Biomedical subjects

J Guérin

Publications and source records attributed to J Guérin.

At least 19 recordsLinked to original sources

PubMed2006

Interferometric coupling of the Keck telescopes with single-mode fibers.

Here we report successful interferometric coupling of two large telescopes with single-mode fibers. Interference fringes were obtained in the 2- to 2.3-micrometer wavelength range on the star 107 Herculis by using the two Keck 10-meter telescopes, each feeding their common interferometric focus with 300 meters of single-mode fibers. This experiment demonstrates the potential of fibers for future kilometric arrays of telescopes and is the first step toward the 'OHANA (Optical Hawaiian Array for Nanoradian Astronomy) interferometer at the Mauna Kea observatory in Hawaii. It opens the way to sensitive optical imagers with resolutions below 1 milli-arc second. Our experimental setup can be directly extended to large telescopes separated by many hundreds of meters.

Journal Article↗

PubMed2005

Sacral neuromodulation in lower urinary tract dysfunction.

Vesico-urethral dysfunction is a major problem in daily medical practice due to its psychological disturbances, its social costs and its high impact on quality of life. Recently, sacral neuromodulation, namely the electrical stimulation of the sacral nerves, appears to have become an alternative for radical bladder surgery particularly in cases of idiopathic bladder overactivity. The mechanism of action is only partially understood but it seems to involve a modulation in the spinal cord due to stimulation of inhibitory interneurons. Temporary sacral nerve stimulation is the first step. It comprises the temporary application of neuromodulation as a diagnostic test to determine the best location for the implant and to control the integrity of the sacral root. If test stimulation is successful, a permanent device is implanted. This procedure is safe in experienced hands. So-called idiopathic bladder overactivity still the major indication for this technique. Patients not likely to benefit from the procedure were those with complete or almost complete spinal lesions, but incomplete spinal lesions seemed to be a potential indication. This technique is now also indicated in the case of idiopathic chronic retention and chronic pelvic pain syndrome. When selection is performed, more than three-quarters of the patients showed a clinically significant response with 50% or more reduction in the frequency of incontinent episodes, but the results vary according to the author's mode of evaluation. From the economic point of view, the initial investment in the device is amortized in the mid-term by savings related to lower urinary tract dysfunction. Finally, this technique requires an attentive follow-up and adjustments to the electric parameters so as to optimize the equilibrium between the neurological systems.

Afferent Pathways↗

PubMed2004

[Delayed facial palsy after vestibular schwannoma resection: the role of viral reactivation. Our experience in 8 cases].

OBJECTIVE: To study the role of herpes virus reactivation in the onset of more than three days-delayed facial paralysis (FP) following vestibular schwannoma (VS) surgery and advocate a specific medical management. MATERIAL AND METHODS: Retrospective study on 8 cases from a series of 348 patients operated on of a VS between 1996 and 2002. Seven of the eight patients were given intravenously acyclovir (30 mg x kg(-1) x d(-1) for 5 days) and methyl-prednisolone (2 mg x kg(-1) x d(-1) for 7 days). A serologic testing looking for specific anti-herpes simplex viruses type 1 and 2 (HSV-2) and varicella-zoster virus (VZV) antibodies at the onset of the FP and 2 weeks later could be done in only 3 cases. RESULTS: Mean delay of FP onset was 8.75 days. Mean time for recovery with intravenous treatment was 90 days. All treated patients had a House and Brackmann grade 1 recovery. The last one had only a grade 3 after 400 days of evolution: he could not be treated because of postoperative transient psychiatric problems. Serologic testing revealed in those patients in whom it could be done either a high level of anti-HSV or -VZV antibodies at the time of onset or a dramatic increase in anti-HSV or anti-VZV antibodies between the two samples, strongly suggesting a HSV or VZV reactivation. CONCLUSION: HSV or VZV reactivation can be evocated in most cases of delayed FPs arising in the postoperative course of VSs, suggesting usefulness of emergency-given steroid and acyclovir intravenous regimen to block virus replication and fight secondary oedema and inflammation causative of nerve lesions. Evoked reactivation mechanism is comparable to that already suspected in delayed FP arising with the same delay in middle ear surgical procedures.

