Atypical parkinsonism is a group of brain diseases that look like Parkinson’s disease on the surface, with similar symptoms like slowness, stiffness, and trouble walking, but are caused by different underlying processes and follow a different, often faster, course. These conditions respond poorly to the medications that typically help people with Parkinson’s, and they tend to produce additional symptoms that classic Parkinson’s does not. There are four main types, each with its own distinct pattern of symptoms and brain changes.
How It Differs From Parkinson’s Disease
The core movement symptoms of atypical parkinsonism, such as rigidity and slow movement, overlap heavily with Parkinson’s disease. That overlap makes early diagnosis difficult, and many people are initially told they have Parkinson’s before the picture changes. No single blood test or scan can definitively separate these conditions from one another or from Parkinson’s itself, so diagnosis often evolves over time as symptoms progress.
The biggest clinical clue is medication response. Standard Parkinson’s medications work by replacing or mimicking dopamine, and most people with Parkinson’s see meaningful improvement. In atypical parkinsonism, those same medications provide little or no benefit. When someone’s symptoms fail to improve on treatment, that lack of response is often what first prompts doctors to reconsider the diagnosis.
The pace of the disease also tends to differ. Atypical syndromes generally progress faster. Median survival from diagnosis in one large study was about 7.8 years for Parkinson’s, compared to roughly 5.1 years for multiple system atrophy, 3.3 years for dementia with Lewy bodies, and 2.6 years for progressive supranuclear palsy.
Two Categories of Brain Changes
Despite their clinical differences, the four atypical syndromes sort neatly into two biological categories based on which protein accumulates abnormally in the brain.
Multiple system atrophy and dementia with Lewy bodies both involve the buildup of a protein called alpha-synuclein, the same protein involved in Parkinson’s disease. The difference is where and how it accumulates. In Parkinson’s, it collects inside nerve cells. In multiple system atrophy, it builds up in a different type of brain cell entirely. In dementia with Lewy bodies, the deposits are more widespread across the brain’s outer layers.
Progressive supranuclear palsy and corticobasal degeneration both involve a different protein called tau. These two conditions are classified as tauopathies, and they tend to affect brain regions involved in movement planning, eye control, and higher-level thinking.
Progressive Supranuclear Palsy (PSP)
PSP is the most common form of atypical parkinsonism. Its hallmark is difficulty moving the eyes, particularly looking downward. This creates real problems with everyday tasks like reading, eating, or walking down stairs. Unlike Parkinson’s, PSP rarely causes tremor.
Early and unexplained falls, especially backward falls, are a major red flag. Many people with PSP begin falling within the first year or two of symptoms, which is unusual for Parkinson’s, where balance problems typically appear much later. People with PSP often develop a distinctive facial expression that looks permanently worried or surprised, caused by contraction of the muscles between the eyebrows. Speech and swallowing difficulties tend to appear as the disease progresses.
On MRI, PSP can produce what radiologists call the “hummingbird sign,” a distinctive shape of the brainstem caused by shrinkage of specific structures. This finding, when present, helps confirm the diagnosis.
Multiple System Atrophy (MSA)
MSA is the second most common atypical parkinsonian syndrome, and it stands out because of the heavy involvement of the body’s automatic functions: blood pressure regulation, bladder control, digestion, and sexual function. Significant drops in blood pressure upon standing (causing lightheadedness or fainting), urinary problems, and erectile dysfunction in men often appear early, sometimes before the movement symptoms become obvious.
MSA comes in two subtypes. MSA-P is dominated by parkinsonian symptoms like stiffness and slowness that respond poorly to medication. MSA-C primarily affects coordination, causing an unsteady, wide-based walk and difficulty with precise hand movements. Both subtypes share the autonomic problems.
Other distinctive features include a forward drop of the head, a lean to one side when sitting (called the Pisa sign), and color or temperature changes in the hands and feet, with skin turning reddish-blue and cold. Sleep disturbances are common, including physically acting out dreams and sleep apnea. The disease tends to progress quickly, with many people losing the ability to walk within three to five years of symptom onset.
MRI scans in MSA may show the “hot cross bun” sign, a cross-shaped pattern visible in the brainstem that is considered highly specific to this condition.
Dementia With Lewy Bodies (DLB)
DLB is the second most common cause of dementia in older adults after Alzheimer’s disease, and it most often affects people in their 60s. What sets it apart from other forms of parkinsonism is that cognitive decline, particularly problems with attention and alertness, appears early, usually before or alongside the movement symptoms rather than years later.
A defining feature of DLB is fluctuation. People can shift dramatically between periods of relative clarity and periods of confusion or excessive sleepiness, sometimes sleeping two or more hours during the day. Visual hallucinations are common and often vivid, typically involving small animals, children, or moving shadows at the edges of vision. These hallucinations can be one of the earliest symptoms and are a strong diagnostic clue.
Corticobasal Degeneration (CBD)
CBD is the rarest of the four main atypical syndromes, and it produces some of the most unusual symptoms. It typically affects one side of the body far more than the other. Stiffness, abnormal postures of the limbs, and sudden jerking movements are common early features.
One of the most striking symptoms is “alien limb phenomenon,” where a hand or leg seems to move on its own, as though it has a mind of its own and is no longer under the person’s control. People with CBD may also lose the ability to use familiar objects correctly, struggling with tasks like using a key or a comb despite having full strength and sensation. Difficulty with simple arithmetic can appear early. As the disease progresses, it affects speech, swallowing, memory, and the ability to navigate through space.
How These Conditions Are Diagnosed
There is no single definitive test for any atypical parkinsonian syndrome during life. Diagnosis relies on the pattern of symptoms, the rate of progression, and the response (or lack of response) to Parkinson’s medications. MRI can support the diagnosis by revealing characteristic patterns of brain shrinkage or specific signs like the hot cross bun or hummingbird findings, but a normal-looking scan does not rule these conditions out.
Because the early stages of all these diseases can look similar to one another and to Parkinson’s, misdiagnosis is common. The diagnosis often shifts as new symptoms emerge over months or years. Certain red flags prompt doctors to look beyond a standard Parkinson’s diagnosis: early falls, rapid loss of walking ability, prominent hallucinations or cognitive changes, severe blood pressure drops, poor medication response, or dramatic one-sided symptoms with unusual limb behavior.
Treatment and Management
No current treatments can slow or stop the progression of any atypical parkinsonian syndrome. Management focuses on easing symptoms and maintaining quality of life for as long as possible. A trial of Parkinson’s medication is usually attempted, and while most people see little benefit, a small number with MSA-P or DLB may experience modest temporary improvement.
Much of the practical care involves addressing specific symptoms: physical therapy to help with balance and mobility, speech therapy for swallowing and communication difficulties, medications or compression stockings for blood pressure drops, and bladder management strategies. Occupational therapy can help people adapt to the loss of hand coordination or spatial awareness, particularly in CBD. For DLB, careful management of hallucinations is important, though many standard psychiatric medications can worsen parkinsonism and must be avoided.
Because these diseases affect so many body systems and progress relatively quickly, coordinated care from a team of specialists, including neurologists, therapists, and palliative care providers, tends to produce the best outcomes for both patients and their families.