Comparison of Doppler CO2 test, patterns of infarction in CCT, and clinical symptoms in carotid artery occlusions.

In patients with an internal carotid artery (ICA) occlusion the CO2 reactivity (autoregulatory reserve) is supposed to give information about the function of the collateral supply. To prove this hypothesis we compared the CO2 reactivity measured by transcranial Doppler sonography to the ipsilateral clinical symptoms and the patterns of infarction in cranial computed tomography (CCT). We studied 251 cases of ICA occlusion. Of the 141 cases with normal autoregulatory reserve, 37 (27%) had recently developed an ipsilateral neurological deficit. Of the 44 cases with exhausted CO2 reactivity, 28 (64%) had experienced an event. The difference is highly significant (p less than 0.0001). In 59 of the 75 patients for whom CCT images were available, we found signs of vascular-ischemic lesions. Of the 30 patients with hemodynamic infarctions, 13 showed an exhausted autoregulatory reserve, while of 19 cases with territorial infarctions only 1 and of 10 with lacunar infarctions none had an exhausted CO2 reactivity. The difference is significant (p less than 0.01).