Brain MRI signal abnormalities and right-to-left shunting in asymptomatic military divers.

INTRODUCTION: We conducted a controlled study to assess the prevalence of brain MRI hyperintense signals and their correlation with right-to-left shunting (RLS) in military divers. METHODS: We prospectively enrolled 32 asymptomatic military divers under 41 yr of age and 32 non-diving healthy subjects matched with respect to age and vascular disease risk factors. We examined both groups with a 3-Tesla brain MRI; RLS was detected using transcranial pulsed Doppler in divers only. RESULTS: Hyperintense spots were observed in 43.7% of the divers and 21.8% of the control subjects. In particular, divers with significant shunting exhibited a higher prevalence of hyperintensities compared to those with slight or no RLS (75% vs. 25%, respectively). Linear trend analysis also revealed a positive correlation between focal white matter changes, determined using a validated visual rating scale and the RLS grade. CONCLUSION: Healthy military divers with a hemodynamically relevant RLS have an increased likelihood of cerebral hyperintense spots compared to age-matched normal subjects. The clinical relevance of these MRI signal abnormalities and their causal relationship with diving remain unclear.

Musculoskeletal decompression sickness and risk of dysbaric osteonecrosis in recreational divers.

INTRODUCTION: Dysbaric osteonecrosis (DON) is a complication that usually occurs in professional divers or compressedair workers. Its correlation with a previous musculoskeletal decompression injury (i.e., 'limb bend') remains a controversial subject. There is little information about the prevalence of DON and its relationship to decompression sickness (DCS) in recreational divers. METHODS: We undertook an observational, retrospective study of recreational divers treated for musculoskeletal DCS between 2004 and 2008 in three hyperbaric centres in the south of France using magnetic resonance imaging (MRI) following hyperbaric treatment. RESULTS: Twenty-five (11.5%) musculoskeletal DCS cases were identified amongst 288 diving accidents treated during this period. Average age was 38 years with a mean body mass index of 26 kg/square m. Joint pains were located in the shoulder area in 21 divers, mainly in experienced male divers after performing repetitive long, deep dives with adequate decompression using dive computers. Twenty-one of 25 injured divers were examined by MRI of the affected area shortly after the accident. Six had initial humeral lesions compatible with ischaemic necrosis, but two repeat MRI examinations at three months did not reveal bone abnormalities. Increasing pain during hyperbaric treatment appeared to be the only factor associated with DON occurrence. CONCLUSIONS: Musculoskeletal DCS in recreational diving is particularly seen in provocative dive profiles considered to carry a high risk for bubble production during decompression. The occurrence of this insult appears also to be related to other factors needing further study. The risk of early development of DON should not be ignored.

MRI findings and clinical outcome in 45 divers with spinal cord decompression sickness.

BACKGROUND: Decompression sickness (DCS) affecting the spinal cord is the most dangerous form of diving-related injury with potential sequelae. This study was conducted to evaluate the relationship between spinal cord lesions on MRI and clinical findings in divers with spinal DCS. METHODS: We studied 45 cases of DCS that were referred to our hyperbaric facility with clinical evidence of spinal involvement during the period 2002-2007. The study included only patients who underwent MRI within 10 d of injury. The severity of spinal DCS for each patient was rated numerically for both the acute event and 1 mo later. The presence or absence of back pain was also noted. RESULTS: Spinal cord lesions were significantly more frequent in divers with severe DCS, and did not occur in any diver who experienced a favorable outcome (sensitivity = 67%, specificity = 100%, negative predictive value = 77%, positive predictive value = 100%). The presence of vertebral degenerative changes that impinged on the spinal cord was strongly associated with MRI abnormalities, but not with a negative outcome. Acute back pain was associated with hyperintense lesions and persistence of neurological sequelae [OR = 14 (95% CI, 3.1 to 63.5)]. CONCLUSION: The results show that MRI could be helpful in predicting clinical outcome in divers with spinal cord DCS. The presence of medullary compressive factors and vertebral back pain after surfacing indicate increased likelihood of severe myelopathy with incomplete recovery.

Towards in vivo diffusion tensor MRI on human heart using edge-preserving regularization.

We investigate the noise sensitivity in various Diffusion Tensor MRI acquisition protocols in sixteen human ex vivo hearts. In particular, we compare the accuracy of protocols with various numbers of excitations and diffusion sensitizing directions for estimating the principal diffusion directions in the myocardium. It is observed that noise sensitivity decreases as the number of excitations and the number of sensitizing directions increase (and hence as the acquisition time increases). To reduce the effects of noise and to improve the results obtained with a smaller number of excitations and/or a smaller number of sensitizing directions, we introduce a 3-D edge-preserving regularization method operating on diffusion weighted images. It allows to maintain the quality of the principal diffusion direction field while minimizing the acquisition time, which is a necessary step for in vivo diffusion tensor MR imaging of the human heart.