Home Features Club Nights Underwater Pics Feedback Non-Celebrity Diver Events 18 August 2022
Blog Archive Medical FAQs Competitions Travel Offers The Crew Contact Us MDC LDC
Order Tanked Up Magazine
 Twitter Tanked Up FAQ Dive Medicine  Download the Tanked Up Magazine App


Reef Jewellery
Dive Medical questions & answers for common scuba diving conditions and illness provided in conjunction with the doctors at the London Diving Chamber and Midlands Diving Chamber.
All Categories » Central Nervous System » Brain


I am a PADI Advanced diver and about 4 years ago had a brain scan after my ophthalmologist noticed I had nystagmus on a routine eye test. (Nystagmus is a repetitive involuntary oscillation of the eyes, like watching a lengthy Federer-Nadal tennis rally without moving your head.) The scan showed up Arnold Chiari malformation, type 1. I have no other symptoms and was told by a neurologist that I could carry on diving. However, I am concerned about the pressures on the body whilst diving and would greatly appreciate your opinion as I would not like to make the situation worse. I am a nurse, so as you know, a little knowledge is dangerous and I am seeking reassurances. Have you ever come across this or could you find out about it on my behalf? I would really value your comments.


To tell you the truth, I have never come across this in a diver before. As always, an anatomy lesson for starters. In those human beings lucky enough to possess one, the brain sits happily in the skull, linked to the spinal cord which traverses the whole length of the vertebral column (backbone). The aperture in the skull through which the spinal cord passes is called the foramen magnum (Latin for “ice cream” “big hole”). At this junction there is a chunk of brain called the cerebellum, which deals with co-ordination of various senses and motor control. It’s this portion we’re testing when we do all those “standing on one leg with your eyes shut” manoeuvres in dive medicals. Arnold and Chiari were both German pathologists, who independently noted cases where a part of the cerebellum had protruded (“herniates”) through the foramen magnum, sometimes with other abnormalities such as spina bifida. This herniation can block the flow of blood and the cerebrospinal fluid that bathes and protects the spinal cord, resulting in a variety of symptoms – dizziness, odd eye movements (such as your nystagmus), muscle weakness, numbness, headache, and problems with co-ordination and balance. Basically a checklist of DCI symptoms. There are several types of Arnold Chiari malformation, with type 1 luckily the most benign.

Despite extensive searching I couldn’t find a similar case in the diving literature, so I can only offer my own musings on the potential issues here. Firstly there is the perennial problem of diagnostic confusion, as the symptoms of the malformation can be so similar to those of DCI. Secondly, and more seriously, if you were to suffer a case of cerebral decompression illness then it is possible that some herniation of the lower parts of the brain could occur through the malformation, which could be fatal. How likely this is is anyone’s guess, but it’s the severity of this consequence that leads me to the conclusion that it is probably too risky for you to dive safely. I would have no problem with you snorkelling, but without any other evidence it’s the only safe recommendation I can make.


I am 69 years old and have been diving for about 25 years. Two years ago I was discovered to have an aneurysm in my head. I was having very serious headaches. The investigations done by a neurosurgeon involved angiography to find the aneurysm and then it was treated with tiny metal coils (which form clots and block it off). The last of the coils let go of a clot which lodged itself up in my head, giving me a stroke. The net result was a total absence of short term memory. I had speech therapy for five weeks. I have slowly recovered my memory over the last 18 months. Apart from the memory I had no other symptoms.

The neurosurgeons are confident I can now dive without any problems. But my GP is not confident and suggests I get a diving doctor to decide. My wife however is still very concerned about "diving pressure" on the site of the aneurysm.

Generally I do not go below about 25m and often much less. For the first time since the aneurysm we are going on holiday, somewhere sunny where I will find it hard to resist the urge to dive. What do you think?


I think you’ve been through a tough time over the last two years, particularly suffering a stroke after the coils, but it may be that the neurosurgeons are right. They are the doctors best placed to inform you of the potential risks. The main problems after surgery for cerebral aneurysms are bleeding, seizures and spasm of the blood vessels. As far as I’m aware, the risks of all three of these complications recede relatively quickly, and within six months are as low as they’re going to be – which isn’t necessarily zero, but is not appreciably high. There’s no evidence that the water pressure experienced in diving has any direct effect on blood pressure in the brain, certainly no more than any other form of physical exertion. It’s now two years on, and happily your recovery sounds full. If the neurosurgeons have excluded other aneurysms on your initial brain angiography and you are otherwise well then I think you should be allowed some swansong sub-aqua shenanigans.

Agony Armchair Aunt Best Bride Catch Catch Chamber Club Cooking DCI Deep Dentist Dive Dive Diver Diver Divers Diving Doc Don'ts Dos Downsides Dry Editorial Fish Gimp Guide Horrorscopes Investigates Letters Love Marine Myth Nervous Night Non-Celebrity Part Paul Photo Photography Photostory Practical Quiz Quiz Reasons Rob Salmon Scapa Scuba Sea Shark Sharkipedia Sharm Spiced Story Tech Technical Things Toomer Triggerfish Tyson UK Underwater Versus Water World World Worst your