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F Chollet

Publications and source records attributed to F Chollet.

At least 19 recordsLinked to original sources
PubMed1999

Differential fMRI responses in the left posterior superior temporal gyrus and left supramarginal gyrus to habituation and change detection in syllables and tones.

Using a habituation-recovery paradigm adapted to functional magnetic resonance imaging, we investigated the brain responses to syllables and tones in six right-handed male subjects. We opposed a standard condition (STD) in which the subjects were listening to homogeneous sequences of four identical stimuli, to a deviant condition (DEV) in which the fourth stimulus of the sequence differed in pitch or spectral content for tones and in the initial stop consonant for syllables. The corresponding runs alternated four rest periods with two STD and two DEV conditions. In addition to a marked rightward asymmetry in the primary and secondary auditory cortex for tones and a right inferior frontal activation for the tone condition where the deviant had increased spectral content, the experiment revealed differential activations in the left posterior superior temporal gyrus and in the left supramarginal gyrus. Activations within the left posterior superior temporal gyrus were observed for the DEV condition with tones and for the STD and DEV conditions with syllables. Activation within the inferior part of the left supramarginal gyrus was only observed for the DEV condition with syllables. The analysis of the decreases and increases in the BOLD signal across the STD, DEV, and rest conditions suggests that the left posterior superior temporal gyrus is implicated in the preattentive change detection of acoustic changes in speech as well as nonspeech stimuli, whereas the left supramarginal gyrus is more specifically engaged in the detection of changes in phonological units.

Adult↗
PubMed1998

Normal frontal perfusion in patients with frozen gait.

We have studied the frontal perfusion in the resting condition of two groups of patients with frozen gait: 10 patients with the syndrome of "isolated gait ignition failure" (IGIF) and 8 patients with idiopathic Parkinson's disease (PD) and severe "off" freezing. These patients were compared with two other groups: one including 20 age-matched volunteers as normal control subjects and the other one including 12 patients with progressive supranuclear palsy (PSP) as a positive control with expected frontal hypoperfusion. Frontal perfusion was assessed using single photon emission computed tomography (SPECT) regional cerebral blood flow measurement with intravenous 133Xenon. A significant frontal hypoperfusion was only present in the PSP group but not in the three others. These results do not support the hypothesis that start hesitations and freezing when walking are related to a frontal lobe dysfunction. However, it is possible that frontal neuronal dysfunction occurs without measurable cerebral blood flow changes in the resting condition.

Aged↗
PubMed1998

Event-related potentials elicited by passive movements in humans: characterization, source analysis, and comparison to fMRI.

Cortical areas responsive to proprioceptive stimulation were assessed by ERP technique in normals and in selected patients with stroke and were compared to fMRI data. Repetitive extension of right and left forefinger elicited a P1/N1/P2 complex wave pattern. This pattern was absent in patient with complete sensory loss and present but spatially modified in patient with recovered sensory deficit. Source localization with a simple model showed three sources starting in the contralateral rolandic area (SI), then involving the inferior parietal lobe unilaterally and the supplementary motor area (10 to 134 ms). It was followed by a bilaterally distributed pattern of two sources located in the ipsilateral parietal region and in the contralateral insula. Right and left stimulation led to very symmetrical patterns. Comparison to fMRI obtained from passive extension of the wrist in normals showed very compatible data. We described in this paper, a sequential processing of proprioceptive inputs after passive movements involving primary and secondary sensory motor areas.

Adult↗
PubMed1998

Cortical motor overactivation in parkinsonian patients with L-dopa-induced peak-dose dyskinesia.

We have studied the regional cerebral blood flow (rCBF) changes induced by the execution of a finger-to-thumb opposition motor task in the supplementary and primary motor cortex of two groups of parkinsonian patients on L-dopa medication, the first one without L-dopa induced dyskinesia (n = 23) and the other with moderate peak-dose dyskinesia (n = 15), and of a group of 14 normal subjects. Single photon emission tomography with i.v. 133Xe was used to measure the rCBF changes. The dyskinetic parkinsonian patients exhibited a pattern of response which was markedly different from those of the normal subjects and non-dyskinetic parkinsonian patients, with a significant overactivation in the supplementary motor area and the ipsi- and contralateral primary motor areas. These results are compatible with the hypothesis that an hyperkinetic abnormal involuntary movement, like L-dopa-induced peak dose dyskinesia, is due to a disinhibition of the primary and associated motor cortex secondary to an excessive outflow of the pallidothalamocortical motor loop.

Aged↗
PubMed1997

Polymerase chain reaction on cerebrospinal fluid cells in the detection of leptomeningeal involvement by B-cell lymphoma and leukaemia: a novel strategy and its implications.

