Metabolic disturbances in exo-focal brain areas after cortical stroke studied by positron emission tomography

We have reported that exo-focal delayed neuronal damage was observed in the ipsilateral thalamus and the substantia nigra of the rat brain after occlusion of the middle cerebral artery (MCA). To determine if that phenomenon also occurs in humans, we measured cerebral metabolic rates for glucose (CMRGlc) in the remote brain areas at a chronic stage after cortical infarction using 2-[18F]fluoro-2-deoxy-D-glucose and position emission tomography (PET). The subjects studied were 11 patients who were affected by unilateral cerebral infarction in the cortex supplied by MCA. There were significant decreases of CMRGlc as compared with control values (p < 0.01), not only in the cerebral cortex directly damaged by the ischemic insult, but also in the ipsilateral thalamus and in the contralateral cerebellum, areas in which no lesions had been detected by MRI or CT scan. The present study indicates that different mechanisms may be responsible for multi-focal metabolic disturbances in the remote areas after stroke. The reduction of CMRGlc in the contralateral cerebellum may be explained by the crossed cerebellar diaschisis theory and in the ipsilateral thalamus as being due to retrograde degeneration associated with the infarcted cortex. We suggest that these multi-focal brain dysfunctions caused by neuronal network disturbances may exacerbate clinical symptoms at a chronic stage of stroke.