No Standard Blood Tests to Detect Parkinson’s Disease

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Diagnosing
Parkinson’s Disease

Your doctor may have difficulty diagnosing Parkinson’s disease when it is in the early stages because there are no standard blood tests that detect it. Also, Parkinson’s problems such as stiff muscles may be symptoms of other diseases.

As time passes, the clinical signs of Parkinson’s disease become more obvious, however. These include shaking or tremors while your muscles are still or relaxed; stiff or tight limbs, especially on only one side of your body; slow movements (“bradykinesia”); and difficulty in walking and balancing. Your face may take on a “masked” or rigid look.

Many patients find it hard to get up and suddenly “freeze” in place while walking. They may take short, uncertain steps. Slurred speech, dull thinking, and small cramped handwriting are also linked to Parkinson’s disease.

If your doctor suspects that you have Parkinson’s disease, he or she may ask you to take the Unified Parkinson Disease Rating Scale (UPDRS), a survey of over 40 items that evaluates your movement, your own description of your ailments, and how you perform daily living tasks. The survey can be used to help diagnose Parkinson’s disease as well as to check your progress once you start treatment.

One of the most important signs that you have Parkinson’s disease is a positive response to L–dopa, a chemical that helps you produce dopamine. In the Parkinson’s patient, the portion of the brain that produces dopamine becomes damaged. Dopamine transmits signals in the brain that are involved in movement. When patients are first looked at for Parkinson’s disease, they respond well to L–dopa. This treatment does not always work for other patients with Parkinson–like symptoms.

PET Scans

PET or positron emission tomography may be used to examine the patient’s brain and ability to synthesize dopamine. A PET scan uses radiation and a camera/scanner to produce clear images and to see where certain compounds may accumulate. This allows your doctor to determine biological activity as well as structural changes.

The patient is injected with 18–fluorodopa, a radioactive form of L–dopa, the precursor to dopamine. Parkinson’s disease patients may show decreased uptake of 18–fluorodopa in the caudate and putamen regions of the brain, and have damage in the area known as the substantia nigra. Checking the activity of the radioactive tracer can indicate decreased dopamine activity and help identify Parkinson’s disease. See Parkinson’s Disease, PET Studies Demo, McConnell Brain Imaging Centre for photographs of the normal brain versus the brain of a Parkinson’s disease patient. For diagrams of the basal region of the brain controlling movement, see the Brain Explorer web site, scroll to the subheading “Basal Ganglia” and click on “putamen” and “caudate.”

A PET scan is not yet considered a routine procedure for diagnosing Parkinson’s disease. It is expensive, and PET scanners are not available at all medical facilities.