Role of Pallidum in Genesis of Some Choreic Movements

Abstract

Experiences with pallidotomy showing that this procedure may abolish or diminish the involuntary movements in cases of Huntington''s chorea suggest that the involuntary movements appearing in this disease are due to a release of pallidal mechanisms. A working hypothesis is outlined to explain the neural mechanism in various types of chorea and the effect of operative procedures. According to this concept, impulses arising in extrapyramidal frontal areas and conducted directly or by way of the thalamus to the pallidum are able to activate the mechanisms localized in this ganglion and to produce associated movements, and perhaps also other types of automatic (reactive, expressional) movements. This mechanism will result in pathologic hyperkinesis if either the striatal inhibitory apparatus or the inhibitory dentato-rubro-thalamo-cortical system is injured. Pathologic hyperkinesis may be diminished if activating impulses from the frontal areas particularly from area 6 are abolished by an operative procedure, sometimes also by lesions of those thalamic nuclei which transmit cortical as well as emotional impulses to the pallidum (thalamotomy), and finally by circumscribed lesions in the pallidum itself (pallidotomy). The latter procedure as a rule avoids the serious by-effects (paralysis, aphasia, convulsions) of the cortical operations.