Biomedical subjects

P Celsis

Publications and source records attributed to P Celsis.

At least 37 records · Page 2Linked to original sources

PubMed1998

Brain correlates of memory processes in patients with dementia of Alzheimer's type: a SPECT Activation Study.

Task-induced changes in regional cerebral blood flow (rCBF) during verbal episodic memory activation were compared in 17 right-handed patients with dementia of the Alzheimer's type (DAT) and 20 healthy volunteers. Regional cerebral blood flow was assessed using single photon emission computed tomography (SPECT) and an injection of 133Xe (xenon, isotope of mass 133) in 21 regions of interest (ROI) during rest, passive listening to 36 words, and memorizing of a 12-word list repeated three times. In healthy subjects, memory-listening comparison showed activation of a distributed system involving several left-sided ROI, especially the posterior inferior frontal region. In patients with DAT, the same pattern of activation was found for listening-rest comparison, and no significant changes were found in memory-listening comparison. During listening compared with rest, significant activation was observed in left-sided hypoperfused regions. A significant correlation between memory performance and rCBF recorded in patients with DAT during the memory task was found only in the right lateral frontal region, a region that was not hypoperfused significantly in patients. The involvement of this region might relate to either retrieval effort or actual performance of patients with DAT on the memory task.

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PubMed1997

The ipsilateral cerebellar hemisphere is overactive during hand movements in akinetic parkinsonian patients.

We compared the rCBF changes induced by the execution of a finger-to-thumb opposition motor task in the cerebellar hemispheres of 12 normal subjects, 12 parkinsonian patients whose medication had been withheld for at least 18 h and 16 parkinsonian patients on medication using single photon emission tomography and i.v. 133Xe. The normal subjects and parkinsonian patients on medication exhibited the same pattern of response, with a significant increase in rCBF in the contralateral primary motor cortex and in the supplementary motor areas. No significant rCBF change was detected in the cerebellum of these two groups; this finding was expected since our technique cannot detect cerebellar activation when the motor task is executed at a relatively low rate and small amplitude as it was in this study. The parkinsonian patients off medication exhibited a markedly different pattern of activation characterized by a significant overactivation in the ipsilateral cerebellar hemisphere and a significant underactivation in the supplementary motor areas. These results suggest that parkinsonian patients off medication may try to compensate for their basal ganglia-cortical loop's dysfunction using other motor pathways involving cerebellar relays.

Brain Mapping↗

PubMed1997

Age related cognitive decline: a clinical entity? A longitudinal study of cerebral blood flow and memory performance.

OBJECTIVES: To evaluate the changes in regional cerebral blood flow (rCBF) and memory performance in patients with age related cognitive decline (ARCD) who did and did not become demented during a follow up period. METHODS: Twenty four patients with ARCD were recruited from an outpatient memory clinic, of whom 18 were followed up over a mean period of two years. Eighteen patients with mild to moderate probable Alzheimer's disease and 18 aged normal controls were followed up over a mean period of three years. Memory performance and rCBF were evaluated quantitatively at inclusion and during follow up, using single photon emission computed tomography with xenon-133 injection and three subtests of the Wechsler memory scale (logical memory, paired associated learning, and digit span). RESULTS: Patients with ARCD showed decreased rCBF and memory performance at initial evaluation compared with controls. Five of them became demented during the follow up period, with further decline in memory and rCBF. At inclusion, the only feature that distinguished these five patients as a group from the remainder was a pronounced temporoparietal asymmetry. The 13 patients with ARCD who did not become demented still exhibited impaired memory and rCBF at follow up, but without any further decline and no increase in flow asymmetry. CONCLUSIONS: Apart from patients in the preclinical phase of Alzheimer's disease, the ARCD category includes non-demented patients who have brain dysfunction that may represent a distinct clinical entity.

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PubMed1996

Brain functional profiles in formal and semantic fluency tasks: a SPECT study in normals.

SPECT method is used to analyze changes in regional cerebral blood flow in a group of 19 normal subjects during a baseline task (repetition of two words) and two verbal fluency tasks, a semantic fluency and a formal fluency. The semantic fluency task was associated with a relative CBF increase in the right dorso-lateral and medial frontal region when compared with that seen in the baseline condition. No specific activation was found for the formal fluency task compared to that seen in the baseline task. We suggest that the activation of the right frontal region reflects semantic categorization strategies in semantic fluency. The lack of activation of the left frontal region may be due to an activation induced by the nature of the baseline task (i.e., a self-paced repetition task).

Adult↗

PubMed1996

Living/non-living dissociation in a case of semantic dementia: a SPECT activation study.

