Visualization Versus Intraoperative Neuromonitoring of the Recurrent Laryngeal Nerves in Thyroid Surgery
Condition: Thyroid Surgery
MeSH terms: Thyroid Diseases
Study type: Interventional

Summary: 
      Some recent studies have shown that intraoperative neuromonitoring (IONM) can aid the
      recurrent laryngeal nerve (RLN) identification during thyroid surgery. However, the role of
      IONM in reducing the incidence of RLN injury rate and the value of this method in predicting
      postoperative RLN function remain controversial. Only a few published series represent level
      III of evidence and grade C of recommendation according to the evidence-based criteria
      (Sackett's classification, modified by Heinrich). Thus, the aim of this randomized clinical
      trial was to compare the impact of RLN visualization versus IONM on their morbidity following
      thyroid surgery.
    

Detailed description: 
      Apart from hypoparathyroidism, dysfunction of the recurrent laryngeal nerve (RLN) is the most
      common complication following thyroid surgery. In consequence, the voice impairment leading
      to communication work-related problems and affecting psychological and social aspects of the
      individual's functioning diminishes the overall quality of life, being the common reason for
      medicolegal claims and litigation. The reported RLN palsy rate varies in the literature from
      0% (for first-time thyroid surgery performed by an experienced endocrine surgeon) to as much
      as 20% (for reoperative thyroid surgery or thyroid malignancy surgery performed in low-volume
      centers), depending mostly on the type of thyroid disease (benign vs. malignant goiter), type
      (first-time vs. reoperation) and the extent of thyroid resection (subtotal vs. total
      thyroidectomy), surgical technique (with or without routine RLN identification) and the
      surgeon's experience (low-volume vs. high-volume thyroid surgery center.

      In 1938, Lahey from Boston reported a significantly lower incidence of RLN injuries following
      thyroidectomy with dissection and visualization of the nerves as compared to operations
      without nerve identification. Since that time, many prospective studies have confirmed this
      observation, advocating routine RLN identification as the gold standard in safe thyroid
      surgery. But even in the most experienced hands RLN palsy occurs occasionally, with an
      average frequency below 1% of nerves at risk due to variability in RLNs anatomy and
      difficulties in nerve identification by visual or palpation control in challenging conditions
      (e.g. advanced thyroid malignancy or reoperative thyroid surgery). On the other hand, the use
      of intraoperative electrical stimulation for identifying the RLN nerve was described in 1966.
      However, the technique of intraoperative neuromonitoring (IONM) of RLN did not gain any
      widespread popularity until the late nineties of the last century, when several commercial
      user-friendly systems based on electromyographic signal recording became available. In these
      IONM systems, the RLN nerve stimulation is registered by elicited laryngeal muscles activity
      through the endoscopic insertion of the electrodes into the vocal cords, open insertion of
      the needle electrodes into the vocal muscles through the cricothyroid ligament or with the
      use of endotracheal tube surface electrodes. In addition to a plethora of signal acquisition
      techniques used in IONM, there is no consensus regarding the optimal method for nerve
      activity recording (continuous recording of spontaneous nerve activity versus repetitive
      stimulation) and no agreement as to which quantitative electromyographic parameter should be
      used as a predictor of postoperative vocal cord dysfunction (supramaximal versus minimal
      stimulation of the nerve at the end of the operation).

      Some recent studies have shown that IONM can aid the RLN identification. However, the role of
      IONM in reducing the incidence of RLN injury rate and the value of this method in predicting
      postoperative RLN function remain controversial. Only a few published series represent level
      III of evidence and grade C of recommendation according to the evidence-based criteria
      (Sackett's classification, modified by Heinrich). Large, prospective, randomized trials
      addressing these issues and allowing for grade A recommendations are lacking due to some
      ethical concerns and large numbers of patients in each arm (more than 7000 patients) needed
      to reach the appropriate power of the study. To fulfill this gap in evidence, we designed a
      medium-size, single-center, prospective randomized study suitable for drawing more meaningful
      conclusions. Thus, the aim of this study was to compare the impact of RLN visualization
      versus IONM on their morbidity following thyroid surgery.
    

Intervention name(s): intraoperative RLN visualization; intraoperative neuromonitoring of the RLN
Intervention type(s): Procedure; Procedure
Intervention description(s): intraoperative RLN visualization; IONM
Other intervention name(s): V-G; IONM-G
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: Single (Participant)
Primary purpose: Prevention
Keywords: thyroid surgery; recurrent laryngeal nerves visualization; intraoperative neuromonitoring; predictive values