MINNEAPOLIS—Guitarist Billy McLaughlin was at the top of his game a decade ago, a fingerstyle player noted for his technique of tapping on strings, when he began having problems controlling his left hand, missing notes with no clue why. Audiences thought he was drunk.

After a maddening couple of years in which his playing grew so bad he couldn’t perform his own songs, McLaughlin finally received a diagnosis: an incurable neuromuscular disease.

“When this first started happening, I thought I had done something wrong, I had committed some sort of musician’s sin or something,” McLaughlin said. “I didn’t sleep enough, maybe I was out too many nights after the concerts carousing around.”

McLaughlin has focal dystonia, a mysterious ailment that affects about 10,000 musicians around the world. For horn players, it can mean clenched jaws or immobile lips. For pianists, violinists or guitarists, the result can be frozen fingers that spell the end of a career. In McLaughlin’s case, the pinkie and ring finger on his left hand—the hand a right-handed guitarist uses to form chords or run scales on the fretboard—curled inward.

Instead of giving up, McLaughlin decided to relearn how to play the guitar left-handed—something another Twin Cities acoustic guitar virtuoso, Leo Kottke, likens to “trying to breathe through your feet. It’s exactly that hard.”

Now McLaughlin is back on the road and the subject of a recent documentary, “Changing Keys: Billy McLaughlin and the Mysteries of Dystonia.”

On a late spring day, McLaughlin—in jeans and boots—shows off his skills at a studio in downtown Minneapolis. His eyes closed and his shoulder-length blond hair waving, McLaughlin runs through his composition “Church Bells,” and the familiar Pachelbel’s Canon. His right hand runs across the fretboard while the index and middle fingers of his left hand hold, then release bass strings. The pinkie and ring finger of his left hand remain bent behind the neck of his guitar. The sound is smooth, calming, flawless.

McLaughlin, 47, grew up in Minneapolis and started playing guitar around 13 after “failing” on piano and trumpet. He studied guitar performance at the University of Southern California, switching to steel-string acoustic when his electric hollow-body Gretsch was stolen after graduation in 1984.

Eventually McLaughlin developed a solo act and became a big draw on college campuses, performing 200 days out of the year and logging 400,000 miles on his van.

After self-releasing seven CDs, McLaughlin signed a contract with Narada, an instrumental and world music label, in 1995. His first Narada release, “fingerdance,” reached No. 7 on Billboard’s New Age chart. It was around the time of his second Narada release, “Out of Hand,” in 1998 that McLaughlin’s finger problems began.

McLaughlin slipped on ice on the way to a photo shoot for the album and dislocated two fingers on his left hand. He underwent therapy and had gotten past the injury, but he said “something never felt quite right in that hand.”

McLaughlin found his pinkie wouldn’t reach notes and that he had to refinger even easy pieces. He tried acupuncture, deep tissue massage and a chiropractor, spending “a small fortune trying to get this hand to work.”

Finally McLaughlin visited the performing arts clinic at the Sister Kenny Rehabilitation Institute at Abbott Northwestern Hospital in Minneapolis, where he was told he had focal dystonia.

Focal dystonia is a localized movement disorder that’s part of a family of neurological disorders. In one form, it can cause a person’s eyelids to involuntarily close, effectively resulting in blindness. Writer’s cramp is another form. A generalized dystonia can contort a person’s entire body. The origins of dystonia—which affects about 300,000 people in North America—may be genetic. Treatments can involve anticonvulsants or surgery, but there’s no cure.

Normally muscles work together to raise or lower a joint, but in focal dystonia the muscles don’t act together and instead are in a “tug of war,” explained Dr. Mahlon DeLong, a neurology professor at Emory University in Atlanta.

After his diagnosis, McLaughlin called renowned concert pianist Leon Fleisher, whose own career was derailed by focal dystonia that affects the fourth and fifth fingers of his right hand. Fleisher, 80, switched to a left-hand piano repertoire before undergoing Botox injections in 1995. The injections, combined with deep tissue massage, allowed him to resume playing two-handed (he recently released his first two-handed recording of concertos in more than 40 years).

McLaughlin tours Texas in July. He’s busy being a single dad to his 16- and 13-year-old sons and believes his best days of playing lie ahead. He lives with the possibility that his dystonia will migrate to his healthy hand.

“You know the vase hits the floor and in that moment that it shatters and that sound comes out you realize, ‘Oh, oh, that’s gone forever,”’ McLaughlin said. “And in my case, there’s no new hand to put on. But I found another way around it. And that’s a lesson for every area of my life.”