Dick Wagner had enjoyed a successful life on stage, playing lead guitar for bands like Alice Cooper, Aerosmith and Kiss, when he had a stroke and a heart attack in 2007.
"I woke up from a coma after two weeks with a paralyzed left arm," said Wagner, now 70 and living in Arizona. "My profession as a guitarist, I thought was over."
He and Cooper co-wrote the majority of the band's top-selling songs, including the 1975 hit, "Welcome to My Nightmare."
But Wagner's own personal horror show had just begun. He worked hard at rehabilitation, but new symptoms began to appear: mental fuzziness and an odd gait.
"I couldn't turn to the left as I walked, only to the right, and I would do a spiral and fall," he said. "I fell completely flat on my face in the driveway on the concrete. I didn't know what had happened to me."
Another fall by his swimming pool precipitated a blood clot and surgery. Wagner was convinced his career was over.
But in 2011, Wagner was diagnosed with NPH, or normal pressure hydrocephalus, a condition caused by a build-up of spinal fluid in the ventricles of the brain, which puts pressure on nerves that control the legs, bladder and cognitive function.
Doctors at Barrow Neurological Institute in Phoenix surgically placed a shunt in his head to redirect the fluid through a tube under the skin to his abdominal cavity. A small amount is drained every day for the rest of his life.
Now, Wagner is back on tour with a band in Denmark.
"I am like a new man almost overnight," he said. "For five years, I couldn't even pick up a guitar -- I didn't have the strength or the coordination."
NPH is a condition that typically strikes after the age of 55 and often mimics the dementia of Alzheimer's and the impaired motor skills of Parkinson's disease.
An estimated 5 percent of all dementia patients actually have NPH, which is correctable, according to Dr. Joseph M. Zabramski, the neurosurgeon who placed Wagner's shunt at Barrow.
In Wagner's case, it wasn't the initial stroke that deprived him of his musical ability, but NPH, which took away his coordination and timing.
"The stroke he suffered usually produces relatively mild deficits, and over time patients are able to resume most normal activities," Zabramski said. "Dick cannot raise his left arm as well as he used to, but his fine motor function in his left hand is excellent.
"Music is Dick's life and so he tried to resume playing but couldn't," Zabramski said. "Once we had the shunt in place I saw the improvements. ... Gradually, much to my pleasure, the old Dick Wagner returned."
An estimated 200,000 to 400,000 Americans suffer from NPH, a number that is on the rise because of an aging population, according to Zabramski, who is chief of cerebrovascular surgery at Barrow.
NPH is diagnosed with a CT scan or MRI, followed by a spinal tap to drain fluid from the brain. If the patient's condition improves, NPH is the likely cause.
The reason NPH is easy to miss is that the "triad of symptoms" are so insidious: difficulty walking, failing memory and urinary urgency, all of which go hand in hand with old age.
"None of us wants to admit there is anything wrong when we have a little trouble walking and balancing," Zabramski said. "We just think we are getting older. It's not until it progresses and threatens our independence that we seek evaluation."
Such was the case with Alicia Harper of Orlando, Fla., an active 74-year-old who played piano and organized programs at her church.
"I was losing sleep and confused," said the mother of four and grandmother of eight. "I didn't recognize my own house -- not even my own bed."
For six years, she ignored the symptoms of memory loss and incontinence, as her husband struggled nightly to get her to the bathroom in the middle of the night.
"We thought she was just starting to get old and disoriented," said her husband Nildo Harper, now 83. "She was just sort of absent."
Her right hand and foot shook so badly that she could no longer read or play piano. She ended up in a wheelchair.