Cricothyroid muscle dysfunction impairs vocal fold vibration in unilateral vocal fold paralysis.

OBJECTIVES/HYPOTHESIS The relevance of the cricothyroid (CT) muscle in patients with unilateral vocal fold paralysis (UVFP) remains controversial. To clarify the functional significance of the CT muscle in patients with UVFP, the confounding effect of the severity of recurrent laryngeal nerve injury should be taken into consideration. In the present study, quantitative laryngeal electromyography (LEMG) was used to measure the severity of paralysis of the thyroarytenoid-lateral cricoarytenoid (TA-LCA) muscle complex to allow the functional contribution of the CT muscle to be determined. STUDY DESIGN Cross-sectional study performed in an otolaryngology outpatient clinic. METHODS Thirty-one patients with a main diagnosis of UVFP were recruited. The main outcome measures included LEMG examination, quantitative LEMG analysis of the TA-LCA muscle complex, UVFP-related quality-of-life questionnaire (Voice Outcome Survey [VOS]), voice acoustics analysis, videolaryngostroboscopy, and general quality-of-life questionnaire (Short Form-36 Health Survey [SF-36]) assessments. RESULTS The vocal cord position did not differ between patients with and without CT muscle impairment. Patients with both TA-LCA and CT paralysis showed poorer vocal fold vibration (P = .048) and higher fundamental frequency (P = .02), and the VOS and SF-36 were both poorer compared with patients with only TA-LCA paralysis. CONCLUSIONS Although the vocal cord position was not influenced by CT muscle function, coexisting CT muscle paralysis may damage the voice by impairing vocal fold vibration in UVFP patients.