Sex triggered a life-threatening stroke in a healthy 35-year-old Illinois woman, her doctors report.

Sex- and orgasm-triggered strokes in relatively young women and men are rare, but not unheard of. They require a combination of factors and events not unusual in themselves, but which are highly unlikely to occur at the same time.

The 35-year-old woman's symptoms were typical of this unusual kind of "cryptogenic" stroke, says Jose Biller, MD, professor and chair of the neurology department at Loyola University, Chicago.

"This young woman ... while having intercourse had numbness on the left side of her face, slurred speech, and weakness in her left arm," Biller tells WebMD. "When she was transferred to our care six hours after onset, she was completely unable to move her left arm, her face was paralyzed, her speech was garbled, and she was in a state of panic."

It was too late to inject the woman with the clot-busting drug tPA, which must be given within three hours of a stroke. So Biller's team quickly ran a catheter from an artery in the woman's groin up into her brain to find the blood clot by angiography. Once it was found, they had only one option: to apply tPA directly to the clot.

It was a risky decision. "We did this with a lot of sweat," Biller says.

The woman's symptoms began to improve almost immediately; within an hour she was out of the woods and within 12 hours the symptoms were almost gone. Today she is well, with only an almost imperceptible fold in the skin under her nose and slight loss of dexterity in her left hand.

Stroke From Sex

Why did sex trigger this young woman's stroke? She shared one thing in common with six other young people who suffered sex-related strokes: a small opening in the wall between the two upper chambers of her heart.

One in four adults has this minor heart defect, called a patent foramen ovale or PFO. A PFO allows some blood to flow from the right side of the heart to the left side. This blood bypasses the lung and goes straight to the brain.

Most people with a PFO have no symptoms and don't know they have it. But 40% of people who suffer a cryptogenic stroke -- stroke of no known cause -- have a PFO.

Blood flow through a PFO increases when a person strains, such as bearing down during a bowel movement or breathing out with the mouth closed and nostrils pinched shut.

It also happens during sex, particularly during orgasm, says Brett L. Cucchiara, MD, director of the Penn Stroke Center at the University of Pennsylvania. Cucchiara was not involved in the Biller report, but studied two cases of sex-related stroke in 2006.

"In one of the cases we presented, it is a little embarrassing, one woman had stroke onset coincident with orgasm and having this sort of spontaneous guttural utterance or moan," Cucchiara tells WebMD.

But just having a PFO isn't enough to cause a stroke. A person also must have a blood clot, and that blood clot must break loose and enter the heart just in time to be sucked through the PFO during sex.

Normally a small blood clot would simply get stuck in the lungs and dissolve. But a blood clot that passes through a PFO can lodge in the brain and cause a stroke.

Biller's team did indeed find that their patient had a small blood clot in her leg, probably as a side effect of the oral contraceptives she used for birth control.

"This is a rare occurrence," Biller stresses.

"The vast, vast, vast majority of people with PFOs go through life and never have any problems," Cucchiara says. "You have to keep this risk of stroke during sex in perspective. The risk is very low.

"If you develop sudden neurological symptoms during sex, it could be a stroke and you need to seek help urgently and go to the emergency room," Cucchiara says.

"But you should not spend a lot of time worrying about this. Even if you have a PFO, of all the things to worr about in life, this ranks near the bottom in risk."

There are devices available for closing PFOs. But Biller and Cucchiara both note that doctors currently don't recommend this procedure -- even for most people who have already suffered a stroke.

That recommendation didn't convince Biller's young patient.

"She was scared to death, and she and her boyfriend and family were pushing us very hard to close the defect, so that is what we did," Biller says. "So she had the device implanted to close the PFO."

Biller's report appears in the September issue of the Journal of Stroke
and Cerebrovascular Diseases.