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L Tassi

Publications and source records attributed to L Tassi.

At least 37 records · Page 2Linked to original sources
PubMed1999

Presurgical strategies and epilepsy surgery in children: comparison of literature and personal experiences.

We reviewed 41 studies on epilepsy surgery in 1645 children and adolescents. The available data vary greatly from one paper to another, particularly as regards the age of the patients included, selection criteria, presurgical methodology, and the type of surgical intervention. Moreover, the surgical results are classified according to very different criteria. Our experience in Grenoble concerning 55 children (age < or = 16 years; postoperative follow-up > 18 months) is discussed in the light of data in the literature. The need is stressed for a consensus on the type of information that must be supplied by well-detailed studies on homogeneous groups of epilepsy surgery patients.

Adolescent↗
PubMed1999

Research perspectives in cortical dysplasia and associated epilepsies.

Our understanding of cortical alterations and related epilepsies has grown enormously in the last decade thanks to the explosion of basic information from laboratory neuroscience combined with advances in diagnostic tools, therapeutic approaches and surgical techniques. In the present paper, we briefly review the most important advances in these fields from the point of view of the clinician concerned with cortical malformation-related epilepsies. We propose that a highly effective way forward, expected not only to widen knowledge of the basic mechanisms of seizure generation, but also to improved the management of patients, would be to promote interdisciplinary research programmes on resected human cortex that involve neurosurgeons, neurologists and laboratory neuroscientists.

Cerebral Cortex↗
PubMed1998

Immunocytochemical investigation on dysplastic human tissue from epileptic patients.

In this report we describe three patients with developmental cortical abnormalities (generally referred as cortical dysplasia), revealed by MRI and operated on for intractable epilepsy. Tissue, removed for strictly therapeutic reasons, was defined as the epileptogenic area by electroclinical data and stereo EEG (SEEG) recordings. Tissue samples were processed initially for histology, and selected sections were further processed for immunocytochemical investigation in order to determine whether the region of cortical dysplasia was co-extensive with the epileptogenic area. In two patients with nodular heterotopia, disorganized aggregates of neurons (as revealed by neuronal cytoskeletal markers) were found within the nodules. Both pyramidal and local circuit neurons were present in the nodules, but no reactive gliosis was present. When nodules reached the cortex, the cortical layers were disrupted. In the patient with localized cortical dysplasia, a complete disorganization of the cortical lamination was found, and numerous neurons were also present in the white matter. Disoriented pyramidal neurons weakly labelled with cytoskeletal neuronal markers were also present but no cytomegalic cells were found. One of the patients with nodular heterotopia underwent only partial resection of both the 'epileptogenic area' and of the lesion; this patient still presents with seizures. The other patient with nodular heterotopia is seizure-free after a complete lesionectomy and excision of the epileptogenic area. The third patient, with focal cortical dysplasia, had two surgeries; she became seizure-free only after the excision of the epileptogenic area detected by SEEG recording. The present data suggest that the dysplastic areas identified by MRI should not be considered as the only place of origin of the ictal discharges. From the neuropathological point of view, the focal cortical dysplasia can be considered as a pure form of migrational disorder. However, the presence of large aggregates of neurons interspersed within the white matter, in the subcortical nodular heterotopia, suggests that a defect of neuronal migration could be associated with an exuberant production of neuroblasts and/or a disruption of mechanisms for naturally occurring cell death.

Cerebral Cortex↗
PubMed1996

Double-blind stereo-EEG and FDG PET study in severe partial epilepsies: are the electric and metabolic findings related?

