TITLE:
Continuous Vagus Nerve Monitoring during Carotid Endarterectomy
AUTHORS:
Tamaki Tomonori, Kubota Minoru, Node Yoji, Morita Akio
KEYWORDS:
Carotid Endarterectomy, Vagus Nerve, Vocal Fold, Neuromonitoring, Complication
JOURNAL NAME:
Open Journal of Modern Neurosurgery,
Vol.7 No.1,
December
12,
2016
ABSTRACT: Backgrounds: Injury to the
vagus nerve or one of its branches during carotid endarterectomy can result in
vocal fold paralysis but the exact mechanism of injury responsible for vocal
fold paralysis after carotid endarterectomy is unclear. Aims: This study was
performed to identify potential predictors of vagus nerve injury and obtain
feedback by application of intraoperative continuous vagus nerve monitoring. Materials
and Methods: Seventy-four patients undergoing carotid endarterectomy were
enrolled. A new vagus nerve electrode was designed for less invasive continuous
vagus nerve stimulation and monitoring of the vocal fold electromyogram without
disturbing the surgical procedure. The device was rectangular (13 mm × 9 mm), with two small round
electrodes set on a flexible silicon plate and tube. The electrode was fully
implantable during carotid endarterectomy and was positioned at the most distal
site of the vagus nerve by suturing to the connective tissue without nerve
dissection. All patients underwent laryngoscopy to assess postoperative vocal
fold and pharyngeal wall palsy at one week after carotid endarterectomy. Results:
Sudden loss of the vocal fold electromyogram was noted in two patients (during
plaque removal and during arterial wall suture in one each). In these two
patients, incomplete vocal fold and pharyngeal palsy was confirmed by
laryngoscopy. The cause of vagus nerve injury may have been traction at the
time of distal internal carotid artery manipulation. The vocal fold electromyogram
remained normal during the operation in the other 72 patients. However laryngoscopy revealed postoperative vocal fold and pharyngeal palsy in six patients. These findings suggested that delayed vagus nerve
injury can occur after carotid endarterectomy. Conclusion: The continuous vagus
nerve monitoring may be worthwhile for elucidating the mechanism of vagus nerve
injury related to carotid endarterectomy.