April 20, 1999
"...it's a tremendously important issue for people with epilepsy."
Having a seizure while driving is one worry that nags people with epilepsy, and to date, no good research exists that lets them predict their risk of an accident. A new study at Johns Hopkins and the University of Maryland, however, tells how epilepsy patients and their physicians can assess chances of having an auto accident due to seizures.
The study, in this month's issue of Neurology, is the first to examine specific seizure risk factors and link them with driving mishaps. This approach, the researchers say, may be more effective in reducing auto deaths than the policies state motor vehicle administrations now use which, the study also found, a significant number of epilepsy patients ignore. Most states don't let people with epilepsy drive unless they're seizure-free for a specific interval. Such intervals vary widely, usually from three to 18 months.
The researchers believe the study will let physicians tailor safer individual driving programs for patients by offering them a tool to evaluate their risks.
"For years, people thought you shouldn't drive at all if you have epilepsy," says Hopkins neurologist Gregory Krauss, M.D., who led the researchers. "Then it became clear that risks aren't high for people who have seizures, as long as they're controlled. But there's a gray area for people whose seizures aren't perfectly controlled -- is it safe to drive? How do you decide? That's what we've been able to assess. It's a tremendously important issue for people with epilepsy."
The researchers examined two groups of 50 epilepsy patients from their Maryland clinics, matched for age and sex. Both groups drove, but one had a history of seizure-related car crashes. The scientists found four illness-related characteristics of the patients that could help predict accidents. The single feature most linked with crashes, the researchers report, is the length of time people go without a seizure before they return to driving: the shorter the interval, the greater the likelihood of an accident. Those who didn't drive for a year or longer had a 93 percent reduced risk compared with people behind the wheel after shorter intervals. An interval of six months or more meant people were 85 percent less likely to have an accident.
Some states, such as Maryland, require a shorter, three-month seizure-free interval, which, the study shows, doesn't protect drivers. The interval recently adopted by EEC countries is one year.
People who predictably experience an aura -- an odd sensation or movement that comes before a seizure -- also had reduced odds of crashing, as did people with fewer non-epilepsy- related accidents in general before they were diagnosed. Surprisingly, reducing the number of anti-epilepsy medicines or switching them lowered the accident risk. That's probably because patients at that point have better control of their illness, says Krauss.
One of the surprises of the study is finding that most epilepsy patients fail to report their seizures to their motor vehicle registry, as required by law. Only 36 percent of the group with previous crashes and 40 percent of the control group reported their seizures to authorities. More troubling, the researchers say, is the study's finding that more than half of the patients in the crash group and a third of the non-crash group drove despite having seizure-free intervals shorter than their states legally required.
Other members of the research team were Guohua Li, M.D., Peter Kaplan, M.D., and R. Colin Carter, from Hopkins, and Allan Krumholz, M.D., from the University of Maryland, Baltimore.
Related Web Site:
Epilepsy Foundation of America, Inc. -- http://www.efa.org