Assessment of Benzodiazepine Receptors Using Iodine-123–Labeled Iomazenil Single-Photon Emission Computed Tomography in Patients With Ischemic Cerebrovascular Disease

Abstract

Background and Purpose [ 123 I]Iomazenil (IMZ) is a tracer used for single-photon emission computed tomography (SPECT) that has the characteristics of selectively binding to central benzodiazepine receptors (BZR) in the neuron membrane. To determine whether IMZ SPECT provides new information on assessing neuronal damage after ischemic insult to the brain, we compared IMZ SPECT images with the cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO 2 ), and cerebral metabolic rate of glucose (CMRGlc) studied by positron emission tomography in the chronic stage of ischemic stroke. Methods Five patients (male; mean age, 63.2±6.0 years) with ischemic cerebrovascular disease and 6 age- and sex-matched normal control subjects were studied. IMZ images obtained 180 minutes after injection were analyzed for BZR binding, and these images were compared with the CBF, CMRO 2 , and CMRGlc obtained by positron emission tomography in the same perfusion areas both visually and quantitatively. Results In the visual analysis of data obtained from 4 patients with subcortical infarction, decreased IMZ accumulation was observed locally in the overlying normal-appearing cortices of the affected hemisphere, where extensive hypoperfusion and hypometabolism were seen on the images of CBF, CMRO 2 , and CMRGlc. The regional relative IMZ uptake (regional to cerebellar ratio) for all 5 patients was significantly correlated with the corresponding regional CMRO 2 values ( r =.45, P <.05). However, no significant correlation was found of the IMZ uptake with either the regional CBF or the regional CMRGlc. Conclusions The use of IMZ SPECT provides new information on the neuronal alteration induced by chronic ischemic cerebrovascular disease.