Pauline Anderson

December 07, 2016

HOUSTON — Researchers are making headway in determining which patients with epilepsy should be allowed to drive.

A new analysis suggests that factors such as seizure duration and impaired consciousness influence later driving performance.

"Our goal is to figure out if there are clues" that will "inform doctors and patients" about whether it's safe to drive, said epilepsy specialist and lead study author, Hal Blumenfeld, MD, PhD, professor of neurology, neuroscience and neurosurgery, Yale School of Medicine, New Haven, Connecticut.

All too often, he said, patients with epilepsy who can safely drive are "lumped together" with all patients with epilepsy and discouraged from getting behind the wheel.

The researchers' findings were presented here at the American Epilepsy Society (AES) 2016 Annual Meeting.

For this analysis, patients with epilepsy underwent video/electroencephalographic monitoring that analyzed ictal and interictal driving data captured prospectively from a driving simulator. The simulator had a steering wheel, gas pedal, and brake attached to a laptop computer.

Participants were asked to drive as long as they could and, if possible, to continue to drive if they had a seizure. The test was conducted in an inpatient unit with medical care available if needed. Patients drove from 1 to 10 hours, most for an average of 3 to 4 hours.

The variables researchers considered included car velocity, steering wheel movement, application of the brake pedal, and crash occurrence during the ictal and postictal periods, as well as during subclinical epileptiform discharges.

In a poster presented at the meeting, investigators reported an analysis of a total of 20 clinical seizures in 16 patients. Seven of these seizures resulted in crashes.

The analysis determined that the longer the seizure, the more likely the person was to have an accident. "The average for people who crash is 80 seconds and the average for the ones who don't have driving impairment is 23 seconds, so on average, the seizures are longer" in those who crash, said Dr Blumenfeld.

No Time Limit

But the analysis doesn't provide a time limit for seizures. "So far, this shows that seizures lasting longer are more dangerous; but we don't have a cutoff yet," said Dr Blumenfeld. "That's one thing that could be helpful."

He stressed that these are averages and that other factors, such as severe motor impairment and loss of consciousness, contribute to safety.

The current study also showed that when patients lose consciousness during seizures, they are significantly more likely to crash (P < .05). "That stands to reason based on common sense, but no one had really tested that before," said Dr Blumenfeld.

He and his colleagues plan to do additional research, looking at other things that might affect safety, for example, from what part of the brain seizures originate.

"There may be factors that we can put together in a model and come up with a real decision tree," he said. "We aren't there yet, but that's the goal."

Rules and regulations surrounding driving with epilepsy vary significantly around the world. In India, for example, having a single seizure means you can't drive for life.

In the United States, states variously require 2 years, 6 months, or 3 months of seizure freedom, while others, including Connecticut, don't have a set limit but leave the driving decision to the discretion of the clinician.

"So it goes to show that we really don't know what the limit should be," said Dr Blumenfeld. "We are working basically out of common sense and little bits of information available from retrospective studies and questionnaires."

He thinks there should be uniform global regulations concerning epilepsy and driving because under the current climate, "it's very confusing for physicians, for patients and for the general public."

"When there are accidents, everyone blames everyone else because nobody has agreement on what the guidelines or consensus should be."

Fair Treatment

Robert Fisher, MD, PhD, professor of neurology and neurological sciences, and director, Comprehensive Epilepsy Center, Stanford University, California, wants patients with epilepsy to be treated justly when it comes to driving.

"We don't want people with epilepsy to crash a car, but we don't want them to be unfairly discriminated against either."

Dr Fisher has published articles on driving and epilepsy and has been a defense witness in cases involving patients with epilepsy who have been in a motor vehicle accident.

He pointed out that in the United States, the accident rate for women with epilepsy is lower than for men without epilepsy, especially among drivers 18 to 25 years old.

"That doesn't mean that epilepsy is not a risk factor; it just means that it really ought to be individualized," he said.

While patients with uncontrolled seizures shouldn't drive, those whose seizures have been controlled for a specific length of time "have a risk that's lower than we are willing to accept for a number of conditions," said Dr Fisher.

Driving is "one of the most discussed" topics in the epilepsy clinic and can contribute to significant stress in the doctor–patient relationship, he noted.

American Epilepsy Society (AES) 2016 Annual Meeting. Poster 2.276. Presented December 4, 2016.

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