Pawel Sowa M.D., ENT Department, Medical University of Silesia, Curie-Sklodowskiej St, 10, 41-800 Zabrze, Poland, phone: +48 32 373 23 95, e-mail: paw.sowa@gmail.com

Introduction

Bilateral vocal fold palsy (VCP) is a life-threatening condition usually requiring immediate aid. There are several causes of VCI) different for unilateral and bilateral failure. The most common cause of unilateral palsy has changed in recent years from non-laryngeal malignancies to nonthyroid surgery; however, the major cause of bilateral VCP remains the same: iatrogenic effect after thyroid gland surgery, being as much as 80% [1-4].

Operative techniques (i.e. recurrent laryngeal nerve – RLN identifying, endoscopic approach) or new equipment (intraoperative neuronal monitoring) are very helpful in preserving the safety of RLN during surgery, but the damage rate remains at about 5%. Of course the chance of harming the RLN is significantly greater in the case of malignant tumour surgery or reoperation [5]. The majority of RLN injuries concern unilateral palsy, carrying a small risk; however, one third of those complications are bilateral [5-7]. Therefore, laryngoscopy should be a routine examination prior to thyroid gland surgery [8]. Although there are some new ideas about the methods of vocal fold examination [9], they are still more expensive and hazardous compared with traditional laryngoscopy. It is worth noting that the majority of vocal cord immobility cases are unilateral and temporary, so patients usually return to good health within a few weeks or up to maximum of a few months.

Although the dyspnoea always accompanies bilateral vocal cord palsy, depending on the degree of respiratory problems tracheotomy may be or may not be required. Since it is not possible to easily distinguish the paresis from paralysis right away, an observation time of 6-12 months is needed before the laryngeal corrective surgery can be performed [10]. Numerous different techniques of surgery in the case of the bilateral vocal cord palsy have been proposed [11, 12]. Every technique has its supporters and opponents. So it seems that none of them is perfect and, as usual, the patient’s decision, surgeon’s preferences, and centre’s capabilities are crucial in choosing the optimal method of therapy.

The long-term ventilation results of the surgery depend on the postoperative side effects, mostly local ones. Some time ago mitomycin-C, a chemotherapy drug, was proposed as having a potentially positive impact on local healing and scar formation with lower risk of fibrosis. This effect seems to be long lasting and was supported by both in vitro and in vivo studies [13, 14].

The aim of our study was to show the possibility of widening of the glottis lumen, and to evaluate the techniques and effects of surgical treatment due to bilateral VCP resulting from thyroid gland surgery in patients treated in the ENL Department in Zabrze, Medical University of Silesia.

Material and methods

Our retrospective study included 270 patients who underwent surgical treatment because of bilateral VCI) in the ENL Department in Zabrze, Medical University of Silesia, in the years 1998-2014. Paresis occurred as the result of the iatrogenic effect of thyroid gland surgery in 255 patients (94.4%) vs. 15 (7.6%) from other causes (idiopathic, thyroid pathologies, cardiologic operations, mediastinal illnesses). Further analysis included only those 255 patients after thyroid surgery (197 females and 58 males; average age 56.9 ± 13.9 years, range 24-83 years).

Five methods of surgical treatment in bilateral VCP used in the ENL Department in Zabrze were considered in our study:

• laser-assisted posterior cordectomy according to Denis and Kashima [15] – unilateral or bilateral V-shape excision of the posterior part of the vocal fold
• laser-assisted bilateral medial arytenoidectomy with preservation of the lateral aspect of the arytenoid, proposed by Crumley [16]
• laser-assisted posterior ventriculocordectomy, described by Pia et al. [17]
• laser-assisted total arytenoidectomy with posterior cordectomy, presented by Ossoff et al. [18, 19] (Fig. 1)
• laterofixation – vocal fold transposition according to Lichtenberger [20] (Fig. 1).

All procedures were carried out using surgical microscope and Kleinsasser’s set under full anaesthesia. In laser-assisted procedures a CO₂ laser with maximal power of the beam at the level 7-12 W was used. Laterofixations were made using Lichtenberger’s set.

Mitomycin-C (Nordic Pharma, Paris, France) was applied during the surgery immediately after laser removal of proper tissue by local adhibition for two minutes.

The postoperative patient’s subjective improvement was assessed using the visual analogue scale – VAS. Patients were asked to report their pre- and postoperative breathing problems on VAS rulers. The difference between pre- and postoperative score was taken as the result. For the purpose of evaluating self-reported improvement we divided the VAS results into three clusters: > 5 VAS points – substantial improvement; 5-3 VAS points – average improvement, and < 3 VAS points – negligible improvement. The VAS assessment was performed on the day of surgery and two weeks after the surgery.

