Subtraction ictal SPECT co-registered to MRI (SISCOM) in Sturge-Weber syndrome.
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Adult↗
Biomedical subjects
I J Namer
Publications and source records attributed to I J Namer.
Detection of late epilepsy by the texture analysis of MR brain images in the lithium-pilocarpine rat model.
The aim of the study was to detect by texture analysis non easily visible anomalies of magnetic resonance (MR) images of piriform and entorhinal cortices relevant to the lithium-pilocarpine (Li-Pilo) model of temporal lobe epilepsy in rats. Status epilepticus was induced by Li-Pilo in twenty male rats 21 day-old. T(2)-weighted MR images of their brain, were obtained before injection of Li-Pilo and one day after status epilepticus. An hyperintense signal was found in the piriform and entorhinal cortices of six rats, which developed chronic epilepsy after a latent period of one to three months. Among the 14 other rats which displayed images similar to those obtained before injection, four remained healthy but 10 rats developed late epileptic symptoms, raising the problem of hidden cortical damage which may be too subtle to be detected by classic MRI examination. A numeric treatment of digital images was then undertaken by texture analysis, to derive image information from a purely computational point of view. The combined texture and discriminant analyses based on pixels pattern anomalies, selected 3 texture parameters derived from co-occurrence matrix which characterized structural abnormalities relevant to the hyperintense signal, not only in the modified images of 6 rats but also in images of 10 rats with apparently non modified images. These three texture's parameters allowed to classify the twenty rats of our experiment as follows: sixteen epileptic rats were effectively classified with cortical lesions, two non epileptic were correctly classified with healthy cortex, but two healthy rats were not correctly classified. This misclassification is discussed on the basis of the time dependence of the onset of seizure in the Li-Pilo model. These promising results suggest to apply this method to MRI examinations for an improvement of the early diagnostic of human epilepsy.
Animals↗
Contribution of SISCOM imaging in the presurgical evaluation of temporal lobe epilepsy related to dysembryoplastic neuroepithelial tumors.
PURPOSE: Dysembryoplastic neuroepithelial tumors (DNTs) are a group of glioneuronal supratentorial and intracortical lesions often associated with the early onset of intractable and crippling partial seizures. They are characterized by their location, multinodular architecture, and heterogeneous cell composition, with a specific glioneuronal element in the specific form. Foci of cortical dysplasia may be associated with the tumoral lesion, and identifying the presence and the extent of cortical dysplasia is not always easy on magnetic resonance images (MRIs). The purpose of this article is to evaluate, retrospectively, the usefulness of ictal single-photon emission computed tomography (SPECT) imaging to assess the presence and the extent of cortical dysplasia associated with DNTs in nine patients with intractable temporal lobe epilepsy related to histopathologically confirmed DNTs. METHODS: The results of the subtraction of ictal and interictal SPECT coregistered to MRI (SISCOM) were compared with the results of the examinations of pathological material after surgery. RESULTS: SISCOM showed a strongly hyperperfused area corresponding anatomically to electroclinical abnormalities and to the location of DNTs on MRI. A circumscribed hyperperfusion was present in DNTs without cortical dysplasia, limited to the location of the tumor on MRI. In cases of associated cortical dysplasia, a widespread hyperperfusion including areas corresponding to normal perilesional regions on MRI was found. CONCLUSIONS: SISCOM, used among presurgical investigations, contributes to detecting cortical dysplasia associated with DNTs. Concordance between the symptomatogenic zone (defined from the medical history and electroclinical data), MRI scans, SISCOM pattern, and complete resection of the epileptic zone was predictive of a good postsurgical outcome.
Adolescent↗
Existence of contralateral abnormalities revealed by texture analysis in unilateral intractable hippocampal epilepsy.
We selected 23 patients with unilateral temporal lobe epilepsy characterized by ipsilateral hippocampal sclerosis and an apparently normal contralateral hippocampus on MR imaging. Images were acquired on a 0.28 T MR scanner using a conventional Carr-Purcell Meiboom Gill sequence in all patients and in 9 healthy subjects. Texture analysis was applied to axial MR images of the first and tenth echoes. Texture analysis detects macroscopic lesions and microscopic abnormalities that can not be observed visually. The presence of texture differences in the between normal (controls) and sclerotic hippocampi was ascertained by statistical discriminant analysis. The apparently normal contralateral hippocampi can be classified into three categories in terms of texture: 4 apparently healthy, 8 similar to sclerosis, and 11 different from either healthy or sclerosis. These findings are related to a certain degree of hippocampal alteration, which further investigation might help better characterize.
