gms | German Medical Science

55. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie e. V. (DGNC)
1. Joint Meeting mit der Ungarischen Gesellschaft für Neurochirurgie

Deutsche Gesellschaft für Neurochirurgie (DGNC) e. V.

25. bis 28.04.2004, Köln

Impact of cerebral tumors and EEG–aberrations on the bispectral index in anaesthetized patients

Einfluss zerebraler Raumforderungen und damit verbundener EEG-Veränderungen auf den Bispektralindex von narkotisierten Patienten

Meeting Abstract

  • corresponding author Thomas Reithmeier - Klinik für Neurochirurgie, Universität zu Köln
  • E. Heuser - Klinik für Neurochirurgie, Universität zu Köln
  • C. Wedekind - Klinik für Neurochirurgie, Universität zu Köln
  • P. Pakos - Klinik für Neurochirurgie, Universität zu Köln
  • M. Löhr - Klinik für Neurochirurgie, Universität zu Köln
  • R.-I. Ernestus - Klinik für Neurochirurgie, Universität zu Köln

Deutsche Gesellschaft für Neurochirurgie. Ungarische Gesellschaft für Neurochirurgie. 55. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie e.V. (DGNC), 1. Joint Meeting mit der Ungarischen Gesellschaft für Neurochirurgie. Köln, 25.-28.04.2004. Düsseldorf, Köln: German Medical Science; 2004. DocP 07.69

The electronic version of this article is the complete one and can be found online at:

Published: April 23, 2004

© 2004 Reithmeier et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.




Bispectral analysis of the electroencephalogram (EEG) is a new method for monitoring depth of hypnosis in the intra- and post-operative period and can be used as a guide to the administration of intravenous anaesthetics. Experience with the bispectral index (BIS) in patients with brain tumors does not exist. The purpose of this study was to determine the influence of intracerebal mass lesions and EEG aberrations on the BIS value in narcotised patients.


After approval of the study protocol by the local ethics committee, 18 patients undergoing elective surgery for intracranial tumors gave informed consent and were included in this study. Patients with seizure, EEG modifying medications, or additional neurological diseases were excluded. Tumor location was frontal in 8 patients, temporal in 4 patients, occipital in 4 patients, parieto-frontal in 2 patients and temporo-frontal in 1 patient. Histological diagnosis included gliomas grade III and IV in 11 cases, brain metastasis in 5 cases, and low-grade gliomas in 2 cases. In the post-operative period, sedation of patients was continued with fentanyl and midazolam and depth of hypnosis was clinically assessed according to the Sedation-Agitation-Scale (SAS). Subsequently, we measured BIS values on both frontal sides, calculated the side-to-side BIS difference, and recorded a 12 channel EEG. Depth of hypnosis was correlated to BIS values, tumor location and EEG changes.


At the time of examination, all patients were unarousable (SAS-score = 1) and in 15 patients there was no qualitative side-to-side BIS difference. The BIS values (< 60) correlated in 8 of these 15 patients with a SAS-score of 1. In these 8 patients location of the tumor was frontal four times, temporal three times, and once occipital. EEG analysis was normal in 5 patients and showed predominately alpha/theta activity in the other 3 patients. In 7 patients, recorded BIS values were between 60 and 80 indicating conscious sedation (SAS-Score = 2-3). The tumors invaded the frontal area four times, were located two times occipital and one time temporal. Analysis of the 12 channel EEG in these patients revealed a focal aberration in 4 patients, a generalized alpha-rhythm in 2 patient and a generalized theta-rhythm in another patient. A qualitative side-to-side BIS difference was found in 3 patients (31, 24, 22) with frontal or parieto-frontal tumors and focal EEG aberrations.


The BIS value is mainly influenced by EEG aberrations after surgery of frontal or occipital lesions and is not a reliable indicator of the level of sedation in these cases.