Neurophysiologisches Monitoring des Nervus facialis bei Operationen an Vestibularisschwannomen: Der aktuelle Stand

Zusammenfassung

Hintergrund Nach Operationen an Vestibularisschwannomen gehören funktionelle Defizite des Nervus facialis zu den bedeutendsten Komplikationen. Mit Hilfe des intraoperativen neurophysiologischen Monitorings (IONM) sollen diese möglichst verhindert werden.

Fragestellung Welche Methoden zur Intraoperativen Funktionsüberwachung sind aktuell in Gebrauch, welche Ziele können damit sinnvoll verfolgt werden und welche Schwachpunkte bedürfen einer weiteren wissenschaftlichen Aufarbeitung?

Material und Methoden Auswertung und Zusammenfassung der Literatur, Diskussion der vorhandenen Methoden und ihrer Fähigkeiten, die gesteckten Ziele zu erreichen.

Ergebnisse Aus dem IONM abgeleitete Methoden des sogenannten „Mappings“ sollen den Nervus Facialis intraoperativ sicher identifizieren. IONM soll potenziell schädigende Ereignisse anzeigen und eine Einschätzung über den zu erwartenden postoperativen Funktionszustand des Nervs erlauben. Derzeit verwendet werden die elektrische Direktstimulation, das freilaufende EMG, Evozierte Potenziale des Nervus Facialis (MEP) und das prozessierte EMG. Vor allem in der Ergebnisprognostik haben alle vorhandenen Methoden deutliche Schwächen.

Schlussfolgerungen Das „Mapping“ der Nerven im OP-Situs kann mittels der elektrischen Direktstimulation gut realisiert werden. Nervenschädigungen während der Präparation können mit den anderen Methoden des IONM entweder in Echtzeit (freilaufendes EMG; prozessiertes EMG) oder nahezu in Echtzeit (MEP) angezeigt werden. Die Vorhersage des postoperativen, funktionellen Ergebnisses wird derzeit bei allen verfügbaren Methoden durch falsch positive Untersuchungsergebnisse mit konsekutiv niedrigem positiv prädiktivem Wert belastet.

Abstract

Background Functional deficit of the facial nerve is an important complication after vestibular schwannoma surgery and supposed to be prevented by IONM.

Problem Which IONM methods are in use, what are their strengths and their weak points?

Material and methods Review and summary of the literature.

Results Mapping is derived from IONM techniques and is used to identify the facial nerve during surgery. IONM itself aims at detection of dangerous events in relation to facial nerve function, on the one hand, and prognostic estimation of damage done, on the other. Currently used techniques are direct electrical stimulation, free-running EMG, motor evoked potentials of the facial nerve (MEP) and processed EMG.

Conclusions Mapping of the facial nerve is feasible and reliable. Damage to the nerve may be detected by IONM either in real-time (free-running EMG; processed EMG) or nearly in real-time (MEP). The prognostic value of all methods is limited by false positive monitoring results.

Schlüsselwörter

IONM - Nervus Facialis - Intraoperatives Monitoring - Vestibularisschwannom - Facialisparese - Elektromyogramm

Key words

IONM - facial nerve - intraoperative monitoring - vestibular schwannoma - facial palsy - electromyogram

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