Cohort study of multiple brain lesions in sport divers: role of a patent foramen ovale.

OBJECTIVE

To investigate the role of a patient foramen ovale in the pathogenesis of multiple brain lesions acquired by sport divers in the absence of reported decompression symptoms.

DESIGN

Prospective double blind cohort study.

SETTING

Diving clubs around Heidelberg and departments of neuroradiology and neurology.

SUBJECTS: 87 sport divers with a minimum of 160 scuba dives (dives with self contained underwater breathing apparatus).

MAIN OUTCOME MEASURES: Presence of multiple brain lesions visualised by cranial magnetic resonance imaging and presence and size of patent foramen ovale as documented by echocontrast transcranial Doppler ultrasonography.

RESULTS

25 subjects were found to have a right-to-left shunt, 13 with a patent foramen ovale of high haemodynamic relevance. A total of 41 brain lesions were detected in 11 divers. There were seven brain lesions in seven divers without a right-to-left shunt and 34 lesions in four divers with a right-to-left shunt. Multiple brain lesions occurred exclusively in three divers with a large patent foramen ovale (P = 0.004).

CONCLUSIONS

Multiple brain lesions in sport divers were associated with presence of a large patent foramen ovale. This association suggests paradoxical gas embolism as the pathological mechanism. A patent foramen ovale of high haemodynamic relevance seems to be an important risk factor for developing multiple brain lesions in sport divers.