Parkinson Disease Health (cont.)

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Parkinson's Disease Diagnosis

No blood test exists that definitively diagnoses Parkinson's disease (PD). Currently, a strong presumptive diagnosis of PD is made by a doctor's observation of the patient's symptoms, medical history and neurologic examination, and response to a treatment schedule with the combination medicine generically termed carbidopa-levodopa (Sinemet, Atamet, Parcopa).

Definitive diagnosis of Parkinson's disease can be difficult. As stated above, there is no specific blood test or diagnostic study currently available to make the diagnosis. In fact, a brain tissue sample, though not practical in living patients, is the only way to be relatively sure of the diagnosis. This is usually done at autopsy. Studies have shown that a misdiagnosis rate in the past of 25% to 35% was not uncommon. This rate drops to about 8% when a movement disorder specialist physician (for example, a neurologist) helps make the diagnosis. Consequently, consultation with a specialist is usually recommended.

People that suspect they may be experiencing symptoms of PD should consult with their primary care doctor and ultimately may need a referral to a neurologist who specializes in movement disorders.

  • Early-stage diagnosis
    • In the past, at least two of the cardinal symptoms (tremor, rigidity, and bradykinesia) needed to be present to make the diagnosis of PD. These criteria alone were found to be incorrect in 25% of people diagnosed.
    • Studies that look back at people with PD after the diagnosis is certain have found that the features or signs and symptoms that best predict PD are resting tremor, asymmetric presentation (symptoms on 1 side of the body), and a powerful response to a medication called carbidopa-levodopa; older literature used only levodopa. These criteria may not always provide accurate diagnosis either because of other diseases that have symptoms similar to PD such as Huntington's disease, essential tremors, progressive palsy, and hydrocephalus.
    • In order to increase the precision of an early diagnosis, a PD battery has been suggested. This includes a more complete assessment including motor function, olfaction, and mood. Occasionally, other tests (CT, MRI) may be done to help confirm that the symptoms are not due to other problems.
  • Late-stage diagnosis
    • In the late stages of disease, the symptoms are usually unmistakable and the diagnosis can be confirmed by a simple history and complete physical exam.
    • Slowness and difficulty with movement should be quite apparent in the late stages.
    • Most people will have tremor at this stage, although not all, thus creating a diagnostic challenge.
    • Imaging tests (such as MRI and CT scan) may be performed to rule out other possible causes.
  • Possible imaging technique diagnosis
    • It is hoped that one day a specific imaging technique will be capable of detecting early and late PD and provide a means to follow disease progression and the effectiveness of treatment.
    • Positron emission tomography (PET) and single-photon emission computed tomography (SPECT) are imaging techniques that are both sensitive and specific for the diagnosis and separation of PD from other syndromes that produce similar symptoms as PD.
    • These tests are not cost-effective for obvious cases.
    • The ultimate utility of these techniques will be in screening populations felt to be a high risk; but these tests are done very infrequently.
      • A phase of PD occurs before patients have symptoms (called a preclinical phase). That is, patients will not have symptoms until more than about 80% of dopaminergic cells are lost.
      • At this point in time, with PET, screening can be done in this phase and demonstrate dopaminergic changes before patients have symptoms.
      • It cannot, however, be used to predict which people with these changes will go on to develop PD.
Medically Reviewed by a Doctor on 4/12/2013

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