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Biomedical subjects

S Blond

Publications and source records attributed to S Blond.

At least 19 recordsLinked to original sources
PubMed2001

Influence of chronic bilateral stimulation of the subthalamic nucleus on cognitive function in Parkinson's disease.

BACKGROUND: The clinical efficacy of chronic deep brain stimulation in the treatment of parkinsonian patients with severe levodopa-related motor adverse effects has been repeatedly shown. Bilateral subthalamic nucleus (STN) stimulation has been shown to present an advantage over pallidal stimulation as it induces a higher antiakinetic effect and has positive effects on all parkinsonian symptoms. The morbidity of such surgery is usually considered to be very low. However, few studies have extensively examined the effects of chronic STN stimulation on cognitive function. OBJECTIVE: The aim of the present study was to assess the effects of chronic bilateral STN stimulation on performance in an extensive battery of neuropsychological tests, three months and one year after surgery. METHODS: Nine patients with Parkinson's disease were selected for STN electrodes implantation. They underwent a neuropsychological evaluation at one month before and at three months after surgery. Six of them were examined again at one year after surgery. RESULTS: Before surgery, no patient showed cognitive decline. At three months after surgery, no modification was observed for most tasks. The information processing speed tended to improve. There was a significant reduction of the performance in a delayed free recall test and a trend toward a significant reduction of categorial word fluency. At one year after surgery, most task measures did not change. Slight impairment was observed for tasks evaluating executive function. Examination of individual results showed that some patients (30% at 3 months after surgery) showed an overall cognitive decline. Behavioural changes were also observed in 4 patients with overall cognitive decline in one of them. CONCLUSION: In general, STN deep brain stimulation can be considered as a significant contribution to the treatment of severe Parkinson's disease However, in some patients it can induce overall cognitive decline or behavioural changes.

Cognition Disorders↗
PubMed2000

[Chronic electric stimulation of the internal globus pallidus and subthalamic nucleus in Parkinson disease].

PATHOPHYSIOLOGY: In Parkinson's disease, the neurodegenerative process of the nigrostriatal dopaminergic pathways induces an increase in activity of the subthalamic nucleus and the medial globus pallidus, which cause inhibition of thalamo-cortical outputs explaining parkinsonism. HIGH-FREQUENCY DEEP BRAIN STIMULATION: The adverse effects induced by lesions of subcortical structures (thalamotomy, pallidotomy) have increased interest in chronic electrical stimulation proposed as a new therapy in Parkinson's disease. This technique is reversible and can be modulated with less adverse effects. TWO TARGETS: Two targets may be proposed in case of severe motor fluctuations: the medial globus pallidus and the subthalamic nucleus. Pallidial stimulation improves dramatically levodopa-induced dyskinesia and, with a variable degree, the parkinsonian triad. Subthalamic stimulation rapidly reverses akinesia, rigidity and tremor and also dyskinesias which progressively tend to diminish after decreasing L-dopa dosage. LONG-TERM EFFICACY: A follow-up period of a few years has confirmed that the beneficial effect is maintained. However, stimulation dose not prevent the development of certain symptoms (postural impairment, cognitive decline). LIMITED INDICATIONS: Chronic electrical stimulation of medial globus pallidus and subthalamic nucleus may be proposed for parkinsonian patients with severe motor fluctuations associated with abnormal involuntary movements which are not controlled by different medical therapies. Parkinsonian symptoms must still be levodopa responsive and cause severe clinical disability severely limiting daily living activities. Cognitive impairment and other severe pathologies are contraindications.

Electric Stimulation Therapy↗
PubMed2000

A case of severe dysexecutive syndrome consecutive to chronic bilateral pallidal stimulation.

In treatment for severe Parkinson's disease (PD), a recent procedure was developed which consists of implanting electrodes in the internal Globus Pallidus (GPi) for chronic electrical stimulation. The consequences on cognitive function of such an intervention are quite variable. Although most group studies observed no significant post-operative change, individual cases of post-operative cognitive impairment were reported. The present study reports the case of a PD patient who underwent bilateral implantation of deep brain stimulation electrodes in the GPi and who, after surgery, suffered from a severe dysexecutive syndrome. An extensive neuropsychological examination showed a selective negative effect of pallidal stimulation on tests assessing executive function. When the stimulation was turned off, the impairment was partly reversible. This observation emphasizes the role of the GPi in executive function.

