Thyroid and parathyroid surgery intraoperative nerve monitoring and management of iatrogenic vocal cord paralysis

Thyroid and parathyroid surgeries are common procedures undertaken worldwide by a variety of surgeons ranging from highly specialised endocrine and head-and-neck surgeons in high-volume centres to surgeons in district general hospitals. Recurrent laryngeal nerve (RLN) injury is a well-known and serious complication of thyroid and parathyroid surgery and can lead to serious consequences in addition to important medicolegal implications. The general basic principles of thyroid and parathyroid surgery include the removal of the involved pathological tissue, with preservation of the functioning vital structures including the external branch of the superior laryngeal nerve (EBSLN) and the recurrent laryngeal nerve (RLN). Over the years surgeons have developed strategies to avoid damage of above-mentioned anatomical structures culminating in the development of intraoperative neuromonitoring (IONM). Despite of the use of IONM, the rate of recurrent laryngeal nerve palsy (RLNP) is clearly underestimated. The true rate varies widely according to the method of laryngeal examination. The average incidence of temporary RLNP following thyroid surgery is 9.8% with a 2.3% rate of permanent RLNP. The risk factors for RLNP include malignant histology, neck dissection and revision surgery. Additionally it appears that high-volume departments doing more than 150 thyroid procedures per year seem to perform significantly better.