Mechanism of reduction of cortical blood flow in striatocapsular infarction: studies using [123I]iomazenil SPECT.

Single photon emission computed tomography (SPECT) using [123I]iomazenil (radioligand of central-type benzodiazepine receptors) was employed to examine two patients with striatocapsular infarction. Patient 1 was a 61-year-old female with motor aphasia and hemiplegia on the right side. Magnetic resonance imaging (MRI) showed a lesion in the anterior limb of internal capsule and putamen on the left side. SPECT using 99mTc-HMPAO revealed a reduction of cerebral blood flow (CBF) in the frontoparietal region on the left side, but the delayed images in SPECT using [123I]iomazenil showed only a mild decrease of accumulation in the frontal lobe. Patient 2 was a 55-year-old male with hemiplegia on the left side. MRI showed a lesion localized in the basal ganglia and posterior limb of the internal capsule on the right side. SPECT using 99mTc-HMPAO revealed a reduction of CBF in the frontoparietal region on the right side and in the cerebellar hemisphere on the left side, but the delayed images in SPECT using [123I]iomazenil showed little decrease of accumulation in parietal lobe. The discrepancy between CBF and receptor images suggested that cortical hypoperfusion on striatocapsular infarction might reflect hypometabolism due to disconnection of the neuronal network between subcortical structure and cortex.