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EEG-fMRI in modalità continua su pazienti affetti da epilessia parziale e focolaio irritativo a onde lente all'EGG
No full textIntroduzione. Le epilessie di interesse chirurgico necessitano di essere studiate con tecniche che
permettano di distinguere il focolaio epilettogeno da quello irritativo, poiché solo il primo è di
interesse chirurgico nelle forme farmaco-resistenti. Una di queste nuove tecniche di studio è la coregistrazione
EEG-fMRI, fino ad oggi applicata a pazienti con un focolaio irritativo con attività a
punta. Solo pochi studi (Laufs 2006, Avesani 2008, Manganotti 2008) hanno preso in
considerazione il focolaio a onde lente.
Scopo. Lo studio intende verificare se, in pazienti con epilessia parziale e con EEG di routine
indicativo di focolaio intercritico a onde lente senza punte, la coregistrazione EEG-fMRI riesce a
localizzare il corrispondente focolaio epilettogeno, fornendo così utili informazioni sulla sorgente
della manifestazione critica.
Materiali e metodi. Sedici pazienti con epilessia parziale e con EEG standard indicativo di focolaio
irritativo a onde lente ad alta frequenza (almeno due eventi irritativi per minuto) sono stati
sottoposti a EEG-fMRI. I dati EEG sono stati continuamente registrati per 24 minuti (4 sessioni
concatenate) da 32 elettrodi, mentre le scansioni di fMRI venivano simultaneamente acquisite con
uno scanner di RMN da 1.5 T. I dati EEG sono stati esaminati off-line, dopo le sessioni di
registrazione e dopo la rimozione dell’artefatto da campo magnetico sul tracciato EEG. Abbiamo
posto in confronto i cambiamenti di segnale indotti dalle variazioni dell’emoglobina ridotta
(paramagnetica) al passaggio dei due stati di attivazione e di riposo (ovvero confrontando la
differenza di emoglobina voxel per voxel tra i volumi con EEG privo di focalità e EEG irritativo).
Risultati. In 15 pazienti su 16, alla presenza di una chiara focalità all’EEG, la co-registrazione
EEG-fMRI ha dimostrato una significativa attivazione nella corrispondente area cerebrale. Nei
pazienti affetti da epilessia lesionale, l’area epilettogenica (già nota) corrispondeva ai siti di
attivazione emodinamica.
Conclusioni. Anche nei pazienti affetti da epilessia parziale con focalità a onde lente all’EEG, la
co-registrazione EEG-fMRI può visualizzare una correlata attivazione emodinamica, concorrendo
così a fornire utili informazioni nello studio pre-chirurgico del paziente affetto da epilessia farmacoresistente.Introduction.
Epilepsy of surgical interest needs to be studied with techniques distinguishing epileptogenic vs
irritative areas, because only the first has a surgical interest. One of these new techniques is EEGfMRI,
so now applied to patients with a spiked irritative focus. Only few studies (Laufs 2006,
Avesani 2008, Manganotti 2008) considered a slow wave irritative focus.
Purpose: To verify whether in patients with partial epilepsy and routine electroencephalogram
(EEG) showing focal interictal slow-wave discharges without spikes combined EEG-functional
magnetic resonance imaging (fMRI) would localize the corresponding epileptogenic focus, thus
providing reliable information on the epileptic source.
Methods: 16 patients with partial epileptic seizures whose routine scalp EEG recordings on
presentation showed frequent focal interictal slow-wave activity (almost 2 IEDs/min) underwent
EEG-fMRI. EEG data were continuously recorded for 24 min (four concatenated sessions) from 32
scalp electrodes, while fMRI scans were simultaneously acquired with a 1.5-Tesla magnetic
resonance imaging (MRI) scanner. After recording sessions and MRI artefact removal, EEG data
were analyzed offline. We compared blood oxygen level-dependent (BOLD) signal changes on
fMRI with EEG recordings obtained at rest and during activation (with and without focal interictal
slow-wave discharges).
Results: In 15/16 patients, when the EEG tracing showed the onset of focal slow-wave discharges
on a few lateralized electrodes, BOLD-fMRI activation in the corresponding brain area significantly
increased. We detected significant concordance between focal EEG interictal slow-wave discharges
and focal BOLD activation on fMRI. In patients with lesional epilepsy, the epileptogenic area
corresponded to the sites of increased focal BOLD signal.
Conclusions: Even in patients with partial epilepsy whose standard EEGs show focal interictal
slow-wave discharges without spikes, EEG-fMRI can visualize related focal BOLD activation thus
providing useful information for pre-surgical planning
Chapter 20: Neuroimaging of epilepsy: EEG-fMRI in the presurgical evaluation of focal epilepsy.
