The purpose of this trial is to determine if patients who received embryonic dopamine cell implant surgery showed significantly greater improvement in their Parkinson's disease than a control group undergoing the placebo treatment, and to determine if the cell implant surgery was more effective in younger or older patients.

Parkinson's disease is caused by the death of a small number of nerve cells that produce a critical chemical called dopamine. The drug L-dopa can partially make up for the lack of dopamine. As time goes on, however, most patients notice that the drugs do not work as well. Oftentimes, patients develop great fluctuations in motor control. Off drugs they cannot move, and on drugs they have excess, exaggerated movements. Research in animals over the last 20 years has shown that dopamine cells can be replaced by transplants of new cells obtained from fetal brain tissue. For the past 14 years, several laboratories around the world have been performing similar transplants of human fetal brain tissue on patients with Parkinson's disease. So far, it has been impossible to compare results from the different groups because no two centers are performing transplants in the same way.

This study seeks to get around that problem using a controlled clinical trial that compares the embryonic dopamine cell implant surgery with a placebo treatment. A total of 40 patients were recruited--half received the cell implant surgery, while the other half received the placebo. After the double-blind phase of the study, patients in the placebo group had the option of receiving tissue implants. Fourteen of these patients eventually had transplants. At present, this study is providing long-term follow-up evaluation and treatment for the subjects.

INCLUSION CRITERIA:

• Idiopathic Parkinson's disease of at least 7 years duration and responsive to levodopa. Other Parkinson syndromes excluded.
• Patients previously tried on other available forms of medical treatment.
• Age between 20 and 75 years.
• Presence of an intractable problem, such as "off" periods, dyskinesias, or "freezing," not controlled by dopamine agonists such as levodopa or pergolide.
• No serious depression and no cognitive impairment.
• Successful completion of home diary by patient or responsible party.
• Successful videotape recordings at home of "on" and "off" status.
• Normal MRI of brain within the last 18 months.
• Fluorodopa PET scan compatible with idiopathic Parkinson's disease.
• Medically fit to undergo implant surgery with certification by the patient's physician.
• Able to financially cover expenses not paid for by NIH grant (between $1,000 and $2,000 for unreimbursed travel, video camera, and blood screening as specified in the consent form.

EXCLUSION CRITERIA:

• Severe or moderately severe depression or cognitive impairment.
• Previous brain surgery.
• Presence of diabetes mellitus, severe cardiopulmonary disease or other severe medical disease, or MRI evidence of cerebrovascular disease.
• Not medically cleared to undergo a surgical procedure.