What Is Parkinson's Disease?

What Is Parkinson's Disease?

Parkinson's disease is a progressive neurological disorder that affects movement—and, importantly, can also cause a range of non-motor symptoms. A major feature of the disease is degeneration of dopamine-producing neurons in a small area of the brain called the substantia nigra. Dopamine helps brain circuits involved in movement work smoothly, so when those neurons are lost, movement can become slower, stiffer, and harder to control.

Movement Symptoms of Parkinson's Disease

The movement symptoms most often associated with Parkinson's disease include:

• Slowness of movement (bradykinesia)
• Stiffness or rigidity in the arms, legs, or trunk
• Resting tremor, often starting on one side
• Problems with walking or balance, such as a shuffling gait

It is worth emphasizing that not everyone with Parkinson's disease has a prominent tremor. Some people notice slowness, stiffness, or changes in walking first, which is one reason an evaluation by a neurologist is valuable.

Non-Motor Symptoms

Parkinson's disease is more than a movement disorder. It can also cause non-motor symptoms, including:

• Constipation and other digestive changes
• Sleep problems, including acting out dreams
• Changes in the sense of smell
• Depression or anxiety
• Autonomic symptoms, such as blood pressure or sweating changes
• Cognitive changes, including slower thinking or memory difficulties

These symptoms matter because they can affect quality of life just as much as movement changes—and many of them can be addressed as part of a treatment plan.

How Is Parkinson's Disease Diagnosed?

Parkinson's disease is primarily a clinical diagnosis, based on the medical history and neurological examination. MRI, laboratory testing, or other testing may sometimes be used to evaluate for other causes of symptoms, but there is no single test that diagnoses Parkinson's disease on its own. Because tremor, stiffness, and slowness can have several causes, an accurate diagnosis depends on the overall pattern—an approach similar to the one described in our video on why hands shake, which compares essential tremor and parkinsonian tremor.

If you or a family member has noticed a new tremor, slowness of movement, stiffness, or walking or balance changes, an evaluation can clarify what is happening. You can learn more about how we evaluate and manage Parkinson's disease and related movement concerns on our Parkinson's disease care page and our tremor evaluation page.