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Unusual, abrupt movements, sounds, throat-clearing, blinking — and in rare cases — outbursts of obscenities. These are all symptoms of Tourette syndrome — a neurological disorder characterized by tic behavior, over which patients have little or no control.

It’s a syndrome that can increase the risk of learning, behavioral and social challenges, and as a result, it can really take a toll on self-image. But for Tim Howard — the goalkeeper for the U.S. soccer team in this year’s World Cup tournament — it’s a disorder that he has never let get in the way of his dreams.

"He's an outstanding success," Manchester United Football Club manager Alex Ferguson, who brought Howard to the English Premier League in 2003, said recently. "We're delighted, because I love the lad. Good lad."

Howard was diagnosed with Tourette’s when he was 9 years old after his mother noticed symptoms of obsessive-compulsive disorder, which is a neurobehavioral problem often associated with the syndrome.

“Ninety percent of cases start before the age of 10,” Dr. Roger Kurlan, director of the Movement Disorders Program at the Atlantic Neuroscience Institute at Overlook Hospital in Summit, N.J., told FoxNews.com. “The current definition of Tourette syndrome requires that tics appear before the age of 21 and last at least a year before someone can be diagnosed.”

Tics can be simple or complex and can affect motor or vocal skills. They often worsen when patients are experiencing anxiety or stress, and are significantly reduced during sleep.

Simple tics often involve sudden, brief, repetitive movements or vocalizations like:

—Eye blinking and other vision irregularities;

—Facial grimacing;

—Shoulder shrugging; —Head or shoulder jerking;

—Throat-clearing;

—Sniffing;

—Barking;

—Grunting.

Complex tics may appear purposeful, involving coordinated patterns of movement and can include:

—Touching objects;

—Hopping, jumping, bending, or twisting;

—Repetitive words or phrases;

—Movements that result in self-harm;

—Uttering swear words;

—Repeating others.

Sheer Willpower

In a 2005 interview with CBS’s “60 Minutes,” Howard said he has been controlling his tics by using sheer willpower since he was a child. A feat that Kurlan said can be both physically and mentally exhausting.

“A lot of people will try to suppress their tics in public and as soon as they get home – they will have a big flurry of tics that could go on for a long period of time,” he said. “But it would take a tremendous effort, as Tim describes, to use willpower to suppress your tics. There’s a mental cost to it.”

Growing up, Howard immersed himself in sports, playing basketball and soccer, and excelled at both. He spent his teen years playing on U.S. youth teams, and was 19 when he made his debut with Major League Soccer. In his third full season, he was voted MLS goalkeeper of the year, and remains the youngest player ever to receive the honor. Two years later, Howard was on his way to England to play for Manchester United – one of the most successful clubs in history.

“I think it certain settings, like on a sports field, it’s not necessarily socially debilitating to have repetitive throat-clearing, or blinking of the eyes,” Kurlan said. “Also, often times when people are involved in distracting activities, the tic does get better to some extent, Tim is fortunate he’s out on a soccer pitch and not stuck in an office someplace where the tics could be much more debilitating.”

It’s estimated that as many as 200,000 Americans are living with the most severe form of Tourette syndrome, according to the National Institutes of Health (NIH), but as many as one in 100 people may have milder symptoms like chronic motor or vocal tics.

“The prognosis is actually quite good, Kurlan said. “A lot of people don’t realize it, but about a third of people grow out of the syndrome when they become adults.”

Treatments for the Tourette’s vary from person to person and include therapy such as habit reversal training and medication, but Kurlan said, if the tics are mild, treatment is not necessary. What is necessary is education.

“It’s mostly about educating the child and the parents and the school district about why the child tics and that it’s not a sign of anything dangerous and they’re not trying to create problems when they make noises in class,” Kurlan said. “There are a lot of people who live with fairly mild symptoms. In fact, there’s probably more people that have mild Tourette’s than severe but that hasn’t really been appreciated until recently. Very few people actually have the swearing that’s so notorious.”

For people who have severe symptoms and do not respond to therapy or medication, doctors are now using deep brain stimulation, which is a surgical procedure used to treat a variety of disabling neurological symptoms. So far, it has been used on about 100 patients around the world with many of them reporting positive results, Kurlan said.

Although the cause of Tourette’s is unknown, current research is zeroing in on genetics as well as abnormalities in certain brain regions — including the basal ganglia, frontal lobes, and cortex — the circuits that interconnect these regions, and the neurotransmitters responsible for communication among nerve cells, according to the NIH.

“It’s what we call a complex genetics, where it’s not clearly passed from one generation to the next,” Kurlan said. “There’s probably a number of what we call susceptibility genes. And it looks like you can probably get them from the mother’s or father’s side, or both. So, it’s a complicated genetics.”

If parents are concerned about their child, Kurlan said there are very specific things to keep an eye out for. “There is something called the Tourette Syndrome Triad meaning there are three things that go together very commonly,” he said. “The first thing a parent would look out for is the tics themselves. They would be the repetitive movements like eye blinking, making faces, jerking the head, or the noises like sniffing and clearing the throat. The second part of the triad is obsessive compulsive features that include fears about contamination, germs and cleanliness. And then the third part of the triad is attention deficit problems or ADHD.”

Kurlan said about half of all people with Tourette’s will have ADHD.

Inspiration to others

Howard, who has been described as having “unshakable confidence and leadership,” is definitely exceptional, Kurlan said, especially since many people with Tourette’s shy away from very public jobs and career pursuits.

“He’s thrived and has had great success in such a highly competitive and highly physical field where he’s in front of thousands of people and now millions of people in terms of the television,” he said. “Again this shows a tremendous amount of inner strength and self-confidence, which is probably the key to success for people with Tourette syndrome.”

Kurlan said he and colleagues always say that if people with Tourette’s can maintain their self-esteem and self-confidence, that everything will work out in the end and they will find their place in life.

And it’s is obvious to the millions of soccer fans around the world, that Howard has done just that. We’ll see him again on Friday on the world stage as the U.S. team takes on Slovenia.

Click here for more information about Tourette’s from the NIH.

Click here for more information from the National Tourette Syndrome Association.

The Associated Press and FoxNews.com's Jessica Mulvihill contributed to this report.