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C Adam

Publications and source records attributed to C Adam.

At least 55 records · Page 3Linked to original sources
PubMed2000

Spatio-temporal characterizations of non-linear changes in intracranial activities prior to human temporal lobe seizures.

Recent studies have shown that non-linear analysis of intracranial activities can detect a 'pre-ictal phase' preceding the epileptic seizure. Nevertheless, the dynamical nature of the underlying neuronal process and the spatial extension of this pre-ictal phase still remain unknown. In this paper, we address these aspects using a new non-linear measure of dynamic similarity between different parts of intracranial recordings of nine patients with medial temporal lobe epilepsy recorded during transitions to seizure. Our results confirm that non-linear changes in neuronal dynamics allow, in most cases (16 out of 17), a seizure anticipation several minutes in advance. Furthermore, we show that the spatial distribution of pre-ictal changes often involves an extended network projecting beyond the limits of the epileptogenic region. Finally, the pre-ictal phase could frequently (13 out of 17) be characterized with a marked shift toward slower frequencies in upper delta or theta frequency range.

Cerebral Cortex↗
PubMed2000

A quantitative study of gamma-band activity in human intracranial recordings triggered by visual stimuli.

This paper studies gamma-band responses from two implanted epileptic patients during a simple visual discrimination task. Our main aim was to ascertain, in a reliable manner, whether evoked (stimulus-locked) and induced (triggered by, but not locked to, stimuli) responses are present in intracranial recordings. For this purpose, we introduce new methods adapted to detect the presence of gamma responses at this level of recording, intermediary between EEG-scalp and unicellular responses. The analysis relies on a trial-by-trial time-frequency analysis and on the use of surrogate data for statistical testing. We report that visual stimulation reliably elicits evoked and induced responses in human intracranial recordings. Induced intracranial gamma activity is significantly present in short oscillatory bursts (a few cycles) following visual stimulation. These responses are highly variable from trial to trial, beginning after 200 ms and lasting up to 500 ms. In contrast, intracranial-evoked gamma responses concentrate around 100 ms latencies corresponding to evoked responses observed on the scalp. We discuss our results in relation to scalp gamma response in a similar protocol [Tallon-Baudry et al. (1996) J. Neurosci., 16, 4240-4249] and draw some conclusions for bridging the gap between gamma oscillations observed on the scalp surface and their possible cortical sources.

Adolescent↗
PubMed2000

Episodic memory in left temporal lobe epilepsy: a functional MRI study.

Left medial temporal lobe epilepsy (MTLE) is associated with verbal memory impairment usually related to hippocampal damage. We used functional MRI (fMRI) to investigate the patterns of functional activity in healthy volunteers and MTLE patients engaged in verbal episodic memory tasks to look for evidence of a reallocation of verbal memory in epileptic patients. fMRI data were collected from seven MTLE patients with left-sided hippocampal sclerosis and 10 healthy right-handed control subjects on a 3T scanner. Subjects were instructed to learn a list of 17 words (encoding) and then to recall them (retrieval) on successive trials. Healthy volunteers and patients both exhibited bilateral activation (right higher than left) of the parahippocampal gyrus during the retrieval. This effect was more marked in the control subjects. In contrast to the control subjects, patients exhibited consistent and extensive left prefrontal activations in all the memory tasks. These findings show that verbal memory tasks did not involve the same functional patterns in patients and healthy volunteers. This may be interpreted as a dysfunctional response due to the epilepsy and left hippocampal sclerosis, and could reflect the early onset and progressive course of the disease.

Adolescent↗
PubMed2000

[Cecal diverticulitis].

INTRODUCTION: Cecal diverticulitis is an important differential diagnosis to acute appendicitis. The diagnosis is often difficult to make and the therapeutic procedure is still a point of discussion. PATIENTS AND METHOD: Seven patients (24-77 years old) who underwent surgery for abdominal reasons were investigated retrospectively. RESULTS: Five patients who had not underwent appendectomy before were operated under the leading diagnosis of acute appendicitis. Despite further diagnostic measures, only in one case of the two patients who had already had an appendectomy before, the diagnosis cecal diverticulitis could be made preoperatively. DISCUSSION: Preoperative diagnostics, if conducted at all, only rarely lead to the diagnosis of cecal diverticulitis. In prolonged courses and in patients after appendectomy, laparoscopy can be of diagnostic and therapeutic value. If it is possible to diagnose cecal diverticulitis preoperatively, conservative treatment can be indicated. If the diagnosis is made intraoperatively and malignancy can be securely excluded, we recommend ileocecal resection, but not appendectomy and further conservative treatment. If a carcinoma can not be excluded definitively, a hemicolectomy must be performed.

