Parkinsonism is a syndrome, or collection of symptoms, characterized by motor issues – bradykinesia (slowed movements), tremors, loss of balance, and stiffness. There are many types of parkinsonism classified by their cause and how they progress. Knowing which type of Parkinson’s someone has helps neurologists prescribe effective treatments and better predict how the disease will progress.
There is no conclusive test to identify what type of parkinsonism someone has. For some people, years may elapse between experiencing the first symptoms and receiving a definitive diagnosis of a specific type. Since all parkinsonisms share similar motor symptoms, Parkinson's diagnosis can be very difficult. A correct diagnosis is more likely when performed by an experienced neurologist who specializes in movement disorders. Some people have multiple chronic conditions, making it difficult for doctors to identify whether parkinsonian symptoms are caused by a disease or a medication. In some cases, it is possible to have more than one type of parkinsonism.
The most common type of parkinsonism is Parkinson’s disease (PD), which accounts for about 80 percent of cases. No one is sure what causes most cases of Parkinson’s disease, so it is also known as idiopathic Parkinson’s. Idiopathic means “cause unknown.”
Deep inside the brain, regions called the basal ganglia and substantia nigra work together to ensure that the body moves smoothly. The substantia nigra produces a neurotransmitter – a chemical that helps nerves communicate – called dopamine. Messages sent by the brain to muscles to cause movement pass through the basal ganglia with the help of dopamine. In Parkinson’s disease, cells in the substantia nigra gradually stop producing dopamine and die off. With too little dopamine, the basal ganglia cannot facilitate movement as well. Researchers believe parkinsonian symptoms begin when the level of dopamine falls to about half of normal levels.
Subsets of Parkinson’s disease include:
Symptoms develop after age 50.
Most PD is late-onset.
Symptoms develop before age 50.
Accounts for approximately 10 percent of PD cases
Tends to have slower progression, more medication side effects
Dystonia (painful spasms and abnormal postures) is more common in early-onset PD.
Symptoms develop before age 20.
Often strong family history of Parkinson’s
Directly caused by genetic variants inherited from parents
Accounts for 10 to 15 percent of Parkinson’s disease cases
Parkinson’s disease dementia (PDD)
Between 50 and 80 percent of those with Parkinson’s disease eventually develop Parkinson’s disease dementia. On average, most people begin to develop PDD about 10 years after they receive a Parkinson’s disease diagnosis. PDD is often confused with Alzheimer’s and dementia with Lewy bodies. Parkinson’s disease dementia is usually diagnosed when motor symptoms occur first, at least a year before dementia symptoms.
In some cases, Parkinson’s symptoms are not a disease in themselves, but are caused by certain medications or by other conditions. These types of parkinsonism are referred to as secondary parkinsonism. Unlike Parkinson’s disease, secondary parkinsonisms are usually not progressive and do not respond to the same drugs. Secondary parkinsonisms include drug-induced and vascular parkinsonism.
Certain medications can cause parkinsonian symptoms as a side effect. Drug-induced parkinsonism is the second-leading cause of parkinsonism after Parkinson’s disease.
Drug-induced parkinsonism may be caused by a range of medications, including:
These drugs do not cause parkinsonism in every person who takes them.
The symptoms of drug-induced Parkinson’s are usually temporary. Symptoms typically fade and disappear within a year of stopping the medication that caused the condition, sometimes within weeks. In some cases, the symptoms of drug-induced parkinsonism are permanent, but they are usually not progressive like other forms of parkinsonism.
Vascular parkinsonism is caused by small strokes in the brain where blood vessels have become blocked. Also known as arteriosclerotic or multi-infarct parkinsonism, vascular parkinsonism is usually limited to the legs. Unlike other forms of parkinsonism, vascular parkinsonism appears suddenly rather than gradually and is not usually progressive. Hypertension (high blood pressure), high blood cholesterol, diabetes, and heart disease can contribute to the development of vascular parkinsonism. Unlike most other types of Parkinson’s, vascular parkinsonism can often be seen in computerized tomography (CT) or magnetic resonance imaging (MRI) scans of the brain.
Typical Parkinson’s medications do not improve symptoms of vascular parkinsonism. Treatments are aimed at preventing additional strokes and may include Aspirin or blood thinners and recommendations to stop smoking, eat a diet low in salt and saturated fat, and get more exercise.
