Although the actual causes and risk factors for getting Parkinson's Disease (PD) are still mysterious, the primary signs that signal the presence of PD are very clear. You may have noticed one or more of these signs but then dismissed it as something slight, easily explained, or due to an entirely different condition.

Several resources use the acronym TRAP to illustrate the four primary signs of PD. And, because PD seems to trap your body with your brain's compromised ability to communicate, the acronym makes the top four symptoms easy to remember.

T = Tremor at rest (uncontrolled shaking)

PD was originally called shaking palsy because the resting tremor (it goes away as soon as the hand is engaged) rarely occurs in other illnesses. Characteristically, the resting tremor begins in one hand and moves to the other hand years later in the disease. The tremor may extend to the leg or foot on the same side and sometimes to the lips and jaw — or you may have no tremor at all. Tremor in the head and neck, however, is less common in primary Parkinson's disease.

Variations of the resting tremor include:

  • Postural tremor (obvious when arms are extended to hold a position or posture)
  • Action tremor (present when certain tasks, such as holding, are performed)
  • Internal tremor (the patient feels the tremor but can't show it, almost as if it's coming from inside)

While tremor is the most obvious symptom of PD, it doesn't have to be present for diagnosis.

R = Rigidity (stiff muscles)

Rigidity is probably the most ignored and easy-to-explain-as-something-else sign. In plain English, rigidity means stiffness. (Who doesn't experience stiffness in joints and limbs that makes movement more difficult as they age?) If your doctor observes rigidity (without other signs of PD), he may first suspect arthritis and prescribe an anti-inflammatory medication. But, if medicine doesn't relieve the stiffness, you need to let your doctor know.

A = Akinesia (absence or slowness of movement)

Especially early on, people with PD (PWP) may experience slight bradykinesia (unusually slow movement).Much later in the progression, that slowed movement may become akinesia (no movement).

Get to know these terms because, if indeed you or a loved one has PD, you'll hear these words again and again. Kinesia means movement in the sense of knowing what you want your body to do. So akinesia and bradykinesia indicate problems initiating or continuing an action. For example, to walk across the room, you stand up and your brain tells your foot to step out — but with bradykinesia, your body doesn't move right away.

The problem can extend well beyond simply walking from here to there. Bradykinesia can also affect

  • Facial expression because it slows blinking eye movement and the ability to smile.
  • Fine motor movements, such as the ability to manage buttons or cut food because the fingers lack the necessary speed and coordination to perform these detailed actions. In addition, fingers may curl or stiffen because of rigidity.
  • The ability to easily turn over in bed because of lack of coordination between the various parts of the body that need to move in sequence; again muscle stiffness and rigidity may further complicate this normally routine task.

P = Postural instability (impaired balance)

In a healthy person, the natural movement is to alternately swing the arms and step forward with assurance. For PWP, however, the swing slowly decreases; in time the person moves with small, uncertain, shuffling steps. (PWP may adapt by propelling themselves forward with several quick, short steps.) Other PWP experience episodes of freezing (their feet feel glued to the floor).

Problems with balance (resulting in falls that can cause major injuries, hospitalization, and escalation of symptoms) are usually not a factor until later stages in PD. In time, PWP may lose the ability to gauge the necessary action to regain balance and prevent a fall. They may grasp at doorways or other stationary objects in an effort to prevent the loss of balance. Unfortunately, these maneuvers can make PWP appear to be under the influence of alcohol or other substances.