Acyclovir↗

PubMed2003

[Acoustic neuroma surgery. Results and complications in 348 cases].

OBJECTIVES: The aim of this study was to evaluate post-operative complications after acoustic neuroma surgery. METHODS: This was a retrospective study of 348 patients, who had acoustic neuroma surgery between 1984 and 1999. Symptoms, pre-operative evaluation, surgery and post-operative complications were analysed. RESULTS: 174 men and 174 women had an operation. Mean age was 51.8 years (11-78). 31 patients had a grade I tumour, 106 a grade II, 71 a grade III and 140 had a grade IV tumour. 195 patients have been operated through the translabyrinthine approach, 110 through the retrolabyrinthine approach, 42 through the sub-occipital approach, and one through the transcochlear approach. Mortality was 0.85%, 59.2% patients had a post-operative facial paralysis. Most of patients had post-operative dizziness, and 30% still had vestibular disturbances after one year. 9 patients (2.6%) had a cerebrospinal rhinorrhea and 24 patients had a cerebrospinal wound leak (6.9%). 22 patients had post-operative meningitis (6.3%). 2 patients had a cerebello pontine angle haemorrhage, and 3 patients had a brain stem infarct. CONCLUSION: Transpetrous approaches are safe for acoustic neuroma removal and the post-operative complication rate is low. The retrolabyrinthine approach seems to be a good hearing preservative approach, regardless of tumour volume.

Adolescent↗

PubMed2002

[Neurosurgical and endovascular treatment of intracranial aneurysms: a cost analysis of two different strategies at the University Hospital of Bordeaux (France)].

BACKGROUND: Rupture of intracranial aneurysms causes major mortality and morbidity. Moreover, treatment of this vascular malformation generates high medical costs. We compared the cost of two different strategies employed at the University of Bordeaux to prevent aneurysms from rebleeding: a classical neurosurgical technique consisting in clipping the neck of the aneurysm and a new less invasive neuroradiological technique based on embolization using platinum coils. METHOD: A micro-cost study was carried out retrospectively from May 1998 to June 2000) comparing data from 44 patients admitted for ruptured intracranial aneurysm: 22 operated patients and 22 patients treated with an endovascular approach. Each operated patient was matched with an embolized patient for clinical status at admission (World Federation of Neurological Surgeons Scale) and complications resulting from cerebral hemorrhage (hydrocephalus, vasospasm, rebleeding). RESULTS AND CONCLUSION: Our results showed the same cost for the same efficiency . Expenditures are however made differently. The endovascular technique allows a shorter hospital stay (8 days less), balancing the high cost of single use medical supplies (coils, microcatheters.). The endovascular technique has many advantages for the patients, but cannot be successful in all types of intracranial aneurysms. Both techniques remain indispensable.

Aneurysm, Ruptured↗

PubMed2001

In vitro study of the effect of titanium on porphyromonas gingivalis in the presence of metronidazole and spiramycin.

Septic peri-implantitis is the main clinical complication encountered following the insertion of titanium implants. It may be resistant to conventional antibiotic treatments. Reports in the literature about antibiotic behavior in the presence of titanium remain controversial. They vary from a bacteriostat to a decreased effect of antibiotic. This study examined, in vitro, the viability of Porphyromonas gingivalis, frequently associated with periodontal diseases, in the presence of titanium and antibiotics (spiramycin and metronidazole alone or in combination). Viability of P. gingivalis was determined, versus a standard curve using the Live/dead Baclight Bacteria Viability Kit on 96 well microplates. The results of 48 experiments (60 measurements each) were compiled in a database and compared to each other using the chi2p < 0.05 test. When used alone, titanium enhanced bacterial growth as the nickel-chrome control. However, when titanium was used in the presence of antibiotics, antibiotics kept their own effects. Even more, titanium was shown to potentialize the effect of metronidazole. The strengthening of effectiveness of metronidazole by titanium may be due to the oxidation potential of the metal. This chemical property could explain the conflicting data reported in the literature.

Anti-Bacterial Agents↗

PubMed2000

[Fractionated radiation therapy long-term effectiveness in the treatment of cerebello-pontine angle schwannomas: 12 years of experience in 30 cases].