Acute Disease↗
PubMed2000

A simulation approach to study planning for large-scale epidemiological surveys.

In study planning for large-scale epidemiological studies with multi-type examinations, important resource questions have to be answered, e.g. study horizons, personnel and other resources and cost estimates are needed. A simulation approach for scheduling that uses relevant parameters to simulate examination times gives simulation distributions that can be utilised to answer planning questions.

Adult↗
PubMed1999

Association of ipsilateral motor automatisms and contralateral dystonic posturing: a clinical feature differentiating medial from neocortical temporal lobe epilepsy.

BACKGROUND: Clinical features that may help to differentiate medial temporal lobe epilepsy (MTLE) from neocortical temporal lobe epilepsy (NTLE) are lacking. OBJECTIVE: To investigate the localizing and lateralizing value of the association of ipsilateral motor automatisms and contralateral dystonic posturing in patients with medically refractory temporal lobe epilepsy. PATIENTS AND METHODS: Videotapes of 60 patients with well-defined MTLE, NTLE, or both were reviewed to assess the presence and the localizing value of unilateral dystonic posturing associated with motor automatisms. RESULTS: Twenty-eight of the 60 patients exhibited unilateral dystonic posturing. This sign was observed in patients with MTLE and NTLE. It was mostly contralateral to the seizure focus in patients with MTLE and exclusively ipsilateral in patients with NTLE. Unilateral motor automatisms occurred in 26 of the 60 patients with MTLE or NTLE. It was predominantly ipsilateral to the seizure focus in patients with MTLE and exclusively contralateral in patients with NTLE. The association of ipsilateral motor automatisms and contralateral dystonic posturing was found in 14 patients with MTLE but in none of the patients with NTLE. Two patients who had medial and neocortical seizure onset also exhibited this clinical feature. This association was not significantly correlated with the postoperative outcome in patients with MTLE. CONCLUSIONS: The association of ipsilateral motor automatisms and contralateral dystonic posturing may help to differentiate MTLE from NTLE with a reliable lateralizing value. This clinical association may reflect a specific pattern in the spread of the ictal discharge.

Adult↗
PubMed1999

Quantitative determination of joint incongruity and pressure distribution during simulated gait and cartilage thickness in the human hip joint.

The objective of this study was to provide quantitative data on hip-joint incongruity and pressure during a simulated walking cycle and on articular-cartilage thickness in the same set of specimens. Using a casting technique in eight specimens of the human hip (age: 18-75 years), we determined the width of the joint space (incongruity) required at minimal load for contact at four phases of the gait cycle. The pressure distribution, measured with pressure-sensitive film, was determined at physiologic load magnitudes on the basis of in vivo measurements of hip-joint forces. Cartilage thickness was assessed with A-mode ultrasound. At minimal loading, the average maximum width of the joint space ranged from 1.1 to 1.5 mm in the acetabular roof, with the contact areas located ventro-superiorly and dorso-inferiorly throughout the gait cycle. At physiological loading, the width decreased and the contact areas covered the complete articular surface during midstance and heel-off but not during heel-strike or toe-off. The pressure distribution was inhomogeneous during all phases, with average maximum pressures of 7.7 +/- 1.95 MPa at midstance. The cartilage thickness varied considerably throughout the joint surfaces; maxima greater than 3 mm were found ventro-superiorly. These data can be used to generate and validate computer models to determine the load-sharing between the interstitial fluid and the solid proteoglycan-collagen matrix of articular cartilage, the latter being relevant for the initiation of mechanically induced cartilage degeneration.

Adolescent↗
PubMed1999

[Drug therapy of hyperkinetic diseases in adults].

