title: Post-thyroidectomy superior laryngeal nerve injury.
abstract: Voice dysfunction after thyroidectomy may be caused by damage to laryngeal nerves or lesions to strap muscles with laryngo-tracheal movement impairment. Injury to an external branch of the superior laryngeal nerve (EBSLN) is sometimes difficult to recognize clinically and its electromyographic incidence ranges from 0% to 58%. In this study we evaluated, 12-18 months postoperatively, 45 patients who had undergone thyroid surgery (6 total lobectomy, 5 subtotal thyroidectomy, and 34 total thyroidectomy), using a subjective interview, laryngeal videostroboscopy and spectrographic analysis with a multidimensional voice program. Vocal parameters included fundamental frequency, jitter, shimmer, noise-to-harmonic-ratio (NHR) and degree of sub-harmonics. Laryngeal electromyography (LEMG) of the cricothyroid (CT) muscles was performed in 21 subjects with voice problems (35 EBSLNs) using a modified method for the CT recording. In 3 patients of this group (14%) LEMG documented a unilateral EBSLN injury. Easy voice fatigue and decreased pitch range were the most common symptoms after surgery. Average values of vocal parameters pre- and postoperatively in patients without neural damage (n = 42) were: jitter 0.64% and 0.78%, shimmer 3.25% and 3.54%, and NHR 0.12% and 0.13%, respectively (P > 0.05). Acoustic analysis revealed altered patterns in some patients with no objective evidence of damage to EBSLNs, suggesting an extralaryngeal cause of vocal dysfunction, such as laryngo-tracheal fixation or lesions to strap muscles. We conclude that laryngeal videostroboscopy and spectrographic analysis are very useful to assess voice problems after thyroidectomy, including in patients without LEMG-proven neural lesions, in order to suggest early speech rehabilitation, especially in professional voice users.
authors.affiliation: Department of Otorhinolaryngology, University of Piemonte Orientale, Novara, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Aluffi
authors.forename: M
authors.initials: M
authors.lastname: Policarpo
authors.forename: C
authors.initials: C
authors.lastname: Cherovac
authors.forename: M
authors.initials: M
authors.lastname: Olina
authors.forename: R
authors.initials: R
authors.lastname: Dosdegani
authors.forename: F
authors.initials: F
authors.lastname: Pia
mesh_terms: D000328:Adult; D000368:Aged; D020209:Cranial Nerve Injuries / Q000150:complications* / Q000453:epidemiology / Q000209:etiology; D004576:Electromyography; D005260:Female; D006801:Humans; D015994:Incidence; D007558:Italy / Q000453:epidemiology; D061224:Laryngeal Nerve Injuries; D007828:Laryngoscopy; D008297:Male; D008875:Middle Aged; D013965:Thyroidectomy / Q000009:adverse effects*; D014741:Video Recording; D014832:Voice Disorders / Q000453:epidemiology / Q000209:etiology*