Altered patterns of blood flow response during visual stimulation in carotid artery occlusive disease.

To correctly interpret the results of functional neuroimaging studies in stroke, it is essential to understand how cerebrovascular disease influences hemodynamic response during neural activation. To investigate the effect of internal carotid artery (ICA) occlusive disease on the pattern of cerebral blood flow (CBF) response during visual stimulation, we used positron emission tomography to study 13 patients with ICA steno-occlusive lesions. We measured the changes of CBF during visual stimulation in the primary visual cortex and in the surrounding region, including the higher-order visual cortex, and examined their correlation with the baseline value of oxygen extraction fraction, a measure of hemodynamic impairment, in the ICA distribution. With visual stimulation, CBF in the primary visual cortex significantly increased in all patients, while in the surrounding region, CBF showed variable changes, including decreases in some patients. In 9 patients with unilateral ICA lesions, the CBF change in the surrounding region ipsilateral to the ICA lesion was significantly decreased compared with the value in the contralateral hemisphere, while the CBF change in the primary visual cortex showed no hemispheric difference. The hemispheric values of oxygen extraction fraction in the ICA distribution and the amount of CBF increase in the visual cortex were independently and negatively correlated with the CBF change in the surrounding region. We conclude that the pattern of CBF response during visual stimulation may change in ICA occlusive disease. We suggest that the redistribution of CBF during visual stimulation may be a contributing mechanism.