Stereotactic treatment of action myoclonus in a case of combined status marmoratus and multiple sclerosis. A contribution to the pathophysiology of basal ganglia with multiple lesions in both the striatum and the substantia nigra.

A patent, who suffered from nonprogressive athetotic-myoclonic hyperkinesia of the left arm and spastic paresis of the underdeveloped left leg since early childhood, experienced a febrile episode at the age of 23, after which a weakness and ataxia of the right limbs with frequent falling persisted; at the age of 28, he developed a right-sided rigidity, tremor at rest and mask-like face as sequelae of encephalitis disseminata exacerbations. The violent intention myoclonus of the left side of the body could be abolished by stereotactic coagulation in the V.o.p and V.o.a and zona incerta until death 11 days later. The athetotic myoclonic hyperkinesia is the consequence of a left-sided severe status marmoratus of the right putamen with extensive loss of nerve cells and shrinkage. The additional nerve cell loss in the right substantia nigra due to demyelinating encephalitic foci did not produce Parkinson symptoms, because these require a normal striatum. This loss did, however, exaggerate the original hyperkinesia to a violent intention myoclonus, which was abolished by interruption of denatatothalamic afferents to the V.o.p nucleus and of pallidothalamic afferents to the V.o.a nucleus. The Parkinson syndrome of the right side is due to demyelinating foci of different ages. The Parkinson symptoms were manifest on the right side, because the left status marmoratus did not severely reduce the striatal nerve cells. In this case, there is no indication that the introduction of the stereotactic electrode has precipitated new demyelinating foci.