The aim of this study was to evaluate, in 16 patients with drug-resistant partial epilepsy who were waiting to undergo surgical treatment, the relation between positron emission tomography (PET) findings with fluorine-18 fluorodeoxyglucose ([18F]FDG) in the interictal state and the different stereo-electroencephalography (SEEG) patterns that characterize: (a) the epileptogenic zone (low-voltage fast-activity discharge before or concurrent with ictal clinical symptoms), (b) the irritative zone (spikes, spikes and waves, isolated or grouped in short bursts) and (c) the lesional zone (continuous, sometimes polyrhythmic slow waves or continuous delta waves or very important voltage depression). SEEG was performed following an individually defined electrode implantation strategy. Whereas at least one area of hypometabolism was detected by visual interpretation of PET/[18F]FDG images in all the subjects in the study, there was poor agreement between PET/[18F]FDG quantitative measures of regional metabolism and SEEG findings. Normal metabolic rates were found in up to 62% of the areas with abnormal SEEG activity, independent of the type of electrical activity, i.e. epileptogenic, irritative, or lesional, while abnormal metabolic rates were found in up to 23% of the areas with normal SEEG activity. In conclusion, whereas the visual interpretation of interictal studies of glucose utilization in our series of drug-resistant epileptic patients consistently allowed the localization of an area of temporal hypometabolism, the quantitative and regional metabolic analysis demonstrated that such a finding is not specifically related to any of the three very different SEEG patterns (epileptogenic, irritative, lesional) or combinations thereof. These results complement those of previous interictal and ictal single-photon emission tomographic studies and of receptor studies in epileptics, suggesting functional and biochemical heterogeneity within the interictal hypoperfused/hypometabolic area in epileptic patients, and contribute to the debate on the use and interpretation of interictal PET/[18F]FDG studies in patients with medically refractory partial seizures.

Adult↗
PubMed1996

[Clinical characteristics critical for patients "recovered" after surgical treatment for temporal lobe epilepsy].

We analyse subjective and objective clinical manifestations, in 33 patients, among the 63 with "pure" temporal lobe epilepsy, for which we obtained at least a video-EEG or video-stereo-EEG ictal recording. We compared video-EEG recordings (103 seizures, mean 3.9; min 1, max. 23) and video-stereo-EEG recordings (77 seizures, mean 3.2; min 1, max. 13) with anamnestical data, in order to define the degree of reliability of patient and relatives reports. Overall agreement between anamnestic and video-recorded informations is excellent for subjective symptoms, and fairly good for objective signs. Subjective manifestations (reported in 90.1% of this group) are described in detail as well as the objective ones, these latter split divided into early and late manifestations.

Electroencephalography↗
PubMed1996

[EEG video recording].

We analyse EEG data from video-EEG recordings of 24 patients, selected among the 63 with "pure" temporal lobe epilepsy. As to interictal EEG features, 62.5% of patients show a less regular background activity on the affected side, in 70% of patients slow waves are either localised or lobar, while in 58% are spikes. Slow waves and spikes have the same well-defined localisation in 37.5% of the patients. Ictal recordings show an initial EEG pattern with high localising value (low-voltage fast activity, flattening or slow waves interruption) in 74/121 seizures (61%). Five out of these 24 patients were operated on without invasive recordings on the basis of ictal video-EEG data. In the 19 patients left, video-EEG ictal informations were used for the planning of the stereo-EEG exploration.

Electroencephalography↗
PubMed1996

[Surgical treatment of temporal lobe epilepsy: reality and prospectives].

This chapter provides a synthetic overview of the topics treated in this issue. Presurgical diagnostic procedures are schematically described and an analysis of surgical results is made in comparison with those obtained from other epilepsy surgery groups. Surgical complications linked both to invasive presurgical diagnostic procedures and therapeutic surgical acts are described. Finally, the creation of new epilepsy surgery centres is suggested on the basis of epidemiological data, which demonstrate the discrepancy among the patients operated on at present and those who could benefit from the surgical treatment.

Decision Making↗
PubMed1996

[Characteristics of the global population].

