What Is Parkinson's Disease?
Illustration by Mira Norian for Health
Medically reviewed by Smita Patel, DO
Parkinson's disease is a progressive neurological disorder that affects motor function. The disorder results in tremors, slow and interrupted movements (bradykinesia), and rigidity. The exact causes of Parkinson's disease are unknown, but people older than 60 and men are more likely to develop it.
Parkinson's disease is the second most common neurodegenerative disorder, affecting 2% to 3% of adults aged 65 or older. The disorder is not fatal, but it's incurable and can severely impact your quality of life, with symptoms worsening over time. Treatment plans are individual—including options like medications and lifestyle changes—but focus on easing the severity and progression of symptoms.
Related: What Is Guillain-Barré Syndrome?
Types
Parkinson’s disease is often broken down into different types based on the causes of symptoms. Those types include idiopathic, early-onset, and familial Parkinson's disease.
Idiopathic
The majority of Parkinson's disease cases are idiopathic, meaning there's no identified cause for the onset of symptoms. You're considered to have this type of Parkinson's disease if you develop cardinal signs like tremors and bradykinesia in absence of any other condition, environmental exposure, genetic predisposition, or medication usage. This type is seen in those who are older than 60.
Early-Onset
The symptoms set in when people are younger, with 55 often serving as the cut-off age, in early-onset Parkinson's disease. This subtype is rare: Only 5% to 10% of people experience symptoms before age 50. It's characterized by slower onset, preserved cognitive ability, and a higher rate of motor effects in response to medications used to manage symptoms.
Familial
Some rare forms of Parkinson's disease are familial, meaning that they're passed from parent to child. Researchers have identified about 20 specific gene mutations known to cause symptoms. These mutations, which may also account for some early onset cases, directly account for 5% to 10% of cases and may influence overall susceptibility to the disease.
Parkinson's Disease Symptoms
Symptoms of Parkinson's disease can be somewhat variable. There are four cardinal symptoms, plus a multitude of potential motor and non-motor symptoms.
Cardinal Signs
Parkinson's disease primarily affects motor function and the ability to coordinate movements. It's considered to have four cardinal signs, which are used to define the condition:
Bradykinesia: This is slow or interrupted movements, which is present in the onset of about 80% of cases. Bradykinesia causes weakness, lack of coordination, and a lessened ability to control movements.
Postural instability: An inability to maintain a normal, erect posture is another cardinal sign. This symptom is often present at later stages of the disease, causes a feeling of imbalance, and increases the risk of falls.
Rigidity: Rigidity is characterized by stiffness and tension that leads to pain and discomfort. It's seen in 75% to 90% of those with Parkinson's disease. Rigidity can affect any body part but often affects one side more than the other.
Tremor: Uncontrollable trembling is a common feature of Parkinson's disease. Tremor occurs while the limbs are at rest, typically worsening over time.
Other Motor Symptoms
Parkinson's disease can cause a range of other motor symptoms. These secondary symptoms affect different parts of the body and include:
A shuffling gait (way of walking) characterized by short, awkward steps
Excessive drooling
Festination, or speeding up when making repetitive movements
Freezing, or suddenly stopping when making repetitive movements
Impaired ability to gaze upwards or to move eyes
Inability or difficulty with chewing (dysphagia)
Speech impairments and inability to articulate words
Stooped or angled posture
Non-Motor Symptoms
Alongside the effects of motor function are several other types of symptoms. Some of these emerge before the onset of the cardinal symptoms.
Non-motor signs include:
Autonomic symptoms, such as dizziness, constipation, or inability to control urination and erectile dysfunction
Dermatitis or other skin disorders
Fatigue and daytime sleepiness
Hallucinations and psychosis
Impacted cognition and dementia, such as concentration and memory problems
Mood disorders, especially depression and anxiety
Olfactory dysfunction, or a loss of smelling and tasting ability
Pain
What Causes Parkinson's Disease?
