Cerebral metabolic differences between the severe and critical hypoperfused brain.

Occlusion or severe stenosis, with a reduction in the diameter of the extracranial arteries of more than 70%, may lead to hypoperfusion of the brain with an increased risk of cerebral infarction. The aim of this study was to investigate whether a decrease in metabolism in noninfarcted hypoperfused cerebral areas is correlated with the level of hypoperfusion. Fifty-one patients without infarcts, with borderzone infarcts, with territory infarcts, and fourteen healthy control subjects were investigated with MRI and MR spectroscopic imaging. The NAA/choline ratio in the symptomatic hermisphere was significantly decreased in patients with borderzone infarcts compared with patients without infarcts, with patients with territory infarcts, and with control subjects. Furthermore, patients with borderzone infarcts had a relatively high frequency of cerebral lactate. These results indicate that there might be a lower limit of hypoperfusion that can be measured indirectly with MR spectroscopic imaging, below which irreversible cerebral damage occurs.