We analyse clinical characteristics, presurgical investigations, surgical procedures and outcome of 137 patients operated-on for a drug-resistant partial epilepsy, in Grenoble from January 1990 to December 1993. Moreover we present data of 63 patients suffering from a "pure" temporal lobe epilepsy selected using the following criteria: 1. surgery limited to temporal lobe structures 2. totally cured after surgery (Engel's class la).

Adolescent↗
PubMed1995

Role of the hypothalamic hamartoma in the genesis of gelastic fits (a video-stereo-EEG study).

Patients having a hypothalamic hamartoma frequently present epileptic attacks of laughter, and they later experience multiple additional seizure types, which invariably lead to a severe drug-resistant epilepsy. If this association is now well-known, relationships between the hypothalamic mass and the different types of seizures remain still mysterious. We report the case of a 16-year-old girl suffering from this peculiar epileptic picture, in whom a stereo-EEG study was performed, allowing us to record both the hamartoma, the neighboring hypothalamic structures, and other bilateral cortical areas. It showed that gelastic fits were strictly linked to ictal discharges which began and remained well localized in the hamartoma. Conversely, atonic seizures, which might result from a secondary epileptogenesis, admitted a widely extended bilateral frontal cortical origin, sparing the lesion, and slightly involving the posterior hypothalamus. Stereotactic radiosurgery of the hamartoma proved to be ineffective on both types of seizures, probably because of the too low dose of X-rays delivered (18 grays), as suggested by the absence of hypothalamic mass changes on MRI. Such data, never reported to our knowledge, seem able to contribute to a better understanding of this very peculiar epileptic syndrome, and perhaps to a better adapted therapeutic management.

Adolescent↗
PubMed1994

Phosphorylated HSP27 associates with the activation-dependent cytoskeleton in human platelets.

The three prominently phosphorylated 29-kD proteins in thrombin-activated human platelets are forms of the mammalian 27-kD heat-shock protein (HSP27). Though the function of HSP27 is not yet known, its phosphorylation is highly correlated with platelet secretion, and recent evidence in nonhematopoietic cells suggests that HSP27 regulates cortical actin filament assembly. Therefore, the subcellular location and phosphorylation state of HSP27 in resting and thrombin-activated platelets was studied. Platelets were fractionated by established Triton X-100 lysis methods followed by differential centrifugation to obtain the 14,000g fraction (low-speed cytoskeleton), 100,000g fraction (membrane skeleton), and the 100,000g supernatant fraction containing soluble cytosolic proteins. In resting platelets, HSP27 was present principally in the 100,000g supernatant fraction. Platelet activation with thrombin led to translocation of the majority of HSP27 to the low-speed cytoskeleton. This association was reversible by DNase, supporting the idea that HSP27 is a specific component of the actin cytoskeleton. Immunofluorescence studies similarly showed HSP27 is cytoplasmic in resting platelets but colocalizes with actin in fully spread, glass-activated platelets. Immunoprecipitation studies showed a small amount of constitutively phosphorylated HSP27 in resting platelets, but phosphorylation of the majority of HSP27 after thrombin activation. After activation, virtually all phosphorylated HSP27 was found in the low-speed cytoskeletal fraction, and each of the three phosphorylated forms of HSP27 were present by two-dimensional autoradiography. Furthermore, in time-course studies, the phosphorylation of HSP27 occurred just before localization of HSP27 to the low-speed pellet. These results show that, after platelet activation, HSP27 is first phosphorylated and then translocated from the cytoplasm to the assembling cytoskeleton, and suggest that HSP27 phosphorylation may be important to the binding of HSP27 to cytoskeletal components and the cytoskeletal rearrangements characteristic of platelet activation.

Actins↗
PubMed1994

Specific binding of the transglutaminase, platelet factor XIII, to HSP27.

