The Brain and Diving

[LeadTurn_SD]

Hi Bubbletruble,

Thanks again for posting the original info, and for sending the link to the study!

I am officially and publicly prying my foot from my mouth (don’t worry, there is no danger, I’m a pro, I do this all the time ).

That study was interesting, and there was enough data there for more than a “Hmmm, that is interesting” from me. My bad.

The brain lesions are beyond what I know much about, so I can’t comment.

The cervical spine disc herniations in the diver-group were more than I’d expect in the general population, especially considering the relatively young age of the divers. It also looked significant, at least maybe.

But since those types of lesions are not unheard of in non-divers, I’m not sure what to think. The level of the disc herniations is normal (from a spinal biomechanical standpoint... same % at same levels as in the general population).

I’d also question what the mechanism behind the herniations was (doesn’t mean they we not dive related, just means I don’t understand how they were caused by breathing compressed air at depth, versus the more “routine” mechanical/degenerative causes seen in the general population).

Interesting stuff for sure.

Thanks again for posting it.

Best wishes.

 

[Plane Trouble]

I appreciate the link as well Bubbletrouble... Although I find it deeply disturbing. I did a semesters worth of neurophysiology research when I was an undergraduate. Are you a grad student in neuroscience? Obviously you are quite an avid diver and don't seem too terribly concerned about CNS damage... Why is that? (That is not meant to be a smart@#$ question at all). I just find it troubling that a hobby that has always interested me and given me great pleasure could in fact unbeknownst to me (for now) be damaging my cognitive abilities etc....

 

[Bubbletrubble]

Are you a grad student in neuroscience?

Yes.

Obviously you are quite an avid diver and don't seem too terribly concerned about CNS damage... Why is that? (That is not meant to be a smart@#$ question at all).

I really enjoy diving. It is my personal belief that if one dives conservatively keeping well within NDLs, adhering to recommended ascent rates, and conducting appropriate safety stops, the risks of sustaining short-term and long-term damage to the brain and spinal cord are very low. I view commercial divers and scuba instructors (essentially people who dive for a living) with significantly higher levels of exposure to decompression stress as "canaries in the coal mine." If this demographic ever starts coming down with a high incidence of severe cognitive deficits in mid-to-late adulthood that can be reliably linked to diving, then I'll be the first person to curtail my diving habits...or probably give it up altogether. (Nevermind that the damage to my brain might already be done.)

If you want to worry about your future cognitive health, take a look at the epidemiological statistics for Alzheimer's disease. Considering that people are living longer due to advances in medical technology, this means that the prevalence of Alzheimer's disease is going to markedly increase with the aging Baby Boomer generation. I shudder to think what our poor health care system will look like in another 10-20 years. Mark my words, there will be a huge spike in the numbers of long term care facilities to care for Alzheimer's patients.

I guess I have a slightly different view of the CNS from the average non-science person. From my research and the work of others, I see that the CNS is far more plastic than we give it credit for. Many new neurons are being born every day in the brain and being functionally integrated. I'm not saying that in vivo neurogenesis can completely compensate for massive neuronal losses due to stroke, but it's possible that it could mitigate it somewhat. My point is that there is some hope even if your neurons start to die.

I didn't mean to scare you away from the sport. I just wish that more divers would acknowledge that we still know very little about the long-term consequences of diving. If you're going to dive, all the more reason to try to do it safely IMO.

 

[LeadTurn_SD]

I can't answer for Bubbletrubble, but for me, I'm more concerned with the effects of surface enviromental factors on CNS and overall health than I am with diving.

If it really is a pressure-change-induced lesion, I'd be interested in seeing a study on military, commercial, and civilian pilots too. Pilots are routinely going from sea level to 8,000 feet(?) in pressurized cabins, so I wonder if these types of changes would show up...

Anyway, I'll try not to agonize too much about it this weekend when I dive I just think about Jacques Cousteau when he dove deep and dark and cold on the Brittanic.... he was old as the ocean itself at that point in his life, triple tanks and double hose regulator, no stinkin' BC, wearing his trademark red knit cap instead of a dive hood, and faced a long decompression in a diving bell suspended below the Calypso afterwards.... if that kind of adventure is what dive-related CNS lesions have in store me, I'll Take It!!

Best wishes!

Edit: Sorry, Bubbletrubble answered as I was typing. Nice post Bubbletrubble.

