Long-term follow-up after stereotaxic basal ganglia surgery in parkinsonism. A neuroanatomical study of a case showing unusual postural disorders.

A 60-year-old man who had Parkinson's disease for 25 years became unable to maintain the upright position of the trunk while standing or walking. Because of a loss of postural fixation, his trunk sank forward until his back was horizontal. Fifteen years before, a bifocal implantation of radioactive yttrium-90 had been performed by a stereotaxic procedure at the level of the globus pallidus (GP) and the ventrolateral thalamus, respectively on the right side. A second operation, 2 years later, had been made by electrocoagulation in the left ventrolateral thalamus. Postmortem examination showed the following features (a) neuronal cell loss in the pigmented nuclei of the brainstem with intracellular Lewy bodies and gliosis. These data corresponded with the usual pathology of idiopathic Parkinson's disease; (b) surgical lesions resulting from the previous stereotaxic operations in the right GP and the ventrolateral thalamus on both sides and (c) neuronal cell loss without gliosis in the right GP that was evident in regions spared by the surgical lesion. Moreover, these degenerative changes were particularly seen in the left GP, which was surgically unlesioned. The ansa lenticularis was demyelinated on both sides. These data might be consistent with a retrograde degenerative process affecting the pallidothalamic projections. Beside the role of the neuronal cell loss affecting the pars compacta of the substantia nigra (SN) in akinesia, the role of the lesions affecting the G.P. in the genesis of postural disorders is suggested.