Ictal onset localization of epileptic seizures by magnetoencephalography

Tilz, Christian; Hummel, Cornélia; Kettenmann, Birgit; Stefan, Hermann

doi:10.1034/j.1600-0404.2002.02047.x

Cited by 54 publications

(45 citation statements)

References 21 publications

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“…Para aumentar la probabilidad de obtener registros MEG ictales se realizan pruebas en pacientes monitorizados con reducción de medicamentos anticonvulsivantes o mediante inducción farmacológi-ca 5,13 . Aún así, existen pocos estudios que describan la localización mediante MEG del inicio ictal 3,[5][6][7]12,14,15 , que es posible debido a que el artefacto de movimiento ocurre después del inicio de la crisis y habitualmente no interfiere en los datos utilizados en el cálculo de las fuentes de actividad magnética 5 .…”

Section: Discussionunclassified

“…Aún así, existen pocos estudios que describan la localización mediante MEG del inicio ictal 3,[5][6][7]12,14,15 , que es posible debido a que el artefacto de movimiento ocurre después del inicio de la crisis y habitualmente no interfiere en los datos utilizados en el cálculo de las fuentes de actividad magnética 5 . En nuestro caso se describe una crisis parcial registrada casualmente durante un registro MEG en un paciente mal controlado con dosis terapéuticas de anticonvulsivantes y con una alta frecuencia de crisis.…”

Section: Discussionunclassified

“…La localización del foco epiléptico mediante MEG ha sido confirmada con técnicas intraquirúrgicas tal como la estimulación eléctrica cortical 2 , la electrocorticografía (ECoG) 3 y la monitorización invasiva con electrodos subdurales 4 . A pesar de que la capacidad de localización espacial se reduce por los movimientos de la cabeza durante la crisis generalizadas, bajo condiciones especiales se pueden obtener del trazado MEG datos sobre el inicio ictal 5 . Así la localización basada en datos ictales claramente definidos es considerada como superior a la basada en datos intercríticos 6 y puede aportar información equivalente o superior a la de los registros EEG invasivos 7 .…”

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Crisis del lóbulo temporal registrada mediante magnetoencefalografía: caso clínico

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et al. 2004

Arq. Neuro-Psiquiatr.

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RESUMEN -La localización del inicio de las crisis es un factor importante para la evaluación prequirúrgica de la epilepsia. En este trabajo se describe la localización del inicio de una crisis registrada mediante magnetoencefalografía (MEG) en un niño de 12 años que presenta crisis parciales complejas farmacorresistentes. La RM muestra una lesión de 20mm de diámetro en el hipocampo izquierdo. EEG de superficie con ondas theta temporales izquierdas. Registro MEG interictal con punta-onda aislada posterior e inferior a la lesión de la RM. Registro MEG ictal con punta-onda (2 Hz). La localización de los dipolos indica el inicio de la crisis en la circunvolución temporal inferior en la misma localización que la actividad interictal MEG. Esta actividad ictal se propaga bilateralmente a áreas frontales. El registro corticográfico intraquirúrgico confirma los resultados de la localización interictal mediante MEG.PALABRAS CLAVE: electrocorticografía, inicio ictal, magnetoencefalografía, propagación. Temporal lobe seizure recorded by magnetoencephalography: case reportABSTRACT -Ictal onset localization is a important factor in presurgical evaluation of epilepsy. This paper describes the localization of a seizure onset recorded by magnetoencephalography (MEG) from a 12-year-old male patient who suffered from complex partial drug-resistant seizures. MRI revealed a 20mm diameter lesion located in left hippocampus. Scalp EEG showed left temporal theta waves. Interictal MEG registrations detected isolated spike-wave activity posterior and inferior to the MRI lesion. Ictal MEG showed continuous spike-wave activity (2 Hz). Dipole localization sited seizure onset in the inferior left temporal gyrus, the same localization of the interictal MEG activity. This ictal activity spreads bilaterally to frontal areas. Intrasurgical electrocorticography recording confirmed interictal MEG results.KEY WORDS: electrocorticography, magnetoencephalography, seizure onset, spreading.La magnetoencefalografía (MEG) en combinación con las imágenes de resonancia magnética (RM) proporciona excelente resolución espacial (milíme-tros) y temporal (milisegundos) en el diagnóstico de la epilepsia, aumentando la capacidad de localización anatómica de la actividad en episodios clíni-cos y subclínicos 1 . La localización del foco epiléptico mediante MEG ha sido confirmada con técnicas intraquirúrgicas tal como la estimulación eléctrica cortical 2 , la electrocorticografía (ECoG) 3 y la monitorización invasiva con electrodos subdurales 4 . A pesar de que la capacidad de localización espacial se reduce por los movimientos de la cabeza durante la crisis generalizadas, bajo condiciones especiales se pueden obtener del trazado MEG datos sobre el inicio ictal 5 . Así la localización basada en datos ictales claramente definidos es considerada como superior a la basada en datos intercríticos 6 y puede aportar información equivalente o superior a la de los registros EEG invasivos 7 . En este artículo se describe la localización anatómica del inicio de una crisis parc...

