Specific Imaging Findings

T1 hyperintensity in the contralateral striatum, especially putamen, without edema or mass effect is the characteristic imaging finding of nonketotic hyperglycemia with hemichorea–hemiballismus (NK hyperglycemia with HCHB). CT commonly shows corresponding hyperdensity, while some lesions may remain isodense and therefore undetectable. Mild to moderate decrease in diffusion (low ADC signal) is commonly found, while increased susceptibility change (hypointensity) may also be present, suggesting paramagnetic mineral deposition. There is no contrast enhancement of the lesions, which demonstrate variable and frequently normal T2 signal. In addition to the putamen and caudate, globus pallidus and midbrain (subthalamic nucleus) may also be involved; bilateral lesions also occur (with bilateral clinical presentation) but are much less common. There is also decreased perfusion within the lesions and reduced FDG uptake on PET scans. MR spectroscopy shows decreased NAA, increased choline, and elevated lactate peak. The lesions may disappear with appropriate treatment or persist for years.

Pertinent Clinical Information

HCHB is usually a continuous, nonpatterned, involuntary movement disorder caused by basal ganglia dysfunction, described in nonketotic hyperglycemic patients. It occurs in elderly individuals with primary diabetes mellitus, more commonly in women and Asian populations. Inmost patients hemichorea improves along with the disappearance of the lesions. Correction of underlying hyperglycemia and supportive care results in resolution within days to weeks.