Research is being done in these areas in order to give scientists and clinicians a better model for this disease that will ultimately lead to better diagnosis and treatment of this disorder. Research is also being done on why certain treatments seem to help hemiballistic patients when they should seemingly do more harm. An example of this is why lesioning the globus pallidus seems to reduce hemiballistic movements. The mechanism behind the effect of dopamine on patients symptoms remains unknown. History
The work of J.R. Whittier, F.A. Mettler, and M.B. Carpenter in the mid-1900s helped scientists and clinicians form a more complete picture of hemiballismus. In their experiments, several lesions were made in the basal ganglia structures in monkeys and then they monitored the results. They noticed that the majority of the time, the monkeys did not have any unusual movements. However, when at least twenty percent of the subthalamic nucleus was damaged, abnormal movements were seen in the limbs opposite to the side of the brain that was damaged. This observation caused scientists to believe that hemiballismus outside the subthalamic nucleus did not occur. It was not until much later that this classical model began to expand to include other areas of the basal ganglia and even some cortical structures. They also noticed that unlike human patients, the unusual movements in the monkeys were mainly in the lower extremities.
This scale gives scientists and clinicians a way to compare patients and determine the range of the disorder.The name hemiballismus literally means "half ballistic", referring to the violent, flailing movements observed on one side of the body. Causes
In examining the causes of hemiballismus, it is important to remember that this disorder is extremely rare. While hemiballismus can result from the following list, just because a patient has one of these disorders does not mean they will also experience hemiballismus. Stroke
Hemisballismus as a result of stroke occurs in only about 0.45 cases per hundred thousand stroke patients. Even at such a small rate, stroke is by far the most common cause of hemiballismus. A stroke causes tissue to die due to a lack of oxygen resulting from an impaired blood supply. In the basal ganglia, this can result in the death of tissue that helps to control movement. As a result, the brain is left with damaged tissue that sends damaged signals to the skeletal muscles in the body. The result is occasionally a patient with hemiballismus. Traumatic brain injury
Hemiballismus can also occur as a result of a traumatic brain injury. There are cases in which survivors of assault or other forms of violence have developed hemiballismus. Through these acts of violence, the survivors brain has been damaged and the hemiballistic movements have developed. Amyotrophic lateral sclerosis
This disease causes neuronal loss and gliosis, which can include the subthalamic nucleus and other areas of the brain.