Predictive indicators of an unfavorable prognosis for the restoration of laryngeal functions in unilateral lesions of the recurrent laryngeal nerve in thyroid surgery

Abstract

Recurrent laryngeal nerve (RLN) damage in thyroid surgery is a very dangerous complication. An otolaryngologist, especially at pri­mary care institutions,should administer conservative or surgical treatment in a timely manner and depending on the type of nerve damage (transient, permanent), i. e., to analyze possible prognosis of the disease. Only few studies to predict disease developmentin RLN have been performed. One of the most modern and informative methods is laryngeal electromyography using needle electrodes, but despite the sufficient number of patients with this pathology, in most medical institutions in Ukraine it is not performed, given the technical difficulties of implementation, invasiveness and difficulty in interpreting the results of this method.Aim — to analyze the laryngoscopic signs of paresis and paralysis of the larynx in thyroid surgery and to identify the most significant from them, which together can serve as prognostic criteria of the lack of recovery of laryngeal mobility (paralysis).Materials and methods. A single-site prospective study was conducted in the years 2018—2021 that involved 164 patients with postoperative laryngeal movement disorders, who were divided into two groups: subjects with laryngeal paralysis (n = 33) and patients with laryngeal paresis (n = 131). All patients underwent phoniatric examination. The following signs have been identified: general signs, including age, number of operations, scope of surgical intervention, and 18 laryngoscopicsigns, each of them had two to seven grades. For the convenience, the grades were coded with numbers and, if possible, arranged in ascending order of severity. The obtained results were processed with Fisher angular transformation.Results. Among 18 laryngoscopic and general signs, 10main (predictors) were identified, that affect the absence or presence of laryngeal paralysis. They included:elements of mobility of the paralyzed vocal cords (VC) (absent), flotation of the «paralyzed» VC (insignificant and pronounced), mobility of the arytenoid cartilage (absent), closure of the VC (complete non-closure), synchronicity of oscillations VC (absence of movement of the paralyzed VC), restriction of the movement of the «paralyzed» VC (absent (the GE is motionless), level of the VC in the vertical plane (not on the same level), the tension of the median edge of the VC (incurvate), patient’s age > 45 years, the position of the «paralyzed» VC (median and intermedian). The mathematical analysis showed that none of the isolated laryngoscopic signs can be used as an independent criterion in assessing the predictions of the laryngeal mobilityrestoration.Conclusions. Prognostic laryngoscopic signs of recurrent laryngeal nerve damage in the thyroid surgery allow to create a prognostic model of recovery or lack of recovery of laryngeal motility, which is important for the appointment of timely adequate treatment.