Attention↗
PubMed2000

[Stereotactic applications in third ventricle tumors].

Stereotactic procedures are especially indicated for deep lesions within the brain substance, surrounded by functional structures, such as third ventricle tumors. Despite recent technological advances, the basis for stereotaxis remains minimally traumatic procedures, with the safety of vascular and ventricular anatomical definitions. Stereotactic procedures were performed in 63 patients of the national series. The indications, procedures, results and complications were reviewed. Stereotaxis was used with a diagnosis purpose in 34 patients. In all cases, the histological diagnosis was identified, which allowed the definition of the therapeutic strategy, and avoidance of useless direct approach to the third ventricle. Stereotaxis was used with a therapeutic purpose in 29 other patients : the procedure allowed the evacuation of colloid or glial tumor cysts, ventriculostomy, intracavitary irradiation, or radiosurgery. The stereotactic procedure should take in account the grade of associated hydrocephalus. Stereotactic evacuation of colloid cysts in this series (25 cases) often resulted in a recurrence of the cyst. Endoscopic procedures, eventually associated with stereotactic guidance, should be preferred for the treatment of colloid cysts.

Cerebral Ventricle Neoplasms↗
PubMed2000

[Neurostimulation in the treatment of chronic pain].

Different types of neurostimulation are proposed essentially in cases of chronic neuropathic pain, non controlled by anticonvulsivants and antidepressants. The aim is usually to activate a failing inhibitory system, involved in the transmission and the modulation of the nociceptive stimulus. The site of stimulation (transcutaneous, spinal cord, thalamic) is choosen according to the severity of pain and especially the degree of lemniscal dysfunction evaluated by clinical and electrophysiological data. Transcutaneous electrical stimulation and spinal cord stimulation are efficient for neurogenic pain secondary to partial deafferentation. When dysfunction or lesion extend to the pre-ganglionic portion, it's preferable to propose stereotactic thalamic stimulation or central gyrus stimulation. The analgesic effect concerns permanent burning pain in the context of sensitive deafferentation: after distal nervous lesions, radicular, plexular or spinal lesions or after stroke with ischemic lesions along the nociceptive pathways. These different methods must only be proposed if there is a frequent clinical and technical monitoring.

Chronic Disease↗
PubMed2000

[Clinical manifestations and therapeutic approach in neurosarcoidosis].

Neurological impairment is a frequent cause of morbidity and mortality in patients with sarcoidosis. The aim of this study was to evaluate the clinical manifestations of the disease, the response to corticosteroids and alternative treatments. During a 5 year period, diagnosis of neurosarcoidosis was performed in 40 patients. We retrospectively analyzed clinical, laboratory data and response to treatments. Mean age was 41.3 years (range 17-72). Mean time of follow-up was 46 months. Neurologic signs were the first symptom in 50 p. 100 of cases and an isolated manifestation in 12.5 p. 100. Central nervous system impairment was seen in 60.7 p. 100, meningitis in 27 p. 100. Other clinical manifestations were cranial nerve palsies (27 p. 100), peripheral neuropathy (33 p. 100), myopathy (16 p. 100). Eighty percent of the patients were treated by corticosteroids. Because of a lack of efficacy 40 p. 100 of patient required alternative treatment (including methotrexate, cyclophosphamide, azathioprin, cyclosporin). Complete recovery was observed in only 27.5 p. 100 of cases confirming the severity of neurosarcoidosis. Forty percent of patients were clinically stable and 10 p. 100 worsened. No patient died. This study confirms that intensive initial treatment is often necessary to prevent irreversible lesions. Alternative treatment should be rapidly initiated in resistant forms.

Adolescent↗
PubMed1999

Improvement of levodopa induced dyskinesias by thalamic deep brain stimulation is related to slight variation in electrode placement: possible involvement of the centre median and parafascicularis complex.

