Intraoperative nerve monitoring during thyroid surgery (interventional procedures consultation)


Interventional Procedure Consultation Document

Intraoperative nerve monitoring during thyroid surgery

The thyroid gland lies close to the vocal cords and the nerves that control movement of the vocal cords (recurrent laryngeal nerves). When surgery is performed on the thyroid gland, a nerve monitor is sometimes used during the operation with the aim of helping to prevent potential damage to the nerves.

The National Institute for Health and Clinical Excellence is examining intraoperative nerve monitoring during thyroid surgery and will publish guidance on its safety and efficacy to the NHS in England, Wales, Scotland and Northern Ireland. The Institute's Interventional Procedures Advisory Committee has considered the available evidence and the views of Specialist Advisers, who are consultants with knowledge of the procedure. The Advisory Committee has made provisional recommendations about intraoperative nerve monitoring during thyroid surgery.

This document summarises the procedure and sets out the provisional recommendations made by the Advisory Committee. It has been prepared for public consultation. The Advisory Committee particularly welcomes:

  • comments on the preliminary recommendations
  • the identification of factual inaccuracies
  • additional relevant evidence.

Note that this document is not the Institute's formal guidance on this procedure. The recommendations are provisional and may change after consultation.

The process that the Institute will follow after the consultation period ends is as follows.

  • The Advisory Committee will meet again to consider the original evidence and its provisional recommendations in the light of the comments received during consultation.
  • The Advisory Committee will then prepare draft guidance which will be the basis for the Institute's guidance on the use of the procedure in the NHS in England, Wales, Scotland and Northern Ireland.

For further details, see the Interventional Procedures Programme manual, which is available from the Institute's website.

NICE is committed to promoting through its guidance race and disability equality and equality between men and women, and to eliminating all forms of discrimination. One of the ways we do this is by trying to involve as wide a range of people and interest groups as possible in the development of our guidance on interventional procedures. In particular, we aim to encourage people and organisations from groups in the population who might not normally comment on our guidance to do so. We also ask consultees to highlight any ways in which draft guidance fails to promote equality or tackle discrimination and how it might be improved.

Closing date for comments: 18 December 2007
Target date for publication of guidance: March 2008

Note that this document is not the Institute's guidance on this procedure. The recommendations are provisional and may change after consultation.

1 Provisional recommendations
1.1 The evidence on intraoperative nerve monitoring (IONM) during thyroid surgery raises no major safety concerns. In terms of efficacy, the procedure may be helpful to surgeons in performing more complex operations such as reoperative surgery and operations on large thyroid glands. Therefore, it may be used with normal arrangements for consent, audit and clinical governance.
2 The procedure
2.1 Indications
2.1.1 Removal of part or all of the thyroid gland (partial or total thyroidectomy) may be indicated in the treatment of thyroid enlargement (goitre), thyrotoxicosis or malignancy. The thyroid gland is located close to the right and left recurrent laryngeal nerves (RLNs) which innervate the vocal cords. Damage to a RLN during thyroid surgery may result in temporary or permanent hoarseness, or, in the case of bilateral damage, breathing difficulties and an inability to speak.
2.1.2 Conventionally, thyroid surgery is done without the aid of continuous IONM. Under general anaesthesia, an incision is made in the front of the neck and the underlying muscles are retracted to expose the thyroid gland. The RLNs are identified visually to avoid injuring them, but this is not always straightforward. A hand-held nerve stimulator can also be used, in combination with a finger placed behind the larynx to detect contraction of the vocal cord muscles and the arytenoid cartilages on nerve stimulation.
2.2 Outline of the procedure
2.2.1 IONM is used as an adjunct to conventional thyroid surgery under general anaesthesia. It requires placement of electrodes close to the vocal cords. This can be achieved either by the use of a specially adapted endotracheal tube with surface or integral electrodes, which are positioned close to the vocal cords; or by the placement of electrodes into the vocal muscles on each side of the thyroid gland, when using a standard endotracheal tube. Following tracheal intubation, non-paralysing anaesthesia is used for the rest of the procedure as muscle relaxants can interfere with the nerve monitoring process.
2.2.2 The electrodes are connected to the neuromonitoring device, which uses sound and graphics on the monitor screen to alert the surgeon when a surgical instrument comes close to either RLN during surgery. A hand-held probe can also be used to confirm the location of either nerve at any time during the operation. Postoperative laryngoscopy is used to assess RLN function.
2.3 Efficacy
2.3.1 Four non-randomised controlled trials of 16,448, 684, 639 and 136 patients (29 998, 1043, 1000 and 190 nerves) reported permanent rates of vocal cord paralysis ranging from 0% to 2% in the IONM groups, compared with 0% to 1% in the control groups (visual RLN identification or no RLN identification). No statistically significant differences were seen between procedures undertaken with or without IONM. Three case series of 328, 288 and 171 patients reported rates of permanent vocal cord paralysis in 3% (15/502), 1% (6/429) and 1% (2/271) of RLNs, respectively.
2.3.2 Four non-randomised controlled trials of 684, 639, 165 and 136 patients (1043, 1000, 236 and 190 nerves) reported rates of transient vocal cord paralysis ranging from 3% to 5% in the IONM groups, compared with 3% to 4% in the control groups (none were statistically significant). The three case series of 328, 288 and 171 patients reported rates of transient RLN palsy as 9% (43/502), 9% (37/429) and 5% (13/271), respectively.
2.3.3 The non-randomised controlled trial of 639 patients (1000 nerves at risk), which compared IONM with visual identification of the RLN, reported that IONM indicated no nerve damage in 10 out of 21 vocal cords that were paralysed as a result of surgery. Conversely, IONM indicated nerve damage in 27 out of 480 patients who were found to have normal postoperative vocal cord function. For more details, refer to the sources of evidence (see appendix).
2.3.4 The Specialist Advisers considered key efficacy outcomes to be reduction in nerve damage and subsequent vocal cord palsy. Two of the eight Advisers stated that this procedure is useful for teaching. One Adviser commented that there are significantly different opinions between surgeons as to whether this technology improves outcomes or whether it gives false reassurance to inexperienced surgeons.



2.4 Safety
2.4.1 No adverse events resulting from IONM were reported in the studies.
2.4.2 The Specialist Advisers considered the main safety concerns to be false-negative or false-positive readings leading to the misidentification of the nerve. In particular, a false-negative reading may lead to RLN damage. One Adviser suggested that there is also a potential for false signals if the electrodes are placed incorrectly.
3 Further information
3.1 All cases of RLN damage during thyroid surgery using IONM should be recorded at local clinical audit meetings and reported to the National Patient Safety Agency through local clinical governance mechanisms, as this may be associated with failure to identify the nerve (false-negatives) when using the technique.

Bruce Campbell
Chairman, Interventional Procedures Advisory Committee
November 2007

Appendix: Sources of evidence

The following document, which summarises the evidence, was considered by the Interventional Procedures Advisory Committee when making its provisional recommendations.

  • 'Interventional procedure overview of intraoperative nerve monitoring during thyroid surgery', August 2007

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This page was last updated: 30 March 2010