Attention deficit hyperactivity disorder (ADHD) is often diagnosed in children. Some major studies proved that symptoms can persist until the patients are grown up and that the prevalence of adult ADHD is underestimated. The classification systems ICD-10 and DSM-IV allow a diagnosis for adults, they differ, however, from childhood regarding symptoms. The diagnostic procedure requires extensive exploration and information from parents and school. Diagnostic interview procedures and questionnaires for self and expert rating are available to date only for English speaking countries. Apart from counselling and psychotherapeutic intervention pharmacotherapy is a third option. Especially stimulants proved to be an efficient treatment. Alternatively tricyclic antidepressants can be considered, other agents play only a minor role. Clinical trials trying to evaluate the efficacy of different pharmacotherapeutic agents are lacking.

Adult↗
PubMed1999

[Interactions between the epileptic network and brain function: an approach by nonlinear analysis of intracranial EEG].

Recent advances in the non-linear dynamics analysis have made it possible to identify hidden recurrences in EEG signals that could be missed by more traditional linear techniques such as power spectrum or coherence analysis. This is particularly true for epileptic EEG recordings either in animals or in humans as epileptic phenomena are usually concomitant with the emergence a strong non-linear EEG behavior. Non-linear dynamical analysis techniques quantify the relations between EEG signals. The literature concerning the spatio-temporal characteristics of the epileptic processes during seizures and interictal periods is reviewed. Our attention has been mainly focused on the interdependences between brain structures or on the dynamical changes of one particular brain region during intracranial recordings. These data could explain in part the dysfunctioning of the cerebral cortex induced by epileptic activities and provide an insight into the spatio-temporal organization of the epileptic network. Futhermore, by tracking the time variation of non-linear indices, one can anticipate the occurrence of seizures in temporal lobe epilepsies. All this information could contribute to improve definitions of the epileptogenic zone in partial epilepsy and also open the way to preventive interventions.

Brain↗
PubMed1999

Source localization in refractory partial epilepsy.

In this paper, 51 patients with refractory complex partial seizures (CPS) and intracranial structural abnormalities demonstrated with optimum MR (space-occupying: n = 16; atrophic: n = 32; dysplastic: n = 3) were studied. Video-EEG monitoring showed CPS in all patients. In 13 patients, additional intracranial EEG monitoring demonstrated hippocampal seizure onset in 12 and medial occipital ictal onset in 1 patient. Interictal and ictal dipole modeling using a spherical head model and realistic electrode coordinates were performed. Spatiotemporal dipole mapping of interictal epileptic discharges revealed two distinct dipole patterns. Patients with lesions located in the medial temporal lobe (n = 41) and medial occipital lobe (n = 2) uniformly presented a dipole with an elevation of more than 15 degrees relative to the axial plane. Eight out of ten patients with extratemporal lesions and 1 patient with a pure neocortical temporal lesion had a less stable dipole with an elevation less than 15 degrees relative to the axial plane. Dipole modeling of epochs of early ictal discharges revealed a striking correspondence with the interictal findings in individual patients. Ictal dipole modeling identified the ictal onset zone correctly when compared with intracranial EEG recordings from bilateral hippocampal depth electrodes in patients with medial temporal seizure onset. Mapping of dipoles on MR images of individual patients facilitated clinical interpretation of the EEG data. Interictal and ictal dipole mapping provided additional and clinically relevant information and may obviate the need for intracranial EEG studies in some surgical candidates for refractory CPS.

Adolescent↗
PubMed1998

Kinetic mechanism of the inhibition of cathepsin G by alpha 1-antichymotrypsin and alpha 1-proteinase inhibitor.

Uncontrolled proteolysis due to cathepsin G (cat G) may cause severe pathological disorders. Cat G is inhibited by alpha 1-antichymotrypsin (ACT) and alpha 1-proteinase inhibitor (alpha 1PI), two members of the serpin superfamily of proteins. To see whether these two inhibitors play a physiological proteolysis-preventing function, we have made a detailed kinetic investigation of their reaction with cat G. The kinetics of inhibition of cat G in the presence of inhibitor and substrate evidenced a two-step inhibition mechanism: E + I EI EI. The cat G/ACT interaction is described by Ki = 6.2 x 10(-)8 M and k2 = 2.8 x 10(-)2 s-1, while the cat G/alpha 1PI association is governed by Ki = 8.1 x 10(-)7 M and k2 = 5.5 x 10(-)2 s-1. The reliability of these kinetic constants was checked using a number of experiments which all gave consistent results: (i) both EI complexes were found to be enzymatically inactive, (ii) the Ki values were determined directly using initial velocity experiments of cat G-catalyzed hydrolysis of substrate in the presence of inhibitor, (iii) the second-order rate constants k2/Ki were measured using second-order inhibition experiments in the absence of substrate, and (iv) the ratio of the two second-order rate constants was determined by measuring the partition of cat G between the two fluorescently labeled serpins. Since the plasma concentrations of ACT and alpha 1PI are much higher than their Ki values, cat G released from neutrophils will be fully taken up as rapidly forming EI complexes, that is, 70% with ACT and 30% with alpha 1PI. Both ACT and alpha 1PI are thus physiological cat G inhibitors whose inhibitory potential does not depend on the formation of the stable inhibitory species EI characteristic of serpins. Such an in vivo inhibition mechanism might take place with other serpin/proteinase systems.

