[Cerebral blood flow and oxygen extraction in lacunar hemiplegia. Semi-quantitative study using oxygen 15 and emission tomography].

The oxygen 15 non invasive continuous inhalation technique coupled with positron emission tomography (P.E.T.) allows the local study of cerebral blood flow and oxygen metabolism. Recent P.E.T. studies have demonstrated the frequent occurrence of widespread metabolic depression remote from the site of middle cerebral artery territory infarct per se, especially over the cortical mantle and thalamus ipsilaterally, and over the cerebellar hemisphere contralaterally. These phenomena have been taken as indicative of transneural depression (i.e. diaschisis). We thought it interesting to study the possible occurrence of such abnormalities in patients with lacunar syndromes. We have applied the (15)0 technique to six patients (2 with pure motor hemiplegia, 4 with ataxic hemiparesis) for whom no large causal ischemic lesion could be demonstrated on CT scans; in only one patient was a lacunar lesion, presumably responsible for the clinical deficit demonstrated. Compared to a set of 19 patients without brain disease, the semi-quantitative results (analyzed in terms of asymmetry indices between homologous brain regions) in our patients did not disclose any pathophysiologically significant abnormality. More specifically, no evidence of physiological dysfunction similar to that reported in internal carotid artery territory infarcts, was detected over the cerebral or cerebellar cortices. These findings are commented upon in view of the presumably small size and the uncertain topography of the causal lesion.