Continuous Vagus Nerve Monitoring during Carotid Endarterectomy

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.