An analysis of six patients with Parkinson's disease who have been unresponsive to L-dopa therapy.

Six patients diagnosed as Parkinson's disease on a clinical basis alone are described, and their response to L-dopa and to alpha methyl dopa hydrazine (MK 486) and L-dopa. They are compared with 239 other patients with Parkinson's disease treated in the same time period. These six patients were unusual in that they did not have a clinical response to L-dopa, nor did they develop dyskinesias on L-dopa or on L-dopa with MK 486, although they showed high blood levels of L-dopa and high homovanillic acid levels in the spinal fluid. Unresponsiveness to L-dopa is attributed to a specific brain mechanism and not to problems of transport of L-dopa to the brain or to abnormal peripheral metabolism of L-dopa. The term `motor unresponsiveness to L-dopa' may be useful to describe such patients who may eventually be shown to be suffering from diseases other than Parkinsonism.