Angelina Jolie said she had a rare condition. Here's what we know about it

In a recent interview with Vanity Fair, actress and humanitarian Angelina Jolie opened up about her personal health struggles - threats of cancer that led her to the decisions to have a preventive double mastectomy and then to have her ovaries removed.

She said she developed hypertension and Bell's palsy, a condition she said had caused her face to droop on one side.

"Sometimes women in families put themselves last until it manifests itself in their own health," she told Vanity Fair.

What is Bell's palsy, a condition that affects about 40,000 other people in America each year? Although alarming, the condition is not as scary as it may seem.

"Most people will go through life without having a Bell's palsy," Lyell Jones Jr., a neuromuscular neurologist at the Mayo Clinic, told The Washington Post. "But for most patients who have it - whether or not they get treatment for it - they tend to do very well, and most patients will have a complete recovery."

Over the years, numerous other well-known figures have battled their bouts with the rare condition, including Ralph Nader, Roseanne Barr and George Clooney.

"It was the first year of high school, which was a bad time for having half your face paralyzed," Clooney told Larry King in 2006 about the time he had Bell's palsy.

"It's a weird - it's one of those things, I remember what happened," Clooney said. He said he had been watching a film called "The Pride of the Yankees," which follows the life of Lou Gehrig. "And he's trying to pick up a bat and it falls out of his hand. And the next day we were sitting in church and I was in the back of the pew and my tongue was numb. And then we would always go out to dinner, go up to Frisch's Big Boy, which is, you know, that's where everybody went for lunch after church, after Mass.

"And I was drinking and milk was pouring out of my mouth. And I thought 'Oh, my God, I have Lou Gehrig's disease.' Because you know, I wasn't the brightest kid, and eventually, your eye and everything gets paralyzed."

Bell's palsy, a sudden but temporary facial paralysis, occurs when the nerve that controls the muscles on one side of the face becomes inflamed or swollen, making them too weak to move, according to a fact sheet from the National Institute of Neurological Disorders and Stroke (NINDS). Though the exact cause is not known, it has been linked to viral infections, such as the cold sore virus (herpes simplex), respiratory illnesses or the flu, according to the Mayo Clinic.

The Mayo Clinic lists the symptoms as:

- Rapid onset of mild weakness to total paralysis on one side of your face - occurring within hours to days

- Facial droop and difficulty making facial expressions, such as closing your eye or smiling

- Drooling

- Pain around the jaw or in or behind your ear on the affected side

- Increased sensitivity to sound on the affected side

- Headache

- A decrease in your ability to taste

- Changes in the amount of tears and saliva you produce

Jones, the neurologist at the Mayo Clinic, said due to the sudden onset of facial weakness, the primary thing Bell's palsy patients fear is a stroke.

"And, to be honest, you do have to do a pretty careful clinical evaluation to make sure that it's not something else besides a Bell's palsy," Jones said.

Jones did caution, however, that people who experience facial weakness, and have any risk factors for a stroke, should seek prompt medical attention to rule out something more serious.

The NINDS states that mild cases do not typically require treatment and go away on their own within several weeks; in other cases, some steroids can help reduce inflammation and swelling in the nerve, and some antiviral medications can help fight an underlying virus. Physical therapy or acupuncture "may provide a potential small improvement in facial nerve function and pain," according to the NINDS fact sheet. In Jolie's case, she said acupuncture helped her recover.

Surgical treatment is not typically recommended.

"The large majority of folks have a complete recovery," Jones said. "It's an unpleasant memory; it's not something that affects them in the long term."