Is the external laryngeal nerve an exclusively motor nerve?: The cricothyroid connection branch

Objectives: To obtain an accurate morphological description of the nerve that provides communication between the external laryngeal nerve and the recurrent laryngeal nerve in a large sample of human larynges. Study Design: Morphological study of human larynges. Methods: Microdissection of 103 human larynges obtained from necropsies was performed. Both the external laryngeal nerve and the recurrent laryngeal nerve were identified and dissected. The existence of a communication between the two nerves was evaluated. Results. A neural communication between the external laryngeal nerve and the recurrent laryngeal nerve was found in 85% of the larynges studied (bilaterally in 44% and unilaterally in 41%). Two patterns of communication (with single or double branches) were found. The communication between the nerves can appear at different levels, giving off collateral branches to the cricothyroid muscle (23%), the cricothyroid joint capsule (49%), and the subglottic mucosa (50%). Conclusions. The nerve supply of the human larynx is more complex than classically considered. Our study does not support the classic neuroanatomical belief that the external laryngeal nerve is purely a motor nerve to the cricothyroid muscle. Our results reveal that it carries sensory and motor fibers on to other muscles (thyroarytenoid) or regions (subglottis mucosa and cricothyroid joint), as has been demonstrated in experimental studies in cats and dogs.