Adult↗
Language functional neuro-imaging changes following focal left thalamic infarction.
The involvement of the left thalamus in language function has been largely demonstrated through the effects of thalamic lesion and/or stimulation upon language. However, the pathophysiological mechanisms underlying thalamic aphasias remain a matter of debate. We report here on changes in the pattern of brain activity in auditory word processing, verb generation and visual lexical decision in a patient who sustained left thalamic infarct following the surgery of intractable mesio-temporal epilepsy with left hippocampal sclerosis. To some extent, our findings exemplify the way the left thalamus brings on line the cortical networks involved in language processing, suggested in the term 'selective engagement'.
Aphasia↗
Antibody directed against mannan of the Mycobacterium tuberculosis cell envelope provokes blood-brain barrier breakdown.
Previous studies demonstrated that blood-brain barrier (BBB) breakdown observed at the cerebral level during experimental allergic encephalomyelitis (EAE) arises from the presence of Mycobacterium tuberculosis in Freund's adjuvant and not only from the encephalitogenic antigens. The main objective of this study was to check if the mannan moiety of lipoarabinomannan present in the mycobacterial cell envelope is responsible for an immune response provoking a BBB breakdown. The results showed that: firstly, the complete Freund's adjuvant (CFA) contains a high release of polysaccharides; secondly, the rats immunized with the CFA present important serum concentration of anti-mannan antibody; and finally, a single 2-mg dose of anti-mannan antibody injected intravenously in naive rats provokes an immediate and reversible BBB breakdown. These results suggest that mannan arising from the solubilization of the mycobacterial cell wall in Freund's adjuvant induces a high production of anti-mannan antibody, which, in turn, provokes a BBB breakdown and possibly facilitates the induction of EAE.
Animals↗
Magnetic resonance imaging follow-up of progressive hippocampal changes in a mouse model of mesial temporal lobe epilepsy.
PURPOSE: Hippocampal sclerosis (HS) is the most frequent lesion found in mesial temporal lobe epilepsy (mTLE). MR imaging is considered to be the most sensitive and specific method to detect HS. Despite extensive studies performed on humans and except in a recent study, the morphologic pattern of HS is usually analyzed when the disease has already fully developed, thus not allowing any insight into the mapping of the progressive morphologic changes inducing the development of mTLE. We have recently characterized a model of mTLE that reproduces the unilateral pattern of HS, induced by intrahippocampal injection of low doses of kainate (KA) in mice. METHODS: In this study, we monitored the temporal evolution of the development of HS in this model of mTLE by using T2-weighted sequence, T2-relaxation time measurements, and T1-weighted spin-echo technique after injection of gadolinium, from 1 h to 120 days after KA injection. RESULTS: HS induced by intrahippocampal KA injection occurred in two phases. First, we observed a transient hyperintense T2-weighted signal in the cortex above the injected hippocampus, most likely indicative of vasogenic edema partly due to the neurotoxic effect of KA. The concomitant increase in the T2 signal in the injected hippocampus and ipsilateral amygdala likely reflects the phase of cytotoxic edema occurring probably in relation to the excitotoxic consequences of both KA and seizure activity. Second, from 15 days on, a persistent unilateral increased T2 signal was detected in the hippocampus, which most probably reflects gliosis. CONCLUSIONS: Our findings indicate that longitudinal follow-up would permit a better understanding of the mechanisms underlying the constitution of HS in humans and eventually development of prevention strategies.
Animals↗
Distinct patterns of active and non-active plaques using texture analysis on brain NMR images in multiple sclerosis patients: preliminary results.
The benefits of texture analysis of magnetic resonance images have been assessed in multiple sclerosis (MS) patients. Out of thirty-two lesions identified in eight MS patients, nine were considered active, judging from their gadolinium uptake. Texture analysis allowed to obtain forty-two characterizing parameters for each lesion. Using discriminant analysis as a statistical method allowed to classify the lesions into two groups: active or non-active. An attempt to classify their level of activity by using only co-occurrence matrices was unsuccessful. Alternately, the same type of analysis performed on runlength analysis criteria allowed the accurate classification of 88% of active lesions and 96% of non-active lesions. Using incremental discriminate analysis can reduce the number of useful parameters. This method showed that among the 42 parameters, 8 only were highly significant and permitted an accurate classification. Five of these parameters are runlength parameters, and three others are more directly related to the global distribution. The main interest of runlength parameters is that they allowed to demonstrate that the lesion structure was different in active and non-active plaques. This preliminary work suggests that using texture analysis could be of interest in the follow-up of MS patients because it provides an opportunity to identify active lesions without frequent gadolinium injections.
