Med Bull Sisli Etfal Hosp. 2017; 51(1): 37-42 | DOI: 10.5350/SEMB.20170227041400

The mechanisms of recurrent laryngeal nerve injury during thyroidectomy and the impact of continuous intraoperative nerve monitoring on surgical strategy

Ýsmail Cem Sormaz, Ýbrahim Fethi Azamat, Fatih Tunca, Yasemin Giles Þenyürek
Ýstanbul Üniversitesi, Týp Fakültesi, Genel Cerrahi Ana Bilim Dalý, Ýstanbul - Türkiye

Objective: To evaluate the mechanisms of recurrent laryngeal nerve (RLN) injury during thyroidectomy and the impact of continuous intraoperative nerve monitoring (C-IONM) on surgical strategy.
Material and Methods: The data of 364 consecutive patients who underwent total or hemithyroidectomy between June 2014 and January 2016 were evaluated prospectively. All patients underwent thyroidectomy by using C-IONM. The mechanisms of RLN injury and the outcomes of the patients with combined events (CE) and loss of signal (LOS) were evaluated.
Results: Combined events (CE) occurred in 6 (1.6%) of these 364 patients. The reduced electromyographic (EMG) amplitude and prolonged latency recovered in all patients intraoperatively by the reversal of the medial traction maneuver. Loss of signal (LOS) occurred in 7(1.9%) patients. The mechanisms of LOS was ligation of the anterior branch of the nerve in 1 (14.3%) patient and traction in 4(57%) patients. The probable mechanism of LOS was traction or transection in 2 (28.6%) patients in whom LOS occurred during the dissection of the intrathoracic portion of large substernal goiter. Of these 7 patients, LOS recovered intraoperatively after 20 minutes of waiting in 1(14.3%) patient. In the remaining 6 (85.7%) patients, unilateral vocal cord paralysis (VCP) was verified on the postoperative laryngoscopic examination. The overall temporary and permanent unilateral VCP rates were 1.6% (n=6) and 0.8% (n=3), respectively in these 364 patients. No bilateral VCP was recorded. Continuous intraoperative nerve monitoring (C-IONM) prevented bilateral VCP in 1 (0.3%) patient.
Conclusion: The major advantage of C-IONM is to alert the surgeon for imminent RLN injury. Combined event (CE) is a pathognomonic sign of impending nerve injury that may progress to LOS. This situation enables the surgeon to adverse (reverse) the surgical maneuver before permanent damage to the nerve sets in. Continuous intraoperative nerve monitoring (C-IONM) can also immediately spot RLN injury during thyroidectomy. This property of C-IONM gives the surgeon the opportunity for an early corrective action to release the affected nerve promptly. In case of permanent LOS, staged thyroidectomy could be planned to prevent bilateral VCP.

Keywords: Continuous intraoperative neuromonitoring, Thyroid surgery, IONM, C-IONM, recurrent laryngealnerve injury, vocal cord palsy, loss of signal.

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Tiroidektomi esnasýnda rekürren laringeal sinirin yaralanma mekanizmalarý ve devamlý intraoperatif sinir monitorizasyonunun cerrahi strateji üzerine etkisi

Ýsmail Cem Sormaz, Ýbrahim Fethi Azamat, Fatih Tunca, Yasemin Giles Þenyürek
Ýstanbul Üniversitesi, Týp Fakültesi, Genel Cerrahi Ana Bilim Dalý, Ýstanbul - Türkiye

Amaç: Tiroidektomi esnasýnda rekürren laringeal sinirin (RLN) yaralanma mekanizmalarýný ve devamlý intraoperatif sinir monitorizasyonunun (D-ÝONM) cerrahi strateji üzerine etkisini deðerlendirmek
Gereç ve Yöntemler: Haziran 2014-Ocak 2016 arasý total veya hemitiroidektomi yapýlan ardýþýk 364 hastanýn verileri prospektif olarak deðerlendirildi. Tüm hastalar D-ÝONM kullanýlarak ameliyat edildi. RLN yaralanma mekanizmalarý, kombine olaylar (KO) ve sinyal kayýplarý (SK) deðerlendirildi.
Bulgular: Üç yüz altmýþ dört hastanýn 6’sýnda (%1.6) KO geliþti. Elektromiyografideki (EMG) amplitüd azalmasý ve latensdeki artýþ medial manevraya dönülmesinden sonra tüm hastalarda düzeldi. Yedi hastada (%1.9) SK saptandý. SK’nýn mekanizmasý; 1 hastada (%14.3) sinir ön dalýnýn baðlanmasý, 4 hastada (%57.0) ise gerilmeydi. Ýntratorasik büyük guatrý olan 2 hastada (%28,6) ise SK’nýn muhtemel mekanizmasý aþýrý gerilme veya transeksiyon olarak deðerlendirildi. Bu yedi hastanýn 1 tanesinde (%14.3) SK ameliyat esnasýnda 20 dakika bekleme sonrasý düzeldi. Kalan 6 hastanýn (%85.7) ise ameliyat sonrasý yapýlan laringoskopik muayenelerinde vokal kord paralizisi (VKP) saptandý. Tüm hasta grubunda tek taraflý geçici ve kalýcý VKP oraný sýrasýyla %1.6 (n=6) ve %0.8 olarak saptandý. Hiçbir hastada kalýcý VKP saptanmadý. D-ÝONM, bir hastada (%0.3) bilateral VKP’yi önledi.
Sonuç: D-ÝONM’nin en büyük avantajý RLN hasarý durumunda cerrahý anýnda uyarmasýdýr. KO geliþebilecek SK’ný gösteren patognomonik bir bulgudur. Bu durumda cerrah ters yöne doðru bir manevra yaparak kalýcý hasar geliþmesini önler. D-ÝONM ayrýca tiroidektomi esnasýnda RLN yaralanmasýný anýnda gösterir. Böylece cerrah etkilenen sinir bölgesine yönelik rahatlatýcý bir harekette bulunabilir. Kalýcý SK’da ise bilateral SK’yý önlemek için aþamalý tiroidektomi planlanabilir.

Anahtar Kelimeler: Devamlý intraoperatif sinir monitorizasyonu, tiroid cerrahisi, ÝONM, D-ÝONM, rekürrenlaringeal sinir yaralanmasý, vokal kord hasarý, sinyal kaybý.

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