Heterogeneity of cerebral hemodynamics and metabolism in carotid artery disease.

METHODS

Eight patients with severe unilateral carotid stenosis (> 70%) were evaluated using PET to assess parametric changes in cerebral blood flow, blood volume, metabolic rate for oxygen, metabolic rate for glucose, oxygen extraction fraction and glucose extraction fraction. We performed these examinations because clinical history and physical exam results suggested possible cerebral vascular disease. Four patients were neurologically asymptomatic with other signs of peripheral vascular disease (e.g., episodic vertigo, TIA and claudication). All patients had normal neurologic examinations and normal CT or MRI studies. PET images were analyzed by two methods. First, regions of interest were used for the entire hemisphere, vascular territories and borderzones. Regions ipsilateral to the carotid stenosis were compared to respective regions in the contralateral hemisphere using Student's t-test. Second, visual inspection of each image was performed.

RESULTS

Statistical analysis demonstrated no significant differences between hemodynamic and metabolic parameters for regions ipsilateral to the carotid stenosis and contralateral homotopic reference regions. Upon visual examination, however, all patients had focal changes in either cerebral blood flow, blood volume, glucose extraction fraction and/or oxygen extraction fraction.

CONCLUSION

Visual inspection is important in the evaluation of pathophysiological changes caused by unilateral carotid stenosis. Clinical decisions in patients with carotid artery disease should be based on careful visual examinations and statistical analyses of appropriately selected regions.