A category-specific dissociation with massive deficits in semantic knowledge of animals and preservation of knowledge of objects was observed in a demented patient with a left inferior temporal cortical atrophy responsible for a deficit of visual semantic processing. When the patient successfully processed the semantic feature of aurally presented object names, a SPECT study showed an activation of the left posterior and middle temporal cortex (Wernicke's area). This haemodynamic pattern was not observed during an unsuccessful processing of animal names that was associated with an activation of the left and right inferior frontal regions. Activation in Wernicke's area probably reflects an adequate matching between auditory lexical input and semantic knowledge for entities with multimodal representations, such as man-made objects. Activation in Broca's area and its right homologous region may correspond to an unsuccessful phonological strategy to evoke semantic features of animals, a category that is mainly visually represented.

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PubMed1995

Non-comatose patients with acute carbon monoxide poisoning: hyperbaric or normobaric oxygenation?

Twenty-six non-comatose patients with acute carbon monoxide (CO) poisoning were randomized into two groups. Both groups were treated as soon as possible and for 2 h, the first group by 100% normobaric oxygen (NBO) and the second by 100% hyperbaric oxygen. At the end of this period, patients treated by HBO had a significant improvement of their clinical and biological conditions compared with patients treated with NBO. Both groups then received the same NBO therapy for 10 h. At the end of this second period, carboxyhemoglobin level was normal in both groups. However, patients treated with NBO showed some clinical impairments, and 3 wk after onset had significantly more electroencephalogram abnormalities and a reduced cerebral blood flow reactivity to acetazolamide. We conclude that HBO reduces the time of initial recovery and the number of delayed functional abnormalities in non-comatose patients with acute CO poisoning. A practical scheme for the use of NBO and HBO in such patients is proposed.

Acute Disease↗

PubMed1994

Right temporal compensatory mechanisms in a deep dysphasic patient: a case report with activation study by SPECT.

A brain activation study using SPECT and 133Xe in a deep dysphasic patient with left temporal lesion is presented. The activation paradigm consisted of a passive listening to foreign language as baseline, a phoneme monitoring condition and a semantic word monitoring condition. The specific activation of the right middle temporal cortex observed in the semantic condition is congruent with the hypothesis of a compensatory role of the right hemisphere in processing concrete words. This case illustrates the interest of functional imaging for a better understanding of neural mechanisms of functional recovery after brain injury.

Adult↗

PubMed1994

The functional anatomy of attention in humans: cerebral blood flow changes induced by reading, naming, and the Stroop effect.

We measured changes in regional cerebral blood flow (rCBF) induced by reading, naming, and the Stroop effect in 12 right-handed normal volunteers. rCBF was quantified with a single-photon emission computerized tomograph after intravenous injection of 133Xe. Data were analyzed using predetermined regions of interest and a linear model. A significant relative activation was revealed in the right superior mesial frontal region during the Stroop effect.

Adult↗

PubMed1994

Activation of regional cerebral blood flow by a memorization task in early Parkinson's disease patients and normal subjects.

Task-induced changes in regional cerebral blood flow (rCBF) during memory activation were compared in 18 right-handed patients with early Parkinson's disease (PD) and 20 normal volunteers using the same activation paradigm. We used single-photon emission computed tomography and 133Xe in 21 regions of interest during rest, passive listening of a work list, and memorization of another word list, which was followed by a free recall test immediately after completion of the rCBF measurement. The average performance on free recall was not significantly lower in PD patients than in controls. In normal subjects, five left-sided regions (anterior middle frontal, posterior inferior frontal, superior middle temporal, thalamic, and lenticular) showed a significant increase in memorizing compared to passive listening. This pattern of activation suggests the existence of a verbal rehearsal strategy during the memorization task in normals. In PD patients, increases in these regions did not reach significance, whereas significant activations were noted in superior prefrontal regions. Such alterations in the pattern of activation in PD patients, despite a memory performance similar to that of controls are viewed as a consequence of an early dysfunction of the articulatory loop system and of compensatory mechanisms in other parts of the frontal lobe emerging in the early stages of the disease.

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PubMed1994

Normal activation of the supplementary motor area in patients with Parkinson's disease undergoing long-term treatment with levodopa.

