Almost 200 years after Parkinson's was first discovered and after many new discoveries about the biology of the disease, a diagnosis still depends on identifying the core features — tremor, slowness and stiffness — described by James Parkinson. The diagnosis of Parkinson’s does not come from a test, but instead requires a careful medical history and a physical examination to detect the cardinal signs of the disease, including:
- Resting Tremor: In the early stages of the disease, about 70 percent of people experience a slight tremor in the hand or foot on one side of the body, or less commonly in the jaw or face. A typical onset is tremor in one finger. The tremor consists of a shaking or oscillating movement, and usually appears when a person's muscles are relaxed, or at rest, hence the term "resting tremor." The affected body part trembles when it is not performing an action. Typically, the fingers or hand will tremble when folded in the lap, or when the arm is held loosely at the side, i.e., when the limb is at rest. The tremor usually ceases when a person begins an action. Some people with PD have noticed that they can stop a hand tremor by keeping the hand in motion or in a flexed grip. The tremor of PD can be exacerbated by stress or excitement, sometimes attracting unwanted notice. The tremor often spreads to the other side of the body as the disease progresses, but usually remains most apparent on the initially affected side. Although tremor is the most noticeable outward sign of the disease, not all people with PD will develop tremor.
- Bradykinesia: Bradykinesia means “slow movement.” A defining feature of Parkinson’s, bradykinesia also describes a general reduction of spontaneous movement, which can give the appearance of abnormal stillness and a decrease in facial expressivity. Bradykinesia causes difficulty with repetitive movements, such as finger tapping. Due to bradykinesia, a person with Parkinson’s may have difficulty performing everyday functions, such as buttoning a shirt, cutting food or brushing his or her teeth. People who experience bradykinesia may walk with short, shuffling steps. The reduction in movement and the limited range of movement caused by bradykinesia can affect a person’s speech, which may become quieter and less distinct as Parkinson’s progresses.
- Rigidity: Rigidity causes stiffness and inflexibility of the limbs, neck and trunk. Muscles normally stretch when they move, and then relax when they are at rest. In Parkinson’s rigidity, the muscle tone of an affected limb is always stiff and does not relax, sometimes contributing to a decreased range of motion. People with PD most commonly experience tightness of the neck, shoulder and leg. A person with rigidity and bradykinesia tends to not swing his or her arms when walking. Rigidity can be uncomfortable or even painful.
- Postural Instability: One of the most important signs of Parkinson’s is postural instability, a tendency to be unstable when standing upright. A person with postural instability has lost some of the reflexes needed for maintaining an upright posture, and may topple backwards if jostled even slightly. Some develop a dangerous tendency to sway backwards when rising from a chair, standing or turning. This problem is called retropulsion and may result in a backwards fall. People with balance problems may have particular difficulty when pivoting or making turns or quick movements. Doctors test postural stability by using the “pull test.” During this test, the neurologist gives a moderately forceful backwards tug on the standing individual and observes how well the person recovers. The normal response is a quick backwards step to prevent a fall; but many people with Parkinson’s are unable to recover, and would tumble backwards if the neurologist were not right there to catch him or her.
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