Abstract
Objectives: The article describes a procedure for the intraoperative neurophysiological placement
of electrodes to control the spinal cord function during thoracoabdominal aortic aneurysm
repair. Material and Methods: Intraoperative monitoring is performed by motor-evoked myogenic potentials after
transcranial electric stimulation (tcMEP) and somatosensory-evoked potentials (SSEP).
In tcMEP, the stimulating percutaneous needle electrodes are placed at C3 and C4 according
to the 10 - 20 system for EEG recordings. TcMEP are recorded from the anterior tibial
and gastrocnemius muscles on both sides. The SSEP electrodes are placed laterally
and caudally onto the malleolus medialis in order to stimulate the tibial nerve. The
stimulus is documented via electrodes attached to the scalp within the sensory cortex
region. Results: The application of the electrodes is both easy to learn and can be performed without
further difficulties. Once attached, the electrodes provide a quick assessment and
interpretation of spinal cord function. The identification of external sources of
disturbance during the monitoring (e. g. insufficient impedance, unfavourable electrode
positioning, and technical interference caused by medical equipment) enables the supervisor
to differentiate between normal and abnormal neurological responses. Conclusions: TcMEP and SSEP allow an adequate, direct, and reliable intraoperative assessment
of spinal cord function, enabling the surgeon to diagnose an impending ischaemia and
act accordingly. This measurement technique provides the surgical team with a means
of integrating neurological aspects during thoracoabdominal aneurysm repair.
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1 Presented at the Fourth Joint Meeting of The German, Austrian, and Swiss Society
for Thoracic and Cardiovascular Surgery, Hamburg, Germany, February 15 - 18, 2004
MD Ernst Weigang
Department of Cardiovascular Surgery, University Hospital Freiburg
Hugstetter Straße 55
79106 Freiburg
Germany
Phone: + 497612702881
Fax: + 49 76 12 70 23 68
Email: weigang@ch11.ukl.uni-freiburg.de