Adult↗
Combined measurements of hippocampal N-acetyl-aspartate and T2 relaxation time in the evaluation of mesial temporal lobe epilepsy: correlation with clinical severity and memory performances.
PURPOSE: In this study we tried to find a correlation between the clinical severity and memory performances, by comparing proton magnetic resonance (MR) spectroscopy and T2 relaxation time measurements in the hippocampi, in a homogeneous group of 27 patients with unilateral mesial temporal lobe epilepsy with ipsilateral hippocampal sclerosis on MR imaging, with a view to answer the following questions: (a) how sensitive is this approach for the assessment of the apparently normal contralateral hippocampus, (b) do the results relate to the clinical severity, and (c) does it allow evaluation of the degree of hippocampal dysfunction. METHODS: Volume-selective proton MR spectroscopy of the head of both hippocampi was performed at 3 T, by using the PRESS sequence, with an echo time of 135 ms, to estimate NAA/(Cho + Cr) ratios. The relaxation times were measured at 0.28 T, by using a conventional Carr-Purcell-Meiboom-Gill sequence, with a repetition time of 2,000 ms, an echo time of 15 ms, and 48 echoes. RESULTS: The combination of NAA/(Cho + Cr) ratio and T2 relaxation time values was allowed to classify contralateral hippocampus abnormalities in two groups: first, decreased NAA/(Cho + Cr) ratio with strongly increased T2 relaxation time values corresponding to abnormalities observed in sclerotic ipsilateral hippocampi; and second, decreased NAA/(Cho + Cr) ratio with normal or slightly increased T2 relaxation time values. Whereas the NAA/(Cho + Cr) ratio or T2 relaxation time value alone was not correlated with memory performances, their association shows that left hippocampal injury evaluated both by NAA and T2 relaxation time measurements was clearly correlated with verbal memory scores, and right hippocampal injury, with visual memory scores. On the other hand, the maximal seizure frequency reported by the patients was correlated with ipsilateral NAA/(Cho + Cr) ratio and T2 relaxation time values but not with contralateral results. CONCLUSIONS: We showed that the combination of NAA and T2 relaxation time measurements can be used to examine the degree of ipsi- and contralateral hippocampal dysfunction or injuries and their relations with memory performances in the presurgical evaluation of patients.
Adult↗
NMR studies in demyelinating and non-demyelinating experimental allergic encephalomyelitis. An approach involving a dehydration procedure.
The spinal cords of rats, involved as part of two distinct and reproducible experimental allergic encephalomyelitis animal models, presenting inflammatory white matter lesions with and without demyelination, were studied in vitro by NMR, before and after a dehydration procedure, in order to characterize demyelination. All the parameters of the T1 and T2 relaxation times were determined, as well as the initial proportion of the very quickly decaying component of the free induction decay, and the magnetization transfer ratio. The relaxation decays were fitted with the discrete and Contin methods. Magnetization transfer ratio measurements permitted first to evaluate the magnetization transfer at the apex, and secondly to decompose the post-irradiation curves into two components: a gaussian and a lorentzian line, with their relative proportions and widths. The results presented in this study clearly demonstrate that it is not possible to evidence demyelination in fresh spinal cord preparations by NMR. However, the dehydration procedure, which was introduced with the aim of reducing the amount of free water in our samples, seems sufficient to enable the detection of demyelination from the T2 relaxation spectra and magnetization transfer data. As a conclusion, we think that the NMR properties of water protons allow to achieve tissue characterization on condition that the parameters concerning free water and its exchanges are eliminated.
Animals↗
Magnetic resonance imaging of PLP-induced experimental allergic encephalomyelitis in Lewis rats.
