After an initial assessment of symptoms, a physician may use imaging tests to confirm a diagnosis of Parkinson’s disease or atypical parkinsonism (Parkinson’s-like disorders that do not respond to treatment with levodopa). Imaging tests can help physicians distinguish between these diseases and other neurological disorders, which in early stages may resemble Parkinson’s disease.
Magnetic resonance imaging (MRI)
MRI is a technique in which radio waves and a magnetic field are used to generate a high-resolution image of the body. In Parkinson’s patients, MRI can be used to observe the structure of the brain and determine any abnormalities that might explain the patient’s symptoms. MRI cannot be used alone to make a diagnosis of Parkinson’s (especially in the early stages of the disease) but can be used with other tests to support or disprove a diagnosis.
An MRI scan is performed in a hospital or clinic. The patient lies on a bench that slides into the bore of the instrument which resembles a long tube. A sequence of radio pulses is used to gather an image in seconds or minutes. Because some of these sequences are quite loud, patients may have to wear earplugs during the scan.
Not all patients can be scanned using MRI. Because the process uses a large magnet, patients with metal implants (pacemakers, and some surgically implanted hearing aids, and plates and screws used to repair bone breaks) cannot be scanned.
DaTscan is an imaging test approved by the U.S. Food and Drug Administration to detect dopamine function in the brain. DaTscan can be used to distinguish Parkinson’s disease from other neurological disorders and, unlike MRI, may only be available at large hospitals or clinics.
For a DaTscan, patients are injected with trace amounts of a radioactive compound called Ioflupane about 30 minutes before being scanned. The level of radioactive material is very small, and should not cause side effects. Ioflupane binds to the dopamine transporter in the brain; the tracer is visible using single photon emission computed tomography brain imaging.
DaTscan cannot distinguish between Parkinson’s disease and other diseases that cause abnormal dopamine trafficking, such as progressive supranuclear palsy, corticobasal ganglionic degeneration, and multiple system atrophy.
Other imaging tests
Other tests are occasionally used to confirm Parkinson’s disease or disprove other potential diagnoses. These include functional MRI (fMRI), and positron emission tomography, both of which are imaging techniques that are used to measure certain brain functions. fMRI can also be used to monitor Parkinson’s disease function, including changes in cognition.
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