Hi HB,
This is an area of interest of mine and there have been a surprising number of studies on the topic over the years. These mostly involve commercial/military/technical divers, many of whom had sustained neurological DCS.
Some work has been done with sports divers without histories of DCI and some of this has shown gray & white matter lesions, impairment of neuropsychological function, and abnormal EEGs & MRIs. For better or for worse, for just about every study that finds abnormalities there is another that finds nothing of concern. The following is a smattering of those reporting positive findings:
1. Undersea Hyperb Med. 2011 May-Jun;38(3):197-204.
Neuropsychological deficits in scuba divers: an exploratory investigation.
Kowalski JT, Varn A, Rottger S, Seidack S, Kahler W, Gerber WD, Andrasik F, Koch A.
German Naval Medical Institute, Kronshagen, Germany.
CONCLUSIONS: The findings support the proposed possibility that minimal cerebral lesions occur after diving even without DCS. Further studies with this highly selective population of very experienced divers using more elaborate neurocognitive and neuromotor tasks seem warranted.
2. Ann Intern Med. 2001 Jan 2;134(1):21-4.
Relation between directly detected patent foramen ovale and ischemic brain lesions in sport divers.
Schwerzmann M, Seiler C, Lipp E, Guzman R, Lövblad KO, Kraus M, Kucher N.
Swiss Cardiovascular Center Bern and University Hospital.
CONCLUSIONS: Regardless of whether a diver has a patent foramen ovale, diving is associated with ischemic brain lesions.
3. Eur Neurol. 1999;42(4):194-9.
Magnetic resonance signal abnormalities and neuropsychological deficits in elderly compressed-air divers.
Tetzlaff K, Friege L, Hutzelmann A, Reuter M, Höll D, Leplow B.
German Naval Medical Institute, Kronshagen, Germany.
Abstract
We investigated the association between MR signal abnormalities of the central nervous system, neuropsychologic performance and exposure indices in 20 experienced elderly compressed-air divers who had no history of neurological decompression illness (DCI). Results of MRI of the brain and psychometric testing were compared with 20 matched healthy commercial employees who never dived: 60% of the divers and 45% of the controls had hyperintense MR abnormalities. Among divers, both the number and the size of abnormalities correlated with hours diving in the deep air-diving range of 40-60 m (p < 0.05). Divers' mental flexibility and visual tracking performance were decreased in comparison with controls (p< 0.05 and p < 0.01). Divers thus are at risk of detrimental long-term effects of compressed-air diving on the central nervous system even in the absence of a history of neurological DCI.
4. Lancet. 1995 Jun 3;345(8962):1403-5.
Central nervous system lesions and cervical disc herniations in amateur divers.
Reul J, Weis J, Jung A, Willmes K, Thron A.
Department of Neuroradiology, Technical University, Aachen, Germany.
Abstract
Permanent neuropsychological changes such as memory disturbances and depression have been found in professional divers, even in those who have never had decompression sickness. The changes are probably the result of intravascular gas bubbles insufficient to cause acute symptoms. We examined amateur divers with long histories of self-contained underwater breathing apparatus diving by magnetic resonance imaging and compared them with normal controls. Hyperintense lesions of the subcortical cerebral white matter and degenerative changes of the cervical disks were significantly more common in the divers. 27 of 52 divers had a total of 86 focal hyperintensities versus 10 of 50 controls with 14 focal hyperintensities (p < 0.01). 32 divers had at least one degenerated intravertebral disc versus 9 controls (p < 0.0001). These results suggest that amateur divers are at risk of accumulating lesions in the central nervous system and in cartilage.
There are a number of important points to bear in mind when thinking about such findings, including:
1. There are no well-controlled studies that substantiate that scuba actually causes these abnormalities.
2. Assuming that these abnormalities in fact are dive-related, it is not known at what point these changes might be expected to occur in sports divers, e.g., depths, times, number of lifetime dives, temperatures.
3. The clinical significance of these abnormalities of brain is often unclear. In many cases, they are silent, that is, they dont seem to be adversely impacting neurocognitive status. And in most cases where they do seem to have an effect, the impact is trivial in any real world sense.
BTW, I am aware of no studies in respected, peer-reviewed journals that suggest an increase in psychiatric disorder (mood disorder or any other) in sports divers without histories of DCI.
This is a complicated subject and much remains unknown. While its being sorted out, IMHO there is no reason for alarm. I have been aware of such studies for decades and havent changed my diving practices one iota solely as a result of them.
The recreational diver who carefully follows customary safe diving protocols appears to be at little meaningful risk of scuba-related cerebral damage or dysfunction even over a very long period of regular participation.
Regards,
DocVikingo
This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual, and should not be construed as such.