Regional cerebral blood flow (rCBF) changes in cortical motor areas were measured during a movement of the dominant right hand in 15 patients with Parkinson's disease deprived of their usual levodopa treatment, in 11 patients with Parkinson's disease undergoing long-term treatment with levodopa, and in 15 normal volunteers. The supplementary motor areas were significantly activated in the normal subjects and in the patients receiving levodopa but not in the patients deprived of levodopa. The contralateral primary sensory motor area was significantly activated in all three groups. The ipsilateral primary sensory motor cortex was not activated in the normal subjects and the non-treated patients but was in the patients treated with levodopa. It is concluded that the supplementary motor area hypoactivation which is observed in akinetic non-treated patients with Parkinson's disease is not present in patients undergoing long-term treatment with levodopa. This result suggests that (a) levodopa improves the functional activity of supplementary motor areas in Parkinson's disease and (b) there is no pharmacological tolerance to this effect. The ipsilateral primary motor cortex activation observed in the patients treated with levodopa could be related to levodopa-induced abnormal involuntary movements.

Adult↗

PubMed1993

Effect of side and rate of stimulation on cerebral blood flow changes in motor areas during finger movements in humans.

We measured, using single photon emission computed tomography, the regional CBF (rCBF) changes in the motor areas of 24 right-handed normal volunteers during the performance of a motor task consisting of sequential finger-to-thumb opposition. Twelve of them performed the task with their right and their left hands consecutively with a fast frequency and large amplitude. The other 12 subjects performed the task with their right hand only at a slow frequency and small amplitude. The contralateral primary sensorimotor areas (S1/M1), supplementary motor area (SMA), and ipsilateral cerebellum were significantly activated during right and left finger movements performed at fast frequency and large amplitude. No significant difference was found between the rCBF changes induced by the right dominant and left nondominant hands. When the task was performed with a slow rate and small amplitude, the SMA was significantly activated while no significant changes were observed in the contralateral S1/M1 or in the ipsilateral cerebellum. These results demonstrate (a) that hand dominance evokes no differences in the activation of the main motor areas and (b) that the frequency and amplitude of the movement have a major effect on the quantitative and qualitative aspect of activation of motor areas in humans.

Adult↗

PubMed1992

Supplementary and primary sensory motor area activity in Parkinson's disease. Regional cerebral blood flow changes during finger movements and effects of apomorphine.

We have measured with single-photon emission tomography the regional cerebral blood flow changes that occurred in the supplementary motor areas and in the primary sensory motor areas during sequential finger-to-thumb opposition movements of the right hand in seven akinetic patients with Parkinson's disease and in nine normal volunteers. Parkinsonian patients were studied before ("off" condition) and after a subcutaneous injection of apomorphine hydrochloride which was able to switch them "on" (on condition). In normal volunteers and parkinsonian patients in the on condition, regional cerebral blood flow significantly increased in the supplementary motor areas and in the contralateral primary sensory motor cortex but not in the ipsilateral primary sensory motor cortex. On the contrary, no significant regional cerebral blood flow change was observed in these areas in parkinsonian patients in the off condition. These results support the hypothesis that a functional cortical motor area deafferentation is involved in the pathophysiological makeup of akinesia and that this abnormality is reversed by dopaminergic drugs.

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PubMed1992

Cerebral blood flow correlates of word monitoring in sentences: influence of semantic incoherence. A spect study in normals.

The aim of this study was to assess the cerebral blood flow (CBF) changes induced by the semantic incoherence of sentences whose words were to be monitored by the subjects. According to Marslen-Wilson and Tyler, word processing would be parallel (global) in semantically coherent sentences, and serial (local) in semantically incoherent ones. We hypothesized that, in comparison with the parallel mode, the serial mode of word processing would result in a preponderant activation of the frontal lobes and/or of the left hemisphere, hence in a flow increase in these regions. In addition, one could assume that the increase in task complexity resulting from the breaking of semantic coherence would reinforce the functional links between hemispheres. Furthermore, as interactions between the processing of semantically coherent vs incoherent of verbal materials and the processing of imageable vs non-imageable stimuli was recently suspected, we designed a study combining coherent vs incoherent sentences and imageable vs non-imageable words. The results we obtained in 12 normal volunteers by measuring regional cerebral blood flow by SPECT and IV injection of Xenon 133 during the four experimental conditions, did not allow us to firmly establish our hypotheses. Indeed, we failed to demonstrate any significant CBF changes across conditions and there was no interaction between coherent vs incoherent and imageable vs non-imageable conditions. However, the analysis of the inter-regional correlations pointed to an increase in the functional links between the hemispheres in the incoherent conditions, whatever the imageability.

Adult↗

PubMed1991

[Cerebral imaging and aphasia].

In the field of aphasiology, cerebral imaging has greatly helped in modifying our concepts concerning the physiopathological mechanisms underlying language. Morphological imaging, and particularly computerized tomography (CT), has provided a critical appraisal of established doctrines as well as evidence that subcortical structures participate in language. A more dynamic and evolutive approach of brain organization for language has been introduced by CT and emission imaging techniques which have shown on one side the existence of age-related modifications in the language area, and on the other side the possibility of recovery by activation of structures other than those classically involved. Finally, magnetic resonance imaging has recently revived interest in the study of strict anatomico-clinical correlations.

