Decoding Your Scans: MRI and DaTscans in Diagnosis

Diagnosing vascular parkinsonism (VaP) is rarely a matter of a single “yes or no” test. Instead, it is a clinical-radiological diagnosis, meaning your doctor must piece together the story of your symptoms with the evidence found on brain imaging ^[1]. Because the symptoms of VaP can overlap so significantly with idiopathic Parkinson’s disease, specialized scans like MRI and DaTscans are used to look for clues rather than provide a definitive “smoking gun” ^[2][3].

Interpreting Your MRI Results

A magnetic resonance imaging (MRI) scan uses strong magnets to create a detailed map of your brain’s structure. In VaP, doctors look for specific signs of “vascular burden” or damage to the blood vessels.

White Matter Hyperintensities (WMH)

On an MRI report, you may see these described as “bright spots,” leukoaraiosis, or “small vessel disease.” They represent areas where the “insulation” (white matter) around brain cells has been damaged by poor blood flow ^[1][3].

• The Nuance: Many healthy older adults have some WMH without ever developing movement problems ^[3]. Therefore, finding these spots is not enough for a diagnosis; there is no validated MRI severity threshold that automatically proves VaP. They must be interpreted alongside your clinical symptoms to be considered a cause of your parkinsonism ^[4].

Lacunar Infarcts

These are tiny, old “silent strokes” that leave small fluid-filled holes in the brain ^[5]. Lacunes may be symptomatic, silent, incidental, or related to different vascular mechanisms. Finding them in the basal ganglia (the brain’s movement coordinator) supports the diagnosis only when their location matches your physical symptoms ^[6].

Strategic Infarcts

A strategic infarct is a stroke that happens in “just the wrong place” ^[5]. Even one small stroke in the pathways that carry dopamine can cause sudden parkinsonism, even if the rest of the brain’s blood vessels look healthy ^[3].

The Limitations of the DaTscan

While an MRI looks at the brain’s structure, a DaTscan measures dopamine-transporter availability in the striatum ^[2]. It is ordered selectively when the result is likely to change your medical management.

• What it shows: A DaTscan identifies a presynaptic striatal dopamine-transporter deficit. It does not measure total brain dopamine function ^[7].
• It is not definitive: A reduced signal does not by itself prove idiopathic PD; it can occur with other degenerative parkinsonian disorders, age, or after a strategically placed vascular lesion ^[8]. Conversely, a “normal” scan does not absolutely rule out early parkinsonism, nor does it guarantee “pure” VaP ^[9][10].
• Mixed Disease: Many people have mixed disease (both vascular lesions and neurodegenerative PD). Because of this, interpreting a DaTscan requires expert correlation with your clinical exam ^[11].

Why One Test Isn’t Enough

There is currently no blood test or single scan that can provide a 100% certain diagnosis of VaP ^[3]. Doctors must weigh the “imaging burden” against your clinical history, and consider if other issues—such as normal-pressure hydrocephalus (NPH), medication side effects, neuropathy, arthritis, or another neurologic disorder—are contributing to your walking problems ^[12].

They will look at:

1. Temporal Relationship: Did your symptoms start or get worse right after a stroke? ^[1]
2. Symptom Pattern: Is it mostly your walking and balance (lower-body) that are affected? ^[13]
3. Treatment Response: Do you respond well to Parkinson’s medications, or do they have little effect? ^[1]

Because of these complexities, a diagnosis may change over time as your doctor observes how your symptoms progress and how you respond to different therapies ^[14]. Monitoring your vascular health—such as blood pressure and cholesterol—is often as important as managing the movement symptoms themselves ^[12].