Vocal cord palsy in thyroid surgery is due to injury to

Reccurent laryngeal nerve injury is classically described as a paralyzed vocal cord with loss of movement from the midline (supplies all the intrinsic muscles of the larynx, except cricothyroid muscles). Injury to the external branch of the superior laryngeal nerve leads to loss of tension in the vocal cord (supplies cricothyroid) with diminished power and range in the voice Source : Bailey and Love 26th edition Pg: 762