Diagnosis

Since there is no specific test or marker for PD, diagnosis is by a physician and depends on the presence of at least two of the three major signs: tremor at rest, rigidity, and bradykinesia, as well as the absence of a secondary cause, such as antipsychotic medications or multiple small strokes in the regions of the brain controlling movement. Patients tend to be most aware of tremor and bradykinesia, and less so of rigidity.

To diagnose PD, the physician will perform a standard neurological examination, involving various simple tests of reactions, reflexes, and movements.

• Bradykinesia is tested by determining how quickly the person can tap the finger and thumb together, or tap the foot up and down.
• Tremor is determined by simple inspection.
• The physician assesses rigidity by moving the neck, upper limbs, and lower limbs while the patient relaxes, feeling for resistance to movement.
• Postural instability is tested with the pull test, in which the examiner stands behind the patient and asks the patient to maintain their balance when pulled backwards. The examiner pulls back briskly to assess the patients ability to recover, being careful to prevent the patient from falling.

The examination also involves recording a careful medical history, especially for exposure to medications that can block dopamine function in the brain. Several drugs with similar properties are also used for other purposes, and the physician inquires about these other drugs. A list of such medications is shown in the Table below.

Several other disorders have certain features that are similar to those of PD, and are sometimes mistaken for PD. These include:

• Essential tremor, in which tremor is the only symptom
• Progressive supranuclear palsy, characterized by inability to look downward
• Multiple system atrophy, characterized by early and prominent autonomic symptoms
• Vascular (related to blood vessels) parkinsonism, caused by multiple small strokes
• Poisoning by carbon monoxide, manganese, or certain pesticides