Biomedical subjects

G Demeurisse

Publications and source records attributed to G Demeurisse.

At least 19 recordsLinked to original sources

PubMed2001

Subcortical neglect as a consequence of a remote parieto-temporal dysfunction. A quantitative EEG study.

In patients with a right-sided deep-seated lesion, a causal relationship between a cortical dysfunction in the right temporo-parietal region and the occurrence of neglect has been suggested. In the present study we tried to correlate clinical and quantitative EEG data from a sample of 33 right stroke patients divided into two subgroups according to the presence or absence of neglect. A 20-channel EEG cartography system was used for EEG mapping. Delta and theta activities were calculated in sixteen regions of interest. The analysis of raw values stressed the importance of the right parieto-temporal cortex to discriminate between the two subgroups of patients. These results suggest that in patients with right subcortical damage, a remote cortical parieto-temporal dysfunction within an intra-hemispheric network is necessary to provoke neglect.

Adult↗

PubMed2000

Mechanisms of functional restoration after brain injury.

The mechanisms accounting for clinical improvement after brain injury are still a matter of debate. Better knowledge of the recovery process is important for it might be influenced by therapy. This article reviews a number of studies devoted to the physiopathology of recovery from aphasia and visuo-spatial neglect after the acute stage, using various methods (cerebral blood flow and metabolism measurements, dichotic listening, transcranial Doppler ultrasonography, functional magnetic resonance imaging) with special reference to the contribution of methods using activation procedures.

Brain Injuries↗

PubMed1999

Complete mutism after midbrain periaqueductal gray lesion.

Several neurophysiological studies have highlighted the role of the midbrain periaqueductal gray matter (PAG) in the initiation of vocalization in various animal species, from frogs to primates. With regard to humans, only two cases of complete mutism following a lesion to the PAG have been reported so far. This article describes a new case of a patient (GM) who, following an ischemic lesion to the periaqueductal gray region of the midbrain, presented with complete and irreversible mutism, though her language comprehension functions and her non-verbal expression capacity were preserved. This clinical case provides evidence that in humans the PAG also acts as a link between different vocalization-eliciting external and internal stimuli (which reach the PAG from sensory and emotional structures) and the vocal-motor coordinating mechanisms in the lower brain stem.

Aged↗

PubMed1999

[Lower limb monoplegia and dissociated hypoesthesia after peridural anesthesia].

Neurological sequelae reported after epidural anesthesia include epidural hematoma, spinal cord ischemic injury and lumbosacral nerve root injury. We describe here a case of monoplegia of the right lower limb associated with an ipsilateral loss of perception of pain and temperature following an epidural anesthesia. MRI was compatible with a right centrolateral infarction in the gray matter of the spinal cord below D8. Hypotension, vascular spasm, trauma, arteriosclerosis, pressure increase in the epidural space are potential causative mechanisms. Unilateral symptoms might result from injury to a sulcocommissural artery or an anterior spinal artery when duplicated.

Aged↗

PubMed1999

[Communication with the aphasic patient].

The consequences of aphasia with reference to the WHO ICIDH classification are evoked. The role of the physician and the behaviour of the relatives are underlined as well as the main parameters to be taken into consideration to communicate with an aphasic patient. As a rule, a dialogue in quiet surroundings will make communication easier with an aphasic patient. Our attitude will be modulated according to the behaviour of the patient, his past and the aphasiological picture. At the early stage of the disease, verbal means of communication will be mainly used, whereas later on, in a pragmatic approach, all means (verbal and non verbal) will be used to improve communication.

Aphasia↗

PubMed1998

Quantitative EEG in subcortical neglect.

Right-sided capsulo-lenticular strokes may cause left visuo-spatial neglect. The neural mechanism most frequently evoked to account for the occurrence of related cognitive disorders is remote cortical dysfunction in the posterior part of the right hemisphere. We studied 33 patients with capsulo-lenticular stroke, with (n = 16) or without (n = 17) associated subcortical neglect. A 20-channel EEG cartography system was used. Four regions of interest were delineated on the topographic map. Absolute delta and thêta amplitude peaks were obtained, as well as left-to-right ratios between activities in homologous regions of interest. The population was subdivided into two groups according to the presence or absence of neglect. Delta activity was higher in neglect patients than in patients without neglect, but the magnitude of delta activity differences between the two groups of patients did not depend on the site. The left-to-right ratio of delta activity between posterior homologous regions was lower in neglect patients, suggesting that right posterior dysfunction producing an imbalance between these regions might contribute to the emergence of the attention disorder.

Adult↗

PubMed1997

Pathogenesis of subcortical visuo-spatial neglect. A HMPAO SPECT study.

