Diagnosis and Treatment of Parkinson's Disease

Objectives:

Parkinson's Disease (PD) is estimated to affect over 1 percent of the population over age 65. The objective of this systematic review is to assess the quantity and quality of published evidence regarding diagnosis and treatment of patients with PD.

Search Strategy:

English-language literature published from 1990 to 2000 was searched using electronic databases. Searches were supplemented by manually reviewing bibliographies of all accepted studies and selected review articles.

Selection Criteria:

Studies were required to evaluate at least 10 human patients and address pre-defined areas of interest. Only randomized controlled trials (RCTs) were accepted for studies regarding pharmacological treatment.

Data Collection and Analysis:

Pertinent data were evaluated for quality and level of evidence, extracted from accepted studies by one researcher, and reviewed by a second. Data were summarized and synthesized qualitatively. Meta-analyses were performed, comparing standardized mean changes from baseline to outcome in PD severity rating scales.

Main Results:

The database includes 59 studies (3,369 patients) regarding diagnosis, 49 studies (9,968 patients) on pharmacological treatment, 42 studies (1,380 patients) on surgery, 10 studies (392 patients) on psychiatric treatment, and 20 studies (1,049 patients) on ancillary treatment of PD.

PD is diagnosed clinically; evidence does not show that specific tests improve diagnostic accuracy. There is no evidence that different dopamine agonists (DAs) vary in treatment effects. Meta-analysis suggests that in early PD, treatment with DAs plus levodopa (L-dopa) may control PD symptoms better than treatment with L-dopa alone, but this was not a consistent finding. Similarly, no consistent difference in symptom control was found between L-dopa alone and the combination therapy of L-dopa plus selegiline. In patients with advanced disease, treatment with catechol O-methyl transferase (COMT) inhibitors combined with L-dopa provides significantly greater PD symptom control than treatment with L-dopa alone and is associated with lower L-dopa doses; however, long-term (greater than 7 months) results are lacking, and hepatotoxicity is a rare but potentially lethal side effect associated with tolcapone.

For pallidotomy and deep brain stimulation (DBS), endpoint PD scale scores are significantly better than baseline scores. DBS of the subthalamic nucleus (STN) and globus pallidus (GPi) result in significant improvement in PD symptoms, but only STN DBS is associated with decreased L-dopa doses. There are insufficient studies of thalamotomy and tissue transplantation to draw any conclusions regarding their efficacy and safety.

Ancillary treatments, such as physical therapy, improve some symptoms on a short-term basis, but long-term data are lacking. Intensive speech therapy has been shown to improve vocal intensity up to 12 months after treatment; however, long-term results are from only one study of 22 patients.

Conclusions:

PD is diagnosed clinically; there is currently no gold standard premorbid diagnostic test for PD. Meta-analyses of different pharmacological treatments showed that the only medication that consistently controlled PD symptoms better than L-dopa alone was the combination of L-dopa plus COMT inhibitors in patients with advanced PD. Meta-analyses suggest that pallidotomy and DBS result in improvement of PD rating scores. The published literature regarding PD suffers from lack of reporting standardized outcomes.