Hemiballismus: CT and MR findings

Our aim was to determine the frequency with which a lesion responsible for hemiballismus was detectable on CT and MR examinations.

The CT and MR examinations of six patients with hemiballismus were reviewed. Three patients underwent MRI alone, two CT alone, and one underwent both CT and MRI. Sites considered as possible locations for a lesion causing hemiballismus included the subthalamic nucleus on the side contralateral to the movements, contralateral putamen, caudate nucleus, thalamus, corpus striatum, lenticular nucleus, substantia nigra, and the premotor and motor cortex.

A lesion likely to account for hemiballismus was found in five patients (contralateral subthalamic nucleus in four patients, contralateral putamen in one patient). Causes of hemiballismus included infarction (one patient), hemorrhage (two patients), trauma (one patient), and an abscess (one patient). A responsible lesion was detected in all five patients who underwent MRI. In one patient who underwent CT alone, a responsible lesion was not identified.

A lesion responsible for hemiballistic movements can generally be found on cross-sectional imaging examinations. Because the multiplanar imaging capability of MR appears to allow for sensitive detection of even small lesions in sites likely to cause hemiballismus, MRI offers the best means of imaging these patients.