The pathophysiology of neuropsychological disorders due to right deep-seated hemispheric lesions remains a debated point. We undertook this study to check the hypothesis according to which remote cortical dysfunction could be responsible for the occurrence of neglect. Twenty-eight patients presenting with a right-sided subcortical stroke were studied. A neuropsychological battery of tests suitable for assessment of possible visuo-spatial neglect was performed as well as HMPAO SPECT. Neglect was observed in 15 cases out of 28. The lesion's site (at CT and/or MRI) did not allow discrimination between patients without neglect and patients with neglect. The latter however could be distinguished from the former by the presence of a remote decrease in cortical blood flow in the right temporo-parietal region. By suggesting that cortical involvement is necessary for the occurrence of neglect, the results were interpreted according to a network approach in which subcortical neglect is attributed to a cortical deprivation from afferent input in the posterior part of the brain.

Aged↗

PubMed1995

Remote cortical dysfunction as a possible cause of subcortical neglect? A regional cerebral blood flow study.

Cortical remote effects of right deep-seated lesions were studied with two cerebral blood flow measurement methods (two-dimensional xenon-133 inhalation and 99mTc HMPAO SPECT) in a population of 13 right-handed stroke patients. A neuropsychological battery of tests suitable for assessment of possible visual neglect was performed. Neglect was present in 7 cases. A regional cortical hypoperfusion was observed in all patients. However, in neglect patients it was more extended and involved the right inferior parietal region suggesting a causal relationship between cortical dysfunction and neuropsychological deficit. This finding supports the model attributing neglect to a unilateral attention-arousal defect in a cortico-limbic-reticular loop.

Aged↗

PubMed1994

Functional dissociations following bilateral lesions of auditory cortex.

We present two patients with bilateral lesions of the superior temporal cortex who manifested a number of functional dissociations in the auditory domain. The perception of speech and environmental sounds were preserved; yet, the perception of tunes, prosody and voice was impaired. As the processing of melodic but not rhythmic variations in musical sequences was selectively disturbed, the deficit cannot be attributed to a general impairment in auditory memory or sequential processing. These findings suggest that melody processing is not mediated by a general-purpose auditory architecture but by specialized cortical subsystems residing within the lesioned areas. Current taxonomies of auditory agnosia and models of normal music cognition are evaluated in light of the functional dissociations manifested by these patients.

Adult↗

PubMed1992

Pure topographical disorientation due to a deep-seated lesion with cortical remote effects.

Lesions producing pure topographical disorientation syndromes are classically located either in the right parietal region either in the right parahippocampal gyrus. The patient described in the present study was admitted to hospital after sudden onset of a left hemiparesis. The lesion at CT scan was located in the posterior limb of the right internal capsule. Neuropsychological assessment was normal except for the presence of a major topographical disorientation and of mnestic disturbances for visuo-spatial material leading us to attribute topographical disorientation to a specific loss of topographical memory. Regional cerebral blood flow measurements disclosed a right parietal hypoperfusion. This remote cortical effect could account for the presence of the neuropsychological disorders.

Aged↗

PubMed1992

Seasonal variation of cerebral hemorrhage in 236 consecutive cases in Brussels.

BACKGROUND AND PURPOSE: Seasonal variation in the incidence of cerebral hemorrhage has been previously demonstrated. In this study, we sought to identify the climatological data best correlated with this seasonal variation. METHODS: In a retrospectively studied sequential series of 236 patients with nontraumatic cerebral hemorrhage observed in Brussels over a period of 8 years, we cumulatively grouped the dates of stroke occurrence into a single calendar year. RESULTS: We found marked seasonal variation in incidence, with the highest value (23%) observed in November-December and the lowest (10%) in July-August. Seasonal variations in incidence of cerebral hemorrhage were shown to be correlated not only with the inverse of ambient temperature, but also with the inverse of hours of sunshine and with ambient humidity. We found no difference between hypertensive and normotensive patients. CONCLUSIONS: Our study fails to bear out the hypothesis that the higher incidence of cerebral hemorrhage in late autumn and winter is due to the influence of low ambient temperature on blood pressure.

Adolescent↗

PubMed1991

Brain activation during a linguistic task in conduction aphasia.

In order to investigate functional cortical reorganization during recovery from conduction aphasia, regional cerebral blood flows (rCBF) were measured by the two-dimensional 133 Xenon inhalation method in ten stroke patients. rCBF measurements were performed at rest and during the performance of a linguistic task, one month and three months after onset. The analysis of flow changes from rest to test condition indicates an increasing contribution of the right hemisphere as time goes on. The absence of flow increase in Broca's region suggests that this region is definitively disconnected from posterior language "centers" by the arcuate fasciculus lesion.