In the search of B-cell lymphoma/leukaemia dissemination to cerebrospinal fluid (CSF), we used the highly sensitive semi-nested PCR (snPCR) for the analysis of IgH gene rearrangements. This method detects a rearranged IgH gene from a single B lymphocyte which may or may not represent the neoplastic B-cell population. We therefore performed multiple snPCR (three to five) experiments on the same CSF sample, postulating that the detection of a band of the same size and sequence in different PCR runs was highly indicative of a clonal population. 17 consecutive cases with a differential diagnosis of primary (PCNSL) (n=10) or secondary (SCNSL) (n=7) CNS lymphoma or leukaemia were investigated by the new strategy. The clonal nature of the B-cell population was confirmed in 3/10 of suspected PCNSL, and in six other cases the PCR study was indicative of reactive lymphocytosis. One case revealed a clonal B-cell population in the clinical context of an autoimmune disorder. Evidence of clonal B-cell population was found in 4/7 of suspected SCNSL. In one of these cases the detected band and its sequence proved identical to that of the primary nodal lymphoma. We believe that the evaluation of B-cell clonality in CSF requires multiple snPCR amplification on the same sample to compare the size of the products and, if necessary, the DNA sequences to ascertain the diagnosis of malignancy in equivocal cytologic and clinical findings.

Adult↗
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

Impairment and recovery of left motor function in patients with right hemiplegia.

OBJECTIVE: To assess the motor function of the left, supposedly unaffected, limbs of patients with an acute right vascular hemiplegia. METHODS: Fifteen patients with an acute vascular right hemiplegia and 16 matched healthy controls were studied. Motor function of the left limbs of each patient was evaluated on days 20 and 90 after their stroke using four validated tools (hand dynamometer, isokinetic dynamometer, finger tapping, and nine hole peg test). RESULTS: There was a significant impairment of motor function of the left limbs of patients at day 20 compared with controls. The impairment had recovered almost completely at day 90 after the stroke. CONCLUSION: These results show the bilateral cerebral representation of the human motor system and suggest the participation of ipsilateral motor pathways in recovery after a stroke.

Aged↗
PubMed1997

Fou rire prodromique heralding a left internal carotid artery occlusion.

BACKGROUND: Four rire prodromique, described as pathological laughter preceding the onset of an apoplectic attack, is a rare phenomenon. CASE DESCRIPTION: A 61-year-old man manifested pathological laughter before a sudden right hemiplegia. MRI showed a left lenticular and caudate nucleus infarct with involvement of the external capsule and prerolandic area. MRA revealed a left internal carotid and middle cerebral artery occlusion. CONCLUSIONS: The clinicoanatomic correlates of this phenomenon are discussed.

Arterial Occlusive Diseases↗
PubMed1996

Recurrent right hemiplegia associated with progressive ipsilateral carotid artery stenosis.

BACKGROUND: Ipsilateral sensory motor symptoms associated with carotid artery stenosis are rare, and few reports are available in the literature. CASE DESCRIPTION: We report the case of a 50-year-old man who presented with right hemiplegia that recurred 14 months later. A left hemisphere watershed infarction was detected. Repeated angiograms showed a left internal carotid occlusion and a right internal carotid stenosis that initially measured 50% and worsened to 80% after the second stroke. CONCLUSIONS: Repeated quantitative measurements of cerebrovascular reserve demonstrated the hemodynamic mechanism of the strokes and the role of a right internal carotid lesion in causing the recurrence of right hemiplegia.

Brain↗
PubMed1996

[Ischemic cerebrovascular complications in Rendu-Osler disease: a case].

Rendu-Osler disease is a familial disorder transmitted as an autosomal dominant trait of high penetrance. It is characterized by telengiectasias of the skin, mucous membranes and viscera, associated with recurrent bleedings. Neurological complications (brain abcesses and hemorrhagic manifestations) occur in 10% of the patients. Neurological symptoms are often associated with arteriovenous fistula of the lung (50%). Ischaemic strokes occuring in such patients with an hemorrhagic disease while unfrequent, have been described. The pathophysiology of stroke in that case remains unclear. Polycythemia causing hyperviscosity, air embolism following hemoptysis, paradoxical embolism through right-to-left shunt have been proposed. We report a new case of ischaemic strokes occuring in a caucasian forty-year-old woman, with Rendu-Osler disease (familial history, epistaxis, telengiectasias) and with an arteriovenous malformation of the right lung. She presented two strokes and one transient ischaemic attack. Her pulmonary malformation was occluded by embolization. The role of arteriovenous malformation in the pathophysiology of strokes is discussed.

Adult↗
PubMed1996

[Value of the study of latent atrial vulnerability in unexplained ischemic cerebrovascular accident of young subjects].