Some types of parkinsonian movement disorders have similar motor symptoms as Parkinson’s disease and are also caused by progressive damage to the brain, but do not improve when treated with medications that are effective in Parkinson’s disease. These conditions are known as atypical parkinsonisms or “Parkinson’s plus.” Atypical parkinsonisms may show slight differences in motor symptoms from Parkinson’s disease. For instance, motor symptoms may start on both sides of the body instead of one side, or problems with thinking, memory, and mood may occur first, before motor symptoms.
Multiple system atrophy (MSA)
MSA is a rare condition with about 1,900 new cases diagnosed each year in the U.S. MSA is also known as Shy-Drager syndrome (SDS). MSA seems to affect men and women at equal rates. MSA has motor features in common with other types of Parkinson’s but is more likely to present with symptoms related to the autonomic nervous system. The autonomic nervous system regulates blood pressure, digestion, and temperature, and people with MSA are more likely than those with Parkinson’s disease to experience bladder or bowel problems, excess sweating, and orthostatic hypotension (fainting or dizziness after standing).
In MSA, an abnormal protein called alpha synuclein builds up in regions of the brain including the basal ganglia, the cerebellum, and the brain stem. Alpha synuclein buildup also occurs in Parkinson’s disease, but is usually seen later in the course of the condition, and mostly confined to the substantia nigra region of the brain. MSA affects different types of brain cells than those affected by Parkinson’s.
There are two subtypes of MSA:
MSA-P more closely resembles Parkinson’s, but it progresses more quickly and stops responding to Parkinson’s drugs sooner.
In MSA-C, progressive loss of coordination and balance are prominent. People with MSA-C may show an “action tremor,” or tremor that happens when they reach for an object. Muscle weakness can cause slurring and trouble swallowing. MSA-C can develop as early as a person’s 40s.
Progressive supranuclear palsy (PSP)
Also known as Steele–Richardson–Olszewski syndrome, PSP causes motor symptoms very similar to those seen in Parkinson’s, but they tend to be much more severe and progress much more quickly. Most people develop severe disabilities within three to five years of a PSP diagnosis.
In addition to motor symptoms, people with PSP are likely to have mood and personality changes and cognitive difficulties. Tremors are rare in PSP. In progressive supranuclear palsy, people are more likely to tilt and fall backward, while people with Parkinson’s lean and fall forward.
PSP is also considered a type of frontotemporal dementia (FTD), a collection of conditions that cause progressive damage to the frontal and temporal lobes of the brain. In healthy brains, there is a normal protein called tau that helps form the structure of cells. In PSP, tau protein tangles together in abnormal clumps, and brain cells are destabilized.
Unlike other forms of parkinsonism, PSP can significantly reduce life expectancy. With treatment, a person with PSP may live 10 years after diagnosis.
Dementia with Lewy bodies (DLB)
DLB is characterized by the early development of cognitive symptoms (related to memory, attention, and thinking) and psychotic symptoms such as hallucinations. Parkinsonian motor symptoms occur later in the progression of the disease. After Alzheimer’s, DLB is the leading cause of dementia. DLB typically does not occur before the age of 65. In DLB, alpha synuclein protein builds up throughout the cerebral cortex of the brain, forming collections called Lewy bodies.
DLB is often misdiagnosed as Alzheimer’s. Symptoms of DLB may respond to medications for Parkinson’s or Alzheimer’s, but certain Alzheimer’s medications carry high risk for dangerous side effects if given to those with DLB. DLB and Parkinson’s disease dementia have many features in common, and together they are known as the Lewy body dementias.
Corticobasal degeneration (CBD)
CBD, also called corticobasal syndrome, is a rare type of parkinsonism that usually progresses more quickly than Parkinson’s disease. In CBD, brain cells in the cerebral cortex and the basal ganglia shrink and die. CBD affects men and women approximately equally. Symptoms usually begin between the ages of 50 and 70. Corticobasal degeneration may be considered a type of frontotemporal dementia (FTD).
Motor symptoms in CBD are nearly always asymmetrical – occurring on one side of the body. CBD may also cause cognitive and behavioral symptoms. People with CBD may also have Parkinson’s disease, dementia with Lewy bodies, progressive supranuclear palsy, frontotemporal dementia, and Alzheimer’s-like dementia.