The difference between the superior laryngeal nerve and the recurrent laryngeal nerve mainly lies in the different innervation areas and the different performance after injury.
1. Superior laryngeal nerve: the outer branch of the superior laryngeal nerve is a motor nerve, innervating the cricothyroid muscle; the inner branch is a sensory nerve. Generally speaking, it is rare to have paralysis of the superior laryngeal nerve alone after injury, and it is even more rare to have paralysis of the outer branch alone.
After paralysis of the superior laryngeal nerve, the vocal cords lose their tone, and the voice is coarse and weak. In unilateral palsy, the sensation of the contralateral laryngeal mucosa still exists. In bilateral cases, because of the complete loss of laryngeal mucous membrane sensation, diet, saliva accidentally choked into the lower respiratory tract, aspiration pneumonia can occur.
2. Laryngeal recurrent nerve: The laryngeal recurrent nerve is mainly a motor nerve, which innervates the internal laryngeal muscles except the cricothyroid muscle. When the laryngeal recurrent nerve is paralyzed due to injury, the nerve fibers innervating the abductor muscles are involved earlier, and the nerve fibers innervating the adductor muscles are involved later. Or only the nerve fibers innervating the adductor muscles are involved.
In unilateral incomplete paralysis of the recurrent laryngeal nerve, there may be transient hoarseness, which recovers immediately. In bilateral cases, the vocal folds on both sides are close to the midline and cannot be abducted, leaving only a small fissure between them, which can easily cause laryngeal obstruction.
In unilateral paralysis of the recurrent laryngeal nerve, there may be hoarseness, easy fatigue, speaking and coughing with a sense of leakage of air, later due to the compensatory effect of phonation improved. When both sides are paralyzed, the voice is hoarse and weak, monotonous, and it is hard to speak, often feeling short of breath, but without dyspnea, easy to cause accidental choking, and difficult to expel sputum, and respiratory wheezing sound.
When the above symptoms occur, it is recommended to actively seek medical advice from neurosurgeons, improve relevant examinations to clarify the diagnosis and further standardize the treatment.