Cobalt-55 positron emission tomography in symptomatic atherosclerotic carotid artery disease: borderzone versus territorial infarcts

BACKGROUND

Borderzone as well as territorial infarcts can occur in severe atherosclerotic carotid artery disease. It remains controversial whether the borderzone distribution of infarcts is due to hypoperfusion or due to artery-to-artery embolism.

PURPOSE

The present study investigates whether cobalt-55 (55Co) positron emission tomography (PET) shows a different pattern of ischaemia according to the topography of the infarct in severe atherosclerotic carotid artery disease.

PATIENTS AND METHODS

Five patients with a cortical borderzone and seven with a territorial infarct, due to symptomatic carotid artery disease, were investigated with 55Co PET 3-6 months after stroke. Average 55Co counts in the infarct area, the adjacent cortical zone, the deep white matter and, contralateral cerebral cortex and white matter, were compared to the values in the cerebellum used as reference.

RESULTS

No differences in 55Co ratio were observed in the different regions of interest (ROIs) between patients with cortical borderzone and those with territorial infarcts. The 55Co uptake was similar or lower than the reference value for all ROIs in all individual patients.

CONCLUSION

In patients with borderzone as well as with territorial infarcts no evidence was found for subclinical ischaemic injury in or around the infarcts. These data do support the conclusion that cortical borderzone infarcts may not be due to ongoing chronic haemodynamic impairment, but by no means is this conclusive evidence.

Cerebral blood flow and oxygen metabolism in symptomatic internal carotid artery occlusion by atherosclerosis and by cervical dissection

Symptomatic internal carotid artery occlusion by atherosclerosis and by cervical dissection are distinct conditions with different long-term prognoses. The purpose of the present study is to investigate if regional cerebral blood flow and oxygen metabolism, after onset of stroke, differ between both conditions. Seventeen patients with symptomatic unilateral atherosclerotic internal carotid occlusion and 10 patients with symptomatic internal carotid occlusion due to cervical dissection were submitted to a positron emission tomographic (PET) study between 1 and 2 months after stroke onset. The steady state technique with 15O was used in order to determine regional cerebral blood flow, regional oxygen extraction fraction, and regional cerebral metabolic rate for oxygen in the infarct area, the peri-infarct zone, the remaining homolateral hemisphere, and the contralateral hemisphere. The results were compared between both patient's populations. The patients with cervical dissection were on average much younger than those with atherosclerotic occlusion, but neurological impairment on admission and disability at 3 months were comparable. Between both patient populations, no differences in rCBF, rOEF, and rCMRO2 could be demonstrated in the different regions of interest when the results were age-adjusted. Except for age-related changes, no differences in PET findings could be demonstrated between patients with symptomatic internal carotid occlusion caused by either atherosclerosis or cervical dissection.