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Parkinson's Disease

  • A neurodegenerative disorder that affects a person's movement
  • Early symptoms include tremors, a change in handwriting, unexplained muscle stiffness, and more
  • Treatments include physical activity, medications, botulinum injection, and deep brain stimulation
  • Involves Movement Disorders, Memory Disorders & Cognitive Neurology, and Botulinum Program
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Parkinson's Disease


The number of Americans living with Parkinson's disease is estimated to be about 930,000. There is currently no cure for this neurodegenerative disorder, but medications, exercise, and diet changes can help manage symptoms.

While a diagnosis of Parkinson's disease is unquestionably upsetting, "you can still live many years without a disability," says Yale Medicine neurologist Sule Tinaz, MD.

What are the risk factors of Parkinson’s disease?

In a patient with Parkinson’s, specific groups of brain cells are affected: the dopamine-producing cells. Dopamine is a chemical that is essential for motor control, balance, and muscle movement.

While the exact cause of this cell type depletion is unknown, age is the greatest risk factor, Dr. Tinaz explains. The typical age range for onset is between 55 and 65. 

Researchers continue to investigate other factors that may influence the disease's development, which may include exposure to pesticides. About 15% of cases have a clear genetics component, Dr. Tinaz says. 

What are the symptoms of Parkinson's disease?

Early warning signs for Parkinson's disease include:

  • An occasional tremor
  • A change in handwriting
  • Unexplained muscle stiffness
  • Occasional mood changes
  • A loss in sense of smell
  • Frequent constipation

After about five to 10 years, these symptoms—especially loss of motor control—will become more pronounced as the nervous system continues to deteriorate. Activities that require hand-eye coordination, like driving, writing, or sports, will become more difficult.

In later stages, as nerve damage becomes more extensive, Parkinson’s disease can lead to dementia, mood disorders, anxiety, and severe loss of motor control, such as bladder function and the ability to walk. It’s important to note that Parkinson’s disease manifests itself differently in each patient. Some people will be able to continue working and enjoy regular hobbies for many years after diagnosis, while others will have more severe symptoms that require major lifestyle adjustments.

What are the different sub-types of Parkinson's disease?

The two main types of Parkinson's include the following:

Akinetic-rigid: In this type of the disease, a patient will move slowly and experience muscle stiffness throughout their body. 

Tremor-dominant: Patients with this subtype experience shaking or tremors, and milder muscle stiffness. 

How is Parkinson's disease diagnosed?

A doctor who suspects that a patient might have Parkinson’s disease will ask for a medical history and perform a few movement tests to check for tremors and muscle stiffness. Since Parkinson’s can also be confused with other parkinsonisms, which are conditions that look like Parkinson's disease (such as essential tremor), it's beneficial for patients to receive a diagnosis from a specialized clinic like the Yale Medicine Movement Disorders Program.

In cases where a diagnosis is difficult—a test called DaTscan can be used to confirm a diagnosis. has been proven to diagnose parkinsonism. DaTscan is an injection composed of small amounts of radioactive dye to mark dopamine receptors in the brain. Once administered, doctors can use an imaging device called a single-photon emission computed tomography (SPECT), to identify reduced dopamine levels in the brain—a clear sign of parkinsonism.

How is Parkinson's disease treated?

Parkinson’s disease is a progressive disease, and patients are sometimes not treated with medication initially, Dr. Tinaz says.  

Instead, patients are encouraged to participate in physical activity and it's even better if it is done together with a group. "There has been a lot of evidence that exercise can help with symptom control and has potential to delay clinical progression of disease," Dr. Tinaz says. Other lifestyle changes to try first include following a Mediterranean diet, getting enough sleep, and seeking intellectual stimulation.

Once symptoms start interfering with daily life, patients will be prescribed a medication that will help boost levels of dopamine that diminish as nerve cell damage progresses. (Dopamine helps the nervous system send signals between nerve cells and muscles.) While there is no cure for Parkinson’s disease, these medications have been proven to reduce symptoms.

  • Levodopa: Considered to be the most effective drug for Parkinson’s disease, levodopa is metabolized by enzymes in the brain to create dopamine. Levodopa is available in a variety of formulations: oral (sold under the brand names Sinemet and Rytary), sublingual (Parcopa), and in liquid form (Duopa). When treating a patient with a more advanced disease, a surgeon can place a thin tube into the small intestine to allow for levodopa to be continuously infused directly into the body for even greater control of symptoms.
  • Dopamine Agonists: These drugs (sold under the brand names Requip, Mirapex, Neupro, and Apokyn) work by stimulating the same sites within the brain that dopamine does, in order to produce a similar effect. These drugs aren’t as effective as levodopa, however; they also have more side effects, such as nausea and vomiting.
  • MAO-B inhibitors: While not very effective on their own, this class of drugs (sold under brand names Zelapar and Azilect) has also been shown to boost the effectiveness of dopamine.
  • COMT inhibitors: These medications (sold under brand names Comtan and Tasmar) can help “even out” the effects of levodopa, reducing the chances that a patient will be left feeling symptoms of Parkinson’s between doses. The current medications for Parkinson’s disease can lose effectiveness as the disease progresses, so it’s important to consider a long-range strategy for managing the condition. For example, the most effective medication, levodopa, might stop working for short periods of time. These “off periods” can be very disruptive, causing tremors and muscle problems, sometimes suddenly and without warning.

In some cases, such as for those with severe tremor or frequent “off periods,” the most effective treatment is a surgical procedure called deep brain stimulation. Here, surgeons implant small electrodes in specific sites in the brain, and a battery under the skin in the chest wall. The battery sends electrical signals to the electrodes, which then block targeted areas of brain activity without damaging healthy tissue.

Other Parkinson’s disease symptoms can be treated with injection therapy. For example, some patients develop painful curling of the toes, which impairs their ability to walk; others develop excessive drooling, which can be both bothersome and embarrassing. Both of these symptoms can be treated with botulinum toxin therapy.

"I don't give patients false hope, but I do tell them they still have agency over this. There are so many things patients can do to improve their quality of life," Dr. Tinaz says. 

How is Yale Medicine's approach to treating Parkinson's unique?

Patients at the Yale Medicine Movement Disorders Program have access to the most advanced treatments and clinical trials for Parkinson’s disease. Patients' symptoms are thoroughly assessed before doctors create a treatment plan that will give the patient a good quality of life for as long as possible. 

Physicians at Yale Medicine can perform and manage surgical procedures like deep brain stimulation. 

Clinicians also understand that effective care goes beyond medication and surgery. Each doctor at the practice devotes considerable time to educate patients and caregivers. The doctors understand the nuanced challenges facing patients and how seemingly small adjustments—from a change to a medication’s dose, to a new approach to coping with tremors—can make a big difference in the life of a Parkinson’s patient. "We have all the resources needed to take care of patients," Dr. Tinaz says.