It's not surprising that Michael “Rich” Clifford is the recipient of this year's Public Leadership in Neurology Award from the American Academy of Neurology (AAN) and its Foundation—because he practices what he preaches. The former astronaut for the National Aeronautics and Space Administration (NASA) lives his advice that people with Parkinson's disease (PD) shouldn't let it “drive what [they] do.”
When Clifford was diagnosed in 1994, PD didn't keep him from climbing aboard the shuttle Atlantis and rocketing off into space for the third time. Had he been diagnosed before his first flight, in 1992, the astronaut knows exactly how he would have handled it.
“If I'd have known about it in 1990, I wouldn't have told anyone,” Clifford asserts, “because I wanted to fly into space.”
Such determination comes as no surprise regarding the “driven” (as he calls himself) Clifford. After graduating high school in Utah, Clifford was accepted into the United States Military Academy at West Point, earning a degree in engineering in 1974. He then spent 21 years in the U.S. Army, including earning a Master's degree in aerospace engineering at Georgia Institute of Technology. He also became an experimental test pilot; after earning top honors in his class, Clifford first became an Army aviator and then graduated from the elite U.S. Naval Test Pilot School.
But Clifford's greatest honor occurred in 1990, when after four interview cycles over the previous five years, he was asked by NASA to join the astronaut corps.
“Kind of a select crowd,” Clifford says about joining the few hundred humans who have travelled into space.
Between December 1992 and March 1996, he made three trips into orbit, totaling 665 hours aboard the shuttles Discovery, Endeavor, and Atlantis. “It was fantastic,” Clifford says. “The launch is a thrill.”
Regarding his first lift-off, Clifford explains how he prayed for some minor problem so he could solve it and “be a hero.”
“Then the rockets lit,” he says, “and I thought, ‘cancel that last request.’”
THE PRIME OF LIFE
It was after his second shuttle flight that Clifford discovered he had PD, a neurologic disease primarily affecting movement. It entails the loss of nerve cells (neurons) in the brain that produce the chemical messenger dopamine. Without dopamine, neurons cannot properly send messages to control body movements.
“The brain cells most prominently affected in PD are located in the basal ganglia, which is an area involved in motor function,” says Lisa Shulman, M.D., professor of neurology at the University of Maryland, secretary of the AAN Board of Directors, and Fellow of the AAN. (Motor functions are those involved in moving the body.) “A pathway of brain cells within the basal ganglia becomes injured over time in people with PD,” Dr. Shulman continues. “That's the very pathway that produces the chemical messenger dopamine.”
PD progresses over time, leading to increased symptoms in patients. “PD is a neurodegenerative disease,” explains Michael J. Zigmond, Ph.D., professor of neurology and psychiatry at the University of Pittsburgh. “That means there is a gradual loss of particular types of neurons.” (See box, “Parkinson's Disease: The Basics.”)
The lack of dopamine-producing cells can be seen on autopsy, Dr. Zigmond says. “If you look at someone who has died who had the disease, you see that there was a very large loss of these cells,” he notes.
The motor symptoms that result from those lost brain cells include resting tremor (it's most obvious when a person with the disease isn't moving), rigid muscles, slow movement (bradykinesia), balance problems, abnormal posture, and a shuffling gait or way of walking. People with PD may also experience non-motor symptoms such as cognitive difficulties, problems with smell or hearing, trouble with speaking or swallowing, cardiovascular problems, constipation, and interruptions of sleep.
“The non-motor symptoms can include changes in mood, such as depression or anxiety, or cognitive changes like more difficulty with multitasking,” says Dr. Shulman.
In 1994, at 42 years old, Clifford seemed an unlikely candidate to get PD. “I had a negative medical history,” he says, mentioning a broken bone as his only problem ever. “As a military aviator, you get watched all the time, physically and mentally, and I was in good shape.”
After his shuttle flight in April of that year, Clifford's annual check-up in August seemed to confirm his overall fitness. “I'd finished my physical exam and the neurologic exam, which is part of our annual physical,” Clifford explains, “and the doctor said, ‘everything's fine.’”
But when Clifford mentioned that his right arm “didn't swing right,” his evaluation began to change. The arm wasn't painful but did hang limp at his side when he walked, Clifford says. The racquetball player in him had hoped for a quick fix.
“When I said the arm didn't move but also didn't hurt, that set off some signals for the doctor,” Clifford recalls.
NASA medical staff sent Clifford to see Joseph Jankovic, M.D., professor of neurology at the Baylor College of Medicine in Houston, TX, and Fellow of the AAN. The next day, within minutes, the astronaut's problem had been identified. “Dr. Jankovic examined me and said, ‘You may have PD,’” Clifford recalls. Another three months were spent confirming the diagnosis by ensuring no other neurologic condition was causing his symptoms.
