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Biomedical subjects

S Pappata

Publications and source records attributed to S Pappata.

48 records · Page 3Linked to original sources
PubMed1990

Effects of capsular or thalamic stroke on metabolism in the cortex and cerebellum: a positron tomography study.

We used positron emission tomography to study the cortical and cerebellar metabolic rates in 21 strictly selected patients with pure internal capsular infarct (n = 8), thalamocapsular hemorrhage (n = 6), or pure thalamic stroke (n = 7). Significant diffuse ipsilateral cortical hypometabolism relative to 62 controls free of cerebrovascular risk factors was frequently, although not consistently, found in the 13 patients with thalamocapsular or thalamic lesions and neuropsychological impairment but was absent from the eight patients with pure internal capsule infarct and free of neuropsychological deficit. These data suggest that damage to the thalamus or the thalamocortical projections is important in the development of ipsilateral cortical hypometabolism and that the latter may underlie the associated neuropsychological impairment. Significant contralateral cerebellar hypometabolism relative to 49 controls was found in three of six patients with pure internal capsule infarct, suggesting a pathogenetic role for the corticopontocerebellar system. However, the occurrence of hypometabolism in two of six patients with thalamic lesions indicates that this phenomenon may also result either from damage to the ascending cerebellothalamocortical system or indirectly from hypofunction of the cerebral cortex. No systematic association was observed between crossed cerebellar hypometabolism and ipsilateral ataxia.

Analysis of Variance↗
PubMed1990

Left prefrontal glucose hypometabolism in the depressed state: a confirmation.

The resting-state cerebral metabolic rates for glucose of 10 severely depressed patients (seven bipolar and three unipolar) were compared, before and after treatment with tricyclic antidepressants, to those of 10 control subjects of similar age by means of positron emission tomography and the fluorodeoxyglucose method. Significant left-right prefrontal asymmetry was present in the patients before but not after successful treatment, suggesting that medication can reduce this asymmetry. Also, significant hypofrontality and whole-cortex hypometabolism were found in the patients in the depressed state and persisted in the treated state, despite clinical improvement, suggesting that these abnormalities are not state dependent.

Adult↗
PubMed1989

Time course of effects of unilateral lesions of the nucleus basalis of Meynert on glucose utilization by the cerebral cortex. Positron tomography in baboons.

In order to investigate the effects of a partial cholinergic deafferentation on the functional activity of the cortex, the cerebral metabolic rate of glucose (CMRGlu) was measured with positron emission tomography and 18F-2-fluoro-2-deoxy-D-glucose in 5 baboons (Papio anubis) both before and serially following stereotaxic electrocoagulation of the left nucleus basalis of Meynert (NbM). Four days postlesion, significant metabolic depression was present in the entire ipsilateral cerebral cortex, most marked in the frontotemporal region, and which slowly recovered close to normal within 6-13 weeks. Postmortem studies showed that the lesions were located largely in the NbM, and that a significant decrease in choline-acetyltransferase (ChAT) activity was present in the ipsilateral frontal, temporal and parietal cortices. The animal with the most limited histological lesion showed the least decrease in both ChAT activity and CMRGlu. There was a highly significant linear correlation between the regional cortical decreases in CMRGlu (early postlesion data) and in ChAT activity. These results indicate that cholinergic deafferentation induces a proportional metabolic depression in the cortex. However, compensatory mechanisms operate to restore the cortical metabolic activity gradually despite sustained cholinergic denervation, pointing to pre- and/or postsynaptic adaptation (plasticity). Moreover, unilateral NbM lesions also induced a significant reduction in contralateral CMRGlu, which also demonstrated recovery. Several mechanisms are discussed to explain this contralateral effect, but the most likely implicates a transcallosal depression of function as a result of ipsilateral effects of the NbM lesion. These metabolic effects of cholinergic deafferentation in the primate provide new insight into the mechanisms of cortical dysfunction, and the recovery thereof, following subcortical lesions. In addition, our findings have some relevance to the cortical consequences of cholinergic deafferentation observed in dementia of Alzheimer type.

Animals↗
PubMed1989

Local brain haemodynamics and oxygen metabolism in cerebrovascular disease. Positron emission tomography.