 

[Plane Trouble]

Thats really cool about the neuroscience Grad program. You at Scripps? I know Floyd Bloom and Gerald Edelman were huge at Scripps for a long time.

I really enjoy diving. It is my personal belief that if one dives conservatively keeping well within NDLs, adhering to recommended ascent rates, and conducting appropriate safety stops, the risks of sustaining short-term and long-term damage to the brain and spinal cord are very low.

I would agree all things considered.

I view commercial divers and scuba instructors (essentially people who dive for a living) with significantly higher levels of exposure to decompression stress as "canaries in the coal mine." If this demographic ever starts coming down with a high incidence of severe cognitive deficits in mid-to-late adulthood that can be reliably linked to diving, then I'll be the first person to curtail my diving habits...or probably give it up altogether.

Fortunately I think we can take comfort in the fact that if this particular demographic was to come down with more frequent then normal cases of CNS conditions than the general population, we'd probably have seen it by now...

I guess I have a slightly different view of the CNS from the average non-science person. From my research and the work of others, I see that the CNS is far more plastic than we give it credit for. Many new neurons are being born every day in the brain and being functionally integrated.

Thank you Fred H. Gage! And Pasco Rakic! I actually attended at Rakic neurogenesis lecture at Vanderbilt University a few years ago and it was spectacular.

I can't answer for Bubbletrubble, but for me, I'm more concerned with the effects of surface enviromental factors on CNS and overall health than I am with diving.

If it really is a pressure-change-induced lesion, I'd be interested in seeing a study on military, commercial, and civilian pilots too. Pilots are routinely going from sea level to 8,000 feet(?) in pressurized cabins, so I wonder if these types of changes would show up...

This is actually what I do for a living. I have been a pilot since I was a teenager and worked as a commercial pilot and flight instructor through college and its what I still do to this day. I can say that the risks of decompression in an aircraft are a lot less than that of SCUBA diving. The pressure changes that take place in the atmosphere are much more gradual than what takes place in aqueous solution. The risk of decompression below FL180 (18,000ft) is almost unheard of in healthy individuals and people who don't have the most known risk factor - SCUBA diving within the preceding 24 hours. There is still a low but documented risk between FL180 and FL250 but most altitude associated decompressions come at altitudes above 25,000ft.

Unless you have been SCUBA diving, 8,000ft (what most jet cabins are pressurized to) is pretty low. Its rare to get HACE (High Altitude Cerebral Edema) and HAPE (High Altitude Pulmonary Edema) at 8,000 ft MSL (Mean Sea Level) or below. These two conditions by the way don't involve the evolution of gases in the blood, but involve a permeation of the vascular endothelium and result in fluid leakage in turn resulting in edema in the affected regions.

 

[Bubbletrubble]

Thats really cool about the neuroscience Grad program. You at Scripps? I know Floyd Bloom and Gerald Edelman were huge at Scripps for a long time.

Nope. UCSD. Quite close to TSRI, though.

Fortunately I think we can take comfort in the fact that if this particular demographic was to come down with more frequent then normal cases of CNS conditions than the general population, we'd probably have seen it by now...

I don't know about this. I think one could argue that with the widespread use of dive computers nowadays, the recreational diving population and perhaps these "canaries" are diving more aggressively than ever. I don't think we'll really know for several more decades. I bet 30 years from now, divers using new-fangled, sophisticated decompression algorithms will look back and wonder why we continued to dive when we knew so little about DCS.

Thank you Fred H. Gage! And Pasco Rakic! I actually attended at Rakic neurogenesis lecture at Vanderbilt University a few years ago and it was spectacular.

Gage is a really generous guy. He was nice enough to let me use his lab's sliding microtome for brain-cutting.
I never met Pasko. He's well known in the field, though. For a long, long time he denied the existence of adult neurogenesis occurring in the mammalian brain. Here's the abstract of one of his Science papers published in 1985:

Systematic analysis of autoradiograms prepared from postpubertal rhesus monkeys given single and multiple injections of tritium-labeled thymidine and killed 3 days to 6 years later displayed a slow turnover of glial cells but failed to reveal any radiolabeled neurons. Therefore, unlike neurons of some nonprimate species, all neurons of the rhesus monkey brain are generated during prenatal and early postnatal life. A stable population of neurons in primates, including humans, may be important for the continuity of learning and memory over a lifetime.

Wrong. Wrong. Wrong. They should make him remove that Science pub from his C.V.
However, he has made significant contributions with regard to mammalian brain development, in particular the stuff about how layers are formed in the cerebral cortex.

