gms | German Medical Science

The primary objective of intraoperative neurophysiological monitoring during surgery is to avoid permanent neurological injury resulting from surgical manipulation. To achieve this objective, somatosensory (SEP) and motor evoked potentials (MEP) are used in neurosurgery as standard technique. This study was conducted to provide evidence for the accurate detection of the integrity of spinal cord pathways by combined SEP and MEP monitoring during surgery.

A retrospective analysis was performed on data from 76 patients with combined SEP and MEP monitoring during surgery. Repetitive transcranial electric or magnetic motor cortex stimulation were used to elicit MEP. Stimulation of tibial and median nerve was performed to record SEP.

In most patients, no significant MEP and SEP changes were recorded. In three patients, SEP monitoring was unchanged during surgery, whereas MEP demonstrated significant changes. In case 1, MEP were abolished without intraoperative recovery. The patient experienced a transient motor deficit. In case 2, MEP amplitude decreased, but returned to baseline value during surgery. Postoperatively the patient neurological status was unchanged. In case 3, MEP amplitudes also declined requiring higher intensity stimuli. However, amplitudes did not regain baseline value. There was no change in postoperative clinical status.

Out data suggest that combined MEP and SEP monitoring is mandatory to detect impairment of the functional integrity of spinal cord pathways during surgery. On the other hand, intraoperative monitoring is still feasible, if one of both methods is not applicable.