You just had the most incredible sex of your life. Only you can’t remember it. Sounds like a sick joke, but forgetting the absolutely unforgettable is a real occurrence.

Lovers have been known to blank out on entire sexual experiences, having no recollection of the event or their orgasmic responses.

What exactly is this phenomenon? And could it ever happen to you?

Sexual amnesia can happen to anyone, and most unexpectedly. Did you and your lover really have sex this morning or is your sweetie pulling your leg? Why do you have no recollection of that night of passion? What exactly happened with the hottie you brought home last night?

In many of these baffling cases, alcohol or drugs aren’t to blame. But you can point the finger at another culprit. Well-described in medical literature since 1956, transient global amnesia (TGA) is known as "recurrent coital amnesia" when it is triggered by sex. During such sudden, temporary memory loss, a person’s ability to recall recent events and new information totally disappears.

Suddenly, you can’t remember where you are or how you got there. You do know who you are, and can recognize and name the familiar, including your sexual partner (unless you just met). You just can’t remember what happened during this memory impairment and possibly anything that happened several hours before its onset.

So what brought on this state? Surprisingly, this rare, short-lived phenomenon isn’t due to a neurological condition, like epilepsy or stroke, or recent head injury. Instead, TGA is typically traced to a stressful emotional or physical event. These include:

— Hard physical exertion;

— Sudden cold or hot water immersion;

— Overwhelming emotional distress from bad news, conflict or working too hard;

— Medical procedures, like an endoscopy (a minimally invasive medical procedure);

— Sexual intercourse.

With sex in particular, TGA is typically triggered after climax. Medical practitioners have also noticed that using the Valsalva method -- a discouraged sex move involving squeezing the pelvic floor muscles while pressing down, as though having a bowel movement -- precedes TGA in some males.

Sex-related or not, one thing all of these factors have in common is a sudden lack of blood flow to the brain. Brain scans indicate that blood flow to areas of the brain involving memory appears disrupted during TGA. And any time blood flow is restricted to the brain, a person’s ability to record new memory is severely impaired.

Because it cannot be distinguished from other life-threatening conditions, immediate medical attention needs to be sought when TGA strikes during or after intercourse. Dead giveaways that something is wrong include babbling, apparent confusion and repeatedly asking questions about ongoing events like "What are we doing?" or "What time of year is it?"

When asked by their partner or later by a doctor, they’re unable to correctly answer questions like "Who is the president?" or "What year is it?" Equally perplexing, however, is the fact that one’s vocabulary and movement are not impaired. There is no clouded consciousness.

Other symptoms may include headache, nausea, vomiting, anxiety, agitation, dizziness, chills, fear of dying, "pins-and-needles" sensation, trembling, sweating, visual disturbance, racing heartbeat, cold hands and feet, and great emotionality.

TGA episodes last an average of six hours (going for no more than 24 hours), with one’s memory returning gradually. Thankfully, all indicators are that a person’s memory is OK afterward, and the TGA has apparently done no damage. One’s immediate recall ability appears to be preserved.

TGA is equal opportunity when it comes to sex and race, but those over 49 are at higher risk of experiencing this sudden memory loss. Physical events tend to precipitate TGA in men, while emotional events, a history of anxiety, or pathological personality are more associated with women.

While the underlying cause is unknown, a history of migraines is a prime suspect for any individual. Experiences with migraines or coital headaches (sex headaches) have been linked to some who experience TGA.

Overall, incidence in the U.S. is 5.2 cases per 100,000 individuals. Interestingly, this is higher than incidence estimates in Alcoi, Spain, which is at 2.9 cases per 100,000, but lower than the 10 cases per 100,000 in Belluno, Italy. While the annual recurrence is low, over one’s lifetime, recurrence can be as high as 24 percent, which may work to your advantage.

After all, almost any lover is open to a good excuse when it comes to rationalizing having done anything regrettable. TGA may just be the perfect fib for that unfortunate time you forget your partner’s birthday, anniversary or seemingly most amazing sex session.

Dr. Yvonne K. Fulbright is a sex educator, relationship expert, columnist and founder of Sexuality Source Inc. She is the author of several books including, "Touch Me There! A Hands-On Guide to Your Orgasmic Hot Spots."

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