Adult↗

PubMed1991

Subcutaneous apomorphine increases regional cerebral blood flow in parkinsonian patients via peripheral mechanisms.

1. We have measured regional cerebral blood flow (rCBF) and motor function before and after the subcutaneous (s.c.) injection of apomorphine in parkinsonian patients deprived of their usual treatment for at least 48 h. 2. Nineteen patients, pretreated with domperidone (20 mg three times daily for 48 h), received a mean dose of 5.8 mg s.c. apomorphine. All patients switched 'on'. The mean motor score was significantly improved (-65%, P less than 0.01) but no significant change in rCBF was observed. 3. Seven other patients, not pretreated with domperidone, received a lower dose (0.3 mg) of s.c. apomorphine. No change in motor score was observed while the mean rCBF significantly increased (+12%, P less than 0.05). 4. We conclude that s.c. apomorphine increases rCBF in parkinsonian patients. This effect is independent of the central therapeutic effects of the drug. It is mediated by the stimulation of dopaminergic receptors of the cerebral vessels. These receptors are located outside the cerebral blood brain barrier and can be considered as 'peripheral' ones.

Aged↗

PubMed1991

Cognition and cerebral blood flow in lateralised parkinsonism: lack of functional lateral asymmetries.

Cognitive and cerebral blood flow (CBF) lateral asymmetries have been quantified in 23 right handed patients with lateralised idiopathic Parkinson's disease. Thirteen patients who had predominant right-sided symptoms (RPD) were compared with ten who had predominant left-sided symptoms (LPD). The patient subgroups were matched for age, education, duration of illness, disease severity and medication. Normalised asymmetries scores were calculated from the data obtained with a test battery and SPECT. No correlation was found between laterality of motor Parkinsonian symptoms and cognitive or haemodynamic asymmetry scores.

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PubMed1991

Quantitative assessment of cerebral blood volume by single-photon emission computed tomography.

We implemented a technique for measuring regional cerebral blood volume using single-photon emission computed tomography and in vivo technetium-99m-labeled red blood cells and then evaluated it in nine normal human volunteers (controls) and seven patients with bilateral occlusion or severe stenosis of the internal carotid artery. We also measured regional cerebral blood flow using single-photon emission computed tomography and intravenous xenon-133 in the same subjects. We studied regional cerebral blood flow, regional cerebral blood volume, and their ratio before and after the intravenous injection of 1 g acetazolamide. Mean +/- SD baseline regional cerebral blood volume was higher in the patients than in the controls (4.1 +/- 0.6 versus 3.2 +/- 0.3 ml/100 g, p less than 0.01), and mean +/- SD baseline regional cerebral blood flow was lower in the patients than in the controls (40.5 +/- 11 versus 55.6 +/- 11 ml/100 g/min, p less than 0.05). Acetazolamide induced similar mean +/- SD increases in regional cerebral blood volume in both the controls and the patients (0.3 +/- 0.1 and 0.3 +/- 0.2 ml/100 g), while the mean +/- SD regional cerebral blood flow reactivity was significantly less in the patients than in the controls (12.6 +/- 7.6 versus 24.5 +/- 9.6 ml/100 g/min, p less than 0.05). Our study shows that single-photon emission computed tomography can provide quantitative estimates of both regional cerebral blood volume and regional cerebral blood flow in humans.

Acetazolamide↗

PubMed1991

[Cerebral blood volume, endarterectomy and SPECT].

Cerebral blood flow and cerebral blood volume were measured and quantified using single photon emission computed tomography before and after unilateral endarterectomy in 3 patients with bilateral severe lesions of the internal carotid artery. These parameters were measured using an intravenous injection of 133 Xenon and 99m Technetium respectively. Before endarterectomy cerebral blood volume was high in all patients suggesting a focal vasodilatation in response to a reduced cerebral perfusion pressure. After endarterectomy a decrease of cerebral blood volume and an increase of cerebral blood flow were observed. These preliminary results confirm that the hemodynamic adaptative mechanisms secondary to carotid occlusion are reversible when the stenosis is removed and demonstrate that these changes can be accurately measured using single photon emission computed tomography. Positron emission tomography was previously considered to be the only method able to quantify cerebral blood volume in man. Single photon emission computed tomography can also be considered a reliable technique to measure both cerebral blood flow and cerebral blood volume. This technique can then be used to assess individual cerebral vascular adaptative states and to evaluate the influence of cerebral hemodynamic changes on stroke occurrence in large longitudinal studies.

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