An in vivo magnetic resonance (MR) imaging study was performed on experimental allergic encephalomyelitis (EAE) induced in Lewis rats through proteolipid protein (PLP). PLP was solubilized in water or in an aqueous solution of 1% 10-tridecyl ether (TDE), a non-ionic detergent used in membrane protein research. All 16 rats immunized with 500 microg of TDE-solubilized PLP developed clinical signs and MR abnormalities fully comparable to those observed in MBP-induced EAE. Total paraplegia was observed in 12.5% of rats, mild or moderate paraparesis in 68.8% of rats and tail paralysis in the remaining 18.7% of rats. Whereas only 37.5% of the eight rats immunized with 500 microg of water-solubilized PLP developed minor clinical signs (tail weakness or paralysis). Our observations confirm that the difficulties encountered when trying to induce EAE by means of PLP arise from the highly hydrophobic nature of this protein. Accordingly, if a reproducible model is to be developed, it seems more judicious to use non-ionic detergents in both the extraction and solubilization phases of PLP preparation, this would allow maximal solubilization of the protein while avoiding aggregates, which may otherwise form during either of the PLP preparation.
Animals↗
Contribution of T2 relaxation time mapping in the evaluation of cryptogenic temporal lobe epilepsy.
In this study we compared the results of visual analysis of MR imaging with T2 relaxation time mapping of the mesial structures in a group of 97 patients with cryptogenic temporal lobe epilepsy. All patients underwent a clinical neurological examination, neuropsychological investigation, prolonged video-EEG monitoring, SPECT imaging, MR imaging, and T2 relaxation time mapping. T2 relaxation times were estimated with a Carr-Purcell-Meiboom-Gill pulse sequence with 48 echoes (15 to 720 ms). The mean T2 relaxation time value was 118.5 +/- 2 ms in the hippocampi and 120.3 +/- 1.9 ms in the amygdala of 21 healthy subjects used as controls. T2 relaxation mapping revealed mesial temporal sclerosis in 91.8% of the patients (often involving both the hippocampus and the amygdala) and evidenced bilateral involvement in 44.6% of the patients against 72.2 and 6.2%, respectively, for MR imaging. The ipsilateral and contralateral hippocampal T2 relaxation time values did significantly correlate with seizure frequency and the contralateral hippocampal T2 relaxation time value with the duration of epilepsy. In conclusion, this quantitative method is highly sensitive for the detection of mesial temporal sclerosis and permits a better evaluation of the apparently normal contralateral mesial structures.
Adolescent↗
Registration of MR/MR and MR/SPECT brain images by fast stochastic optimization of robust voxel similarity measures.
This paper describes a robust, fully automated algorithm to register intrasubject 3D single and multimodal images of the human brain. The proposed technique accounts for the major limitations of the existing voxel similarity-based methods: sensitivity of the registration to local minima of the similarity function and inability to cope with gross dissimilarities in the two images to be registered. Local minima are avoided by the implementation of a stochastic iterative optimization technique (fast simulated annealing). In addition, robust estimation is applied to reject outliers in case the images show significant differences (due to lesion evolution, incomplete acquisition, non-Gaussian noise, etc.). In order to evaluate the performance of this technique, 2D and 3D MR and SPECT human brain images were artificially rotated, translated, and corrupted by noise. A test object was acquired under different angles and positions for evaluating the accuracy of the registration. The approach has also been validated on real multiple sclerosis MR images of the same patient taken at different times. Furthermore, robust MR/SPECT image registration has permitted the representation of functional features for patients with partially complex seizures. The fast simulated annealing algorithm combined with robust estimation yields registration errors that are less than 1 degree in rotation and less than 1 voxel in translation (image dimensions of 128(3)). It compares favorably with other standard voxel similarity-based approaches.
Algorithms↗
Data-driven curvilinear reconstructions of 3D MR images: application to cryptogenic extratemporal epilepsy.
This paper presents a data-driven method for the reconstruction and visualisation of curvilinear slices from three-dimensional (3D) magnetic resonance (MR) scans of the head. Visualisation of curvilinear slices, rather than standard planar slices, produces symmetrical views of the cortex and allows small abnormalities to be detected by comparing the two hemispheres of the brain. In our method, the surface defined by the upper half of the brain is used as a reference shape for curvilinear reconstructions. The brain is first segmented from the 3D scan using a 3D region growing method associated to an unsupervised threshold selection technique. The upper half of the segmented brain is then extracted and fitted by a deformable surface model. This surface is finally interactively moved by the operator in the 3D scan, to visualise the desired curvilinear slice, which is projected on the screen as a two-dimensional image. We show an application of this visualisation technique to the localisation of cerebral epileptogenic lesions. The procedure has proven efficient and handy in clinical use.
