Internal Branch of the Superior Laryngeal Nerve

ramus internus nervi laryngei superioris

The internal branch of the superior laryngeal nerve is the larger sensory branch that pierces the thyrohyoid membrane with the superior laryngeal artery to enter the laryngeal interior. It supplies sensory innervation to the mucosa of the epiglottis, the laryngeal vestibule, and the supraglottic larynx down to the level of the vocal folds, including taste fibres from the epiglottis. It mediates the laryngeal protective cough reflex to foreign material touching the supraglottis.

Region: Neck

Clinical Relevance

Clinical Notes

The internal branch of the SLN is the nerve blocked in internal superior laryngeal nerve block, performed by infiltrating local anaesthetic at the thyrohyoid membrane lateral to the midline where the nerve pierces it. This block is used to facilitate awake fibreoptic intubation and for laryngeal procedures. Injury during thyroid surgery or carotid endarterectomy produces supraglottic sensory loss with impaired laryngeal reflexes and increased aspiration risk. Recurrent laryngeal nerve palsy and internal SLN injury together produce complete laryngeal anaesthesia and paralysis.

Pathology

Common Injuries & Conditions

Internal SLN Injury and Silent Aspiration

Division of the internal branch of the superior laryngeal nerve during upper thyroid lobe surgery or from neck pathology eliminates supraglottic sensation, impairing the cough reflex to material entering the laryngeal vestibule and producing silent aspiration without protective coughing, detectable by modified barium swallow study.