Diagnosis of Parkinson's Disease
PD is usually diagnosed clinically, meaning that a physician looks for the presence or absence of the possible symptoms of PD by interviewing the patient and performing a detailed neurologic examination.
While there is presently no definitive test for PD, it can often be identified by a general neurologist, who is trained to diagnose and treat neurologic disorders. To avoid misdiagnosis, consultation with a movement disorder specialist is recommended. A movement disorder specialist is a physician who has undergone additional, subspecialty training in the diagnosis and treatment of movement disorders, such as PD, after training in general neurology.
What to expect during your visit with a physician
When you or someone you know first visits a physician for the evaluation of possible PD symptoms, it is helpful to know what to expect. During the first visit, the physician should:
- Take a complete and careful medical history
- Take your blood pressure while you sit and stand
- Assess your thinking (or cognitive) skills
- Examine your facial expression
- Look for tremor in your face, hands, arms, or legs
- Examine whether there is stiffness in your arms, legs, torso, or shoulders
- Determine whether you can get up easily from a chair, especially without using your arms
- Examine your walking pattern
- Assess your balance as you stand
Typically, a trained physician will only consider the diagnosis of PD if the person being examined has at least two of the core motor symptoms of PD, including tremor, the characteristic bradykinesia (slowness of movement), or rigidity. At the end of your visit, the physician should discuss with you why you may or may not have PD and the level of certainty about the diagnosis. This determination is based on your medical history and examination at this visit.
Brain Imaging & Other Tools to Aid Diagnosis of Parkinson's
In addition to taking a history and performing a detailed neurologic examination, physicians sometimes use brain imaging to help support a particular diagnosis. However, these studies have their limitations in the diagnosis of PD and are typically used only in select patients. Brain imaging is not routinely performed by neurologists or movement disorder specialists when they are considering the diagnosis of PD, especially if the person's symptoms strongly suggest to the physician that idiopathic PD is the correct diagnosis.
Rather, use of imaging is most helpful when the diagnosis is uncertain, or when physicians are looking for changes in the brain that are more typical of one of several Parkinsonian syndromes (and not idiopathic PD) and other conditions that can mimic PD. Imaging studies to evaluate PD and Parkinsonian syndromes include magnetic resonance imaging (MRI), which examines the structure of the brain, and DaTscan, an imaging test approved by the Food and Drug Administration (FDA) to detect the dopamine function in the brain. A DaTscan may help differentiate idiopathic PD from other disorders that cause tremor or other Parkinsonian syndromes. Most physicians' offices will have access to MRI; however, DaTscan imaging may only be available at larger hospitals or medical centers.
Other imaging studies that can be done, but that are not used routinely in the clinic, include functional MRI (fMRI), a specialized form of brain imaging that examines brain function, and positron emission tomography (PET), which can measure certain brain functions. Although PET and fMRI imaging can be used as tools to assist with the diagnosis of PD and Parkinsonian syndromes, they are largely reserved for research purposes at this point.
Determining diagnosis through response to Parkinson's medication
If a person's symptoms and neurologic examination are only suggestive of PD or if the diagnosis is otherwise in doubt, the physician may, nevertheless, prescribe a medication intended for PD to provide additional information. In the case of idiopathic PD, there is typically a positive, predictable response to PD medication; in the case of some related Parkinsonian syndromes, the response to medication may not be particularly robust, or it may be absent entirely A DaTscan may be particularly useful for the refinement of a diagnosis if a person with PD symptoms does not respond to the usual PD medications.
Unfortunately, there are no standard biological tests for PD, such as a blood test. However, researchers are actively trying to find “biological markers" in blood and other bodily fluids that could help confirm the diagnosis of PD.
If it's not Parkinson's Disease, what else could it be?
There are several other conditions that might produce symptoms that can be mistaken for PD. Here are some possibilities:
- Medication side effects: Certain drugs can produce or exacerbate the symptoms of PD.
- Essential, or familial, tremor: This is a relatively common and benign cause of recurrent tremor and is often confused with the tremor of idiopathic PD. A general neurologist or movement disorder specialist is the best physician to help differentiate between these two conditions.
- A Parkinsonian syndrome: The symptoms of several neurologic conditions are similar to those of idiopathic PD, but they are often managed differently and often do not respond to the typical medications for PD.
Remember: Only a general neurologist or movement disorder specialist can tell you with reasonable certainty if you have idiopathic PD. If for some reason you are not comfortable with the results of your first physician visit, getting a second opinion from another general neurologist or movement disorder specialist is always an option. It is important that you feel comfortable with your physician to ensure the best possible outcome for you.
Once you or your loved one has a diagnosis of PD, it is time to discuss treatment options with your physician.
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