Algorithms↗
Reduction of traumatic brain injury-induced cerebral oedema by a free radical scavenger.
Oxygen derived free radicals have been proposed to be in part responsible for the cerebral oedema resulting from head injury. In the present study the effects of free radical suppression with MDL 74,180 (2,3-dihydro-2,2,4,6,7-pentamethyl-3-(4-methylpiperazino)-methyl-1 - benzofuran-5-ol dihydrochloride), an alpha-tocopherol analogue free radical scavenger, on the development of cerebral oedema resulting from head injury has been assessed. Fluid percussion head injury in rats caused a regional oedema 48 h after injury. Infusion of MDL 74,180 for 2 h after the injury significantly attenuated oedema development in a dose-related manner. Using magnetic resonance imaging, cerebral oedema development was monitored in head injured mice. Oedema was apparent 4 h after head injury and was greatest in the vicinity of the olfactory bulb and surrounding the ventricles. Treatment with MDL 74,180 (1-10 micrograms/kg intravenously, administered 3-5 min after the injury) significantly reduced the oedema development. MDL 74,180 is a potential treatment for the oedema caused as a result of head injury.
Animals↗
Biological assessment and MRI monitoring of the therapeutic efficacy of a monoclonal anti-T CD4 antibody in multiple sclerosis patients.
An initial group of 21 patients plus a second group of 14 patients with active multiple sclerosis (MS) (18 progressive and 17 relapsing-remitting forms) were treated with a murine monoclonal anti-T CD4/BF5 antibody as part of a phase I open trial. Tolerance was relatively good: minor general side-effects occurred in 22 patients only upon the first mAb infusion. One year later, functional disability was stabilised in only six of the 35 patients and after 2 years in two patients only (among 21). One year after treatment, nine of the 17 relapsing-remitting patients were relapse-free. CD4 counts decreased dramatically 2 h after treatment. These counts were back to baseline counts at 3 months. A transient increase was found in IL-6 and TNF alpha levels 2 h after treatment, which probably accounts for the observed side effects. Cell adhesion molecule levels were not modified. Serial MRI scans were performed in the second group of 14 patients. In all of these patients, lesion modifications were observed in the three scans performed prior to treatment. Yet, no changes in the lesions were noted on the MRI scans performed over the following 3 months. These findings demonstrate the feasibility of this treatment insofar as it induced a marked CD4 lymphocyte depletion. However, it did not seem to stabilise the evolution of the disease--although one must be careful in drawing such conclusions in a phase I trial--or to curb the evolution of MRI-documented lesions.
Antibodies, Monoclonal↗
Localized T2 measurements using an OSIRIS-CPMG method. Application to measurements of blood oxygenation and transverse relaxation free of diffusion effect.
This work presents a new method allowing localized T2 measurements, based upon the OSIRIS scheme. A train of 180 degrees pulses is applied after the OSIRIS preparation cycle, recording directly the transverse magnetization decay. The method was verified for two nuclei, 1H and 19F, with phantoms and in vivo on rats. The accuracy of the T2 values is discussed, as well as possible applications of the OSIRIS-CPMG method to proton transverse spin relaxation measurements, free of diffusion effects, and to non-invasive in vivo blood oxygenation measurements, through the use of an emulsion of perfluorooctylbromide, a blood substitute containing fluorine.
Animals↗
Hyperbaric oxygen treatment in acute experimental allergic encephalomyelitis. Contribution of magnetic resonance imaging study.
Magnetic resonance imaging (MRI) has been performed to determine the efficacy of hyperbaric oxygen treatment (HBO) on experimental allergic encephalomyelitis (EAE) in Lewis rats. The animals were exposed for 2 x 3 h in a 24-h period at 2 ATA pure O2. Three HBO treatment protocols were used: a 10-day preventive treatment (beginning on the 1st day postimmunization), a 3-day preventive treatment (beginning on the 1st day postimmunization), and a 10-day symptomatic treatment (beginning on the 11th day postimmunization). Based on clinical and MRI observations, this study demonstrates: (i) that HBO treatment does not reduce the blood-brain barrier (BBB) disturbance and cerebral edema in EAE, (ii) that in an opposite way, it provokes reversible BBB breakdown, and (iii) that preventive HBO treatments results in modification of the course of EAE, possibly by immunosuppression effect during the initial sensitization step.
Animals↗