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EEG-fMRI Evaluation of Patients with Mesial Temporal Lobe Sclerosis
No full textThis preliminary study sought more information on blood oxygen level dependent (BOLD) activation, especially contralateral temporal/extratemporal spread, during continuous EEG-fMRI recordings in four patients with mesial temporal sclerosis (MTS). In two patients, EEG showed unilateral focal activity during the EEG-fMRI session concordant with the interictal focus previously identified with standard and video-poly EEG. In the other two patients EEG demonstrated a contralateral diffusion of the irritative focus. In the third patient (with the most drug-resistant form and also extratemporal clinical signs), there was an extratemporal diffusion over frontal regions, ipsilateral to the irritative focus. fMRI analysis confirmed a single activation in the mesial temporal region in two patients whose EEG showed unilateral focal activity, while it demonstrated a bilateral activation in the mesial temporal regions in the other two patients. In the third patient, fMRI demonstrated an activation in the supplementary motxor area. This study confirms the most significant activation with a high firing rate of the irritative focus, but also suggests the importance of using new techniques (such as EEG-fMRI to examine cerebral blood flow) to identify the controlateral limbic activation, and any other extratemporal activations, possible causes of drug resistance in MTS that may require a more precise pre-surgical evaluation with invasive techniques
Effects of intravenous antidepressant drugs on the excitability of human motor cortex: a study with paired magnetic stimulation on depressed patients
No full textThe effect of various drugs was investigated by using transcranial magnetic stimulation (TMS) both in healthy subjects and patients, and the results indicated an influence of antidepressant drugs (ADs) on motor excitability
Effects of intravenous antidepressant drugs on the excitability of human motor cortex: a study with paired magnetic stimulation on depressed patients.
No full textBACKGROUND: The effect of various drugs was investigated by using transcranial magnetic stimulation (TMS) both in healthy subjects and patients, and the results indicated an influence of antidepressant drugs (ADs) on motor excitability. OBJECTIVE: The aim of our study was to analyze the effects of two ADs, the tricyclic (TCA) clomipramine and the serotoninergic antidepressant (SSRI) citalopram on the motor cortex excitability in major depressed patients with TMS. METHODS: Thirty affected subjects were placed into three groups: two received an intravenous dose of 25 mg clomipramine or 40 mg citalopram, and one received an injection of a placebo. Motor cortex excitability was studied by single and paired TMS before and after 3.5, 8, and 24 hours from administration of the drugs and placebo. Motor cortical excitability was measured using different TMS parameters: resting motor threshold (RMT), motor-evoked potential (MEP) amplitude, intracortical inhibition (ICI), and intracortical facilitation (ICF). RESULTS: The results indicated a temporary but significant increase of RMT and ICI and a decrease of ICF after the administration of both drugs, with a longer inhibition for the clomipramine rather than the citalopram. MEP amplitude was not significantly affected by the antidepressant injections. CONCLUSIONS: Our findings highlight that a single intravenous dose of clomipramine or citalopram exerts a significant but transitory suppression of motor cortex excitability in depressed patients. TMS represents a useful research tool in assessing the effects of motor cortical excitability of drugs used in the treatment of mental disorders
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
f-MRI in epilepsy with spike and wave activity evoked by eye closure: Different bold activation in a patient with idiopathic partial epilepsy with occipital spikes and a control group
No full textSUMMARY – We performed functional magnetic resonance imaging (fMRI) in a 30-year-old man
with idiopathic partial epilepsy with occipital spikes whose scalp EEG activity was characterized
by persistent epileptiform discharges on eye closure, ceasing upon eye opening. We compared BOLD
activation in the patient and in a control group of three normal volunteers. f-MRI showed that occipital
cortex and frontal areas were activated in relation to eye movement in normal subjects during
eye opening but not during eye closing. While persistent interictal spike and wave activity was
present over the posterior and anterior scalp in the patient upon eye closing, f-MRI showed bilateral
activation of the parietal and temporal regions. This fMRI study documents the activation of posterior
and temporal areas related to continuous intercritical spikes evoked by eye closure, which are
diffuse over the scalp. This activation was absent in the control group during eye closure
Corticospinal excitability in human subjects during nonrapid eye movement sleep: Single and paired-pulse transcranial magnetic stimulation study
No full textThe mechanisms responsible for changes in brain function during normal sleep are poorly understood. In this study, we aimed to investigate the effects of sleep on human corticospinal excitability by estimating resting motor threshold (RMT), and latency and amplitude of motor-evoked potentials (MEPs) after delivering transcranial magnetic stimulation (TMS) in ten healthy subjects. We also aimed to study short-interval intracortical inhibition (SICI) during sleep with paired-pulse TMS (pp-TMS). Ten healthy volunteers were studied. They were monitored immediately before, during and after a 3-h sleep (from 1 p.m. to 4 p.m., immediately after the mid-day meal). EEG was continuously recorded during sleep and the various sleep stages were identified off line. Every 10 min, subjects received ten single stimuli (to estimate RMT, MEP latency and amplitude) and six paired stimuli (to estimate SICI). MEP amplitude decreased and latency and RMT increased during the various sleep stages and returned to baseline values on awakening. Post hoc comparisons showed a significant difference in pp-TMS MEP amplitudes between the sleep and all the other conditions. The changes in TMS evoked variables during the different sleep stages indicate that during nonrapid eye movement sleep, cortical pyramidal neuron excitability (as measured by RMT, MEP latency and amplitude) progressively diminishes and the efficiency of the intracortical GABA-ergic network (as assessed by three pp-TMS) increases. On awakening, these sleep-induced changes in corticospinal excitability return rapidly to values observed during wakefulness
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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