Drug-induced dyskinesia--an electrophysiological analysis of dyskinesia induced by L-DOPA and anticholinergic drugs.

The application of L·DOPA (L-3, 4-dihydroxyphenylalanine) to the treatment of extrapyramidal disorders has been extremely beneficial for parkinsonism 1)-8). At the same time several side-effects have been recognized. Among them, the appearance of dyskinesia poses an important problem 8)-13l , but causative mechanisms of L·DOPA induced dyskinesia are not yet sufficiently elucidated. Such dyskinesia appears particularly in perioral muscles, the tongue, and less frequently in other facial muscles, neck and extremities. In general there are irregular involuntary movements of the mouth such as chewing, gnawing or mumbling with involuntary protrusions or rotations of the tongue. The same type of dyskinesia has been found in patients treated by major tranquilizers, in particular, phenothiazine derivatives 14) -21). This type of involuntary movement was first described by French neurologists as "faciobucco-linguo·masticatory dyskinesia ",22) and then written by British authors in terms of "persistent oral dyskinesia" 23)24). It has also been reported under the name of "tardive dyskinesia "25)26) because of its appearance after an extensive period of neuroleptic medication. But L-DOPA induced dyskinesia is not "tardive" in its character. It would be called as "early dyskinesia", since it appears in general after a short period of L·DOPA administration. Anticholinergic drugs have been used for a long time in the treatment of parkinsonism. As to their side-effects, clinical symptoms such as blurred vison or dry mouth have been recognized because of their inhibitory effects on the peripheral parasympathetic nervous system. Much less frequently, symptoms of the central nervous system such as hallucination or mental deterioration have been reported as their side-effects, but an appearance of the dyskinesia has never been described. Recently the author has found and already eported that the same types of dyskinesia could be also induced in cases of senile parkinsonism during treatment by synthetic anticholinergic