[Effect of cricothyroid and thyroarytenoid muscle botulinum toxin injection on patients with dyspnea caused by bilateral recurrent laryngeal nerve paresis].

To discuss the clinical effect of small dose of botulinum toxin injection in cricothyroid muscle and thyroarytenoid muscle on patients with incomplete bilateral recurrent laryngeal nerve paresis. Six patients were selected with Ⅰor Ⅱ or Ⅲ degree of dyspnea diagnosed as bilateral recurrent laryngeal nerve injury by laryngeal electromyography, and small dose of botulinum toxin injection was performed in cricothyroid muscle and thyroarytenoid muscle as a treatment. Degree of dyspnea was assessed one month before and after the treatment, and the stroboscopic laryngoscope results, acoustic parameters and CT image of the patients were collected in the 6 patients. The relevant parameters were also collected one month before and after treatment, including the degree of dyspnea, stroboscopic laryngoscope results, acoustic parameters and CT image of the patients. The angle between bilateral vocal cords in stroboscopy at full inspiratory was calculated, acoustic parameters (F0, jitter, shimmer) were analysed, and vocal length, width and the vocal region were measured. Then, the paired test was performed for statistical analysis between before and after one month injection, the one way analysis of variance was performed among vocal parameters in CT image. Botulinum toxin injection was successfully completed in the 6 patients, followed without any serious complications. The degree of dyspnea was alleviated to some extent after treatment in all 6 patients; the angle between bilateral vocal cords at the end of a deep inspiration was significantly increased (=2.44, <0.05) after the treatment. The changes of F0 and jitter between before and after treatment were not statistically significant (=0.72, =1.42, >0.05). Shimmer was significantly decreased after treatment (=2.61, <0.05). Vocal fold length, width and vocal region increased with F0, there was a statistically significant difference between different F0 before injection, and there was no statistically significant difference between different F0 after injection. The follow-up time was respectively seven months, 1 year, 1 year, 18 months, 22 months and 2 years respectively. Small dose of botulinum toxin injection in bilateral cricothyroid muscles and thyroarytenoid muscles can relieve the dyspnea caused by bilateral vocal cords paresis to some extent, accompanied without serious complications, despite the sound quality was slightly worse.