Using position emission tomography (PET) and equilibrium imaging with oxygen-15 labelled gases, the cerebral blood flow (CBF), blood volume (CBV), oxygen extraction fraction (OEF) and oxygen consumption rate (CMRO2) were measured in multiple regions of interest over the cerebral cortex of 5 control subjects, 4 patients with strictly unilateral longstanding carotid artery occlusion, 1 patient with middle cerebral artery embolic stroke in the acute stage, and 4 patients with subcortical stroke and no cervical arterial disease. In each control subject, the regional CBV was linearly and positively correlated with both CBF and CMRO2, while the local mean transit time (t = CBV/CBF) was uniformly distributed, reflecting the local adaptation of both the vascular tone and the capillary density to the metabolic demand at constant cerebral perfusion pressure that characterizes the normal brain. In patients with subcortical stroke, cortical blood volume was reduced in proportion to the matched reduction in CBF and CMRO2, suggesting that the metabolic depression resulting from cortical deafferentation increases the resting tone of pial vessels. Unilateral carotid occlusion induced larger CBV and t, and steeper slopes of the CBV-CBF relationship, particularly on the occluded but also on the patent side. The assessment of the local cerebral perfusion pressure (CPP) as judged by the ratio CBF/CBV in 3 patients with focally raised OEF and preserved or reduced CMRO2, allowed the demonstration in multiple cerebral regions of single patients of two well-known physiological phenomena: the autoregulation of CBF, followed by the rise of the OEF as local CPP falls further. In addition, the depression of CMRO2 in the ischaemic cortex was associated with a trend for CBV to return towards normal values, compared with the maximally elevated CBV found in oligaemic but metabolically normal areas. This suggests that a process of metabolic vasoconstriction may participate, among other factors, in the vascular collapse that occurs, and would serve to regenerate some haemodynamic reserve, at very low CPP levels.

Arterial Occlusive Diseases↗
PubMed1989

SPECT analysis of recent cerebral infarction.

We measured regional cerebral blood flow and [123I]iodoamphetamine (IMP) uptake in 16 patients with unilateral brain infarcts during the subacute period (Day 3 to Day 50) and again after 3 months. Our results show that the central and peripheral areas described earlier in the chronic period were already differentiated in the subacute period. The central area presented a short phase of luxury perfusion and a longer phase of IMP hyperfixation. The peripheral area showed both a slight regional cerebral blood flow decrease and an early IMP uptake decrease similar to those previously found in the chronic period. Contralateral regional cerebral blood flow during the subacute period, considered normal, was significantly lower than that during the chronic period.

Acetazolamide↗
PubMed1988

[18F]setoperone: a new high-affinity ligand for positron emission tomography study of the serotonin-2 receptors in baboon brain in vivo.

The potential usefulness of 18F-labelled setoperone, a high-affinity antagonist of the serotonin-2 (S2) receptors, to study the S2 receptors in vivo with positron emission tomography (PET) was investigated in four baboons. In the control state, there was a rapid wash-out of intravenously injected tracer from the cerebellum, a structure essentially devoid of S2, receptors, and marked retention in both the cerebral cortex and the striatum (region/cerebellum ratios up to 3 and 3.5 after 60 min in cortex and striatum, respectively). The retention of radioligand in the cerebral cortex was abolished after pretreatment with spiperone or ketanserin at saturating doses. In striatum, however, radioligand retention was fully prevented by spiperone but only partly by ketanserin. These results demonstrate that [18F]setoperone was bound to the S2 receptors in the cerebral cortex, whereas the radioligand was bound to both the S2 and the dopamine D2 receptors in the striatum. The high cortex/cerebellum ratio achieved indicates that [18F]setoperone should be a useful radiotracer for PET studies of the S2 receptors.

Animals↗
PubMed1988

Regional specific binding of [11C]RO 15 1788 to central type benzodiazepine receptors in human brain: quantitative evaluation by PET.

