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Biomedical subjects

N Cochard

Publications and source records attributed to N Cochard.

8 recordsLinked to original sources
PubMed2002

[Use of auditory brain stem implant in a patient with bilateral vestibular schwannoma (type 2 neurofibromatosis].

Surgical technique and functional results of implantation of the acoustic implant of the brain stem (BS) are described for a 16-year-old patient with bilateral vestibular shvannoma (neurofibromatosis of type 2). Initially, a large (IV degree) tumor was removed from the left cerebellopontile angle using the translabyrinthine-transcochlear approach. The function of the facial nerve recovered completely. The BS implant was implanted a year later in the course of removing shvannoma from the right cerebellopontile angle using the above approach. The patient received 22-channel implant Nucleus-CI22M. Speech intelligibility improved by 90-100%. BS implantation is today the only effective method of reestablishment of acoustic sensations in patients with bilateral destruction of the acoustic nerves due to bilateral vestibular shvannoma.

Adolescent↗
PubMed2000

Steady state plasma levels of the enantiomers of trimipramine and of its metabolites in CYP2D6-, CYP2C19- and CYP3A4/5-phenotyped patients.

Steady state plasma concentrations of the (L)- and (D)-enantiomers of trimipramine (TRI), desmethyltrimipramine (DTRI), 2-hydroxytrimipramine (TRIOH) and 2-hydroxydesmethyl-trimipramine (DTRIOH) were measured in 27 patients receiving between 300 and 400 mg/day racemic TRI. The patients were phenotyped with dextromethorphan and mephenytoin, and the 8-hour urinary ratios of dextromethorphan/dextrorphan, dextromethorphan/3-methoxymorphinan, and (S)-mephenytoin/(R)mephenytoin were used as markers of cytochrome P-450IID6 (CYP2D6), CYP3A4/5 and CYP2C19 activities, respectively. One patient was a CYP2D6 and one was a CYP2C19 poor metabolizer. A stereoselectivity in the metabolism of TRI has been found, with a preferential N-demethylation of (D)-TRI and a preferential hydroxylation of (L)-TRI. CYP2D6 appears to be involved in the 2-hydroxylation of (L)-TRI, (L)DTRI and (D)-DTRI, but not of (D)-TRI, as significant correlations were measured between the dextromethorphan/dextrorphan ratios and the (L)-TRI/(L)-TRIOH (r = 0.45, p = 0.019), the (L)-DTRI/(L)-DTRIOH (r = 0.47, p = 0.014), and the (D)-DTRI/(D)-DTRIOH (r = 0.51, p = 0.006), but not with the (D)-TRI/(D)-TRIOH ratios (r = 0.29, NS). CYP2C19, but not CYP2D6, appears to be involved in the demethylation pathway, with a stereoselectivity toward the (D)-enantiomer of TRI, as a significant positive correlation was calculated between the mephenytoin (S)/(R) ratios and the concentrations to dose-to-weight ratios of (D)-TRI (r = 0.69, p = 0.00006). CYP3A4/5 appears to be involved in the metabolism of (L)-TRI to a presently not determined metabolite. The CYP2D6 poor metabolizer had the highest (L)-DTRI and (D)-DTRI concentrations to dose-to-weight ratios, and the CYP2C19 poor metabolizer had the highest (L)-TRI and (D)-TRI concentrations to dose-to-weight ratios of the group.

Adult↗
PubMed1998

Simultaneous determination of human plasma levels of citalopram, paroxetine, sertraline, and their metabolites by gas chromatography-mass spectrometry.

A gas chromatography-mass spectrometry method is presented which allows the simultaneous determination of the plasma concentrations of the selective serotonin reuptake inhibitors citalopram, paroxetine, sertraline, and their pharmacologically active N-demethylated metabolites (desmethylcitalopram, didesmethylcitalopram, and desmethylsertraline) after derivatization with the reagent N-methyl-bis(trifluoroacetamide). No interferences from endogenous compounds are observed following the extraction of plasma samples from six different human subjects. The standard curves are linear over a working range of 10-500 ng/mL for citalopram, 10-300 ng/mL for desmethylcitalopram, 5-60 ng/mL for didesmethylcitalopram, 20-400 ng/mL for sertraline and desmethylsertraline, and 10-200 ng/mL for paroxetine. Recoveries measured at three concentrations range from 81 to 118% for the tertiary amines (citalopram and the internal standard methylmaprotiline), 73 to 95% for the secondary amines (desmethylcitalopram, paroxetine and sertraline), and 39 to 66% for the primary amines (didesmethylcitalopram and desmethylsertraline). Intra- and interday coefficients of variation determined at three concentrations range from 3 to 11% for citalopram and its metabolites, 4 to 15% for paroxetine, and 5 to 13% for sertraline and desmethylsertraline. The limits of quantitation of the method are 2 ng/mL for citalopram and paroxetine, 1 ng/mL for sertraline, and 0.5 ng/mL for desmethylcitalopram, didesmethylcitalopram, and desmethylsertraline. No interferences are noted from 20 other psychotropic drugs. This sensitive and specific method can be used for single-dose pharmacokinetics. It is also useful for therapeutic drug monitoring of these three drugs and could possibly be adapted for the quantitation of the two other selective serotonin reuptake inhibitors on the market, namely fluoxetine and fluvoxamine.

1-Naphthylamine↗
PubMed1998

[Development of different linguistic systems in children with a cochlear implant].

The authors have studied a population of 21 pre-lingually deaf children equipped with a cochlear implant for at least 24 months. Their linguistic progression after implantation has been compared with the standard language development in normally hearing children, using a model published by Marie Therese Le Normand in 1996. 3 types of development can be distinguished: Profile 1 (shown by 9 children) in which language development after implantation is rapid and homogeneous: profile 2 (shown by 8 children), in which it is slower and more heterogeneous, with a longer pre-linguistic phase; Profile 3 (shown by 3 children) in which there are diverse problems with development. The authors then searched to establish the influence of the age at implantation and the mode of communication on this development.

Child↗
PubMed1997

Selection criteria for cochlear implants in children.

OBJECTIVE: To determine the selection criteria for cochlear implantation in children. SETTING: Hospital pediatric implant center. PATIENTS AND INTERVENTIONS: Selection of patients depends on medical evaluation, audiometric data, speech discrimination, communication skills, cognitive skills, and psychosocial factors. Patient selection is based on tonal audiometry, computed tomography, magnetic resonance imaging, and electrophysiologic tests. Side of implantation is chosen according to cochlear structure, duration of deafness, and dominant handedness. RESULTS: Ninety-eight cochlear implantations with the Nucleus multichannel implant have been performed at this center since 1990. CONCLUSION: The selection of children for cochlear implantation require close collaboration between the pediatric surgical team, the educational team, and the family.

Auditory Threshold↗
PubMed1991

[General principles of conception of cochlear implants].

Cochlear implants have greatly been developed on last ten years. Their diversity makes their use and choice more complex. The authors expose simply the physiopathology of the implanted auditory system and basic principles of cochlear implants. Cochlear implants are caracterised by the number of channels and electrodes (monochannel, multichannel), the strategy of encoding (analogiq, digital), the transmission of signal (per-cutaneous, electro-magnetic induction), the site of stimulation (extra or intra-cochlear), the signal wave (sinusoid, pulse), the diffusion of current (monopolar, bipolar).

Cochlear Implants↗