The effect of subcortical lesions on production and alleviation of hemiballic or hemichoreic movements

Seven cases of hemiballismus and hemichorea treated by chemopallidectomy and chemothalamotomy were presented as a contribution to the search for a formulation of physiopathological as well as therapeutic concepts. Results of surgical subcortical lesions in these cases were studied together with those reported previously by several authors. Study of these data enabled us to reach the following conclusions: 1. (1) Hemichoreic and hemiballic symptomatology can be permanently alleviated by placement of lesions in the globus pallidus and/or ventrolateral nucleus of the thalamus and subjacent structures. Distal choreic movements seem more difficult to arrest than proximal ballistic components. 2. (2) Alleviation can be obtained in patients with these dyskinesias independently of the etiology or evolution of these syndromes. Pallidectomy or thalamectomy may become an emergency surgical procedure for acute hemiballismus in exhausted patients and in cases where spontaneous recovery seems unlikely. 3. (3) No significant differences could be established between thalamic or pallidal location. However, some data seem to indicate that the effect of lesions in the ventrolateral nucleus of the thalamus and underlying structures is more immediate and complete. In the last three cases of our series, subcortical lesions were surgically placed for alleviation of the symptoms of postencephalitic parkinsonism and ‘triggered’ hemiballic manifestations. These cases were considered of considerable importance because their study was supplemented in two instances by post mortem anatomical analysis of the brain. The assessment of previous anatomo-pathological as well as experimental evidence have led us to the following physio-pathological suggestions: 1. (1) No consistent explanation of the hemiballic and hemichoreic manifestations in terms of focal neuroanatomical areas can be sustained. 2. (2) In spite of previously described surgical results produced by lesions of the thalamus, pallidum, corticospinal paths and locus niger, the lesions cannot always arrest or reduce the hyperkinesia. On the contrary, similar lesions can ‘trigger’ hyperkinetic manifestations at least under certain conditions such as, occasionally, pathology of postencephalitic parkinsonism. 3. (3) Results following a surgical lesion will depend on the underlying pathology of each brain. 4. (4) Surgical alleviation of the dyskinesia seems to lie in a non-specific effect of the lesion, i.e., in a change of the parti