OBJECTIVE: To define the reason why two teams using the same procedure and the same target for deep brain stimulation (DBS) obtained different results on levodopa induced dyskinesias, whereas in both, parkinsonian tremor was improved or totally suppressed. METHODS: Deep brain stimulation can replace lesions in the surgical treatment of abnormal movements. After 10 years of experience with DBS in Parkinson's disease, a comparison of results between the teams of Lille (A) and Grenoble (B) was carried out, for as long as they used intraoperative ventriculography. Both teams aimed at the same target, the ventralis intermedius nucleus of the thalamus (VIM), but team A found a clear improvement of choreic peak dose dyskinesias, whereas team B did not consistently. Therefore all teleradioanatomical data of both teams were re-examined and compared with the therapeutic effects. Location of 99 monopolar electrodes of thalamic stimulation applied to treat parkinsonian tremor has been retrospectively measured (team A included 21 patients, 22 electrodes; team B included 52 patients, 74 electrodes). Peak dose levodopa dyskinesias were suppressed by DBS in all nine patients of team A, four of which were severely disabling. Only eight out of 32 patients from team B experienced a moderate (four) or clear (four) improvement of dyskinesias, whereas in the remaining 24 patients, dyskinesias were unchanged with stimulation. RESULTS: The mean centre of team A's electrodes was on average 2.9 mm deeper, more posterior and medial than team B's (t=8.05; p<0.0001). This does not correspond to the coordinates of the VIM, but seems to be closer to those of the centre median and parafascicularis complex (CM-Pf), according to stereotaxic atlases. Considering only the dyskinetic patients, significant differences were found in the electrode position according to the therapeutic effects on levodopa dyskinesias, but they were not related to the team membership. Improvement in levodopa dyskinesias was significantly associated with deeper and more medial placement of electrodes. CONCLUSION: The retrospective analysis of patients treated with DBS using comparable methodologies provides important information concerning electrode position and therapeutic outcome. The position of the electrode is related to the therapeutic effects of DBS. The results support the hypothesis that patients experiencing an improvement of dyskinesias under DBS are actually stimulated in a structure which is more posterior, more internal, and deeper than the VIM, very close to the CM-Pf. These results are consistent with neuroanatomical and neurophysiological data showing that the CM-Pf is included in the motor circuits of the basal ganglia system and receives an important input from the internal pallidum. This suggests that the CM-Pf could be involved specifically in the pathophysiology of levodopa peak dose dyskinesias.

Aged↗
PubMed1999

[Importance of cerebral tomoscintigraphy using technetium-labeled sestamibi in the differential diagnosis of current tumor vs. radiation necrosis in subtentorial glial tumors in the adult].

CT scan and MR imaging are not always reliable in the differential diagnosis between radionecrosis and recurrence of brain tumor. We describe the results of a prospective study using 99mTc Sestamibi. 22 patients were included. The histology of the tumor was astrocytoma (grade 2-4) oligodendroglioma (grade 2-3) or mixed (grade 2-3). SPECT was performed using a Tomomatic 564, 1 h after the injection i.v. of 370 MBq of 99mTc Sestamibi. Ten slices parallel to the orbitomeatal plane were obtained. Two index were calculated i) CI: ratio of the mean counts in the lesion to the mean counts in the contralateral choroid plexus and ii) MI: ratio of the mean counts in the lesion to the contralateral mirror area. The results were compared to stereotactic biopsies or to clinical course at 6 months. Twelve patients out of 22 showed an increased uptake of the tracer and 11/12 presented with a recurrence. In 10 patients without fixation, 4 were false negative. The sensitivity for the detection of tumor recurrence was 73% and specificity was 85%. The positive predictive value was 91% and the negative predictive value was 60%. The use of a cut-off value superior to 2 for MI and superior to 0.5 for CI appears to be a good criterion for helping the diagnosis of relapse according to the analysis of Receiver Operating Characteristic curves (ROC). A positive SPECT was conclusive for the diagnosis of recurrence but a negative SPECT did not allow to assess the absence of recurrence. Limits of methods have to be stressed and searched for a better understanding of false negatives.

Aged↗
PubMed1999

[The effect of thalamic stimulation on levodopa induced dyskinesias--evaluation of a new target: the center parafascicular median].