UNLABELLED: The purpose of this research was to evaluate long-term results of fractionated radiation therapy (RT) in the treatment of cerebello-pontine angle schwannomas. METHODS: from January 1986 to October 1995, 29 patients with stage III and IV scwhannomas were treated with external fractionated RT. One patient was irradiated on both sides and indication for RT was as follows: a) poor general condition or old age contraindicating surgery, 16 cases; b) hearing preservation in bilateral tumors after contralateral tumor removal, 6 cases; c) partial resection or high risk of recurrence after subsequent surgery for relapse, 5 cases; d) non surgical relapse, 3 cases. Most patients were irradiated with 6 to 10 MV photons. A three- to four-field technique with coplanar static beams and conformal blocks was used. Doses were calculated on a 95 % isodose and were given 5 days a week for a mean total dose of 51 Gy (1.8 Gy/fraction). RESULTS: Median follow-up from RT was 66 months (7 to 120); seven patients died, two with progressive disease, five from non tumoral cause. Two patients underwent total removal after RT (1 stable and 1 growing tumor). On the whole, tumor shrinkage was observed in 13 patients (43.3 %), stable disease in 14 (46.6 %), and tumor progression in three. Hearing was preserved in 4 out of 6 hearing patients (1 class A hearing, 2 class B and 1 class C). No patient experienced CN5 or CN7 neuropathy. CONCLUSION: long-term efficacy or fractionated RT is well documented in this series. Acute and delayed tolerance was excellent. Hearing can be preserved for a long time.

Adolescent↗

PubMed1999

Psychometric appraisal of the Scale for Interpersonal Behavior (SIB) in France.

The present study was carried out in France to evaluate the reliability and validity of the Scale for Interpersonal Behavior (SIB), a multidimensional measure of difficulty and distress in assertiveness that was originally developed in The Netherlands. This appraisal was conducted with a clinical sample (N = 166) and a general population sample (N = 150). The clinical series comprised 115 patients with social phobia and 51 patients with personality disorder, 28 of whom were of the avoidant type. Support was found for internal consistency and test-retest reliability of the French SIB. Compared to controls, both social phobics and patients with an avoidant personality disorder had significantly lower mean scores on all performance scales and significantly higher ones on all distress scales, with the social phobics occupying a position in between. Findings in relation to convergent and divergent validity were quite satisfactory. Sensitivity of the French SIB for detecting change was demonstrated in a subgroup of the clinical Ss who had undergone 15 sessions of cognitive-behavioral group therapy for underassertiveness.

Adult↗

PubMed1998

Prognostic factors in pediatric spinal cord astrocytoma.

BACKGROUND: Factors that could optimize the management of pediatric spinal cord astrocytoma remain unclear and controversial. METHODS: To determine the factors that influence the prognosis of pediatric patients with spinal cord astrocytomas, a series of 73 consecutive patients at 13 French treatment centers with histologically proven spinal cord astrocytomas was retrospectively reviewed. Hospital records, operative records, and results of radiologic investigations were available in all cases. Follow-up was achieved in 94% of cases. RESULTS: Seventy percent of the patients had low grade (1 or 2) tumors. Total or subtotal surgical resection was achieved in 43%. Thirty-six patients were irradiated following surgery. Fifty-one patients were alive at a median follow-up of 54 months. Twenty-three patients relapsed. Univariate analysis showed that good outcome was correlated with male gender, age younger than 7 years, duration of presenting symptoms longer than 2 months, the presence of spinal deformities, and low grade histology, whereas sensory loss was associated with decreased survival. Multivariate analysis using the Cox proportional hazards model confirmed that histology (relative risk [RR] = 7.69) and the interval between first symptoms and diagnosis (RR = 4.93) were significant independent prognostic factors. The extent of surgery or radiotherapy had no clear influence on survival. CONCLUSIONS: This review sheds light on the prognoses of pediatric patients with spinal cord astrocytomas and may help to determine therapeutic strategies based on patients' clinical, radiologic, and pathologic features.

Adolescent↗

PubMed1998

Suppression of heparinization of central venous catheters between cycles of chemotherapy. Results of a phase I study.

