A migraine headache is a periodic, usually one-sided, throbbing ache, sometimes preceded by warning signs and symptoms and of variable severity.
Migraine, though dreaded, is common. More than half the people in the world will have some experience with migraine during their lives, and about 5 percent will
see doctors. A few of these will suffer significant disruption of their activities.
Fitness & Diving:
Migraine poses little danger to divers. Even those with frequent migraine do not usually experience an increased incidence while diving. An elevated level of carbon dioxide in the blood, which occurs with decreased ventilation and breath-holding / hypoventilation, can theoretically precipitate a migraine headache because carbon dioxide (CO2) causes vasodilation in the brain. Increased levels of oxygen in the blood (which occurs in diving as well as in hyperbaric chambers) has been used with variable success to treat severe migraine, because it is a powerful brain vasoconstrictor.
Very complex migraine, with visual loss or paralysis, might lead to confusion in diagnosing a diving accident. However, little data exists to suggest that migraine poses a significant hazard to divers. Severe and incapacitating migraine headaches while in the water would create a hazard for the individual.
People with severe and incapacitating migraine should probably not dive.
(Hugh Greer MD, Alert Diver, May-June 1999.)