This study searched for abnormalities of the atrial electrophysiological substrate in young subjects with unexplained ischaemic cerebrovascular accidents. Thirty-seven patients (18 to 45 years) underwent programmed atrial stimulation at 2 sites in the right atrium after an unexplained ischaemic cerebrovascular accident. Seventeen of them underwent repeat study at 6 months. The following parameters were analysed: indices of atrioventricular conduction and sinus node automaticity; indices related to atrial hyperexcitability: effective refractory period; adaptation of the refractory periods to heart rate, intraatrial conduction and the index of latent vulnerability; the inducibility test by the extrastimulus technique. The following results were obtained: 54% of patients had an inducible atrial arrhythmia; the effective refractory periods and index of latent vulnerability were lower (204 +/- 21 ms and 2.25 +/- 0.7) in the inducible patients than in the non-inducible patients (232 +/- 28 ms and 3.4 +/- 1.1) (p < 0.001 and p < 0.002 respectively); 76% of patients had latent atrial vulnerability indicating and underlying arrhythmogenic substrate; this substrate was still present 6 months later in 80% of these cases; in patients with an abnormality of the interatrial septum, there was an abnormality of the electrophysiological investigation in 85% of cases compared with 65% in those with normal transoesophageal echocardiography. These results confirm the presence of an arrhythmogenic substrate similar to that of patients with paroxysmal atrial fibrillation in over two thirds of cases. Programmed atrial stimulation is a reproducible technique. The relationship between latent atrial vulnerability and abnormalities of the interatrial septum requires confirmation in a series with a larger numbers of patients.

Adolescent↗
PubMed1995

[Transverse myelitis caused by Mycoplasma pneumoniae infection].

A twenty-six year old man was admitted for febrile atypical pneumoniae. Few hours later, he presented an acute flaccid paraplegia with dorsal pain. Cerebrospinal fluid analysis showed a high leukocyte count with raised protein level. Neuroradiological examinations (myelography and MRI) were normal. Seric immunological disorders were reported. High complement-fixing antibody titers to Mycoplasma pneumoniae were found in the serum and in the CSF. The patient was treated with antibiotic and corticosteroids. He improved dramatically within one month. Neurological complications of Mycoplasma pneumoniae infections have been described (meningoencephalitis, meningitidis, polyradiculoneuropathies, cerebellar ataxia, cranial nerve palsies). Nineteen cases of transverse myelitis induced by Mycoplasma pneumoniae have been previously reported. Pathophysiological mechanisms of nervous system complications induced by Mycoplasma pneumoniae were discussed. Vascular mechanisms, direct invasion by the pathogen, toxic, immunological causes were examined.

Adult↗
PubMed1994

[From heart to brain and from brain to heart: impact of an anticoagulant treatment with aspirin in secondary prevention].

Aspirin given as a platelet antiaggregant has been shown to be effective for secondary prevention both in cardiology (myocardial infarction, uncontrolled angina pectoris, coronary bypass, etc.) and in neurology (after a cerebral vascular event or an episode of temporary ischaemia). For example, the risk of non-fatal recurrence is reduced by 31% after myocardial infarction and by 22% after cerebral vascular events. In the large scale trials which led to these findings, patients were usually included on the basis of one type of illness, heart disease of neurological disorder. However, these studies have also revealed a cross-over effect. For example a 35% reduction in non-fatal myocardial infarction after secondary preventive treatment for cerebral vascular events and a 42% reduction in cerebral vascular events after secondary preventive treatment for myocardial infarction. Such arguments suggest the importance of evaluating the dual brain/heart and heart/brain impact of secondary prevention. In addition, aspirin has been shown to be effective in certain forms of non-valvular atrial fibrillation and in vascular dementia. Recommended doses vary between 160 and 300 mg/day. Secondary cardiologic prevention with such doses has a favourable effect both on the cardiologic indications after infarction or poorly controlled angina pectoris and has an additional impact on primary prevention of neurological events. The Scientific Committee of the American Heart Association recommends the dose of 160 mg/day after myocardial infarction. For secondary neurological indications, recent studies demonstrate that the dose of 300 mg/day is as effective as higher doses which are less well tolerated and haematologists have underscored that doses below 160 mg/day would not have a sufficient anti-thrombotic effect. The recommended doses for neurological indications would thus be within this range. It is reasonable to expect a dual impact of secondary prevention with doses near 300 mg/day.

Anticoagulants↗
PubMed1994

Imaging recovery of function following brain injury.

The past years have seen significant advances in our understanding of recovery of function after brain lesions. This results from the development of sophisticated methods for exploring the human living brain, especially by using positron emission tomography scans. From the recent literature, it appears that two main mechanisms may participate in the recovery process: recruitment of cortical areas in the undamaged hemisphere and extension of specialized areas adjacent to the lesioned site.

Amyotrophic Lateral Sclerosis↗
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

[Study of the effect of internal carotid artery diseases on cerebral hemodynamics].

The cerebral artery system is richly anastomosed. These anastomoses can compensate for the effects of a stenosis or an occlusion of the internal carotid artery. In addition, control of cerebral blood flow occurs via a double process of haemodynamic and metabolic adaptation to a drop in perfusion pressure. Direct or indirect measurement of the cerebral perfusion reserve can evaluate the haemodynamic effects of an internal carotid stenosis.

Carotid Artery Diseases↗