Wagner and Grossman theory
This is the most popular and widely accepted theory which could account for the varying positions assumed by a paralysed vocal cord. This theory was first proposed by Wagner and Grossman (1897). This theory states that in complete paralysis of recurrent laryngeal nerve the cord lies in the paramedian position because the intact cricothyroid muscle adducts the cord. (Because the superior laryngeal nerve is intact). If the superior laryngeal nerve is also paralysed the cord will assume an intermediate position because of the loss of adductive force. This theory has been confirmed by electro myological studies. According to this theory, chest lesions should cause recurrent laryngeal nerve paralysis alone, but in many patients with lung cancer the cord assumes a intermediate position. This has been attributed to the phenomenon of retrograde atrophy of the vagus nerve up to the level of nucleus ambiguus. Paralysed vocal cords may demonstrate some movement due to the action of interarytenoid muscle which gets bilaterally innervated.