The original contribution in this issue of Focus on Parkinson's Disease refers to the discussion about the toxicity of levodopa. The question whether levodopa is toxic and whether it accelerates the natural progression of the disease and contributes to neurodegeneration has been extensively debated for many years. In many clinical reviews, authors have recommended, based on selected in vivo data to delay the initiation of levodopa therapy as long as possible and to avoid high levodopa doses, even if motor impairment is not sufficiently controlled. The paper of Y. Agid is based on the results of an international consensus conference held in Paris in January 1998. The article summarizes all aspects of levodopa toxicity in a very clear and objective manner. The main in vitro data, the experimental in vivo data, as well as the clinical data are report. Toxicity has been shown only under experimental and in vitro conditions using high concentrations, far away from any clinical relevance. It is clearly demonstrated that there is no evidence for levodopa toxicity in parkinsonian patients receiving therapeutic concentrations.
Also in this issue, Schwalen et al. report on sleep disorders in Parkinson's disease in an extended abstract. The authors found that, besides nocturnal akinesia, sleep-related breathing disturbances were present in up to one sixth of their patients. The therapeutic value of a dispersible formulation of levodopa/benserazide, especially in patients with delayed "on" and unpredictable "off" phenomenon, has been shown by Monge et al. The beneficial effect of stereotactic pallidotomy on akinesia as well as on dyskinesia are reported by Shannon et al. in a study over a period of 6 months. A number of other abstracts deal with the etiology of Parkinson's disease. Some new data on genetics and environmental factors are discussed.
This issue of Focus on Parkinson's Disease again presents selected abstracts from recently published high-quality papers dealing with the different aspects of Parkinson's disease and offer the reader comprehensive information on most recent developments of this area.