 

[Plane Trouble]

Yeah I pretty much just threw Rakic in there since he identified the subventricular zone and the site of neurogenesis... If I was him I would personally remove that article.

I don't know about this. I think one could argue that with the widespread use of dive computers nowadays, the recreational diving population and perhaps these "canaries" are diving more aggressively than ever

I use a computer. I was under the impression that, dive computers use conservative calculations to keep divers within NDLs... I know that the advent of the glass cockpit has increased the safety of flying substantially. I figured the advent of the dive computer would have done the same.

 

[Bubbletrubble]

Yeah I pretty much just threw Rakic in there since he identified the subventricular zone and the site of neurogenesis... If I was him I would personally remove that article.

Although Rakic was the first to identify adult SVZ neurogenesis in the primate system, I wouldn't exactly call it "seminal." First, adult SVZ neurogenesis probably only sends newly born neurons to the olfactory bulb -- not much importance there beyond smelling stuff. Second, other groups had already shown this in the rodent, so adult SVZ neurogenesis really wasn't an original idea either.
Rakic did do some very interesting work in the 1970s on how the monkey visual cortex was setup during cerebrocortical development.

I use a computer. I was under the impression that, dive computers use conservative calculations to keep divers within NDLs... I know that the advent of the glass cockpit has increased the safety of flying substantially. I figured the advent of the dive computer would have done the same.

Well, I think a lot of people would argue that diving tables is much more conservative than diving with a computer since the tables don't give you credit for multi-level profiles. With tables, you use max depth to figure NDLs...even if you weren't down at max depth very long. I'd say that the majority of recreational dives are probably multi-level profiles. By diving according to a computer, divers might be placing more decompression stress on their bodies than if they had used tables.

The one exception I see to this is safety with respect to following recommended ascent rates. With a dive computer, it's probably easier to adhere to slower ascent rates, e.g., 30 ft/min.

 

[Plane Trouble]

Although Rakic was the first to identify adult SVZ neurogenesis in the primate system, I wouldn't exactly call it "seminal." First, adult SVZ neurogenesis probably only sends newly born neurons to the olfactory bulb -- not much importance there beyond smelling stuff. Second, other groups had already shown this in the rodent, so adult SVZ neurogenesis really wasn't an original idea either.
Rakic did do some very interesting work in the 1970s on how the monkey visual cortex was setup during cerebrocortical development.

Yeah I heard it required a special grant, and consisted of 200 Rhesus Macaques, and so much radioactive Thymidine that the companies that manufactured it had to increase production all because of HIS experiment.

Well, I think a lot of people would argue that diving tables is much more conservative than diving with a computer since the tables don't give you credit for multi-level profiles. With tables, you use max depth to figure NDLs...even if you weren't down at max depth very long. I'd say that the majority of recreational dives are probably multi-level profiles. By diving according to a computer, divers might be placing more decompression stress on their bodies than if they had used tables.

The one exception I see to this is safety with respect to following recommended ascent rates. With a dive computer, it's probably easier to adhere to slower ascent rates, e.g., 30 ft/min.

I see your point completely. What are your thoughts on Patent Foramen Ovale conditions? I mean apparently up to 20% of the adult population has the condition from birth (in varying degrees of severity) and that the only way to really test for it accurately is using Bubble Echocardiography (which hardly anyone is going to have done). If kept conservatively within a NDL in relatively shallow water (less than 50ft) even with a Patent Foramen Ovale, do you feel the risk of decompression stress is very high?

 

[LeadTurn_SD]

.....What are your thoughts on Patent Foramen Ovale conditions? I mean apparently up to 20% of the adult population has the condition from birth (in varying degrees of severity) and that the only way to really test for it accurately is using Bubble Echocardiography (which hardly anyone is going to have done). If kept conservatively within a NDL in relatively shallow water (less than 50ft) even with a Patent Foramen Ovale, do you feel the risk of decompression stress is very high?

I've been curious about this as well. Hopefully someone with some real knowledge (not me!!!) will chime in...

However, if you assume that the percentage of PFO is the same in the diving population as the general population, and that the rate of DCS among recreational divers is much lower than the occurance of PFO in those same divers, it seems like the risk is pretty minimal for conservative NDL dives.

Otherwise, it would seem that we'd see a much higher rate of "un-deserved hits".

Best wishes.