Physicians are asked from time to time whether patients who have epilepsy should dive. It is my view that they should not and this article is presented to explain that view.
Epilepsy is the tendency to have epileptic seizures. Lest this seem simplistic, consider that about five percent of the world’s population will experience one seizure during their lifetime. Only one-half of one percent, or 1 out of 200, will have two or more. These are the people who are said to have epilepsy.
Seizures come in all sizes and shapes. The clinical seizure is the outward expression of an electrical event which occurs within the brain and which generates abnormal signals, therefore abnormal behavior, ranging from twitching to a generalized convulsion, from a momentary lapse of awareness to grossly disordered social behavior. Seizures are involuntary, occur randomly and often without warning. Seizures often cause loss of consciousness and virtually always interfere with normal behavior. The majority of seizures begin in childhood and some seizure disorders are genetically determined. In most cases, underlying disease, such as tumor, cyst, infection, is not demonstrable.
The most commonly recognized seizure is a generalized grand mal convulsion. This occurs when the electrical discharge involves the entire brain or a large part of it. It characteristically begins with a strangling sort of cry which, in itself, may be frightening. The back and neck are arched and the entire body becomes quite rigid. If the person is standing, he may fall like a log and may sustain injury when he strikes his head. The jaw is tightly clenched and sometimes the tongue, lips, or cheek may be severely bitten between clenched teeth. Breathing stops, sometimes long enough that he or she becomes quite blue. This phase lasts 20 to 30 seconds, rarely as long as a minute. The generalized rigidity relaxes and is followed by convulsions in a series of violent jerks. During this time, breathing is irregular and the subject may chew on his tongue. This phase lasts less than a minute. There may be loss of control of both bowel and bladder.
When the jerking subsides, the subject usually awakens and seems bewildered. This confused state may last for an hour or more, then the subject frequently falls deeply asleep, perhaps for several hours.
Although a grand mal convulsion is frightening to watch, it is not terribly dangerous unless the victim is in a position of exposure. If he is climbing, he will fall; if driving, crash; if diving, drown. The observer should try to keep him from hitting his head if he falls. It is helpful to place a firm object between his teeth, such as a folded belt or billfold – not a finger, which may be severely bitten, and not a spoon, which may break the teeth. The seizure victim must be attended through the period of bewilderment else he may get lost or wander off into traffic.
The diagnosis of epilepsy must be approached with caution because of the social and economic costs that may overshadow the disease itself. A majority of epileptics, upward of 75 percent, can be kept seizure free with anticonvulsant medications, and lead reasonably normal lives. Those with uncontrolled seizures are severely handicapped with respect to driving, employment and social success. It is important to sift out the categories of fever induced seizures in infancy, breath holding spells, postural “sight-of-blood’ fainting and disorder of heart rhythm before labeling a person an epileptic.
Once established, the diagnosis poses three important questions:
- Does diving increase the likelihood of seizures in an epileptic patient?
- Should a person under treatment with anticonvulsant medication dive?
- Should a person who has outgrown his epilepsy dive?
People with epilepsy are said to have a lowered seizure threshold. This means that they are more susceptible to seizures than the general populace. Therefore, stimuli which induce seizures in some percentage of the general populace will be more likely to do so in those who already have epilepsy. Examples of such stimuli are prolonged sleep deprivation, alcohol or sedative withdrawal, visual stimulation with rapidly flashing lights and hyperventilation. The latter is of particular interest to divers. Hyperventilation at atmospheric pressure is routinely used to test for seizure susceptibility in the neurological lab.
The effect of hyperbaric oxygen on epileptic populations has not been studied. However, it is well established that high partial pressure of oxygen may induce seizures in normal individuals. Navy diving standards require that candidates undergo an oxygen tolerance test in which they breathe pure oxygen for 30 minutes at a depth equivalent of 60 feet in a chamber. This test is designed to screen out those candidates who are susceptible to oxygen toxicity. About one percent of normal candidates have grand mal seizures under these conditions.
The oxygen tolerance test is a based on the assumption that all divers will be subject to increased pO2 in their work or perhaps in treatment and on the further assumption that the test will help to eliminate susceptible candidates. It is quite likely that persons with epilepsy have an increased risk of oxygen convulsions.
Patients with uncontrolled epilepsy are at constant risk. They frequently fall and suffer head injuries. They may fall from ladders, burn themselves with hot irons and be knocked down in traffic. Clearly, they should not dive.
The well-controlled epileptic leads a fairly normal life. His illness is not apparent to observers and he has no physical handicap. In most jurisdictions, he can obtain a conditional driver’s license if he has been seizure free for one year, and in almost all jurisdictions, for two years. He cannot get a pilot’s license, a commercial driver’s license and will not meet the physical requirements for military or commercial diving.
What of the sport diver? His own life is certainly at risk. Should a seizure occur underwater, he may drown or suffer air embolism in an uncontrolled ascent. Both of these accidents have occurred in nonepileptic subjects with oxygen convulsions. These are personal risks. There is yet another. The diver who has trouble underwater exposes to risk other members of the diving party and perhaps members of the search party. Value judgments come into play here and no two circumstances are comparable. The law takes notice of the epileptic driver, not because of risk to the individual, but to the public. The public safety is greatly endangered by an automobile driver who has a seizure. With the diver, the public risk is much less but not negligible. The law generally accepts that a seizure-free interval of two years, under treatment, constitutes control sufficient to operate a motor vehicle. The risk of recurrent seizures in the controlled subject is nevertheless several times that of the general population. The controlled epileptic also pays a price in side effects of medications. Virtually all anticonvulsant medications have some sedative effect. Variation among individuals, both with respect to dosage and susceptibility to sedation, is great. The average dose of medication for epilepsy usually produces only mild sedation. These drugs, however, would be expected to increase the hazard of nitrogen narcosis, in the same manner as alcohol does.
About 20 percent of children with epilepsy outgrow the disorder by age 21. Someone with childhood epilepsy who has reached adulthood, seizure free for five years, is generally regarded as cured for legal purposes, except for the requirements of flying and special military service. Although his risk of recurrent seizure is more than random, it is quite small.
Based on these principles, the following recommendations seem reasonable:
- The diagnosis of epilepsy disqualifies anyone for military and commercial diving, without exception.
- Individuals who have been seizure free for five years and take no medication have a small statistical risk of recurrent seizures. There is no definite evidence that diving will increase the risk of recurrence. They should be advised to avoid hyperventilation and cautioned that elevated partial pressures of oxygen may precipitate seizures.
- Individuals with controlled epilepsy, taking medication, seizure free for two years, meeting the requirements of most driving jurisdictions, should nevertheless be advised not to dive. While driving is important to livelihood, diving is not and the risk, both to the individual and his companions, is unacceptable.