CEREBRAL BLOOD-FLOW IN LATERAL MEDULLARY INFARCTS

Background and Purpose The aim of this study was to evaluate the diasc hisis phenomenon in patients presenting with lateral medullary infarct (Wallenberg's syndrome). Methods We examined all patients admitted be tween 1991 and 1993. The localization of lesions was evaluated by MRI. Single-photon emission computed tomographic technique was used to ass ess cerebral blood flow by two methods (Xe-133 and hexamethylpropylene amine oxime) on five slices of brain tissue. Flow values were calculat ed in 11 regions of interest in each cerebral hemisphere and in the ce rebellum and were compared with those obtained in 20 control subjects. Results Three patients had selective lateral medullary infarct: Relat ive reduction of flow (Xe-133) and of tracer uptake (HMPAO) were obser ved in one patient in the ipsilateral cerebellum and contralateral hem isphere; in two patients, hemispheric flow values were relatively low, without significant asymmetry. Two patients also presented with cereb ellar infarct: Flow drop was severe in the ipsilateral cerebellum, and contralateral reduction in the brain hemisphere was observed in both cases. Conclusions Lateral medullary infarct can be associated with ip silateral reduction of flow in the cerebellum, but this phenomenon is inconstant. Severe flow drop suggests infarction in the territory of t he posterior inferior cerebellar artery. Contralateral hemispheric flo w reduction can also be observed. These phenomena of cerebellar and cr ossed hemispheric diaschisis are probably related to lesions of tracts from the olivary and reticular nuclei.