OP39 – Continuous intraoperative nerve monitoring in thyroid surgery using Automatic Periodic Stimulation: A retrospective study of 256 lobectomies

      Morely, Hannah1; Hamilton, Nick J.I.1;  Mochloulis, George1 1 Department of Otolaryngology Head and Neck Surgery, Lister Hospital, Stevenage, UK   Background: Automatic Periodic Stimulation (APS) of the vagal nerve during thyroidectomy provides real-time feedback of recurrent laryngeal nerve (RLN) function intra-operatively. This can predict RLN palsy post-operatively and allows for immediate detection of nerve traction intra-operatively, prompting adjustment of surgical technique to avoid injury. Objectives: Determine the incidence of RLN palsy with APS
    1. Examine whether APS can predict RLN palsy
    2. Assess the safety of APS
    Methods:  All thyroidectomies using APS nerve monitoring (Medtronic) were reviewed over a 27-month period. Changes in signal amplitude and latency during thyroidectomy were recorded from saved data. Post-operative fibre-optic laryngoscopy determined the incidence of vocal cord immobility and recovery of nerve function was assessed from follow-up letters. Results: 256 lobectomies (132 hemi and 62 total thyroidectomies) were performed for benign and malignant disease. Permanent RLN palsy occurred in six (2.3%) lobectomies and transient RLN palsy occurred in two lobectomies (<1%). Sensitivity for detecting post-operative vocal cord immobility was 100% and specificity 86% if the end amplitude was 40% below baseline. Intra-operatively, the amplitude was 50% below baseline more frequently in the vocal cord immobility group (t-test, p<0.015). No vagal nerve complications occurred. Discussion & Conclusion: This study represents one of the largest case series of APS monitored thyroidectomies. Whilst the incidence of RLN palsy is comparable to rates in the literature,1 the incidence of transient palsy is lower than published averages.2,3 APS is able to predict RLN palsy based on end amplitude and can be used to avoid unnecessary fibre-optic laryngoscopy post-operatively.   References:
    1. Jeannon JP, Orabi AA, Bruch GA, Abdalsalam HA, Simo R. Diagnosis of recurrent laryngeal nerve palsy after thyroidectomy: a systematic review. Int.J.Clin.Pract. 2009;63:624–9.
    2. Lo CY, Kwok KF, Yuen PW. A prospective evaluation of recurrent laryngeal nerve paralysis during thyroidectomy. Arch Surg. 2000;135:204-7
    3. Hayward NJ, Grodski S, Yeung M, William JR, Serpell J. Recurrent laryngeal nerve injury in thyroid surgery. A.N.Z.J Surg. 2013;82:15-21.


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