Dr Oli: Diving and seizures

Q: Hello, I hope you can advise me on my future diving prospects please. I have been diving for many years now and have more than 400 dives under my belt. I had a first unprovoked seizure just over a year ago. No cause could be found, despite every test under the sun - MRI of my brain and all bloods were clear. The fantastic NHS even did a full chest X-ray and said I appear to be very fit. I do not drink alcohol, stopped smoking two and a half years ago, and I eat healthily and keep fit. I have not had another seizure and also have no family history of epilepsy whatsoever. I take no drugs for anything. I have never had any history of illness in my life. I am now a nice mature age of 47.

The neurologist has just put it down to 'first unprovoked seizure'. I asked why it happened but totally understand his answer of 'no idea; possibly a little stress at the time'. What are your thoughts on me diving again?

A: Firstly a hearty clap on the back for quitting the fags, not boozing, and for supporting our wonderful but oft-maligned NHS. With commendable behaviour of this sort you are sure to mature gracefully well past the age of 47.

The important fact to make clear here is that a single unprovoked seizure is not automatically epilepsy. The lifetime risk of having one seizure is 8-10% - much more common than people generally realise. After a first fit, investigations such as the ones you've had are generally performed to exclude correctible causes and to estimate the risk of a further seizure. Overall this risk is around 30-40%, greatest in the first 12 months and falling to less than 10% after two years. Clearly a seizure underwater is a dangerous event (invariably fatal, in fact), so we normally ask for some document/letter from your neurologist stating that you are not at higher risk of another seizure than anyone in the general population.

I assume that your neurologist didn't feel it necessary to start any anti-epileptic medication. The decision to offer drugs to prevent fits is a tricky one and needs to take into account lots of factors - side-effects, whether you need to be able to drive, investigation results (medication is usually offered if there is evidence of epileptic discharges on an EEG or a structural cerebral disorder). Unfortunately, if you do start anti-epileptic medications, then diving is out - the potential interactions with pressure and nitrogen are too unpredictable.

So, in your case, I think you need to reach the two-year post-fit mark without recurrence at least. If your neurologist is supportive at this stage, then I think a good case can be made for permitting further diving.

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