silent brain lesions from gas embolism?

[sunfish]

I recently heard of a somewhat old (maybe from seven or so years ago) bit of research done by neurosurgeons and neuroradiologists regarding cerebral angiography. (This is when they inject a dye that will show up on X-ray directly into the blood vessels of a patient's brain, and then take X-rays. The procedure is not without risks, including the chance of accidentally injecting air into the blood vessels, causing a stroke, although there's only a small percentage who actually get a full-blown stroke...)

So, in this study, they took MRIs of patients right after doing the angiography, regardless of whether or not the patients had symptoms of stroke. The results of the study supposedly showed that a far larger percentage of patients receiving angiography were getting air embolisms in the brain than was previously thought. It was just that they didn't show symptoms, and the lesions either went away on their own, or continued to cause the person absolutely no harm.

My question is, has there been any kind of study of this type regarding divers, in which divers NOT showing any neurological symptoms were checked to see if they had any brain lesions large enough to be, well, caught, but not large enough to cause them any problems?

 

[Dr Deco]

Dear sunfish:

Angiography

There is always some worry when the possibility of air entering the circulation to the brain exists, as in agiography. [The references below can be obtained at a university library should one wish to read them. ] The researchers basically found that numerous brain lesions were present on MRI and correlated with the number of gas bubbles measured with the transcranial Doppler. Fortunately, there were not any signs or symptoms of brain damage in this group. [There is about a 1% chance that real problems will develop. ]
_____

Markus H, et al. Microscopic air embolism during cerebral angiography and strategies for its avoidance. Lancet 1993 ;341(8848):784-7

Gerraty RP, et al. Microemboli during carotid angiography. Association with stroke risk factors or subsequent magnetic resonance imaging changes? Stroke 1996 Sep;27(9):1543-7
____

Diving and Brain Lesions

This is a good topic and has been discussed since the early 1990s. There were several observations that SCUBA divers displayed areas of injury on a MRI scan. This has led to the belief that even asymptomatic SCUBA dives could cause some harm. The problem with all of this is that the non-diver controls also have these lesions . These areas are present in fewer numbers among the controls, but they are there nevertheless.

Controversy

Controversy exists over the real meaning of this. Some reports claim that divers with DCS had more of these problem areas, and other studies are contrary (references below). At the current time, this has not been settled.

Dr Deco :doctor:

NO DIFFERENCE IN MENTAL STATUS FOUND

Cordes P, Keil R, Bartsch T, Tetzlaff K, Reuter M, Hutzelmann A, Friege L, Meyer T, Bettinghausen E, Deuschl G. Neurologic outcome of controlled compressed-air diving. Neurology 2000;55(11):1743-5

Sipinen SA, Ahovuo J, Halonen JP. Electroencephalography and magnetic resonance imaging after diving and decompression incidents: a controlled study. Undersea Hyperb Med 1999 ;26(2):61-5

Bast-Pettersen R. Long-term neuropsychological effects in non-saturation construction divers. Aviat Space Environ Med 1999 Jan;70(1):51-7

Calder I. Does diving damage your brain? Occup Med (Lond) 1992;42(4):213-4

Rinck PA, Svihus R, de Francisco P. MR imaging of the central nervous system in divers. J Magn Reson Imaging 1991 May-Jun;1(3):293-9

FOUND DIFFERENCE

Tetzlaff K, Friege L, Hutzelmann A, Reuter M, Holl D, Leplow B.Magnetic resonance signal abnormalities and neuropsychological deficits in elderly compressed-air divers. Eur Neurol 1999;42(4):194-9

Yanagawa Y, Okada Y, Terai C, Ikeda T, Ishida K, Fukuda H, Hirata F, Fujita K. MR imaging of the central nervous system in divers. Aviat Space Environ Med 1998 Sep;69(9):892-5

 

[sunfish]

Thanks so much for your help, Dr. Deco! I think the 2nd one you listed for angiography was the one I saw. I tried searching for the diving ones, but couldn't find any. Thanks to you, I know where to look now! I think it's interesting that of the MRI related studies, the one that DID find a difference is dated fairly recently. I figure it's due to new, more sensitive imaging techniques.

Of course, we must always remember "sensitive" doesn't always mean the same thing as "accurate"!! ut: ut: ut:

 

[John C. Ratliff]

I recently saw an article, that I copied at work, that found an increase in brian lesions amoung divers to a partially open septum between the two heart chambers. This would allow microbubbles from the circulation that should go to the lungs to go to the brain instead. I'll keep my eyes open, and when I get the article in hand again, I'll post more. The interesting thing is that this condition is readily diagnosed, and that many people in our population have this condition. There are also new techniques to repair the problem.

SeaRat

Later in the day:

The article is by Barbara L. Krooss, Ph.D., titled "Diving with a Broken Heart," in the Spring 2001 issue of Immersed. In it, Dr. Krooss stated that 10-30% osf adults have at least a degree of a defect in the heart called an atrial septal defect (intraatrial shunt) called PFO. Under stress, this flap of tissue that may not have closed fully (usually this happens shortly after birth), may open further. This can allow blood destined to the lungs to go to the brain as it bypasses the lungs and goes to the other side of the heart. If there are bubbles, these can therefore go to the brain.

Two paragraphs from this article really tweaked my interest:

Given the high prevalence of PFO and the low incidence of DCS, it's easy to conclude that it's not generally a problem. Yet PFO may be the culprit when DCS hits early and hard, as in neurological symptoms and in undeserved hits taken by those who have violated no known diving rules. According to the British SubAqua Club, between 30 percent and 50 percent of all cases of DCS involve undeserved hits. Evidence suggests that size matters in PFOs.

P Germonpre's group at the Centre for Hyperbaric Oxygen Therapy at the Military Hospital, Brussels, Belgium, compared 37 divers who suffered neurological DCS with a matched control group of divers who never had DCS. The group used transesophageal contrast echocardiography to estimate PFO size. They concluded that PFO plays a significant role in unexplained cerebral DCS, but not of spinal DCS. Their study, published in 1998, reported that divers with DCS with lesions localized in the high cervical spinal cord, inner ear, or cerebellum or cerebrum of the brain had a significantly higher prevalence of PFO than did divers with DCS in the lower spinal cord. In unexplained DCS, this difference was significant only among those with large PFOs. (page 34)

I hope this helps.

SeaRat

 

[Dr Deco]

Dear searat:

Thanks for the reference. That was a good one and not on the list I posted recently. {Germonpre P, Dendale P, Unger P, Balestra C. Patent foramen ovale and decompression sickness in sports divers. J Appl Physiol 1998 May;84(5):1622-6 }

One should note that the authors speak of a “large PFO only.” In other posts, I have spoken of a hemodynamically significant PFO. This means that all PFOs were not created equal. Fortunately, the incidence of “significant” PFOs is much smaller than just a “PFO present.” The former are bad for divers.

Dr Deco:doctor:

On vacation this week.