Histologic study of the recurrent laryngeal nerve in spasmodic dysphonia.

It has been reported that there were no significant changes in the recurrent laryngeal nerves of patients with adductor spasmodic dysphonia, which could explain the cause of this disease. However, the researchers who made these reports appeared to have investigated only the extralaryngeal part of the nerve involved in the neck. Because the recurrent laryngeal nerve contains many components that distribute to various organs, we must study in greater detail a more peripheral part of the motor nerve, which has a much closer relationship to vocal cord movements. At the time of surgery we obtained specimens of the thyroarytenoid branches of the recurrent laryngeal nerves in two female patients with adductor spasmodic dysphonia. Although histologic analysis revealed no apparent signs of either destruction or degeneration, the percentage of thin nerve fibers, the diameter of which may range from 5 to 10 microm, was higher than in normal controls. This suggests the possibility of a neurologic abnormality in the larynges of ASD patients.