“My diagnosis was based on the history and examination,” Dr. Jankovic says, explaining that Clifford had revealed that in previous months his arm had not been swinging well, his handwriting was suffering, and he'd had minor trouble using utensils. Because an MRI of Clifford's brain had been normal and a blood test showed he didn't have Wilson's disease (a rare cause of symptoms similar to PD that is potentially treatable), Dr. Jankovic came to the conclusion that the astronaut had PD. “Those symptoms were some of the typical signs that indicated to me that he had early symptoms of the disease,” he says.
Because Clifford was so young in 1994, so fit, and with no family history of the disease, the diagnosis was “somewhat surprising,” Dr. Jankovic says. However, the cause of the disease remains a mystery for all patients. Neither is it known why dopamine-producing cells die in PD.
“The exact and precise cause of PD is not known,” Dr. Shulman says, “but we have learned more and more about genetic and environmental factors that result in higher susceptibility or greater resistance from one person to another.”
“More than a dozen genes have been linked to PD,” Dr. Zigmond adds. “If you have one of a number of these genetic mutations, you are at risk.” Other risk factors include age (most people with PD are over 60 years old) and sex (more are male than female).
“Some environmental contaminants, such as certain pesticides, can increase one's risk of PD,” Dr. Zigmond says. “For example, farmers that are commonly exposed to these pesticides have a much higher incidence of PD than the average person.”
REACHING FOR THE STARS
Regardless of its cause, by 1994 the astronaut knew he had PD. He admits to being upset about the diagnosis and also going through a phase of denial. He also knew he didn't want to give up space flight. “My NASA medical community knew about my PD and assumed I wouldn't want to fly again,” Clifford says. “But I said ‘no, no, no....’”
After his diagnosis, Clifford saw a 1990 video of his astronaut class that showed his right arm hanging unusually. “Being a test pilot, I'm used to very precise flying,” he says, “and fortunately my flying was not affected.”
By 1994 his symptoms remained mild, most obviously limited to the hanging arm, so Clifford hoped to go to space again. NASA supported his decision. Not only was he selected for his third shuttle flight in March 1996, Clifford says, “I also got selected for a space walk on that flight.”
NASA did pay particularly close attention to Clifford's preparations. The “force capability” of his right hand was regularly tested to ensure he could perform the job requirements of the flight and space walk. During the entire training cycle, however, he lost no strength. “I was fully certified for that flight,” Clifford says. “It didn't affect my performance.”
“We didn't think the symptoms he had at that time would in any way impair his ability to perform his duties,” Dr. Jankovic says. “So there was really nothing being done to further evaluate his PD.”
No medication was prescribed for Clifford's symptoms at the time. “We decided not to treat him for his symptoms then, but to use a strategy that at that time was thought to slow down the progression of the disease,” Dr. Jankovic says. “So I put him on selegiline (brand name Eldepryl).”
While there is no cure for PD, the good news is that the effects of the disease can be managed with medication. “Fortunately, we have treatments to manage the symptoms and delay disability,” Dr. Shulman says. “However, our treatments do not delay or change the underlying degeneration.”
The motor symptoms of PD are treated primarily by replacing the dopamine lost in the brain through the use of levodopa, a medication taken orally throughout the day.
“Levodopa, or L-dopa, continues to be the standard treatment,” Dr. Shulman says. “It ultimately reaches the brain and metabolizes into dopamine, replacing exactly what the person is missing.”
Other medications to treat motor symptoms include dopamine agonists (which are not metabolized into dopamine but mimic its effects) and monoamine oxidase B inhibitors, which protect the dopamine that remains in the brain. In some cases, when the effects of these medications no longer last throughout the day, a surgery called deep brain stimulation (where electrodes are placed precisely in the brain) can help control involuntary movements, especially in patients that have tremors.
“The non-motor symptoms—including depression, constipation, or blood pressure changes—can be treated with both pharmacologic (drugs) and non-pharmacologic (diet, exercise) approaches,” Dr. Shulman says.
“While PD is a gradually progressive disease, fortunately it's not a rapid progression,” Dr. Shulman says.
“PD could develop over 20 or 30 years, so this need not be a disease that shortens a person's life span,” Dr. Zigmond says. “Although I can't say we can get rid of all symptoms, with proper treatment, patients can have a very high quality of life and a normal life span.”
Clifford has certainly found that to be true, although the disease can progress more quickly in some people than others. He was fortunate in that he received an early diagnosis—and his disease progressed slowly. PD didn't slow down his performance on that Atlantis flight or on his six-hour spacewalk, when he and a fellow crew member floated outside the shuttle to attach four experimental devices to the outside of the MIR space station. The walk was historic not only because Clifford had PD but also because it was the first U.S. spacewalk that occurred outside two docked spacecraft.
Clifford did experience one symptom of PD on that flight. “I noticed getting into the suit on orbit, on the space walk, that I had trouble getting my right hand into the glove,” he recalls. “The hand was shaking.”
The third shuttle flight was otherwise a success: Clifford had completed another mission—and he'd done so after being diagnosed with PD. Of course, no one other than NASA medical staff and senior management had known how extraordinary that Atlantis flight had been because Clifford kept his newly diagnosed medical condition private.
