16% and 8%) and 'non-forgetful' off-shore workers (13% and 6%). We have not yet controlled for confounding variables such as age, hypertension or diving history
Conclusion: We have not shown an association between objectively confirmed memory complaints in divers and WML. These results conflict with those of some published studies (3) but confirm those of others (4,5). (1) Macdiarmid J, et al. Underwater and Hyperbaric Medicine 2001;28 p74. (2) Scheltens P, et al. J Neurol. Sci 1993;114:7-12 (3) Sipinen SA, et al. Undersea Hyperb Med 1999;26:61-65. (4) Hutzelmann A, et al. Acta Radiologica 2000;41:18-21. (5) Cordes P, et al. Neurology 2000;55:1743-1745.
(J.A.R. received a Health and Safety Executive Grant.)
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