Intraoperative facial motor evoked potential monitoring for pontine cavernous malformation resection

Abstract

OBJECTIVEThe aim of this study was to predict postoperative facial nerve function during pontine cavernous malformation surgery by monitoring facial motor evoked potentials (FMEPs).METHODSFrom 2008 to 2017, 10 patients with pontine cavernous malformations underwent total resection via the trans–fourth ventricle floor approach with FMEP monitoring. House-Brackmann grades and Karnofsky Performance Scale (KPS) scores were obtained pre- and postoperatively. The surgeries were performed using one of 2 safe entry zones into the brainstem: the suprafacial triangle and infrafacial triangle approaches. Six patients underwent the suprafacial triangle approach, and 4 patients underwent the infrafacial triangle approach. A cranial peg screw electrode was used to deliver electrical stimulation for FMEP by a train of 4 or 5 pulse anodal constant current stimulation. FMEP was recorded from needle electrodes on the ipsilateral facial muscles and monitored throughout surgery by using a threshold-level stimulation method.RESULTSFMEPs were recorded and analyzed in 8 patients; they were not recorded in 2 patients who had severe preoperative facial palsy and underwent an infrafacial triangle approach. Warning signs appeared in all patients who underwent the suprafacial triangle approach. However, after temporarily stopping the procedures, FMEP findings during surgery showed recovery of the thresholds. FMEPs in patients who underwent the infrafacial triangle approach were stable during the surgery. House-Brackmann grades were unchanged postoperatively in all patients. Postoperative KPS scores improved in 3 patients, decreased in 1, and remained the same in 6 patients.CONCLUSIONSFMEPs can be used to monitor facial nerve function during surgery for pontine cavernous malformations, especially when the suprafacial triangle approach is performed.

Utility of Dual Monitoring of the Lower Cranial Nerve Motor-Evoked Potentials Threshold Level Criterion to Predict Swallowing Function in Skull Base and Brainstem Surgery

“…The threshold level warning criterion had unique advantages, such as a lower elicit voltage, stable response, and more sensitivity. [28][29][30][31] Calancie et al found that a significant threshold level increment often preceded minutes and even hours before total MEPs loss during spine procedures. 32 Not only that, Hendriks et al 33 reported that the facial MEPs threshold level changes occurred earlier than A-trains in cerebellopontine angle surgery.…”

Continuous Dynamic Mapping of Cranial Nerve Pathways and Long Tracts Inside the Brainstem: Useful Technique of Intraoperative Neurophysiological Monitoring

“…Special attention should be for SSEPs during bleeding or vascular traction, also, anatomical features of the area surgery, dorsal or ventral brain stem surface, as described in Xuesong Liu and al [24]. The experience described in the numerous articles demonstrates the effectiveness of CoMEPs use to achieve on-line monitoring of control to functional integrity cranial motors fibers [18,[25][26][27][28][29][30], if followed at the all rules, the registration can be without interruption the surgeon's work [16,27]. In recent years, the use of different types of reflexes became frequently [27,[31][32][33][34], oppositely BAEPs technique which was basic in the 90s for brainstem monitoring [35,36], but in our time gives only 20% of the brainstem area [10,26].…”