This disorder of brain function causes episodic alterations of consciousness, called epileptic seizures. Abnormal electrical discharges in the brain cause these episodes; they may occur without warning, and they may vary in character from a brief loss of attention to violent, prolonged convulsion.
People may outgrow the condition; it is often, but not always, controlled by medication.
Fitness & Diving:
Loss of consciousness or loss of awareness while underwater carries a high risk of drowning or embolism from an uncontrolled ascent. An analysis of motor vehicle operators with epilepsy has shown that a seizure occurring behind the wheel will result in an accident in nearly every instance, but no evidence exists that diving with compressed air scuba to the accepted 130 fsw (39 msw) limit increases the risk of epileptic seizures. One is no more likely to "seize" while diving than while driving: the risk is the same. There is no useful data to determine the potential for injury in divers with epilepsy.
Current doctrine among diving medicine physicians advises that individuals with epilepsy not dive. Those with childhood epilepsy, who have outgrown the condition and have been off medication for five years, still face a slightly increased risk of a seizure. To make an informed decision about diving, these individuals should discuss this with their personal physicians, families and diving companions.
Medication Used in Treatment:
Anti-seizure medication acts directly on the brain and may interact with high partial pressures of nitrogen. This may produce unexpected side effects. (See nervous system medical effects, below.)
History of Seizures Without a Clear Diagnosis of Epilepsy
This is a cloudy question since many variables can cause transient alteration of consciousness. These alterations of consciousness include fainting, a reduction of blood pressure, which is very common in young people, an alteration in heart rhythm that is more common in older people, effects of medication and psychological events, such as hallucinations.
Fitness & Diving:
As with epilepsy, any loss of consciousness underwater is likely to have a bad outcome. When diving using nitrox or mixed gas as a breathing gas, increased partial pressures of oxygen can increase the likelihood of seizures. Increased carbon dioxide may also increase seizure risk.
The best advice is to get a precise diagnosis of the cause of altered states of consciousness: effective treatment is often available. You cannot make a reasonable fitness-to-dive decision till this is sorted out. It may take some time and a visit to a neurologist or other specialists. Ask your doctor first.
(Hugh Greer MD, Alert Diver, May-June 1999.)
More Information on Epilepsy & Diving (.pdf)