TRODAT-1 and Tc-99m ECD observations in hyperglycemia hemichorea

ABSTRACT

We describe two cases of right hyperglycemia hemichorea (HGHC) with identical Tc-99m TRODAT-1/ Tc-99m ECD scan findings. While the brain MRI showed signal alterations within the left putamen, there was evidence of hyperperfusion on Tc-99m TRODAT-1 but hypoperfusion on Tc-99m ECD within the left putamen, in association with hyperperfusion within left thalamus on Tc-99m ECD. The discrepancy between the Tc-99m TRODAT-1 and Tc-99m ECD scan provides insight into the imbalance between direct and indirect circuits along the nigrostriatal pathway, as the fundamental genesis of HGHC. Furthermore, the hyperperfusion at the left thalamus represents thalamic disinhibition secondary to loss of pallidal negative control, which ultimately leads to HGHC through re-entrant outflow to the motor cortex.