Binding, Competitive↗
PubMed1998

Nonlinear interdependencies of EEG signals in human intracranially recorded temporal lobe seizures.

The degree of interdependence between intracranial EEG channels was investigated in four epileptic patients with complex partial seizures of mesial temporal lobe origin. With a new method to characterize nonlinear dynamical interdependence-the mutual nonlinear prediction-we demonstrated here a possibility to quantify, during epileptic seizures, the relationships between EEG signals of electrode contacts in the epileptogenic area. During the interictal period, the degree of nonlinear interdependences were very low or absent. In contrast, it was found that transient patterns of nonlinear interdependences emerge at the initial spread of the seizure, during essential parts of its development, and at seizure end, but the maintenance of these interactions are not observed throughout the seizure activity. These results suggest that the nonlinear associations plays an important role in epileptogenesis, and that the process of neuronal entrainment during seizure onset involves a transient interaction between a distributed network of neuronal aggregates, but the maintenance of this interaction is not required for sustained seizure activity. Furthermore, this technique can describe properly the spatio-temporal organisation of the seizures of medio-temporal lobe origin and could become a very useful tool to aid the localization of the epileptogenic regions at the origin of epileptic seizures and their pathways of propagation.

Algorithms↗
PubMed1998

Hippocampal developmental changes in patients with partial epilepsy: magnetic resonance imaging and clinical aspects.

Developmental disorders of the hippocampal formation (HF) have been described in epileptic syndromes associated with lissencephaly, but HF malformations can be found without widespread cortical changes. We report 19 patients with partial epilepsy and abnormal HF patterns on magnetic resonance imaging (MRI). The changes consisted of incomplete folding with abnormal medial location along the choroid fissure, globular shape and/or verticalization, and were observed in the following three contexts: (1) diffuse disorder of neuronal migration (n=1); (2) temporal lobe malformation (n=5), including heterotopia, abnormal gyration, and, in 2 cases, reduced HF volume; and (3) apparently isolated HF changes (n=13, bilateral in 3 cases). The clinical features were heterogeneous in terms of severity of epilepsy and, when the focus could be determined, in localization (temporal or extratemporal). In 4 patients with apparently isolated HF changes, MRI was suggestive of both abnormal development and hippocampal sclerosis. In these patients, presurgical investigation and postoperative results suggested multiple epileptogenic foci, involving the frontal lobes in 2 cases. One HF specimen was large enough for the observation of developmental abnormalities corresponding to the changes seen on MRI. HF changes in shape and/or position should be included among the structural abnormalities associated with partial epilepsies. They may represent the visible part of a more extensive or more distant disorder of brain development.

Adolescent↗
PubMed1998

The distribution of cartilage thickness in the knee-joints of old-aged individuals -- measurement by A-mode ultrasound.

OBJECTIVE: To provide data on the normal distribution of cartilage thickness in the knee joints of old-aged individuals. DESIGN: The accuracy and reproducibility of cartilage thickness measurements were evaluated with A-mode ultrasound, and the cartilage thickness distribution was examined throughout both knee joints of nine individuals aged between 62 and 94 yr. BACKGROUND: Data on the variation of cartilage thickness in the joint surfaces are relevant for the design of computer models of diathrodial joints and for surgical and arthroscopic procedures, particularly the calculation of cartilage material properties from indentation tests. METHODS: A 12.5 MHz A-mode ultrasound transducer was used, and after determining the accuracy and reproducibility of the system in comparison with CT arthrography and anatomical sections, the cartilage thickness was measured throughout the knee at 256 coordinate points. RESULTS: A-mode ultrasound yields results consistent with established methods. The cartilage thickness is distributed regularly in the knee-joint of older individuals. However, the absolute values are considerably lower than those previously reported for younger people, the mean (and maximal) thickness being 2.0 mm (3.3 mm) in the patella, 1.9 mm (3.3 mm) in the femur, and 1.9 mm (3.5 mm) in the tibia. CONCLUSION: If the results of computer models or surgical strategies are to be applied to the demographically important group of older individuals, the typical distribution of articular cartilage thickness in this group should be taken into consideration.

