[Pathophysiologies of dystonia and myoclonus--consideration from the standpoint of treatment]

Pathophysiologies of disorders with dystonia or myoclonus were studied by evaluating the effects of treatment. Naturally, the main lesion of the dystonia responding to levodopa is in the nigrostriatal dopamine neuron. The target of stereotaxic operations is ventrolateral palladium for postural dystonia and the nucleus ventralis oralis posterior (Vop) thalamus for action dystonia. Torsion dystonia with lesion in the striatum and/or the pallidum causes axial torsion, it may be postural through the descending pathway and action through Vop. Stereotaxic operations on these pathways have shown to be effective. Focal dystonia is a reflection of abnormal co-activation of cortical motor neurons, occurring in a particular voluntary movement. Botulinus toxin injected into the affected muscle should be effective. Of myoclonus with epilepsy, cortical reflex myoclonus or cortical induced reticular myoclonus responds to valproic acid. However, no antiepileptic drugs are effective on those with primary brainstem lesion. Reticular reflex myoclonus due to asphyxia responds to ventralis intermedius thalamotomy. Idiopathic myoclonus associated with dystonia is particular because it responds to ventrolateral thalamotomy. Myoclonus except for idiopathic myoclonus with dystonia is associated with atonic NREM suggesting dysfunction of the dorsal raphe serotonergic neuron or the brainstem nucleus reticularis gigantocellularis, the causative neuron for experimental uremic myoclonus. Treatment for these neurons is necessary.