Zusammenfassung
Die Magnetenzephalographie (MEG) ist ein nicht-invasives Verfahren, das derzeit klinisch primär in der prächirurgischen Diagnostik eingesetzt wird. Gemessen werden hierbei durch neuronale Aktivität des Gehirns generierte magnetische Felder. Unter Zuhilfenahme theoretischer Grundannahmen wird hieraus die Quelle des Signals berechnet. Die Ergebnisse werden in die magnetresonanztomographisch gewonnenen Bilder der individuellen Gehirnanatomie eingetragen. Neuere Lokalisationsverfahren nutzen die individuelle Gehirnanatomie für die Quellenberechnung. Aus epilepsietypischen Signalen während spontaner Gehirnaktivität werden epileptogene Hirnareale lokalisiert, ergänzende evozierte Signale erlauben funktionell wichtige Regionen in räumlicher Relation zu epileptogenen Hirnarealen darzustellen und dies für eine funktionserhaltende Chirurgie zu nutzen. Im Vergleich zu Lokalisationsrechnungen aus EEG-Daten ergeben sich physikalisch Vor- und Nachteile, insgesamt bietet eine gleichzeitige Registrierung von MEG und EEG einen klaren Informationsgewinn. Bei invasiver elektrophysiologischer Diagnostik geben MEG-Daten richtungweisende Hinweise, teilweise kann eine invasive Diagnostik auch vermieden werden. Gemeinsam mit bildgebender Diagnostik, EEG-Monitoring und neuropsychologischer Untersuchung ist das MEG bei pharmakoresistenten Epilepsien heute ein wichtiger Bestandteil der Entscheidung für oder gegen ein chirurgisches Vorgehen sowie der Operationsplanung.
Abstract
Magnetoencephalography is a noninvasive procedure of primary clinical use in the presurgical evaluation of epilepsy patients. This technique records magnetic fields generated by spontaneous or evoked brain activity. The source of detected epileptic activity or averaged evoked activity is calculated and then overlaid onto the patient's individual brain architecture acquired by magnetic resonance imaging. Advanced techniques use the individual's own brain architecture for source localisation. The technique can also be used in neurosurgery to localise epileptic activity and important functional regions that need to be protected. Owing to the physical limitations of both methods, improved precision of source localisation can be achieved using MEG and EEG in comparison to EEG alone. MEG allows better planning or avoiding invasive diagnostics. Together with MRI, SPECT, EEG monitoring and neuropsychological testing, MEG plays an important role in decision making for surgery and in the tailoring of resections in drug-resistant epilepsy patients.
Key words
Epilepsy - MEG - presurgical diagnostic - focus localisation - MSI
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Prof. Dr. med. Dr. Prof. h. c. Hermann Stefan
Zentrum für Epilepsie Erlangen · Neurologische Universitätsklinik
Schwabachanlage 6
91054 Erlangen
eMail: hermann.stefan@neuro.imed.uni-erlangen.de
