There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Abstract
There is no clear consensus regarding the frequency (and hence, the risk), of dyskinesias
or motor fluctuations during chronic levodopa therapy for Parkinson's disease (PD).
Multiple clinical series have tabulated these frequencies since the advent of levodopa
over 30 years ago. We were interested in determining: (1) the aggregate frequency
figures in the existing literature; and (2) how clinical series from the early levodopa
era, which included patients with longer durations of parkinsonism, compare to more
recent (modern era) series. We searched MEDLINE for all English language publications
reporting the cumulative frequency of levodopa-induced dyskinesias or motor fluctuations
during discrete intervals of treatment. This generated 2,478 publications spanning
1966 through September 2000. Papers with appropriate titles or abstracts were reviewed;
reference lists from published clinical series were a source of additional papers
for review. This ultimately yielded 74 publications with adequate data, relating to
112 intervals of levodopa treatment. Series that included patients with PD-onset well
before levodopa availability (pre-levodopa era) were separately analyzed from all
subsequent series. Series were grouped by duration of levodopa therapy and the median
frequencies of dyskinesias and motor fluctuations were tabulated for each group. The
data were analyzed both with and without adjustment for the number (N) in each series.
Among series containing pre-levodopa era patients, the median dyskinesia frequency
was already 50% by 5-6 months of treatment. This contrasts with the modern era series
where dyskinesias were reported later in treatment. The median dyskinesia frequency
was slightly less than 40% by 4-6 years of levodopa therapy among modern era patients.
Motor fluctuations (wearing-off) were not tabulated in most of the early levodopa
series. Among modern era reports, motor fluctuations were nil during the first year
of levodopa therapy but were experienced by approximately 40% of patients by 4-6 years
of treatment. Similar results were found when the analyses were restricted to only
prospective studies where levodopa motor complications were targeted outcome measures.
The conclusions reached were: (1) patients from the pre-levodopa era experienced dyskinesias
much earlier during levodopa treatment than modern era patients, perhaps because of
longer durations of pre-existing PD; (2) in the present era, patients treated with
levodopa therapy for 4-6 years have approximately a 40% likelihood of experiencing
motor fluctuations and a risk of dyskinesias just short of 40%; and (3) these findings
represent incident data and the prevalence of clinically important morbidity may be
substantially less.
Copyright 2001 Movement Disorder Society.