HSP27, the unique mammalian low molecular weight heat shock protein, is prominently phosphorylated upon activation of a wide variety of cells and has a role in thermotolerance, growth events, and regulation of actin cytoskeletal dynamics. In thrombin-stimulated platelets, HSP27 is rapidly and prominently phosphorylated in a manner highly correlated with platelet secretion. However, the function of HSP27 and the identity of proteins that interact with HSP27 remain unknown. To identify specific HSP27-protein interactions, a recombinant fusion protein affinity reagent was constructed and used to identify proteins associating with HSP27 from human platelet lysates and erythroleukemia cells. An 84-kDa protein was found to associate specifically with HSP27 and was isolated from platelet lysates, resolved on preparative gels, transferred to nitrocellulose, subjected to enzymatic digestion, and microsequenced. A 20-amino acid sequence derived from p84 proved identical to amino acids 484-503 of the transglutaminase, platelet Factor XIII. Immunoblotting studies were used to confirm the binding of FXIII from fresh platelet lysates to the HSP27 fusion protein. FXIII also was shown to coprecipitate with HSP27 in immunoprecipitation studies and to colocalize with HSP27 in immunofluorescence studies of intact glass-activated platelets. The data thus demonstrate specific binding of platelet FXIII to HSP27 and suggest that HSP27 may participate in the cellular localization and/or enzymatic regulation of platelet FXIII.

Amino Acid Sequence↗
PubMed1994

Stereo-EEG of interictal and ictal electrical activity of a histologically proved heterotopic gray matter associated with partial epilepsy.

Magnetic resonance imaging allows the identification of heterotopic gray matter (HGM) in medically intractable partial epilepsies. The relationships between HGM and the epileptogenic zone remain, however, unclear. In a case of a temporo-parietal epilepsy studied by stereo-EEG, interictal and ictal electrical activity of a temporal HGM were recorded, showing: (1) an intralesional electrical activity, (2) the possible presence of asynchronous spikes, and (3) an early but never initial, or isolated, involvement during ictal discharges. This suggests that the presurgical and surgical management of HGM must be guided, as for other lesions, by the coherence existing between ictal clinical and electrical features, and anatomical data.

Adult↗
PubMed1994

Stereo-electroencephalography methodology: advantages and limits.

Since January 1990, 70 patients with medically intractable partial epilepsy underwent a stereo-EEG investigation in our center. We first described technical requirements, and gave an overview of the variety of the explored cerebral regions and implantation patterns realized, pointing out the low rate of morbidity (1.4%). The three-dimensional epileptogenic zone thus defined led to a tailored individualized surgical excision in 60 patients, while 9 are waiting for surgery and the remaining 1 has been excluded (1.4%). Conceptual and technical aspects of the stereo-EEG methodology were discussed in order to underline its peculiarities in the field of "depth recordings", and more generally among the broader group of "invasive" procedures.

Adolescent↗
PubMed1993

Intracerebral low frequency electrical stimulation: a new tool for the definition of the "epileptogenic area"?

Low Frequency (1 Hz) Electrical Stimulation (LFES) has been systematically utilized, during stereo-EEG investigations, in 24 consecutive young adult patients considered for surgical treatment of severe drug-resistant partial epilepsy. Ninety seizures (1-14/patient) identical to the spontaneous ones previously recorded were thus obtained in 19 patients (79%). LFES is less effective for induction of seizures than high frequency (50 Hz) stimulation (5.9% vs 22.9%), and it also provokes less "false positive" responses (1% vs 17%). The main "sensitive" structures to LFES are the hippocampus, the amygdala, and the hippocampal gyrus. However, seizures were also induced by stimulating the temporal lobe white matter, the temporal pole, and the temporal neocortex, as well as the orbito-frontal cortex (in the only patient with fronto-temporal epilepsy). The more frequently observed electrical pattern is a gradual increase of spikes and spikes and waves frequency, with or without occurrence of low voltage fast activity. The high percentage of early "subjective" manifestations similar to the spontaneous ones, the lack of major electrical artifact, and the good visualization of the spatial evolution of the induced-discharge, strongly suggest that LFES is of great help for defining the "epileptogenic area".

Adult↗