Aged↗

PubMed1991

Remote cortical dysfunction in aphasic stroke patients.

We studied the effect of deep-seated left hemispheric lesions on cortical blood flow in 18 right-handed aphasic stroke patients. Regional cerebral blood flow was measured at rest and during the performance of a functional naming test using the two-dimensional xenon-133 inhalation method. Compared with 10 controls, at rest the patients showed regional cortical hypoperfusion in the left frontoparietal region. In the controls, activation patterns from the rest to the test condition involved mainly the left hemisphere areas. In the patients, a lack of blood flow change was observed in several areas that were usually hypoperfused at rest. However, in patients with slight verbal expression disorders there were obvious blood flow increases in other brain regions in both hemispheres. Such cortical functional reorganization and the presence of a remote cortical dysfunction could play a role in the pathophysiology of language disorders.

Aged↗

PubMed1990

Pathogenesis of aphasia in deep-seated lesions: likely role of cortical diaschisis.

In order to study the pathophysiology of language disorders due to deep-seated left-hemisphere lesions not involving the cortex, a population of 43 right-handed stroke patients (29 aphasic) presenting with such lesions was studied clinically and by regional cerebral blood flow measurements (two-dimensional xenon-133 inhalation method). Most of the patients were studied sequentially between the 1st and 3rd months after stroke. Cortical diaschisis did not account for the whole clinical picture: the remote effect on the cortex could explain the occurrence of aphasia and its severity but not the type of aphasia. Furthermore, the clinical improvement observed in most cases was not accompanied by the disappearance of the diaschisis.

Adult↗

PubMed1990

Remote effect of deep-seated vascular brain lesions on cerebral blood flow.

We measured regional cerebral blood flow using the xenon-133 inhalation method, at approximately 1 month after onset, in 60 stroke patients who had no evidence of major carotid artery stenosis or occlusion. Their single lesions (43 infarcts and 17 hematomas) were located in the capsulothalamolenticular region, sparing the cortex. Hemispheric mean cerebral blood flow was reduced on the side of the lesion in 25 patients and on both sides in 20. Regional hypoperfusion was observed in 46 patients (ipsilaterally in 34, bilaterally in 10, and contralaterally in two). Regional hypoperfusion was observed most frequently in the frontal lobe, particularly in the motor and premotor cortices of the prerolandic area. The 46 patients with regional hypoperfusion were compared with the 14 patients without regional hypoperfusion, considering the size and location of the lesion as well as the functional and analytic motor performances. As a rule, the lesion was slightly smaller and more posterior and the functional (p less than 0.001) and analytic (p less than 0.05) motor performances were significantly better in the 14 patients without regional hypoperfusion. Since the xenon-133 inhalation method examines cortical blood flow, we can attribute blood flow reductions resulting from deep-seated lesions to a functional depression akin to diaschisis. Interpretation of the clinical consequences and pathogenesis of this phenomenon requires further sequential and pathologic studies.

Administration, Inhalation↗

PubMed1989

Evidence of cortical reorganization in hemiparetic patients.

We studied the mechanisms underlying the recovery of motor function of the hand using a bidimensional xenon-133 inhalation technique to measure regional cerebral blood flow at rest and during the performance of a motor task (test condition). The regional cerebral blood flow patterns under rest and test conditions were compared in normal control and in stroke patients with either a cortico-subcortical or a deep-seated lesion. Functional recovery appears to depend upon cortical reorganization involving both hemispheres, particularly in both parietal regions in the subgroup of patients with cortico-subcortical lesions.

Adult↗

PubMed1986

Assessment of hemispheric dominance for language in crossed aphasia by two atraumatic methods.

In a right handed patient with crossed aphasia, two atraumatic techniques (regional cerebral blood flow measurements during the performance of a linguistic task and dichotic listening test) were used to assess language lateralization. The prominence of rCBF activation patterns in the right hemisphere and the presence of a clear-cut right ear extinction on the dichotic listening test provide evidence that, is this case, the right hemisphere was dominant for language.

Aged↗

PubMed1985

Prognostic value of computed tomography in aphasic stroke patients.

In order to evaluate the prognostic value of CT scan in aphasic stroke patients, a prospective study was performed during the first 3 months of the disease. The severity of the language disorders was assessed by means of a quantitative method. In cortico-subcortical lesions, the verbal expression recovery rate and the final verbal expression and comprehension status depended on the infarct size. No relation was observed between the latter and the verbal comprehension recovery rate. In deep-seated lesions, computed tomography provided no information concerning the prognosis.

Aged↗