The strange case of the woman who lost her memory after sex

A healthy, 54-year-old woman living in the Washington, D.C. area awoke one morning to find that she couldn't remember what she was doing. She knew who and where she was, but couldn't seem to form new memories. After a day of confusion and forgetfulness, she went to the Georgetown University Hospital. There, she admitted that the memory losses began right after having sex with her husband.

That was doctors' first clue what was going on. Because this woman wasn't the first to show up with sexual amnesia.

In fact, sex is just one of the activities that can cause a rare condition called "transient global amnesia." The ailment has no known cause — though there are a few theories — and usually lasts for a fairly short period of time. In the case of the Georgetown woman, the symptoms began to clear up after she'd undergone a few tests in the hospital. Like other patients with the condition, her brain had suffered no damage, and her difficulties were only with forming new memories rather than recalling what had happened to her before the mind-wiping sex.

Cases like this woman's can also affect past memories, which is called "retroactive transient amnesia." But no matter which areas of memory are affected, the condition is temporary and basically harmless (though generally quite frightening). There are also no documented cases of temporary global amnesia happening more than once to the same person.

Why would sex cause a temporary memory loss? The main theory is that the way people exert themselves during sex — basically, using muscles in their lower abdomens — can cause a temporary glut of de-oxygenated blood in the brain. Stephanie Pappas writes on Live Science:

The closest thing to an explanation researchers have for this sex-triggered amnesia is that the problem may not begin in the brain, but in the neck. In a January 2010 study published in the journal Stroke, [neuroscientist Sebastian] Ameriso and his colleagues conducted sonograms of the necks of 142 patients who'd experienced transient global amnesia within the last week. They found that 80 percent of the patients had what is called insufficiency of the valves in the jugular vein.

This vein, which runs down the side of the neck, carries spent blood from the brain back to the heart. Valves in the veins prevent blood from flowing backward toward the head, but if the valves don't close sufficiently, blood could seep back upward.

The best guess for what might be happening is that patients unwittingly trigger the transient global amnesia by raising the pressure inside their abdomens. This is called the "Valsalva maneuver," familiar as the "bearing down" people might do when lifting weights, defecating or even having sex. The increased pressure increases the resistance to blood flowing down the jugular veins, and insufficient valves may allow deoxygenated blood to push back up the neck. Oxygen-poor blood then "piles up" in the veins draining the brain, especially in central brain regions that are key to memory formation. The result could be transient amnesia.

Of course, this is just a theory. But one thing is for certain: the problem is most common in people over 50, which just proves that sex gets even more mind-blowing as you get older.

Perhaps the most terrifying part of the ailment is that its symptoms mimic stroke and other life-threatening conditions. So even if you think your memory loss is sex-related, it's a good idea to visit the doctor just to make sure you're not suffering from something more dangerous.

From the Journal of Emergency Medicine, spotted on Live Science

Photo by Martin Cormier via Shutterstock