[Not all vocal cord failure following thyroid surgery is recurrent paresis due to damage during operation. Statement of the German Interdisciplinary Study Group on Intraoperative Neuromonitoring of Thyroid Surgery concerning recurring paresis due to intubation]. / Nicht jeder Stimmlippenstillstand nach Schilddrüsenoperation ist eine chirurgischbedingte Rekurrensparese. Stellungnahme der "Interdisziplinären Studiengruppe Intraoperatives Neuromonitoring Schilddrüsenchirurgie" zur Problematik intubationsbedingter Rekurrensparesen.

Since the phoniatrician H. Bauer described the first case of recurrent laryngeal nerve palsy most likely caused by intubation some 45 years ago, several case reports have been published. However, systematic analyses regarding the frequency of recurrent laryngeal nerve palsies due to intubation are scarce, and none of them has used the proper methods to demonstrate clearly that such a mechanism exists. Currently available data justify the assumption that not every recurrent laryngeal nerve palsy following thyroid surgery is due to the operation itself and that the damage caused by intubation, however, may only account for a minority of these cases. The differential diagnosis of postoperative recurrent laryngeal nerve palsy requires the use of specific tools which go beyond simple laryngoscopy and include stroboscopy as well as intra- and extralaryngeal electromyography. A partial palsy of recurrent laryngeal nerve due to intubation would be associated with severe dysphonia or aphonia, not with dyspnea because of the typical intermediate position of the paralyzed vocal folds with a normal electromyographic function of the cricothyroid muscle. The use of these methods to identify the nature of postoperative recurrent laryngeal nerve palsy is recommended in cases of regular intraoperative neuromonitoring but postoperatively impaired function of the vocal cords.

[Effectiveness and results of intraoperative neuromonitoring in thyroid surgery. Statement of the Interdisciplinary Study Group on Intraoperative Neuromonitoring of Thyroid Surgery]. / Zuverlässigkeit und Konsequenzen des intraoperativen Neuromonitorings in der Schilddrüsenchirurgie. Stellungnahme der "Interdisziplinären Studiengruppe Intraoperatives Neuromonitoring Schilddrüsenchirurgie"

Intraoperative neuromonitoring (IONM) has yielded an increasing effect on thyroid surgery. During IONM, the recurrent laryngeal nerve is stimulated electrically and an acoustically transformed electromyographic signal is derived via either a needle electrode placed in the vocalis muscle or an electrode adjusted to the intubation tube. The IONM is used for identifying and predicting the function of the recurrent laryngeal nerve. Especially under difficult anatomic conditions, IONM has proven a valuable tool for identification of recurrent laryngeal nerves. This can lead to decreased occurrence of nerve palsy rates, as shown in numerous studies. The reliability of the IONM signal (defined as the correlation between intraoperative signal interpretation and postoperative vocal cord function) is reflected by a specificity as high as 98.2%, as shown by German multicenter studies. Thus, normal vocal cord function could be demonstrated postoperatively in over 98.2% of patients with intraoperatively unchanged neuromonitoring signals. If the neuromonitoring signal changed during operation, 39% of the patients suffered from transient vocal cord immobility and 12% had permanent loss of vocal cord function.

[A Critical Estimation of Intraoperative Neuromonitoring (IONM) in Thyroid Surgery]. / Kritische Beurteilung und Fehlermöglichkeiten des intraoperativen Neuromonitoring (IONM) bei Operationen an der Schilddrüse.

We investigated 238 patients with 431 nerves at risk (NAR) undergoing thyroid surgery. Positive identification of the recurrent laryngeal nerve was obtained in 99.3 % of NAR with intraoperative neuromonitoring. 19 patients (4.4 % NAR) suffered from unilateral vocal cord dysfunction in the early postoperative phase. A complete restitution of vocal cord function could be demonstrated in 18 of these patients, leaving one patient (0.23 % NAR) with a permanent vocal cord dysfunction. Our data show that reliable predictions concerning the postoperative outcome of nerve function cannot always be made on the basis of the intraoperative findings. Thus, our own data show a specifity of 98.5 % and a negative predictive value of 96.8 %. On the other hand, sensitivity was 23.5 % and positive predictive value was 40 %. Misinterpretation of the intraoperative signal can lead to risky operative manoeuvres. Possible reasons for the misinterpretation of the intraoperative signal and a critical reflection on the possibilities and predictive values of neuromonitoring will be discussed.

[Identification and surgical anatomy of the external branch of the superior laryngeal nerve]. / Der Ramus externus des Nervus laryngeus superior (RELS): Ein Stiefkind in der Chirurgie der Schilddrüse.

Injury to the external branch of the superior laryngeal nerve (EBSLN) during thyroid surgery can cause serious consequences for patients who depend on control of pitch and a clear and forceful voice, like singers or professional speakers. We used the Neurosign 100(R) nerve monitor to identify 157 nerves in 108 patients undergoing thyroid surgery. The EBSLN was successfully identified in 98.7 % of cases. The recording electrode could be placed either into the cricothyroid muscle or the vocal cord. The latter position proved superior if the recurrent laryngeal nerve had to be identified as well. 16 percent of the nerves crossed the branches of the superior thyroid artery at or below the upper pole of the gland, posing a "high risk" for intraoperative lesions. Our data confirm the results of smaller studies reporting this type of nerve course in 12 % to 14 % of patients. The present findings show a significant number of EBSLN to be in danger of injury when the superior thyroid artery is ligated during thyroid surgery. Neuromonitoring proofed to be a reliable method to identify the nerve, which is an important element in concepts to prevent its injury.