Study on the striatal dopamine availability in Parkinson's disease.

Striatal dopamine availability in connection with the plasma levodopa levels was studied in 12 parkinsonian patients treated with optimal doses of levodopa. Three patients showed the wearing-off phenomenon and the 9 others showed no daily fluctuations in disability. All of the 3 patients with the wearing-off phenomenon showed an up-and-down pattern of dopamine availability index. Out of the 9 patients presenting no fluctuations in disability, 6 showed an ascending pattern of the dopamine availability index and 3 an up-and-down pattern. Of the former 6 patients, 2 received short-term (less than one year) levodopa therapy and the other 4 had the first onset at 42 years or under. In the latter 3 patients, the onset was at over 50 years of age and the duration of levodopa treatment was more than 3 years. In these 3 patients, the mode of action of dopamine in the striatum was considered to be insufficient despite the absence of fluctuations in disability. Thus, the dopamine availability index was considered to be very significant from the viewpoint of prognosis of levodopa therapy.