Monitoring of muscle motor evoked potentials during cerebral aneurysm surgery: intraoperative changes and postoperative outcome

Abstract

Data in this study demonstrated that MMEPs are a useful means of intraoperative neurophysiological monitoring of motor pathway integrity and predicting postoperative motor status. The intraoperative loss of MMEPs reliably predicts both severe and permanent postoperative motor deficits.

The Incidence of Unacceptable Movement with Motor Evoked Potentials During Craniotomy for Aneurysm Clipping

“…Use of MEP monitoring in intracranial neurovascular surgery is often avoided because of concern for unacceptable movement in a nonparalyzed patient (26,29). It was previously reported that in approximately 6%e10% of patients undergoing transcranial MEP monitoring without neuromuscular blockade, recording was impossible during microsurgery because of electrostimulation-induced muscle contraction or failure to elicit a baseline motor response from muscles that were intact in the preoperative period (20,27).…”

“…It has even been suggested that with MEP monitoring the incidence of motor deficits after aneurysm clipping could be reduced to at least the level obtained with aneurysm coiling procedures (31). However, MEPs in intracranial neurovascular surgery have often not been employed because of concern for unacceptable movement in a nonparalyzed patient anesthetized with a limited amount, or in the absence, of inhaled volatile anesthetic (26,29). A survey sent to all members of the American Society of Neurophysiological Monitoring and the American Clinical Neurophysiology Society revealed that only two centers used MEPs during craniotomies for intracranial lesions (from -OBJECTIVE: To review the experience at a single institution with motor evoked potential (MEP) monitoring during intracranial aneurysm surgery to determine the incidence of unacceptable movement.…”

“…Transcranial motor evoked potential (MEP) monitoring that is added to standard somatosensory evoked potential (SEP) and electroencephalogram monitoring may increase the sensitivity of electrophysiologic monitoring during aneurysm surgery and improve outcome (5,29). Because MEPs and SEPs provide complementary information about the patient's nervous system, one of these modalities alone might be less likely to reflect the patient's true postoperative neurologic status (30).…”

Motor-evoked potentials (MEP) during brainstem surgery to preserve corticospinal function

“…In intramedullary spinal cord tumor surgery, total MEP loss was shown to be a valid warning criterion. [5] For supratentorial surgery, a 50% reduction of MEP response amplitude has been proposed as a warning criterion [10,11,17].…”

“…Although MEPs are well established for the early detection of impending motor deficit during surgery of cranial procedures [10,11,14,17,19] and the spinal cord [1,5,15,16], for brainstem surgery a warning criterion has not yet become generally accepted.…”