Semon's law

From Otolaryngology Online

This theory proposed by Rosenbach and Semon in 1881, depends on the concept that abductor fibres in the recurrent laryngeal nerves are more susceptible to pressure than the adductor fibers. After a number of amendments this law is stated as " In the course of a gradually progressing organic lesion involving the recurrent laryngeal nerve three stages can be observed. In the first stage only the abductor fibers are damaged, the vocal folds approximate in the midline and adduction is still possible. In the second stage the additional contracture of adductors occur so that the vocal folds are immobilized in the median position. In the third stage the adductors become paralysed and the vocal folds assume a cadaveric position".

This theory is fraught with clinical and experimental inconsistencies. It was assumed that the nerve fibers supplying the abductors of the vocal folds lie in the periphery of the recurrent laryngeal nerve and any progressive lesion involves these fibers first before involving the deeper fibers that supply the adductors. It was even suggested that adductors being phylogentically older are more resistant to insults than the newer abductors. According to this theory in all progressive lesions involving the recurrent laryngeal nerve the abductors paralyze first followed by the adductors. When recovery takes place the first muscle group to recover will be the adductors before the abductors could recover.