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Intense headaches

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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New Member
Feb 19, 2021
Hi I've had an issue with headaches after swimming underwater in a pool at only 2m depth. 25 yrs ago I was swimming a lap underwater 25m, then a few breaths and another 25 m and I had an strange experience of intense throbbing headache at the back of my head near the base of the skull immediately after surfacing fom an underwater lap. It came back 2 weeks afterthat initial occasion whilst doing some circuit training but never after that. Since then it hasn't happened. I have been spearfishing quite a lot and done a basic free dive course in the last 15 years as well as lots of other sports with no intense headache issues. A few days ago after some time off I went to the pool and did a 25m followed by a few breaths and another 25 m. I came up to the same intense headache and the throbbing lasted 5 mins before settling down to a fuzzy foggy headache for 36 hrs and general lethargy and weakness. I went to Dr 36 hrs later and had scans... no aneurysms or vascular disease. Interestingly my blood report showed higher than normal CO2 levels? Headache has gone but the dr could not give a diagnosis? I am now 46 and consider myself fit and healthy and not at all overweight. Has anyone had anything similar or knows what it might be? I might not be exhaling enough when I breath hold? Maybe holding air in lungs? Any experiences?
36 hours is a dangerously long time to have waited to see a doctor.

Sounds like it was triggered by oxygen deprivation or CO2 build up. For spearfishing, it is generally reckoned that you should rest/breath for at least as long as you dive, between dives and many recommend taking at least twice that time to recover.

I usually try not to breath out while diving, other than to reduce mask compression or clear my snorkel when surfacing (which is controversial but supported by some Italian research, for Spearfishing).
My suggestion, do the simplest thing first. Go see a massage therapist for your neck and shoulder area to help with circulation issues. I have had a similar issue a few times in the past. Generally feeling great but upon exerting myself in specific ways, lifting weights and nothing aggressive either, I would get a severe pain in the back of my head like a headache with dizziness. It came on suddenly but would go away in less than a day but felt like I got punched in the back of the head. I likely incurred this injury by using poor form while riding a bike for extended periods of time trying to hold my head too far back to see where I was going. Reflect on your fitness regimen, are you focusing too much on your back muscles or have an imbalanced workout? This is not something that would show up on scans or blood work.
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I have a few neck injury tales:

An elderly former teacher of mine declined to have an operation for a problem, a blockage I think, in her neck. She was diagnosed with dementia a year or two later - can't help wondering if the former caused the latter.

I know a painter who had avery severe stroke in his 50s. Some say it is was caused by looking up while painting ceilings over the decades. Again, hard to know if that is true.

... I likely incurred this injury by using poor form while riding a bike for extended periods of time trying to hold my head too far back to see where I was going. Reflect on your fitness regimen, are you focusing too much on your back muscles or have an imbalanced workout? This is not something that would show up on scans or blood work.

For bike riding, a stem that is too long will cause neck pain.

I used to race triathlon and used aerobars with a long 140cm stem for an aggressive aero-tuck. When I stopped racing, I used the aerobars far less. As I got older, I started to get neck pains during and after cycling, which increased over time, especially for rides over an hour or two. A friend, a very keen cyclist told me about the stem length (I googled it to double-check, he was right). I tried riding with my hands back from the hoods, which helped, so I acquired and fitted a 120cm stem. That was good for sometime but I eventually decided to go back to the 110cm stem that my bike originally came with (it was designed and configured for short, fast criterions rather than the long time trial of triathlon) and that is even better. As you get older, you get stiffer and so shorter stems become more appropriate/comfortable.
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I understand both times it happened to you in the pool. I would scrutinize what were you doing differently in the pool versus open water, especially the posture. What I am getting at is that vertebrae nerve pinch always manifest itself like something else, often it feels like a genuine headache while it is actually intervertebral disc issue.

The other big thing, for me anyway, is the strap tightness. The strap may be pressing against cerebellum and cause severe headaches. In the pool you may have been wearing some swim goggles which you normally don’t, with narrow strap and poor seal.
I'm not qualified to diagnose this since I'm not a Doctor. But I do know that disturbing the spinal fluid in surgery can cause severe headaches in patients. I'm not sure this really relates to what you have, but it might be worth mentioning to your Doctor.
Thanks. Some great responses. I do also have a cervical degenerative disc issue which could be a problem here... inflames the nerve on my left arm side causing radiculopathy sometimes.
Sudden severe headaches that are new or unlike any previous headache deserve urgent attention.
Sadly nasty things can happen at rest, on exertion or whilst under the water (if you don't know the cause better safe than sorry are get it checked out).

The reason I posted is because due to your CO2. Don't worry it this could be entirely normal for you or could just be due to the blood sampling.
The three things that spring to mind are
1) do you do a lot of apnoea training and potentially tolerate a slightly higher level of CO2 (I am most intrigued with this).
2) Any underlying lung disease
3) The sample could have been taken from a vein or not be accurate. Ideally an arterial blood sample should have been taken - this most likely would be from the radial artery in the wrist. It would have been slightly deeper than a standard blood test and SHOULD have been analysed within a few minutes.
The results should contain the partial pressures of O2 and CO2 in the blood, as well as the PH and bicarbonate. The latter 2 can be useful in working out if this CO2 is an acute issue, or something more chronic in which the body compensates for the reduction in PH caused by CO2. An increased bicarbonate would suggest the body has had time to compensate from the slight acidic nature of co2 in the blood.

If you have the results and don't mind sharing if you have any lung conditions I would be interested!
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