When the Tremors Start Much Misunderstanding Surrounds Parkinson’s Disease

When actor Michael J. Fox contracted Parkinson’s disease at age 30, the diagnosis — revealed publicly years later — brought a wave of media attention to the tremor-inducing condition. But with that attention has come a great deal of misunderstanding.

When people report tremors, they almost universally think of Parkinson’s disease, or PD, first, said Dr. Jagadeesan Udayarani, a movement disorder specialist with Baystate Neurology. But tremors can be caused by any number of movement disorders — a family of medical conditions that also includes Tourette’s syndrome, Huntington’s disease, restless leg syndrome, and dozens of other diagnoses.

“Everyone with a tremor thinks it’s Parkinson’s,” Udayarani said, “but most of the referrals I get in my office don’t conform to that diagnosis.”

Many times, she said, a condition known as essential tremor is the culprit. That’s a common movement disorder that typically affects the head, chin, hands, or voice. The disease can cause disabling tremors, but it’s often mild, and doesn’t progress the way PD does.

Parkinson’s, on the other hand, results from the degeneration of certain cells in the basal ganglia area of the brain. In a normal brain, some nerve cells produce the chemical dopamine, which transmits signals within the brain to produce smooth movement of muscles. In Parkinson’s patients, 80{06cf2b9696b159f874511d23dbc893eb1ac83014175ed30550cfff22781411e5} or more of these dopamine-producing cells are damaged, dead, or otherwise degenerated.

This causes the nerve cells to fire wildly, leaving patients unable to control their movements. Symptoms usually show up in one or more of four ways: tremor, or trembling in the hands, arms, legs, jaw, and face; rigidity, or stiffness of the limbs and trunk; bradykinesia, or slowness of movement; or impaired balance and coordination.

Although cases in people as young as Fox aren’t unheard of, Parkinson’s disease typically strikes older people, and currently affects about 3{06cf2b9696b159f874511d23dbc893eb1ac83014175ed30550cfff22781411e5} of those age of 65 and older. Although full-blown Parkinson’s can be crippling or disabling, early symptoms are often so subtle and gradual that patients sometimes ignore them or attribute them to the effects of aging — a quality that makes PD difficult to diagnose.

“It’s a chronic, progressive disease that progresses slowly, going from mild to moderate,” Udayarani said. “It usually starts on one side and progresses to the other side. There is no textbook case, but if it’s a rapid progression, you have to think it’s something other than Parkinson’s disease.”

When PD is the culprit, she explained, from a quality-of-life perspective, there’s what she called a “honeymoon period” of 10 to 15 years, when most patients will do fine with a combination of medication and physical therapy, including range-of-motion exercises, stretches, and gait and balance training — in effect, reinforcing muscle memory to counter the effects of dopamine depletion.

Battling Back

Although Parkinson’s disease can be brought on by toxins, head trauma, or genetic factors, the vast majority of cases have no known cause. But treatments options are many.

Doctors will often prescribe one of several common medications at the onset of symptoms. The most well-known is levodopa, which replaces some of the missing dopamine in the brain’s neurons; however, much of the drug is metabolized elsewhere in the body, causing a range of side effects. Another series of drugs known as dopamine agonists act to stimulate the dopamine receptors, but unfortunately make those receptors less sensitive over time.

Since Parkinson’s currently has no cure, these medications only act on symptoms, Udayarani emphasized. And for some patients, there’s a surgical option, known as deep brain stimulation, to reduce the tremors.

In fact, surgery for Parkinson’s disease, essential tremor, and tremor due to multiple sclerosis has been available since the 1960s. But in those early days, surgery was mainly used to destroy a small part of the brain called the globus pallidus that’s central to the disease’s progression.

Such procedures have long been effective for many patients, but they carry significant risks. Pallidotomy requires purposeful destruction of the brain, which can lead to complications ranging from paralysis to loss of vision or speech. That surgery is still available, but it’s performed less frequently now because of deep brain stimulation.

In that procedure, an electrode is implanted in the globus pallidus. Rather than destroying a portion of the brain, small electrical shocks are administered, creating the same effects as surgery without destroying any of the brain.

The electrode is connected to a pacemaker-like device that is then implanted under the skin over the chest. Not only can the level of electrical stimulation be adjusted, but the electrode’s four metal contacts can be placed in many different combinations, offering a level of flexibility that one-time surgery does not.

“They put electrodes on the globus pallidus part of the basal ganglia,” Udayarani said. “When you do this, it’s not destruction of the brain; it just sends electrical impulses and stimulates the area in a different way. And from the outside, you can change the strength and frequency of the stimulation.”

However, many doctors insist that no patient should undergo deep brain stimulation without first taking an adequate trial of medications because, with many pharmaceutical solutions available, it would be unethical to expose someone to any type of surgery without first trying a less invasive option.

“This is not for all patients. But when a patient has run through all the other choices, we might refer him to a surgeon,” Udayarani said.

“Everyone thinks the surgery is a miracle, but it’s not a miracle for every patient,” she added. “It’s not good for patients with severe depression or a lot of cognitive difficulties, and older patients don’t tolerate it as well.”

Breaking Through

None of this makes diagnosis of Parkinson’s any easier. No blood tests have been proven to diagnose PD. Doctors sometimes use lab tests and CT and MRI scans to rule out other diseases, but Parkinson’s itself is often diagnosed only after long-term neurological testing and observation.

Udayarani said some suspected PD can be ruled out through a thorough examination of the medications patients take. “A lot of medications used now, some antipsychotics and others, can cause Parkinson’s symptoms,” she said. “We have to go through someone’s medication list, and in some cases take them off something and re-examine if the medication induced tremors, or if it’s Parkinson’s.”

According to Dr. Andrew Siderowf of National Parkinson Foundation (NPF) Center for Excellence, genetic tests can also be used to identify people who are at risk of developing PD. About 5{06cf2b9696b159f874511d23dbc893eb1ac83014175ed30550cfff22781411e5} to 10{06cf2b9696b159f874511d23dbc893eb1ac83014175ed30550cfff22781411e5} of all Parkinson’s instances might have contributing genetic factors, but this number could climb higher as progress in genetics continues.

Tests for genetic mutations known to cause PD are currently performed in research laboratories, Siderowf said, and one of those tests is commercially available — but they have limitations. “Genetic testing is limited because only a fraction of PD is genetic,” he said. “In addition, genetic tests give no indication of the age at which PD will start.”

As Fox and others show, that can be just about any age. And until science discovers a way to end the tremors once and for all, Parkinson’s will continue its slow, and often confounding, progression for millions of Americans.