The major symptoms of Parkinson's disease arise due to the degeneration of neurons (brain cells) in the substantia nigra of the basal ganglia of the brain. This region primarily regulates movements.
Neurons in this area produce dopamine, an important neurotransmitter (brain chemical). The symptoms occur as dopamine levels—as well as the levels of another neurotransmitter called norepinephrine—drop.
Researchers are unsure as to the exact causes of this degeneration in the substantia nigra. Genetic factors play a central role in a small number of cases. These factors may influence susceptibility to the condition. Exposure to toxins in the environment may also play an important role. It's believed that Parkinson's disease arises due to a combination of genetic and environmental factors.
Risk Factors
What's better understood are the risk factors for developing Parkinson's disease. These include:
Age: Being older than 65 greatly increases the risk of developing Parkinson's disease, with approximately 75% of cases seen in this population.
Environmental exposure: Parkinson's disease has been linked to exposure to certain toxins in the environment. The risk of developing it is higher if you live in rural or farming areas or areas with high air pollution, have high dietary iron, and have reduced levels of vitamin D from diet or sun exposure.
Genetics: Certain genes have been identified as influential, with some forms of the disease being directly caused by heredity. A family history of the condition is considered to be a risk factor for Parkinson's disease.
Sex: Men are at a higher risk and are a little less than 1.5 times more likely to develop the condition.
Diagnosis
There's no singular test for Parkinson's disease. Healthcare providers primarily rely on a combination of medical history and symptom assessment to diagnose the condition. They'll ask about any medications you're taking, your history of symptoms or other diseases, any family history of the condition, and any potential environmental exposure to toxins.
A neurological exam is needed to assess the presence and severity of motor symptoms. This exam may include:
Gait assessment: You'll be observed while walking down a hallway for any irregularities with gait.
Pull test: A healthcare provider pulls you from behind while standing to assess your ability to maintain balance.
Repetitive movement tests: These tests assess your ability to perform certain tasks, such as opening and closing a hand or tapping your toes.
Rigidity assessment: A healthcare provider will check the amount of resistance they feel when pushing on a limb near a joint.
Spontaneous movements: A healthcare provider will seek irregular movements while you're sitting, standing, or walking
Tremor assessments: You'll be observed for any resting tremors while staying still and being asked to focus on specific tasks.
Additional tests or imaging may be needed to rule out other neurological conditions or potential causes of the symptoms. These include:
DaTScan: This test is used to distinguish Parkinson's disease from other neurological diseases. A radioactive material is injected into the blood to assist with MRI or X-ray imaging.
Magnetic resonance imaging (MRI): This is used to assess for other neurological conditions that may cause symptoms. MRI relies on magnetic fields and computer-generated radio waves to generate images of the brain.
Olfactory (smell) tests: Loss of your sense of smell is a supportive sign of Parkinson's disease and can be used to rule out other neurological conditions.
Positron emission tomography (PET) scan: A small amount of radioactive material assists in imaging, allowing providers to determine dopamine levels in the brain.
You may also undergo genetic testing. This may be a testing option if a healthcare provider suspects hereditary Parkinson's disease.
Parkinson's Disease Treatment
There is no outright cure for Parkinson's disease. The goal of treatment is to reduce the severity and impact of the symptoms. This typically involves a combination of medications, additional therapies, and certain lifestyle adjustments. The specific course of treatment is individualized and depends on the case.
Prescription Medications
The primary approach to Parkinson's disease involves taking medications that stimulate dopamine production. These medications help replace the lack of dopamine in the brain and control symptoms:
Levodopa-carbidopa: This is available as Sinemet or Rytary. Courses of levodopa-carbidopa represent the first-line medication approach to Parkinson's disease.
Amantadine: This is often indicated alongside Sinemet or Rytary. Gocovri (amantadine) can assist with symptoms as other therapies wear off.
