The topographical anatomy of the external branch of the süperior laryngeal nerve and its importance in thyroid surgery: a cadaver study

Abstract

Objectives: We investigated topographical anatomic features of the external branch of the süperior laryngeal nerve SLN in relation to the süperior thyroid artery STA and its vuİnerability to injury in individuals with a normal thyroid size.Study Design: Thirty fresh cadavers 18 females, 12 males; age range 20 to 50 years with normal thyroid size and no signs of abnormality in the neck were studied. The external branch of the SLN was identified and classified according to system proposed by Cernea et al.Results: The topographical relationship betvveen the external branch of the SLN, the STA, and the upper pole of the thyroid gland was identified in 54 thyroid lobes 90% . Identification was not possible in six lobes because of bleeding or injury.The location of the external branch of the SLN was consistent with type 1 in 28 lobes 51.8% and type 2 in 26 lobes 48.2%; type 2a in 37.1% and type 2b in 11.1% . No significant relationships existed betvveen the type of the nerve, gender, and age, nor was there any symmetry with regard to the location of the external branch of the SLN in the same subject.Conclusion: Nearly half of the Turkish population with a normal thyroid gland size present high surgical risks during thyroid surgery because of the course of the external branch of the SLN.

Keywords

• Cadaver, laryngeal nerves/injuries/anatomy & histology, neck/surgery, thyroidectomy

Süperior larenjeal sinirin eksternal dalının topografik anatomisi ve tiroit cerrahisindeki önemi: Kadavra çalışması

Abstract

Amaç : Normal boyutlarda tiroit bezine sahip kiflilerde sü- perior larenjeal sinirin SLS eksternal dalının süperior ti- roit arter ile iliflkili olarak topografik anatomik özellikleri ve sinirin hasar görme riski arafltırıldı. Çalıflma Planı: Normal boyutta tiroit bezi olan ve boyun- da herhangi bir anomali belirtisi olmayan 30 taze kadavra çalıflmaya alındı. Süperior larenjeal sinirin eksternal dalı ortaya kondu ve Cernea ve ark.nın tanımlamasına göre sınıflandırıldı. Bulgular: Süperior larenjeal sinirin eksternal dalı, s ü p e r i- or tiroit arter ve tiroit üst kutbu arasındaki topografik iliflki 60 tiroid lobunun 54’ünde %90 ortaya kondu. Altı tiroid lobu, kanama ve travma gibi nedenlerle sinir belirleneme- diğinden çalıflma dıflında bırakıldı. Süperior larenjeal sini- rin eksternal dalının yerleflimi 28 tiroit lobunda %51.8 tip 1, 26’sında %48.2 tip 2 %37.1 tip 2a, %11.1 tip 2b özel- lik gösterdi. Sinir tipleri ile cinsiyet ya da yafl arasında an- lamlı iliflki kurulamadı. Aynı kadavranın iki tarafı arasında sinir yerleflimi yönünden simetri saptanmadı. Sonuç: Ülkemizde normal boyutlarda tiroit bezine sahip kiflilerin yaklaflık yarısının SLS eksternal dalının seyri açı- sından cerrahi sırasında yüksek hasar riskine sahip olduğu sonucuna varıldı

Keywords

• Kadavra, larenjeal sinirler/yaralanma/anatomive histoloji, boyun/cerrahi, tiroidektomi

References

1. McIvor NP, Flint DJ, Gillibrand J, Morton RP. Thyroid surgery and voice-related outcomes. Aust NZJ Surg 2000;70:179-83.
2. Kierner AC, Aigner M, Burian M. The external branch of the superior laryngeal nerve: its topographical anatomy as related to surgery of the neck. Arc h Otolaryngol Head Neck Surg 1998;124:301-3.
3. Cernea CR, Ferraz AR, Nishio S, Dutra A Jr, Hojaij FC, Dos Santos LR. Surgical anatomy of the external branch of the superior laryngeal nerve. Head Neck 1992;14:380-3.
4. Lennquist S, Cahlin C, Smeds S. The superior laryn- geal nerve in thyroid surgery. Surgery 1987;102:999- 1008.
5. Hurtado-Lopez LM, Zaldivar- R a m i rez FR. Risk of injury to the external branch of the superior laryngeal nerve in thyroidectomy. Laryngoscope 2002;112:626-9.
6. Eisele DW, Goldstone AC. Electrophysiologic identifi- cation and preservation of the superior laryngeal nerve during thyroid surgery. Laryngoscope 1991;101: 313-5.
7. Crookes PF, Recabaren JA. Injury to the superior laryn- geal branch of the vagus during thyroidectomy: lesson or myth? Ann Surg 2001;233:588-93.
8. Cernea CR, Nishio S, Hojaij FC. Identification of the external branch of the superior laryngeal nerve (EBSLN) in large goiters. Am J Otolaryngol 1995;16: 307-11.

9. Espinoza J, Hamoir M, Dhem A. Preservation of the external branch of the superior laryngeal nerve in thy- roid surg e r y. An anatomic study of 30 dissections. Ann Otolaryngol Chir Cervicofac. 1989;106:127-34. [Abstract]