Terminal branching of internal laryngeal nerve: a cadaveric study

Abstract

Background: Innervation of larynx is much more complicated than previously been thought. Laryngopharynx is the common gateway for many specialists like oral surgeons, ENT surgeons, anaesthetists, UGI endoscopists and bronchoscopists. The sub-mucosal neural network can be anaesthetised by topical application or injection of local anaesthetics. In this study destination of the internal laryngeal nerve and its penetration into the intrinsic muscles of larynx are analysed.

Methods: A total of 40 en bloc cadaveric specimens were investigated in the department of anatomy, Madras Medical College, Chennai and from Melmaruvathur Adhiparasakthi Institute of Medical Sciences and Research, Kanchipuram. Conventional anatomy dissection method was used in the identification of internal laryngeal branch of superior laryngeal nerve and its branches.

Results: Irrespective of the number of divisions at the point of entry into thyrohyoid membrane, 4 branches were constantly traceable. The branches were traced by 2 approaches- (A) those supplying the mucus membrane- (i) to the junction of aryepiglottic fold and lateral border of epiglottis; (ii) to the posterior surface of interarytenoideus; (iii) to the posterior surface of posterior arytenoideus; and (iv) descending to apex of the pyriform fossa behind cricothyroid junction; (B) penetration into intrinsic muscles- (i) a branch terminated after entering interaryteoideus; and (ii) another terminated after entering the posterior cricoarytenoideus muscle.

Conclusions: The knowledge of variation into branches and area of supply of internal laryngeal nerve is essential for anatomists and clinicians. It is not a nerve to be neglected as the knowledge of its branches is very much essential for the surgeons operating in this area of air and food passage.