(1, 4, 5) Instead, the production of involuntary movements met with serious difficulty, and only "choreoid hyperkinesia" as a model of ballism was succeeded by partial destruction of the contralateral subthalamic nucleus, (6) and athetosis by partial destruction of the anterior and posterior putamen in infant monkeys.
Hyperkinetic disorders (chorea, ballism) were explained by hyperactivity of the inhibitory putamino-pallidal pathway, resulting in a decrease in the pallido-thalamic inhibitory activity and hyperactivity of the thalamo-cortical pathways.
Involuntary movements in basal ganglia diseases include (1) tremor, (2) chorea, (3) ballism, (4) athetosis, and (5) dystonia.
In chorea and ballism, in addition to brief involuntary contraction at rest, sudden brief interruption of contraction occurs randomly in tonic isometric voluntary contraction.
Recently, there have been reports that ballism appears in vascular infarctions in the striatum (26) instead of the subthalamic nucleus, which is the classical site for hemiballism.
Chorea, or ballism, involves involuntary movement appearing at rest, and is considered as a purposeless movement by release phenomenon from inhibitory processes caused by disorders of the basal ganglia.
(7) Phasic involuntary movement such as chorea or ballism is considered to result from disinhibition of motor output caused by the disturbance of inhibitory mechanisms in the basal ganglia.