Essentially any disorder that causes some form of neuronal loss or gliosis in the basal ganglia has the potential to cause hemiballismus. Nonketotic hyperglycemia
Patients with nonketotic hyperglycemia can develop hemiballismus as a complication to the disease through the development of a subthalamic nucleus lesion. This is the second most common reported cause of hemiballismus. It can be found primarily in the elderly and many of the reported cases have come from East Asian origin, which suggests that there may be some genetic disposition to development of hemiballismus as a result of hyperglycemia. Hemiballistic movements appear when blood glucose levels get too high and then subside once glucose levels return to normal. This time scale for this is usually several hours. In patients with this type of hemiballismus, imaging reveals abnormalities in the putamen contralateral to the movements as well as the globus pallidus and caudate nucleus. While the hyperglycemia itself is not the cause of the hemiballistic movements, it has been suggested that petechial hemorrhage or a decreased production of GABA and acetylcholine could result secondary to the hyperglycemia. One of these issues could be responsible for the hemiballistic movements. Neoplasms
A neoplasm is an abnormal growth of cells. Cases have shown that if this occurs somewhere in the basal ganglia, hemiballismus can result. Vascular malformations
Vascular malformations can cause abnormal blood flow to areas of the brain. If too little blood is delivered to the basal ganglia, a stroke can occur.
In about half of the monkeys, the hemiballismus continued until the monkey died.Other scientists have also worked on this perplexing disorder and have found that the symptoms can be induced by injecting kainic acid or ibotenic acid into the subthalamic nucleus. I. Hamada and M.R. DeLong found that by using these chemicals, they could destroy only four percent of the subthalamic nucleus and still see hemiballistic movements. However, the abnormal movements would usually disappear within four to five hours even though it did not appear as though the damaged tissue had healed. This suggests that the subthalamic nucleus is plastic enough to adapt to small amounts of damage in order to resume normal function. See also
Movement disorders

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