Parkinson’s disease can be difficult to diagnose in its early stages. Doctors base their diagnosis on the patient’s medical history and symptoms evaluated during a neurological exam. No laboratory or imaging tests can diagnose Parkinson’s, although brain scans such as computed tomography (CT), magnetic resonance imaging (MRI), or positron-emission tomographic (PET) may be used to rule out other neurological disorders.
A medical and personal history should include any relevant symptoms as well as any medications taken, and information on other conditions the patient may have.
In a neurological exam, the doctor will ask the patient to sit, stand, walk, and extend arms. The doctor will observe the patient’s balance and coordination. Parkinson's may be suspected in patients who have at least two of the following four symptoms, especially if they are more obvious on one side of the body:
- Tremor (shaking) when the limb is at rest
- Slowness of movement (bradykinesia)
- Rigidity, stiffness, or increased resistance to movement in the limbs or torso
- Poor balance (postural instability)
Drug Challenge Test
A levodopa challenge test may confirm a diagnosis of Parkinson's disease. If patients' symptoms improve when they take levodopa, they likely have Parkinson's, ruling out other neurological diseases.
Review Date: 06/18/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.