[Neurophysiologic monitoring in neurosurgical vascular operations: specific technical requirements and their conversion].

Several authors have presented evidence for a strict relation between regional cerebral blood flow and EEG. Therefore the EEG can serve as an adequate physiological parameter when monitoring cerebral function in the operating room. However, to exploit the inherent information as far as possible, both multichannel EEG and somatosensory evoked potentials should be recorded simultaneously. In the present article we describe a monitoring system which is capable to handle this task under the conditions of an operating room. In the first step some numerically simple algorithms are applied to detect gross artifacts. In the subsequent processing stage an analysis procedure is performed which is robust with respect to the remaining more subtile artifacts. In addition the raw signals are continually displayed on a monitor to allow for a visual evaluation of the EEG. The results of a trend analysis procedure are presented on the same graphical display by means of a compact topographical scheme. The system has been running under routine conditions for approximately two years now.