“I didn't want to be identified as the man with PD flying in space,” Clifford says of his decision. “Plus I felt the focus should be on the mission, not someone on the mission.”
With that mission complete, Clifford decided he would no longer fly in space. His next trip would probably have included a lengthy stay on a space station, which he didn't think would be a good idea. Clifford retired from the military and left the astronaut corps, opting to continue working in the aerospace industry but as a senior executive at Boeing. He worked at Boeing for 13 years, until September 2011, first as the operations manager for the assembly of the International Space Station and ultimately as the deputy program manager.
“I eventually retired from Boeing because the job went away,” Clifford says, explaining that his PD hasn't hasn't slowed him down much. “I decided it was time to do some traveling, visit my kids more often, and spend time with my wife.” Today, he does “a lot of public speaking” and loves to play golf. “My putting has actually improved!” he says.
Clifford's symptoms have progressed over the years. While he has a tremor now, it remains mostly isolated to the right side. Still, Clifford recognizes that he moves slower, his handwriting has become “terrible,” and he's lost his sense of smell. He also has a “stooped posture,” which the military man finds especially galling because it interferes with his ability “to maintain a good position of attention.”
While at times Clifford experienced side effects from some of his PD drugs (one medicine made him particularly compulsive, mostly in wanting to finish tasks, while another increased his tremor), those lasted only until he found the right dosages and types of medication. Today he takes a combination of carbidopa and levodopa in pill form as well as rasagiline (an MAO-B inhibitor) and amantadine. The former astronaut also keeps himself physically fit, touting the benefits of exercise in general, and walking in particular, to help deal with his disease.
Clifford has experienced some of the emotional effects of PD. “I've had periods of ‘relaxed care factor,’ so to speak,” Clifford admits. “I wasn't depressed, but I wasn't my normal, curious, cheerful self either.”
The engineer in Clifford can't help but be impressed with the work being done regarding the search for a PD gene. As Dr. Jankovic says, “The younger the age of onset, the more likely it is that the disease is of genetic origin.”
In fact, Clifford recently sent his DNA for genetic testing. Although he's yet to receive his results, he is looking forward to them. “Research could lead to early diagnosis of PD based on genome analysis,” Clifford says, “and early diagnosis could give patients the opportunity to change their lifestyle and receive early medications to reduce the decline of dopamine cell production. Knowledge is power,” he says.
In the end, the former astronaut remains optimistic. When diagnosed with PD 18 years ago, he decided it wouldn't put an end to his dreams and took to the heavens again. Clifford feels the same way today, and hopes other PD patients do too.
“Don't let PD drive what you want to do,” he says. “Remember that you're in charge of your future.”
Parkinson's Disease: The Basics
▸ WHAT IS PARKINSON'S DISEASE? PD is a neurologic disorder that primarily affects movement. It is also a degenerative disease, which means it progresses gradually. PD has no cure. Although the cause is not understood, it is known that PD results in the death of neurons (nerve cells) in the brain that produce the chemical transmitter dopamine. This loss of dopamine produces many of the symptoms of the disease.
▸ WHAT ARE THE SYMPTOMS OF PD? The most obvious symptoms are the motor symptoms, including tremor (often of the hand and usually on only one side of the body at first), slow movement (bradykinesia), rigid or stiff muscles, abnormal posture, and a shuffling gait. Non-motor symptoms can include anxiety, depression, constipation, cardiovascular problems, disrupted sleep, loss of hearing or smell, trouble swallowing or speaking, and dementia. The symptoms all tend to increase over time.
▸ HOW IS PD DIAGNOSED? No definitive technology exists for diagnosing PD. The diagnosis is made by a neurologist based on the patient's medical history and a neurologic examination (including tests of balance, coordination, and manual dexterity), as well as the elimination of any other possible causes for symptoms.
▸ HOW COMMON IS PD? Estimates are that at least 5 million people around the world have been diagnosed with PD, including about 1 million in the United States. And at least 60,000 new cases are diagnosed in this country each year.
▸ WHAT CAUSES PD? PD is idiopathic, meaning its cause is not known. However, certain risk factors increase the likelihood of acquiring the disease. These risk factors include age (most patients are over 60 years old), sex (more men than women are affected), heredity (certain genes seem to increase one's chances of getting PD), and exposure to some environmental toxins, including pesticides.
▸ HOW IS PD TREATED? The motor symptoms of PD can largely be controlled with medication, most notably levodopa, which is metabolized in the brain into dopamine to replace what was lost. Other medications include dopamine agonists, which mimic the effects of dopamine in the brain, and MAO-B inhibitors, which protect the dopamine that still exists there. If these (and other) medications begin to lose their effect, some patients undergo deep brain stimulation to bolster the medication effect. Stem cell surgeries may offer hope for the future. Some experts believe that a healthy lifestyle (including vigorous exercise and appropriate nutrition) can help prevent the disease or delay its progression.
For more on PD from the American Academy of Neurology's Neurology® Journal Patient Pages, go to neurology.org/content/by/section/Patient+Pages.