Journal Article↗
PubMed1998

Epileptic seizures can be anticipated by non-linear analysis.

Epileptic seizures are a principal brain dysfunction with important public health implications, as they affect 0.8% of humans. Many of these patients (20%) are resistant to treatment with drugs. The ability to anticipate the onset of seizures in such cases would permit clinical interventions. The view of chronic focal epilepsy now is that abnormally discharging neurons act as pacemakers to recruit and entrain other normal neurons by loss of inhibition and synchronization into a critical mass. Thus, preictal changes should be detectable during the stages of recruitment. Traditional signal analyses, such as the count of focal spike density, the frequency coherence or spectral analyses are not reliable predictors. Non-linear indicators may undergo consistent changes around seizure onset. Our objective was to follow the transition into seizure by reconstructing intracranial recordings in implanted patients as trajectories in a phase space and then introduce non-linear indicators to characterize them. These indicators take into account the extended spatio-temporal nature of the epileptic recruitment processes and the corresponding physiological events governed by short-term causalities in the time series. We demonstrate that in most cases (17 of 19), seizure onset could be anticipated well in advance (between 2-6 minutes beforehand), and that all subjects seemed to share a similar 'route' towards seizure.

Electrophysiology↗
PubMed1998

oPer1 is an early response gene under photoperiodic regulation in the ovine pars tuberalis.

Mammalian Per1 (or RIGUI) is a recently described putative clock gene that is expressed in the suprachiasmatic nucleus. It is also expressed in the pars tuberalis (PT) of the pituitary, where melatonin appears to drive its expression. This study examines the regulation of Per1 expression. In ovine PT cells, oPer1 is an early response gene transiently expressed after stimulation with forskolin, but melatonin has no independent effect on its expression. In sheep, PT tissue photoperiodic background influences the magnitude or timing of expression of oPer1 2 h after lights-on. These data demonstrate that oPer1 mRNA is elevated in the PT following the decline in night-time melatonin, and that the amplitude or timing of this elevation is dependent upon the duration of the nocturnal melatonin signal.

Animals↗
PubMed1998

The distribution of cartilage thickness within the joints of the lower limb of elderly individuals.

The objective of this study was to investigate the normal distribution of cartilage thickness in the major joints of the lower limb in elderly individuals. A 12.5 MHz ultrasound transducer was used to measure the cartilage thickness in the right and left hip, knee and ankle joint of 10 individuals aged between 62 and 99 y. Distribution patterns of cartilage thickness were derived by b-spline interpolation and the average distribution computed in each surface. The maximum cartilage thickness in the hip joint was 2.6 (+/-0.36) mm and the mean thickness 1.3 (+/-0.17) mm. The CV% (a measure of thickness inhomogeneity within the joint surface) was 32%. In the knee, the maximal and mean values were 3.8 (+/-0.46) mm and 1.9 mm (+/-0.24) mm, respectively (CV% = 34%), and in the ankle 1.7 (+/-0.25) mm and 1.0 (+/-0.16) mm (CV% = 32%). Systematic differences existed between both sides in the knee, the distal femur showing a significantly greater thickness on the right. While the mean and maximal thicknesses were systematically higher in the knee than in the hip, and in the hip higher than in the ankle (P < 0.05), there were no systematic differences in the thickness inhomogeneity of the 3 joints. Only the malleolus showed a somewhat more uniform thickness than the other joint surfaces. The variability between individuals was similar for all joints for mean thickness, but the interindividual variability of the maximal thickness values was highest in the knee and lowest in the ankle. Whereas the cartilage thickness distributions in the joints of the lower limb have been suggested to reflect the pressure distribution within the articular surface, the absolute thickness is proposed to be a function of dynamic loading (range of motion) during gait, rather than being a reflection of the static articular pressure.

Adaptation, Physiological↗