Not All Parkinsonism Is Parkinson's Disease: 4 Patterns Every Clinician Needs to Know
Not every patient with parkinsonism has idiopathic Parkinson's disease. Getting this wrong matters. The Parkinson's plus syndromes respond differently to levodopa and progress differently. That conversation about the future looks very different depending on which diagnosis you are dealing with.
Here is how to tell them apart.
Idiopathic Parkinson’s Disease
What Is Idiopathic Parkinson's Disease?
Idiopathic Parkinson's disease is the most common cause of parkinsonism. The classic triad is bradykinesia, rigidity, and a resting tremor. Crucially, it is typically asymmetric at onset. This means one side tends to be affected before the other and over time it can become bilateral.
If a patient's presentation fits this pattern and they respond well to levodopa, idiopathic Parkinson's disease is the likely diagnosis. But when the picture does not quite fit, you need to think about Parkinson's plus.
What Are the Parkinson's Plus Syndromes?
The Parkinson's plus syndromes are a group of neurodegenerative conditions that share features with Parkinson's disease but have distinct clinical patterns, different underlying pathology and crucially, a different prognosis.
The four key conditions to know are PSP, MSA, CBD, and DLB.
Progressive Supranuclear Palsy (PSP)
PSP is characterised by early, unexplained falls, often in the first year of symptoms. This is a red flag that should prompt you to think beyond idiopathic Parkinson's disease.
The other hallmark is difficulty with vertical eye movements, particularly downward gaze. Ask the patient to follow your finger downward. In PSP, this movement is restricted or absent. You should check this by doing both pursuit (getting the patient to slowly follow your finger as it moves around) and saccadic (rapid alternating movements) eye movements. The impaired saccades will help highlight the difficulty with vertical eye movements more clearly.
Patients with PSP also tend to have a more upright, extended posture rather than the flexed posture typical of idiopathic Parkinson's disease.
Key clues: Early falls within the first year. Vertical gaze palsy. Upright posture.
2. Multiple System Atrophy (MSA)
MSA comes in two main variants, but the unifying feature is early autonomic failure appearing before or alongside the parkinsonism. This is the most important distinguishing feature.
Look for postural hypotension, urinary incontinence, erectile dysfunction, or other autonomic symptoms appearing early in the course of the disease. In idiopathic Parkinson's disease, significant autonomic involvement tends to come later.
Some patients with MSA have predominantly cerebellar features such as ataxia, intention tremor, and dysarthria. If you see early cerebellar signs alongside parkinsonism, MSA should be high on your differential.
Key clues: Early autonomic failure. Postural hypotension. Cerebellar features.
3. Corticobasal Degeneration (CBD)
CBD is perhaps the most striking of the Parkinson's plus syndromes clinically. These patients often present with profound limb apraxia, meaning they cannot perform purposeful movements with a limb despite intact motor function.
The most remarkable feature is the alien limb phenomenon. The patient describes their arm moving involuntarily, acting against their conscious intentions. It can be distressing for patients and their families.
CBD also tends to present with marked asymmetric cortical features, including cortical sensory loss, myoclonus, and dystonia. The cognitive and behavioural changes reflect frontal and parietal cortical involvement.
Key clues: Alien limb phenomenon. Limb apraxia. Asymmetric cortical features.
4. Dementia with Lewy Bodies (DLB)
DLB sits on the same Lewy body disease spectrum as Parkinson's disease, but its distinguishing feature is the temporal relationship between cognitive and motor symptoms. In DLB, cognitive changes typically appear first or within a year of the parkinsonism.
The characteristic hallucinations of DLB are vivid, detailed, and often involve people or animals. Crucially, patients are frequently not frightened by them. A patient who describes seeing children running around their living room, and is puzzled rather than scared, should make you think of DLB.
Patients may try to interact with the hallucinations, only to be confused when there is no response. Fluctuating cognition and REM sleep behaviour disorder are additional supporting features.
Key clues: Cognitive decline within one year of parkinsonism. Vivid, non-threatening visual hallucinations. Fluctuating cognition.
Why This Matters Clinically
The Parkinson's plus syndromes behave differently to idiopathic Parkinson's disease in two important ways.
First, levodopa response. Idiopathic Parkinson's disease typically responds well to levodopa. The Parkinson's plus syndromes generally do not, or the response is partial and short-lived. This distinction is both diagnostically useful and therapeutically important.
Second, prognosis. The Parkinson's plus syndromes tend to progress more quickly compared to idiopathic Parkinson's disease.
Recognising these patterns earlier means better referrals to neurology, a more accurate diagnosis sooner and a more informed discussion about what lies ahead.
Frequently Asked Questions
What is the difference between Parkinson's disease and Parkinson's plus syndromes? Parkinson's disease is caused by loss of dopaminergic neurons in the substantia nigra and typically responds well to levodopa. The Parkinson's plus syndromes involve more widespread neurodegeneration affecting multiple systems, respond poorly to levodopa, and progress more rapidly.
What are the four Parkinson's plus syndromes? The four key Parkinson's plus syndromes are Progressive Supranuclear Palsy (PSP), Multiple System Atrophy (MSA), Corticobasal Degeneration (CBD), and Dementia with Lewy Bodies (DLB).
How do you diagnose PSP at the bedside? The two most important bedside features of PSP are early unexplained falls within the first year and impaired vertical eye movements, particularly downward gaze. A supranuclear gaze palsy on examination is highly suggestive.
What causes the alien limb phenomenon in CBD? The alien limb phenomenon in corticobasal degeneration is thought to occur from damage to the parietal lobe on the opposite side to the affected limb (https://pmc.ncbi.nlm.nih.gov/articles/PMC3914666/), which normally integrates sensory information with voluntary motor control. The affected limb moves involuntarily or adopts unusual postures outside the patient's conscious control.
Can DLB be mistaken for Parkinson's disease? Yes. DLB and Parkinson's disease share Lewy body pathology and similar motor features. The key distinguishing features are the timing of cognitive decline (usually within one year of motor symptoms in DLB), prominent visual hallucinations, and fluctuating cognition. Accurate diagnosis matters because antipsychotics used in other dementias can cause severe, life-threatening reactions in DLB.
Does Parkinson's disease always cause a tremor? No. A resting tremor is a classic feature of idiopathic Parkinson's disease but is not present in all patients. Some patients present with akinetic-rigid Parkinson's disease with little or no tremor. The absence of tremor should also prompt consideration of Parkinson's plus syndromes.
Want to Build Your Pattern Recognition in Neurology?
Learning to recognise these patterns is one of the most high-yield skills you can develop as a clinician. Whether you are preparing for MRCP PACES, starting a neurology job, or just want to feel more confident when parkinsonism comes through the door, building a systematic approach makes all the difference.
My Neurology Pattern Recognition Guide breaks down the key conditions, clinical patterns, and examination findings that every doctor should know. Used by clinicians across four continents.
Explore the Neurology Pattern Recognition Guide at medxstart.co.uk
This post is for educational purposes only and does not constitute clinical advice. Always apply clinical judgement in individual patient assessment.
Written by Dr Will Bierrum, Neurology SpR and founder of Medxstart - helping clinicians understand neurology.