Evening Texas Mike,
Here's an edited version of an article I wrote for "Rodale's Scuba Diving" early last year:
"While medical nemeses such as diabetes and asthma have recently become subject to clearance to dive under conditions of proper control, seizure disorder has not fared as well. PADI, DAN and other major dive organizations continue to view adult epilepsy, controlled or not, as precluding scuba. Certain types of early childhood convulsions can be medically excused, but it is mandatory that a potential diver with such a history have a completely normal neurological examination.
This rankles many of those desiring to dive who have only a distant history of seizure and are not on anticonvulsants, or are well or completely controlled by medication.
The reason for the prohibition is that an epileptic event underwater can have fatal consequences, and can occur even in those long seizure-free or well-controlled on medication.
While there are numerous types of seizure disorder, nearly all involve both motor dyscontrol and an alteration of consciousness, in varying degrees of severity. In the most serious forms, consciousness is lost and a major motor convulsion occurs.
During such a serious event, loss of the second stage is almost certain and this could result in drowning. Furthermore, breath holding can be occasioned by spasmodic phases of the motor activity. This increases the risk of pulmonary barotrauma during attempts to bring the stricken diver to the surface.
Even when the seizure does not involve unconsciousness and significant motor dyscontrol, the disturbances of awareness can be life-threatening.
Finally, seizure medications, to a greater or lesser extent, have sedative side effects and could exacerbate nitrogen narcosis or cause its appearance at shallower than expected depths.
The outlook overseas is somewhat rosier for those with a history seizure disorder who are not currently on medication. The British Sub-Aqua Club (BSAC), for example, suggests requirements for medical clearance to dive that include five years free from a convulsion off medication, reduced to 3 years when the convulsions were exclusively nocturnal."
Hope this clarifies the matter somewhat.
Happy holidays.
DocVikingo