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Crisis del lóbulo temporal registrada mediante magnetoencefalografía: caso clínico

Amo

Santiuste

Maestú

et al. 2004

Arq. Neuro-Psiquiatr.

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“…Tilz et al also analyzed ictal MEG activities by SDM for epileptic patients that predominantly experienced mesial temporal lobe epilepsy (Tilz et al, 2002). This study determined the ictal onset area successfully in 6 out of 13 cases, while SDM was not available in the remaining patients.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, ictal activities contain valuable information (Tilz et al, 2002;Jongh et al, 2003), and a reliable confirmatory method for analyzing ictal MEG is needed.…”

Section: Introductionmentioning

confidence: 99%

The applications of time-frequency analyses to ictal magnetoencephalography in neocortical epilepsy

et al. 2010

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SummaryPurpose: Ictal magenetoencephalographic (MEG) discharges convey significant information about ictal onset and propagation, but there is no established method for analyzing ictal MEG. This study sought to clarify the usefulness of time-frequency analyses using short-time Fourier transform (STFT) for ictal onset and propagation of ictal MEG activity in patients with neocortical epilepsy.Methods: Four ictal MEG discharges in two patients with perirolandic epilepsy and one with frontal lobe epilepsy (FLE) were evaluated by time-frequency analyses using STFT.Prominent oscillation bands were collected manually and the magnitudes of those specific bands were superimposed on individual 3D-magnetic resonance images.Results: STFT showed specific rhythmic activities from alpha to beta bands at the magnetological onset in all four ictal MEG records. Those activities were located at the vicinity of interictal spike sources, as estimated by the single dipole method (SDM), and two of the four ictal rhythmic activities promptly propagated to ipsilateral or bilateral cerebral cortices. The patients with FLE and perirolandic epilepsy underwent frontal lobectomy and resection of primary motor area respectively including the origin of high-magnitude areas of a specific band indicated by STFT, and have been seizure free after the surgery.Conclusions: STFT for ictal MEG discharges readily demonstrated the ictal onset and propagation. These data were important for decisions on surgical procedure and extent of resection. Ictal MEG analyses using STFT could provide a powerful tool for noninvasive evaluation of ictal onset zone.

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Assessment of the Utility of Ictal Magnetoencephalography in the Localization of the Epileptic Seizure Onset Zone

et al. 2018

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IMPORTANCE Literature on ictal magnetoencephalography (MEG) in clinical practice and the relationship to other modalities is limited because of the brevity of routine studies. OBJECTIVE To investigate the utility and reliability of ictal MEG in the localization of the epileptogenic zone. DESIGN, SETTING, AND PARTICIPANTS A retrospective medical record review and prospective analysis of a novel ictal rhythm analysis method was conducted at a tertiary epilepsy center with a wide base of referrals for epilepsy surgery evaluation and included consecutive cases of patients who experienced epileptic seizures during routine MEG studies from March 2008 to February 2012. A total of 377 studies screened. Data were analyzed from November 2011 to October 2015. MAIN OUTCOMES AND MEASURES Presurgical workup and interictal and ictal MEG data were reviewed. The localizing value of using extended-source localization of a narrow band identified visually at onset was analyzed. RESULTS Of the 44 included patients, the mean (SD) age at the time of recording was 19.3 (14.9) years, and 25 (57%) were male. The mean duration of recording was 51.2 minutes. Seizures were provoked by known triggers in 3 patients and were spontaneous otherwise. Twenty-five patients (57%) had 1 seizure, 6 (14%) had 2, and 13 (30%) had 3 or more. Magnetoencephalography single equivalent current dipole analysis was possible in 29 patients (66%), of whom 8 (28%) had no clear interictal discharges. Sublobar concordance between ictal and interictal dipoles was seen in 18 of 21 patients (86%). Three patients (7%) showed clear ictal MEG patterns without electroencephalography changes. Ictal MEG dipoles correlated with the lobe of onset in 7 of 8 patients (88%) who underwent intracranial electroencephalography evaluations. Reasons for failure to identify ictal dipoles included diffuse or poor dipolar ictal patterns, no MEG changes, and movement artifact. Resection of areas containing a minimum-norm estimate of a narrow band at onset, not single equivalent current dipole, was associated with sustained seizure freedom. CONCLUSIONS AND SIGNIFICANCE Ictal MEG data can provide reliable localization, including in cases that are difficult to localize by other modalities. These findings support the use of extended-source localization for seizures recorded during MEG.

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Ictal onset localization of epileptic seizures by magnetoencephalography

Abstract: Ictal onset localization is feasible with MEG. Both interical and ictal MEG contribute valuable information to the presurgical assessment of epilepsy patients.

Cited by 54 publications

References 21 publications

Crisis del lóbulo temporal registrada mediante magnetoencefalografía: caso clínico

Crisis del lóbulo temporal registrada mediante magnetoencefalografía: caso clínico

The applications of time-frequency analyses to ictal magnetoencephalography in neocortical epilepsy

Assessment of the Utility of Ictal Magnetoencephalography in the Localization of the Epileptic Seizure Onset Zone

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