There’s an old adage that cowboys don’t cry.

They are said to have a tough interior that matches their rugged exterior.

For country-music star Clay Walker, the cowboy in him was put to the test in 1996 when he was diagnosed with multiple sclerosis.

“I was visibly upset. I was shaken to the core – the world kind of started spinning. Literally, I felt like I was going to faint when they said it. it wasn’t real. And it scared me to death,” Walker said.

“I prayed a lot, and then I really started searching out what MS was and trying to learn about it, because I didn’t even know what it was. I thought it was muscular dystrophy. I didn’t know.”

Multiple sclerosis is a disease of the nervous system that affects the brain and spinal cord when there is damage to the myelin sheath – the material that covers and protects nerve cells – according to the National Institutes of Health.

Symptoms can include vision problems, muscle weakness, trouble with coordination and balance, sensations of numbness or prickling, pain, and thinking or memory deficits. MS affects more than 400,000 people in the U.S., and 2.1 million worldwide, according to the National MS Society.

Walker’s disease presented itself first with double vision, and he then started having weakness and tingling in his right hand and right leg.

After an MRI and spinal tap, he was diagnosed with MS and was told he would be in a wheelchair within four years and dead in eight.

Fifteen years later, the 41-year-old continues to prove that prognosis wrong as he kicks off a U.S. tour tonight at the San Bernardino County fair.

At the time he was diagnosed, new medications were becoming available for treatment of MS, but his first doctor did not prescribe him any, Walker said. his second doctor put him on a drug that did not work.

Finally, a third doctor prescribed him Copaxone, which Walker says has kept him in remission – minimal symptoms and no progression of the disease – for the past 13 years.

So, he says, his message to people suffering from MS is: “If at first you don’t succeed, try, try again.”

“People talk about attitude all the time – having a positive attitude. I think attitude is such an overused word that people don’t really understand where attitude comes from,” Walker said. “So if I could give a little lesson it would be this: Your will is more important than your attitude, because your will affects your attitude – that is where your attitude comes from.”

Walker’s will during the two years he was suffering from the disease kept him going. he was still performing as a musician, though he had a slightly lighter schedule.

He would take steroids to shrink the swelling in his brain – which occurs when the body attacks the nerve cells – but the drugs made his whole body break out into a rash.

“There was some pretty bad things in the first two years, but nothing was worse than the psychological damage that it was doing on me,” said Walker. “I was just scared. And I had never been scared before in my life. But for those two years I was.”

When Walker was first diagnosed, he was a rising star in the country music world. just three years prior, his first two singles – “Live Until I Die” and “What’s it to You” – reached no. 1 on the Billboard country chart. “Dreaming With my Eyes Open” and “If I could make a Living” did the same in 1994.

He decided he had to announce his condition to the music industry and to his fans. it was something he says he couldn’t hide and thought it was fair for people to know the truth.

He also wanted to prove a point.

“I think it can be inspirational because it has not affected my touring or my singing or anything,” Walker said.

“It’s important that other people who are diagnosed with MS, other neurological disorders or any other thing, that they know it doesn’t mean a death sentence and it doesn’t mean the end of your life as you know it,” he said. “It means that you can conquer a lot if you want to, and I’ve done it.”

Though Walker is now in remission, there are still days MS makes him feel weak. he tries to exercise every day because he says circulation is important for those with MS, and it helps boost the immune system.

He is constantly seeking a cure for MS and holds an annual MS fundraiser – the Clay Walker Charity Classic. The golf tournament will take place June 30 through July 2 in Pebble Beach.

He also performed in April, in Century City, at the Race to Erase MS benefit sponsored by the Nancy Davis Foundation for Multiple Sclerosis.

Walker says he feels a sense of duty to help those who are suffering from the disease. his prognosis tested his will, but it proved cowboys are tough and they don’t give up – at least not him.

“The cowboy in me made me want to find a cure and to fight for it. That’s the way I look at it,” Walker said.

“People that know me know I still rope and ride, and I still do all the things I did before I was diagnosed. so that’s important, you know, not to let anything, no disease, nothing, take away your passion and happiness.”

Find out more

Clay Walker

For more information on Multiple Sclerosis, go to nationalmssociety.org.

What: Country-music artist performing at the San Bernardino County fair.

When: 7:30 p.m. todaytonight.5/19

Where: San Bernardino County Fairgrounds, 14800 Seventh St., Victorville.

Tickets: $7.50 and $12.50; includes admission to the fair.

Information: sbcfair.com/2011.