The central type benzodiazepine receptors were studied in 17 healthy human subjects with 11C-RO 15 1788 and positron emission tomography (PET). The brain regional distribution of the tracer in eight control studies performed after injection of trace doses of 11C-RO 15 1788 was consistent with that of benzodiazepine receptors. Saturation studies with co-injected cold RO 15 1788 in the remaining subjects showed a dose-dependent decrease of brain radiotracer until full inhibition of specific binding was achieved with doses above 0.1 mg/kg (four studies). Based on the results, a simple method to estimate the specifically bound 11C-RO 15 1788 regionally in a single PET study is proposed, using the data from the full-saturation studies as a stable estimate of the nondisplaceable radioligand concentration. Using this method, it was found that quasiequilibrium between the estimated specifically bound and nondisplaceable components was achieved at times equal to or longer than 20 min after tracer administration. The validity of this method was partly supported by further results, showing a good agreement between the regional specific binding so calculated and postmortem data of receptor density.

Adult↗
PubMed1988

[Pure sensory stroke caused by thalamic hematoma].

A 59-year-old hypertensive patient presented with dysesthesias and a pure sensory deficit involving face, arm and leg on the left side of the body. CT scan and MRI showed a small hematoma in the posterior and lateral part of the right thalamus.

Hematoma↗
PubMed1987

Remote metabolic effects of cerebrovascular lesions: magnetic resonance and positron tomography imaging.

Combined Positron Emission Tomography (PET) and Proton Magnetic Resonance Imaging (MRI) study were performed in six patients with chronic supratentorial stroke to investigate whether remote hypometabolic regions revealed by PET showed any abnormality on MRI. Either regional oxygen consumption (n = 4) or glucose utilization (n = 2) were measured using PET and the 15O steady state 18FDG technique, respectively. Four patients, with deeply located brain lesions, showed a significant metabolic reduction in the overlying cerebral cortex. In the remaining two patients, affected by a large cortical infarct, there was a significant crossed cerebellar hypometabolism. The MRI weighted by the parameters spin density (rho), spin lattice (T1) and spin-spin (T2) relaxation times were obtained employing various sequences in the same subjects. In no patient did the MRI show any contrast modification in these hypometabolic remote regions, suggesting that subtle loss of tissue and/or biochemical change do not underlie the reduction in metabolic rate.

Adult↗
PubMed1987

Cortical hypometabolism and its recovery following nucleus basalis lesions in baboons: a PET study.

The cerebral metabolic rate for glucose was measured serially with positron emission tomography and [18F]fluorodeoxyglucose in five baboons with stereotactic electrocoagulation of the left nucleus basalis of Meynert (NbM). Four days after lesion, a significant metabolic depression was present in the ipsilateral cerebral cortex, most marked in the frontotemporal region, and which recovered progressively within 6-13 weeks. These data demonstrate that adaptive mechanisms efficiently compensate for the cortical metabolic effects of NbM-lesion-induced cholinergic deafferentation. Moreover, unilateral NbM lesions also induced a transient reduction in contralateral cortical metabolic rate, the mechanisms of which are discussed. Explanation of these effects of cholinergic deafferentation in the primate could further our understanding of the metabolic deficits observed in dementia of the Alzheimer's type.

Animals↗
PubMedDate not supplied

[Sturge-Weber angiomatosis responsible for hemiplegia without cerebral infarction in term pregnancy].

During the third quarter of her pregnancy, a young woman with Sturge-Weber angiomatosis had a severe right hemiplegia with hemianopia and aphasia, followed 48 hours later by focal seizures. Neuroimaging did not show any cerebral lesion but contrast magnetic resonance imaging revealed a left hemispheric pial angiomatosis. The patient recovered progressively from the third day after a ceasarean. The hemianopia disappeared within 15 days, the hemiplegia within one month and the aphasia greatly improved within 3 months. Ten weeks after the clinical onset, we performed a positron emission tomography study. A decrease from 15 to 40% of the cerebral radioactivity was observed after injection of water (H2(15)O) or fluorodesoxyglucose (18FDG) in the left temporooccipital area adjacent to the meningeal angiomatosis. A chronic and focal olighemia, already reported in Sturge-Weber angiomatosis, might participate in the occurrence of this cortical metabolic depression.

Adult↗