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

Abstract

Objective: To investigate the role of a patent 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. An increased prevalence of multiple brain lesions has been reported in scuba divers compared with non-diving controls It has been suggested that the brain lesions were due to arterial gas embolism and that the gas emboli could have entered the arterial circulation via a patent foramen ovale We investigated this hypothesis in volunteer sport divers who had made at least 160 scuba dives Brain lesions occurred in divers even in the absence of reported decompression sickness Multiple brain lesions occurred exclusively in divers with a large patent foramen ovale The association of multiple brain lesions with a large patent foramen ovale suggests paradoxical gas embolism as the pathological mechanism