Flow-related anaerobic metabolic changes in patients with severe stenosis of the internal carotid artery.

BACKGROUND AND PURPOSE: We sought to investigate whether the combination of blood flow measurements in the major cerebral arteries and measurements of cerebral metabolism can provide new insight into the hemodynamic effect of carotid lesions in patients with severe stenosis (> 70% reduction in diameter) of the internal carotid artery (ICA).

METHODS

Fifty-six patients with unilateral severe stenosis of the ICA and 14 control subjects underwent MR imaging, 1H MR spectroscopy, and MR angiography. Anaerobic metabolic changes were studied by assessing N-acetyl aspartate/choline and lactate/N-acetyl aspartate ratios in the symptomatic and asymptomatic hemispheres. Quantitative flow was measured in the common carotid arteries (CCAs), the ICAs, the basilar artery, and the middle cerebral arteries (MCAs).

RESULTS

Blood flow was significantly decreased in the CCA, ICA, and MCA on the ipsilateral side compared with the contralateral side. Flow in the basilar artery was increased, whereas flow in the contralateral MCA was decreased compared with control subjects. We found a significant correlation between anaerobic metabolic changes and the reduction in blood flow in the CCA, ICA, and MCA on the ipsilateral side.

CONCLUSIONS

This study shows that cerebral metabolism is less impaired in patients with relatively high flow in the major cerebral arteries on the ipsilateral side than in patients with relatively low flow on that side. The combination of MR spectroscopy and MR angiography can be of additional value in the understanding of cerebral hemodynamics and metabolism in patients with vascular disorders.