gms | German Medical Science

61. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC) im Rahmen der Neurowoche 2010
Joint Meeting mit der Brasilianischen Gesellschaft für Neurochirurgie am 20. September 2010

Deutsche Gesellschaft für Neurochirurgie (DGNC) e. V.

21. - 25.09.2010, Mannheim

Real-time feedback on the integrity of the auditory system with new electrodes for proximal and distal nearfield recording of the AEP

Meeting Abstract

  • Steffen K. Rosahl - Klinik für Neurochirurgie, HELIOS Klinikum Erfurt, Germany
  • Nicole Creutzburg - Klinik für Neurochirurgie, HELIOS Klinikum Erfurt, Germany
  • Andreas Langbein - Klinik für Neurochirurgie, HELIOS Klinikum Erfurt, Germany
  • Susanne Fichte - Klinik für Neurochirurgie, HELIOS Klinikum Erfurt, Germany
  • Rüdiger Gerlach - Klinik für Neurochirurgie, HELIOS Klinikum Erfurt, Germany

Deutsche Gesellschaft für Neurochirurgie. 61. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC) im Rahmen der Neurowoche 2010. Mannheim, 21.-25.09.2010. Düsseldorf: German Medical Science GMS Publishing House; 2010. DocV1636

DOI: 10.3205/10dgnc109, URN: urn:nbn:de:0183-10dgnc1093

Veröffentlicht: 16. September 2010

© 2010 Rosahl et al.
Dieser Artikel ist ein Open Access-Artikel und steht unter den Creative Commons Lizenzbedingungen (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.de). Er darf vervielfältigt, verbreitet und öffentlich zugänglich gemacht werden, vorausgesetzt dass Autor und Quelle genannt werden.


Gliederung

Text

Objective: Due to the low signal-to-noise ratio, reliable analysis of the auditory evoked potential (AEP) often takes more than a minute. Near-field recordings with electrodes at the brainstem or in the vicinity of the cochlea have been proven to deliver conclusive potentials significantly faster. In cooperation with a biomedical company (Inomed Medizintechnik GmbH) we have developed two new electrodes with the aim to provide optimal anatomical interfaces for these electrodes in a microsurgical setting.

Methods: In 120 operations in the cerebellopontine angle (CPA) an electrode with a spring holder integrated in an insertion headphone has been placed at the tympanic membrane. Another miniature ball electrode with a diameter of 2mm and a straight shaft for handling by forceps was placed near the exit of the lateral recess of the fourth ventricle. Stimulation (13.1 acoustic clicks/sec), recording and averaging were accomplished with an electrophysiological system (ISIS, Inomed). Serial recordings of near-field potentials derived from the tympanon (t-AEP) and the brainstem (b-AEP) as well as far-field potentials from the scalp (s-AEP) were obtained with decreasing number of stimuli per average (2000 to 13). Latency and amplitude of wave I to V of the auditory response have been statistically analysed and compared between the three recording locations.

Results: Waves I and II of the AEP were best identified in recordings from electrodes located at the tympanic membrane, wave III-V in recordings from electrodes adjacent to the brainstem. While latencies of all five peaks were comparable in potentials derived from all electrode locations, amplitudes in nearfield recordings were three to twenty times larger than in s-AEP. Wave III of the h-AEP decreased significantly with increasing distance of the electrodes from the cochlear nucleus. With optimal electrode placement, a reliable analysis of the AEP was possible within 40 seconds in farfield, and within one second in nearfield recordings.

Conclusions: When hearing protection is prioritized in microsurgical operations in the CPA or in the internal auditory canal, nearfield recording with electrodes placed at the tympanic membrane (cochlea, cochlear nerve and their blood supply) and at the brainstem (cochlear nerve and brainstem auditory pathways) allow for conclusive and instantaneous feedback to the surgeon. Farfield recording from the scalp often merely documents damage to auditory structures without being helpful in modifying the course of surgery.