How-to-do-it: Setup of neurophysiological monitoring with MEP/SEP during thoracoabdominal aneurysm repair

Objectives: The video exemplifies our experience with the intraoperative neurophysiological adjustment technique of electrodes controlling the spinal cord perfusion during the thoracoabdominal aortic aneurysm repair of a 63-year-old patient. Material and Methods: Intraoperative monitoring is performed by motor-evoked myogenic potentials after transcranial electrical stimulation (tcMEP) and somatosensory-evoked potentials (SSEP). Concerning the tcMEPs, the stimulating subdermal needle electrodes are placed at C3 and C4 according to the 10–20 system for EEG-recordings. TcMEPs are recorded from the anterior tibial and gastrocnemius muscles on both sides. The SSEP electrodes are located lateral and caudal to 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 method of the electrodes is both easily to apprehend and without further difficulties to perform. Additionally it provides a quick assessment and interpretation of the spinal cord perfusion. The identification of external sources of disturbance during the monitoring (e. g. insufficient impedance, unfavourable electrode-positioning, and technical interferences caused by medical equipment) enables the supervisor to draw a clear line between normal and abnormal neurological responses. Conclusions: The tcMEPs and SSEPs allow an adequate, indirect intraoperative assessment of the spinal cord perfusion and enable the surgeon to diagnose an impending ischaemia and act according to the new situation. This measurement serves as a means for the surgical team to integrate the neurological aspect of the thoracoabdominal aneurysm repair into the surgical focus.