Anticholinergic drugs: Anticholinergics, such as Artane (trihexyphenidyl) and Cogentin (benztropine), are indicated especially for people with early-onset Parkinson's disease and may not be appropriate for older adults.
Non-ergot dopamine agonists: This is a class of drugs that includes Mirapex (pramipexole), Requip (ropinirole), and transdermal rotigotine.
Monoamine oxidase type B (MAO B) inhibitors: These include Zelapar (selegiline), Azilect (rasagiline), and Xadago (safinamide) and may be indicated for milder cases.
Deep Brain Stimulation
Deep brain stimulation is a therapy typically reserved for severe cases of Parkinson's disease. It may also be a treatment considered in cases where medications aren't yielding the desired results.
A neurologist (who specializes in the brain and spinal cord) uses surgery to implant electrodes into the subthalamic nucleus of the brain near the substantia nigra. These electrodes are connected to a device in the chest. This device transmits mild electrical shocks to stimulate parts of the brain affected by Parkinson's disease.
Physical Therapy
Working with a physical therapist can help promote motor coordination and reduce symptoms. Physical therapy approaches may include developing aerobic exercise and resistance training routines and improving gait.
Task-specific training (e.g., practicing holding a pencil) may be used for assistance with fine coordination and limb function. Balance training can also help with postural instability. You may also undergo speech therapy if your speech ability is affected. This work focuses on addressing articulation problems and the breathy, hoarse, or very quiet voice that can result from Parkinson’s disease.
Lifestyle Changes
Certain lifestyle changes may be recommended, including:
Adjusting your diet to include more vitamins, minerals, fiber, and antioxidants
Avoiding processed foods, sugars, and excess carbohydrates
Practicing yoga and stretching will help improve mobility and ease stress
Trying meditation or other means of stress management, such as taking baths
Using massage therapy to help reduce rigidity and associated muscle tension
Prevention
The exact causes of Parkinson's disease are unknown, so there are no known means of preventing this condition. Research has shown that adopting some lifestyle changes may help slow the progression of the disease. Getting regular aerobic exercise—in which heart rate is increased—can help slow the onset of motor symptoms.
The evidence is less robust, but dietary adjustments may be beneficial. Research has found that the Mediterranean diet may slow the progression of Parkinson's disease. This diet is high in fresh vegetables and fruits, unsaturated fats, and nuts. Increasing caffeine and reducing dairy and alcohol intake may also help slow progression.
Related Conditions
There are several health concerns that you're more likely to have if you have Parkinson's disease. Related conditions include
Anemia: This is an insufficient level of red blood cells and low levels of iron. The exact link is unclear, but people who are anemic are more likely to develop Parkinson's disease.
Dementia: Dementia is characterized by cognitive and memory difficulties that impact daily living. It has been found to impact up to 90% of people with Parkinson's disease and can be a sign of an advanced case.
Depression: This is considered a non-motor symptom and a potential risk factor. Depression has been linked to the impact of living with a chronic disease and physiological processes associated with Parkinson's disease.
Diabetes: Diabetes is characterized by the body's inability to digest sugars. It's linked with a number of neurological diseases, including Parkinson's disease. More research is needed on the link between these two conditions.
Hypertension: High blood pressure (hypertension) is also frequently associated with Parkinson's disease. Between 29.4% and 34% of people with the disorder have hypertension.
Related: What Is Lewy Body Dementia?
Living With Parkinson's Disease
Parkinson's disease is chronic and irreversible, so it can significantly impact your quality of life. It isn't fatal on its own, but the mortality of people with Parkinson's disease is three times higher than those living without it. Most people with Parkinson's become disabled within 10 years of diagnosis.
The condition significantly impacts the ability to live independently over time. There are strategies that can help you cope with the condition, including:
Looking for information from and supporting patient advocacy organizations, such as the American Parkinson Disease Association, among others.
Seeking assistance and social support from family and friends and getting help with essential tasks.
Seeking out support groups or online communities that can provide useful information and emotional assistance.
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