10. Intraoperative neurophysiological monitoring implementation during endovascular procedures in the central nervous system

Intraoperative monitoring (IOM) has been introduced in different types of surgical procedures since the 1980s. Nonetheless, its regular use during the daily clinical routine of the interventional neuroradiology unit has been achieved in only a few centers. The aim of this study is to report our experience after standardized IOM implementation during endovascular treatment of central nervous system vascular pathology. From November 2011 to May 2013, 14 patients (11 with brain and 3 with spinal cord pathology) and 21 procedures were monitored. Basic IOM methodologies were somatosensory (SEP) and motor evoked (MEP) potentials. Corticobulbar motor evoked potentials and flash-visual evoked potentials were recorded depending on the topography of the lesion. Intraarterial provocative tests (PT) with amobarbital and lidocaine were also performed. All patients except one were under total intravenous anaesthesia. Clinical outcome was assessed prospectively and correlated with IOM events. In 5/21 (24%) procedures, significant IOM events were detected. We observed temporary MEPs changes in 4 cases, recovered after interrupting embolization or performing corrective measures, without postoperative neurological deficits. In one case, persistent SEP and MEP deterioration were detected secondary to a frontal hematoma leading to mild sensory-motor deficit in the right upper extremity after the procedure (3 months mRankin Scale 2). Overall, 18 provocative tests were performed, 14 in brain and 4 in spinal cord pathology. They included 13 lidocaine and 5 amobarbital injections. Two positive results (11%) occurred after the injection of lidocaine (right MCA aneurysm and left frontal AVM). No false negative results were detected. The implementation of both IOM methodologies and PT during therapeutic interventional neuroradiology is feasible and may contribute to detect early neurological damage in time to prevent irreversible neurological deficits.