A phase I study to evaluate heparinization of tunnelled subclavian catheters (TSC) was conducted in 42 patients who each had a TSC for chemotherapy. They were enrolled in the study from August 1994 to December 1995. The inclusion criteria were: age 18-70, no general anticoagulant treatment, TSC used only for chemotherapy, informed consent. Heparinization was performed at the end of each cycle and then at increasing intervals: 11, 13, 15, 17, 19, and 21 days. A 21-day interval was intended to mimic the suppression of heparinization between cycles. Heparinization was performed with a 250 IU/ml heparin solution. Anti-Xa activity was studied before each heparinization. For each interval, at least 5 patients were followed up for two cycles. If no blockages were present progression to the next step was authorized. If one blockage was observed 5 additional patients were required to have their TSCs heparinized after the same interval. Two blockages (block) after the same interval meant that the previous interval was recorded as the longest tolerable. There were no blocks with the 11-day interval (6 patients), 1 block after 13 days (10 patients), 1 block after 15 days (10 patients), and no blocks after 17 days (5 patients), 19 days (6 patients), or 21 days (5 patients). The median anti-Xa activity (curative rate 0.2-0.6) was, respectively 11 days 6.74; 13 days 5.47; 15 days 4.71; 17 days 3.61; 19 days 3.67; 21 days 5.10 (NS). Heparinization between two cycles of chemotherapy is unnecessary. A high level of heparin activity persisted constantly inside the catheter lumen through the 3-week observation period.

Adenocarcinoma↗

PubMed1998

Oral complications during treatment of malignant diseases in childhood: effects of tooth brushing.

During anticancer treatment, oral lesions considerably aggravate the child's clinical condition and increase the risk of infection. This prospective study evaluated the incidence, nature and chronology of oral complications arising during the first 6 weeks of chemotherapy. 131 children were included in this study, and their oral and dental health evaluated on enrolment. Each child was observed once a week, for 6 weeks. Fifty-two per cent (68/131) of the children presented with at least one oral lesion. Two oral healthcare regimens (with or without tooth brushing) were evaluated. Tooth brushing significantly reduced the number of children affected. Standardised multicentre studies should permit the definition of oral care regimens which would eliminate pain and reduce the risk of infection in children hospitalised for cancer.

Adolescent↗

PubMed1998

[Oculomotor paralysis and head trauma].

Few studies have dealt with post-trauma ocular motor palsy. We analyzed 31 personal cases and reviewed the literature, focusing on pathogenesis. We emphasize the importance of a complete radiological examination including magnetic resonance imaging when the CT-scan does not provide a satisfactory correlation between anatomic findings and clinical presentation. Systematic detection, early management and regular follow-up is mandatory.

Adolescent↗

PubMed1997

[Temporo-sphenoidal giant cell tumors, apropos of a case].

The authors report an extremely rare case: a bony giant cell tumour in the temporo-sphenoidal region presenting with hearing loss and vertigo. The main characteristics of these tumours are given, together with a literature review. This is the 5th published case of this tumour in the temporo-sphenoidal region. The treatment of these tumours is essentially surgical, and the authors emphasise the use of Sekhar's approach.

Adult↗

PubMed1996

[Clinical presentation and prognosis of brain tumors].

The diagnosis of a cerebral tumor is received as dramatic by the patient or his family on account of the fonctional and symbolic idea of the brain and the perspectives of neurosurgical and psychological disabilities. Nowadays it is simplified because actual techniques of imagery are atraumatic and reliable. So the first signs are not to be undervaluated. Prognostic depends of identifiable factors. They lead the choice of therapy and help the medical doctor for the treatment follow-up and for answering to the patient's life questions.

Adult↗

PubMed1996

Glial cell line-derived neurotrophic factor (GDNF) gene expression in the human brain: a post mortem in situ hybridization study with special reference to Parkinson's disease.

