Parkinson disease is diagnosed on the presence of two of the four main or cardinal symptoms. The cardinal symptoms include: a resting tremor, rigidity or stiff-ness, bradykinesia (defined as slowness and incomplete-ness of movement), and postural instability (defined as a loss of balance and difficulty walking). The disease is named for James Parkinson, an English doctor, who first described it in 1817. Most people think of PD as a disease of trembling. Indeed it’s been called the “shaking palsy” or “paralysis agitans” (an agitated or trembling paralysis). Yet, 30% of all people with PD never have a tremor, and people with PD are not paralyzed.
The resting tremor of PD is different than the tremor of essential tremor (ET), a disease sometimes confused with PD. The tremor associated with ET increases when you stretch your hand, activating the muscles, and stops when you rest your hand. This type of tremor can be referred to as an action, sustention, or postural tremor, because you are sustaining a given posture of your hand by activating the muscles.
The tremor of ET can usually (but not always) be distinguished from the tremor of PD, as the ET tremor generally starts in both hands, while the PD tremor generally starts in one hand and spreads to the leg on the same side of the body before spreading to the other hand. Additionally, the tremor of PD may affect the chin, but rarely the head, while the tremor of ET rarely affects the chin. About 50% of people with ET have a family history of it, but only 15% of people with PD have a family history of PD. Sometimes PD can start with an action or sustention tremor, causing it to be mistaken for ET. As other PD symptoms evolve, it becomes apparent that PD is the correct diagnosis. The rigidity, or stiffness, of PD affects the muscles of your neck, arms, and legs, and is usually greater on the same side of your body as the tremor. Sometimes the simultaneous occurrence of tremor and rigidity in an arm or leg gives a “ratchet-like” quality to the movement, like two gears meshing and moving in opposite directions.
This phenomenon, known as “cog-wheeling,” is diagnostic of PD only when associated with other symptoms.The movement disorder of PD consists of slowness andincompleteness of movement referred to as bradykinesia.
Although “brady” in Latin means slow and “kinesia” in Latin means movement, bradykinesia is more than slow movement. A turtle, when he walks, walks slowly, but the turtle is not bradykinetic. Each successive step of the turtle’s legs is equally slow, and each successive step is equally small. When a person with PD walks, he walks slowly and each successive step may become slower and slower and shorter and shorter until he suddenly stops or “freezes.” Or, occasionally, each successive step may become faster and faster until he runs, and often falls. The basal ganglia regulate these kinds of automatic movements (stepping movements made while walking) such that once started, they flow automatically without your conscious awareness of taking each step.
In some ways, the actions of the basal ganglia are like those of a copy machine. Once you put in the “original” (the command to walk), the copies come automatically, each one resembling the original (each step like the next). In PD, the basal ganglia are like a defective copy machine; the first copy is as dark and readable as the original, but each succeeding copy grows lighter and lighter and less readable.
The postural instability, or balance problem, of PD may appear as an inability to stand on one leg, called “static balance.” It may show up as losing your balance while turning or walking downstairs. When you turn or walk down a flight of stairs, for a split second you raise one leg off the ground, and at that moment, without your being aware that you raised your leg, you stumble and lose your balance. Postural instability may also show up as an inability to right or correct yourself when you stumble or are pushed, which is called “dynamic balance.” Dynamic balance depends upon your brain’s ability to receive “messages” from sensors in your feet that subconsciously monitor the position of your feet in space, as well as from sensors in your inner ears. Messages from the sensors in your feet and inner ears are relayed to a part of your brain called the thalamus.
The loss of dynamic balance occurs because of a mismatch of the signals from your feet and inner ears, and the inability of your basal ganglia and spinal cord to adjust your muscles to a changing environment. An important, but not cardinal, symptom is the stooped posture that occurs in up to 60% of people with PD. Stooping of the neck, or stooping or slumping of the shoulders and spine, may be early symptoms of PD . The stooping may result from an uneven pull of the flexor muscles in front of the spine over the extensor muscles in back of the spine and it may be aggravated by osteoporosis. In 1998, my colleagues and I developed the following test that can help you determine if you have PD.
Self-Assessment Test for Parkinson Disease:
- Do you have trouble getting up from a chair?
- Has your handwriting become smaller?*
- Do people say your voice has become softer?
- Do your feet ever seem to get stuck to the floor?
- Do people say your face always seems sad?
- Do your hands or legs shake or tremble?
- Do you have difficulty buttoning buttons?
- Do you shuffle your feet when you walk?
- Do you take tiny steps when you walk?
- Has anyone asked if you have Parkinson disease?
- Have you ever taken levodopa/carbidopa or Sinemet?
*Samples of your handwriting obtained during a doctor’s visit and compared with samples from the past several years (such as your signature on annual tax returns), may be used as an indicator of PD . PD causes a condition called micrographia: when a patient’s hand-writing gets smaller and more compressed. You, as a patient, should write a sentence: “This is a sample of my best handwriting” every day, first thing in the morning before taking any medication. Over the years, these handwriting samples can be a window into the progression or lack of progression of PD.