HSC Section 6 Nov2016 Green Book

Reiter et al

large supra-regional center of thyroid surgery where diffi- cult cases including revision operations are performed. All patients with voice problems after surgery were sent to our department and could be included in this study. Unilateral vocal fold paralysis often causes severe impairment of the voice with dysphonia and reduced inten- sity because of insufficient glottic closure during phonation. However, UVPs have a potential of resolution that usually occurs within 12 months and in most cases within the first 6 months 2-4 (also confirmed in our study). The overall rate of recovery was 75 of 100 (75%) in all patients and 67 of 82 (82%) in the iatrogenic/traumatic group, respectively. Studies have shown that permanent paralysis remains in 15% after thyroid surgery and in up to 20% in 717 patients with an idiopathic paralysis—similar to our study. 2,4 In order to plan therapy and keep the patient informed, it is advantageous to know if any resolution of paralysis is likely. Laryngeal electromyography (LEMG) is an established method of assessing the neuromuscular status of the paralyzed vocal fold. Early evidence of reinnervation or innervation in paresis can be shown by this method. Laryngeal electromyog- raphy criteria for poor prognosis were the presence of sponta- neous activity and absence or reduced recruitment of motor unit potentials. 16 In a meta-analysis by Rickert et al 16 and an analysis by Sittel et al, 17 LEMG predicted defective recovery defined as absence of completely free vocal fold mobility in up to 94%. However, in a study with a small cohort, it was shown that LEMG findings predict only 44.4%of the resolved cases, 18,19 which is less satisfactory. Adrawback of the LEMG is the fact that it takes time and is an invasive procedure not well tolerated by patients. Furthermore, it requires expensive equipment and an experienced investigator. 9 By analyzing the vibrations of the vocal folds, the state of the mucosa (cover), and the underlying laryngeal, muscle tone (body) can be assessed. 9,11 In microlarygostroboscopy, the mucosal wave represents the clinical correlate for mus- cular tonicity of the vocal cord. When present, recurrent nerve function is at least in a sense present, that the epithe- lium of the vocal cord can exactly follow the musculus vocalis movements in pitch as well as in intensity. However, mucosal waves can only be judged when there is no phona- tion gap ≤ 3 mm in UVP, enabling the mucosa to get in con- tact with each other. Furthermore, MWs are reduced or absent if mucosa (cover) adheres/sticks to the musculus vocalis and/or ligamentum vocale (body). This phenome- non is observed in patients with chronic laryngitis/leucopla- kia, carcinoma, and scar formation of the vocal folds. The warning factors for progression of dysplasia to invasive car- cinomas is a nonvibrating segment/absence or reduction of the MW in videostroboscopy. 20,21 A scarred vocal fold has an absent or limited MW 22 as well, and for this reason, such patients were excluded from our study. To our knowledge, this is the first clinical study to report the prognostic relevance of MW in laryngostroboscopy for

Figure 1.  A patient with a unilateral vocal fold paralysis (UVP) on the right side. Positive mucosal waves (MWs) are seen in microstroboscopy on the paralyzed right ( → ) and the non- paralyzed vocal left fold.

Discussion The main reasons for UVP are iatrogenic/traumatic paraly- sis (about 4/5, especially in thyroid surgery) followed by malignancy-associated and idiopathic paralysis, as shown recently in a cohort of 400 patients 1 and confirmed in our study. Iatrogenic paralysis after (thyroid) surgery represents the majority of patients because we are associated with a Table 1.  Recovery of Unilateral Vocal Fold Paralysis (UVP) Dependent on Mucosal Wave (MW) in All Patients. UVP Positive MW Negative MW Total Recovery 73  2  75 No recovery  7 18  25 Total 80 20 100 Figure 2.  A patient with a unilateral vocal fold paralysis (UVP) on the left side. Positive mucosal waves (MWs) are seen in microstroboscopy on the non-paralyzed right side but are absent in the paralyzed left vocal fold ( → ).

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