Glial cell line-derived neurotrophic factor (GDNF) is a potent neurotrophic factor for dopaminergic neurons. Since dopaminergic neurons degenerate in Parkinson's disease, this factor is a potential therapeutical tool that may save dopaminergic neurons during the pathological process. Moreover, a reduced GDNF expression may be involved in the pathophysiology of the disease. In this study, we tested whether altered GDNF production may participate in the mechanism of cell death in this disease. GDNF gene expression was analyzed by in situ hybridization using riboprobes corresponding to a sequence of the exon 2 human GDNF gene. Experiments were performed on tissue sections of the mesencephalon and the striatum from 8 patients with Parkinson's disease and 6 control subjects matched for age at death and for post mortem delay. No labelling was observed in either group of patients. This absence of detectable expression could not be attributed to methodological problems as a positive staining was observed using the same probes for sections of astroglioma biopsies from human adults and for sections of a newborn infant brain obtained at post-mortem. These data suggest that GDNF is probably expressed at a very low level in the adult human brain and its involvement in the pathophysiology of Parkinson's disease remains to be demonstrated. GDNF may represent a powerful new therapeutic agent for Parkinson's disease, however.

Aged↗

PubMed1996

Use of a biodegradable elastin-fibrin material, Neuroplast, as a dural substitute.

Since the new Neuroplast biomaterial is now commonly used in several domains of restorative and curative surgery, its preliminary evaluation as a dura mater substitute in the rabbit was performed and is described herein. Whereas the importance of prosthesis thickness was implicated and solved (0.2 rather than 1.0 mm), both macroscopic examination and histological studies revealed for the neotissue an effective patency, a good continuity and especially no or almost no adherence at all. As Neuroplast is now available for use everywhere in humans, this material is being developed in several fields of neurosurgery.

Animals↗

PubMed1996

Psammomatous melanotic schwannoma of a spinal nerve root. Relationship with the Carney complex.

A 36-year-old man had an oval, black, extradural tumor partly removed from the left C4 spinal root, with total removal 4 months later. In both specimens, most tumor cells were spindle-shaped. A few cells were large, epithelioid-like, with a prominent nucleolus. Mitoses were rarely seen. Many tumor cells contained coarse or fine granules of a brown pigment. Such cells were immunopositive for S-100 protein and HMB-45. Additionally, psammoma bodies were numerous in certain areas, indicating a diagnosis of psammomatous melanotic schwannoma (PMS). Periumbilical spotty pigmentation was found in the patient and in six of his siblings and their mother. The search for cardiac myxoma and endocrine overactivity was negative in the patient. Features of Carney's complex must be sought in a patient with PMS and in their primary relatives. So far, more than 150 patients and seven families with Carney's complex have been reported.

Adult↗

PubMed1995

Fractionated radiation therapy in the treatment of intracranial meningiomas: local control, functional efficacy, and tolerance in 91 patients.

PURPOSE: To evaluate efficacy and tolerance of external fractionated radiation therapy (RT) in the treatment of intracranial meningiomas. METHODS AND MATERIALS: From January 1981 to September 1993, 91 patients with intracranial meningiomas were treated with fractionated RT. Indications were as follows: (a) incomplete surgical resection, 29 patients; (b) tumor recurrences without considering the amount of the second resection, if performed, 14 patients; (c) completely excised angioblastic, aggressive benign, and anaplastic tumors, 8 patients; (d) medically inoperable and basilar tumors where operation would involve considerable danger or permanent neurological damage, 44 patients. Most patients were irradiated with 6 to 9 MV photon beams. A three- to four-field technique with coned-down portals was used. Doses were calculated on the 95% isodose and were given 5 days a week for a median total dose of 52 Gy (1.80 Gy/fraction). RESULTS: Median follow-up from radiation therapy was 40 months. Acute tolerance was excellent, but there were six late delayed injuries. Tumor recurrences occurred in six cases. Six patients died from their tumor or RT complications, 19 from nontumoral reasons. Three, 5- and 10-year survival rates were 82, 71, and 40%, respectively. The most significant prognostic factor was age: 5-year survival rate was 86% for patients less than 65 years and 37% for patients more than 65. However, there were no differences in recurrence-free survival rates between patients younger than 65 and the oldest ones. Of 60 symptomatic patients with neurological deficits, 43 had neurological improvement (72%), beginning in some cases within 15 to 20 days after starting RT. CONCLUSION: These results reassess the role of fractionated RT in the treatment of meningiomas, and stress on its efficacy, especially on cranial nerves palsies, without severe toxicity in most cases.

Adolescent↗