Recurrent laryngeal nerve injury is the most common cause of vocal cord paralysis. It from the Vagus, travels fuher on the left where it loops around the arch of Aoa while on the right, it travels around the subclan aery. Supplies all the muscles (posterior Cricoarytenoid, interarytenoid, lateral Cricoarytenoid, and Thyroarytenoid muscles) except for Cricothyroid.Laryngeal Nerve Paralysis: Three areas where damage can occurBrainstem NucleiCoicobulbar fibers sta from the cerebral coex and descend through the internal capsule and synapse at the nucleus ambiguus in the MedullaVagus NerveRecurrent Laryngeal Nerve is the commonest cause.Recurrent laryngeal nerve:Arises from the Vagus, travels fuher on the left where it loops around the arch of Aoa while on the right, it travels around the subclan aery. The intrinsic muscles of the larynx, all of which are innervated by the recurrent laryngeal nerve, include the: 1. Posterior cricoarytenoid the ONLY abductor of the vocal folds. Functions to open the glottis by rotary motion on the arytenoid cailages. Also tenses cords during phonation. 2. Lateral cricoarytenoid functions to close glottis by rotating arytenoids medially. 3. Transverse arytenoid only unpaired muscle of the larynx. Functions to approximate bodies of arytenoids closing posterior aspect of glottis. 4. Oblique arytenoid this muscle plus action of transverse arytenoid function to close laryngeal introitus during swallowing. 5. Thyroarytenoid - very broad muscle, usually divided into three pas:Thyroarytenoideus internus (vocalis) - adductor and major tensor of free edge of vocal fold.Thyroarytenoideus externus - major adductor of vocal foldThyroepiglotticus - shoens vocal ligamentsThe cricothyroid muscle is considered to be an extrinsic muscle of the larynx because it is innervated by the external branch of the superior laryngeal nerve. It functions to increase tension in the vocal folds, especially at the upper range of pitch or loudness.