After 10 years of clinical practice (1987-1997), chronic thalamic deep brain stimulation (DBS) is considered to be effective in the treatment of drug-resistant parkinsonian tremor. DBS has produced few side-effects, which are usually reversible. More recently, DBS has been applied to other movement disorders (akinesia and rigidity, dyskinesias, dystonia), using new targets: internal pallidum, subthalamic nucleus. These targets have been selected on the basis of neurophysiological or anatomo-clinical data suggesting they could be effective. Control of L-Dopa peak-dose dyskinesias by thalamic ventralis intermedius nucleus (V.im.) stimulation has been reported by the Lille team, but not by the Grenoble team. We therefore re-examined all teleradioanatomical data of both teams, and compared them with the therapeutic effects. Location of 99 monopolar electrodes of thalamic stimulation, applied to treat parkinsonian tremor, has been retrospectively measured. The Lille team included 21 patients (22 electrodes); the Grenoble team included 52 patients (74 electrodes). L-Dopa dyskinesias were suppressed in all 9 patients in Lille, and improved clearly in only 8 out of 32 patients in Grenoble. The mean center of electrodes was significantly different between both teams, being deeper, more posterior and medial in Lille. This did not correspond to the coordinates of the V.im., but seems to be closer to those of the centromedian and parafascicular complex (CM-Pf), according to stereotactic atlases. Considering only the dyskinetic patients, the therapeutic effects on L-Dopa dyskinesias were related to the differences observed in the electrode position, but not to the team membership. Improvement of L-Dopa dyskinesias was significantly associated with deeper and more medial placement of electrodes. Retrospective analysis of ventriculographic data confirmed that the electrode position and therapeutic effects of DBS are strongly related. Our study suggested that CM-Pf stimulation could control both tremor and L-Dopa dyskinesias. This hypothesis is consistent with neuro-anatomical data showing that CM-Pf is connected to internal pallidum, the stimulation of which controls specifically L-Dopa dyskinesias.

Aged↗
PubMed1998

[Brain stem metastasis revealing bronchopulmonary cancer: 2 cases].

INTRODUCTION: Brainstem metastasis is a very rare revealing feature of lung carcinoma. EXEGESIS: We report two cases of brainstem metastasis revealing lung carcinoma. In the first case, diagnosis was made on stereotaxic biopsy. In the second, the biopsy was not necessary as lung lesion was observed on thoracic CT-scan. Diagnosis of metastasis is difficult when a brainstem tumor occurs. CONCLUSION: Stereotaxic biopsy is an interesting tool to distinguish between primary lesion and metastasis, but only when diagnosis work-up of primary cancer is negative.

Adenocarcinoma↗
PubMed1998

[Combination treatment for pilocytic astrocytoma: stereotaxic radiosurgery and endocavitary radiotherapy].

The treatment of a pilocytic astrocytoma located in a functional area can be performed using radiosurgery. We report a 7 year old male, right-handed, who presented with a pilocytic astrocytoma in the left parieto-occipital lobe. After a 7 year follow-up, the tumor became symptomatic (partial and generalized seizures). The CT scan and nuclear magnetic resonance imaging revealed an increased size of the mural tumor and the development of a cystic component. Multi-beam irradiation of the tumor (dose of 30 Gy at the center with 21 Gy on the isodose 70%) was performed with a LINAC for radiosurgery coupling a modified Saturne 18 MeV linear accelerator and a Talairach stereotactic frame. Following multi-beam irradiation, the increase in size of the cyst imposed further intracavitary radiation using Rhenium 186 (186Re) to deliver 400 Gy to the cyst wall. After a period of intense cerebral edema, resolutive with steroid treatment, we obtained progressive cyst disappearance and mural nodule retraction. A PET scan, performed 3 years after this treatment, revealed no metabolic activity in the persistent mural nodule. The patient remains totally asymptomatic.

Astrocytoma↗
PubMed1998

[Acquired lesions of the corpus callosum].

Acquired lesions of the corpus callosum may be related to tumoral, vascular, traumatic or degenerative disorders and, one must not forget, can result from surgical access. Currently, the quality of neuroimaging enables a validation or precision of anatomoclinical, neuropsychological and neurophysiological correlations established from experimental and/or autopsy data. However the "specific" signs of acquired lesions of the corpus callosum are often quite complex and may be readily overlooked or masked within a heterogeneous clinical presentation due to more or less important associated lesions of neighboring structures. Therapeutic management (tumors, arteriovenous malformations, cavernomas) depend on the nature and the extent of the lesion more than the functional nature of this inter-hemispheric commissure with an exceptional functional plasticity, particularly when the lesion is limited.

Brain Diseases↗