Cerebral blood flow in lateral medullary infarcts.

BACKGROUND AND PURPOSE: The aim of this study was to evaluate the diaschisis phenomenon in patients presenting with lateral medullary infarct (Wallenberg's syndrome). METHODS: We examined all patients admitted between 1991 and 1993. The localization of lesions was evaluated by MRI. Single-photon emission computed tomographic technique was used to assess cerebral blood flow by two methods (133Xe and hexamethylpropyleneamine oxime) on five slices of brain tissue. Flow values were calculated in 11 regions of interest in each cerebral hemisphere and in the cerebellum and were compared with those obtained in 20 control subjects. RESULTS: Three patients had selective lateral medullary infarct: Relative reduction of flow (133Xe) and of tracer uptake (HMPAO) were observed in one patient in the ipsilateral cerebellum and contralateral hemisphere; in two patients, hemispheric flow values were relatively low, without significant asymmetry. Two patients also presented with cerebellar 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 ipsilateral reduction of flow in the cerebellum, but this phenomenon is inconstant. Severe flow drop suggests infarction in the territory of the posterior inferior cerebellar artery. Contralateral hemispheric flow reduction can also be observed. These phenomena of cerebellar and crossed hemispheric diaschisis are probably related to lesions of tracts from the olivary and reticular nuclei.

Early and delayed distribution of N-isopropyl-[123I]-p-iodoamphetamine in haemorrhagic and ischaemic brain.

Single photon emission computed tomography (SPECT) was used to study redistribution of N-isopropyl-[123I]-p-iodoamphetamine (IAMP) in 10 patients with intracerebral haemorrhage and 7 with ischaemic stroke. Delayed/early IAMP uptake ratios (D/E) were calculated for four different cerebral zones: haematoma or infarct, perilesional, normal and crossed cerebellar diaschisis areas. Delayed uptake was observed in all areas, but there were no significant differences between the haematoma and infarct results nor between the lesional and perilesional results. Delayed redistribution of IAMP therefore did not seem to be associated with neuronal metabolic activity.

Perfusion mapping with Tc-HMPAO in cerebral haematomas.

The cerebral distribution of HMPAO was mapped tomographically by SPECT in 20 patients with an intra cerebral haematoma. The images were assessed visually and by an analysis of an asymmetry index (AI) for various cerebral areas. Visual inspection identified the lesion in each of the 20 cases. Reduced tracer activity and abnormal AI were consistent findings. Remote effects (diaschisis) were also observed in the adjacent (19 cases) and frontal (14 cases) cortex, and in the controlateral cerebellum (16 cases). Sequential studies at 60, 150 and 300 minutes in 10 patients showed remarkably stable patterns. HMPAO maps were compared with cerebral blood flow (CBF) measured with 133 Xenon (133Xe) in eight cases. The two methods showed similar results in the region of a lesion, but remote effects were more obvious with the 133Xe in two patients.

[Tomographical use of Tc hexamethylpropylene amine-oxime. First experience (78 studies)]. / Utilisation tomographique de l'hexaméthylpropylène amine-oxyme Tc. Première expérience (78 études).

A new radiotracer of cerebral perfusion, 99mTc-labelled hexamethylpropylene amine-oxime, has been tried in 78 subjects: 6 controls and 72 patients. Qualitatively, the distribution of this tracer in healthy subjects was very much the same as that obtained with a reference method using 133xenon inhalation. Quantitatively, there was no correlation between the real blood flow rate and the normalized cerebral uptake rate. On the other hand, the asymmetry indices obtained in controls (but also in 16 patients) correlated very closely with those obtained with 133xenon. Our first results in acute ischaemic diseases as well as in the evaluation of vasospasm or Alzheimer-like presenile dementia point to wide fields of application for the new compound. Unlike its predecessors, it is always available and will probably be used, without any logistic investment, with the standard equipment of all Nuclear medicine departments.

[Computerized tomography of the distribution of N-isopropyl-p-123 iodoamphetamine in cerebrovascular pathology. Comparison with studies using the 133-xenon inhalation method]. / Mesure tomographique de la distribution de la N-isopropyl-p-123 iodo-amphétamine en pathologie vasculaire cérébrale. Comparison avec la mesure par inhalation de Xéno133.

123Iodo-Amphetamine (IAMP) brain distribution was studied with a specially dedicated multilevel tomographic system in 30 patients with vascular ischemic (18) or hemorrhagic (12) disorders. Results were compared with clinical data, CT scan and rCBF measurement obtained by the 133Xe continuous inhalation method. Abnormalities with IAMP were found in 27 cases, in good agreement with the results obtained by the Xenon inhalation technique in 21 studies from the 22 where that method was possible. For 80% cases there was also a good agreement between the results obtained by the IAMP and CT scan: one case normal, and 23 observations with abnormalities. This is true for the localization of lesions, but IAMP appears able to shown remote abnormalities, i.e. crossed cerebellar diaschisis or functional deactivation, in the absence of CT scan lesions in the corresponding areas. This is of particular interest in the protracted regressive ischemic neurologic disorders (PRIND): CT scan were normal in all five observations but IAMP showed abnormalities in four cases. IAMP is however very expensive, so it has to be used only when 133Xe inhalation is technically impossible.