We adopted the scheme of post-operative followup visits: one week, two weeks, one month, three months, six months, one year, and every year. All visits were supported by ENL examination and videolaryngoscopy.

Statistical analyses were performed using Microsoft Office Excel 2010 and Statistica 7.0 PE. The parametric t-Student test and non-parametric U Man-Whitney, χ2, and Wilcoxon tests were used for the analysis. The values were presented as mean ± standard deviation (SD). Values of p < 0.05 were accepted as statistically significant.

Results

In the years 1998-2014 a total of 255 patients with bilateral VCP after thyroid surgery were treated in the ENT Department in Zabrze, Medical University of Silesia. Previously performed tracheotomy was observed in 170 patients (66.7%), while the remaining 85 (33.3%) did not require immediate respiratory aid. Among the patients with tracheotomy, 107 (62.9%) of them were successfully decannulated after first laryngeal surgery. The remaining 63 patients (37.1%) needed multiple procedures before final decannulation (n = 59, 34.7%) or required a sustained tracheotomy (n = 4,2.4%).

The majority of patients underwent laser arytenoidectomy with posterior partial cordectomy according to Ossoff et al. – 198 (77.6%), and in 35 (13.7%) of them the Lichtenberger laterofixation was performed. In 22 patients (8.6%) other laser treatment was chosen in accordance with the patient and surgeon’s choice (Table I). Because the group sizes were extremely different depending on the kind of surgery, further results were not compared between groups but are presented in the most numerous groups, particularly in the Ossoff’s surgery group.

Table I. The characterisation of patients operated because of bilateral vocal cord palsy in the ENT Department in Zabrze, Medical University of Silesia in the years 2002-2014
Tabela I. Charakterystyka pacjentów operowanych z powodu obustronnego porażenia fałdów głosowych w Klinice i Oddziale Klinicznym Otorynolaryngologii i Onkologii Laryngologicznej w Zabrzu, Śląskiego Uniwersytetu Medycznego, w latach 2002-2014

Granulation requiring additional procedure occurred in 15 patients after laser arytenoidectomy with posterior partial cordectomy (7.6%). Although our mitomycin-C patient group are still under observation (43 patients) and the precise results must be presented after sufficient follow-up, it can already be seen that the adhibition of the drug has a favourable impact on healing (data not presented-further follow-up needed).

Minor or major side effects appeared in 16 of 35 (45.7%) patients after Lichtenberger’s laterofixation. The events concerned the following: inflammation/allergic process in the spot of the thread attachment – 9, vocal fold intersection by the thread – 4, thread rupture – 2, and laryngeal oedema – 1. While minor complications (inflammation) occurred in the early postoperative period (1-14 days after procedure), the major ones (thread rupture, vocal fold intersection) occurred in the late postoperative period (two to several weeks) and required immediate action.

The patient’s subjective self-assessment of the respiration improvement after Ossoff’s surgery was performed using the VAS scoring mentioned before. Substantial improvement was reported by 102 patients (51.5%), average by 88 patients (44.4%), and 8 patients (4%) reported negligible improvement (Fig. 2).

Figure 2. Graphical presentation of patient’s subjective self-assessment of the respiration improvement using the VAS scoring
Rycina 2. Subiektywna samoocena poprawy oddechowej pacjentów przy użyciu punktacji VAS – prezentacja graficzna

In the next step of our study we tried to estimate factors like surgeon’s experience, mitomycin-C application, and tire accessibility of modern anaesthesiological or surgical equipment affecting tire results of our operations. Although there was no statistical significance, it could be seen that operator’s experience and new technique application (i.e. mitomycin-C, JET ventilation) had a favourable impact in tire results of the treatment as well as in the improvement in complication rate (data not shown).

Discussion

Regardless of the progress in current operative techniques and available equipment in the surgery of the thyroid gland being supported by more and more accurate anatomical studies [21-23], iatrogenic injury of RLN during such operations remains the main cause of bilateral vocal fold palsy [1, 2]. More than 94% of our patients suffered from bilateral vocal cord paralysis as a post-thyroidectomy complication, supporting this occurrence again [24].

The majority of our patients (66.7%) had had tracheotomy performed previously. An excellent alternative for tracheotomy seems to be the technique of laterofixation after Tichtenberger et al. [10, 20]. The technique is simple, fast, and inexpensive and most importantly of all – reversible. However, our experience shows a high complication rate for this surgical treatment. Most of the side effects were minor and appeared in the early follow-up (within two weeks) and therefore were easy to handle (inflammation/allergic process on the skin).

On the other hand, the most hazardous complications (vocal fold intersection by the thread, thread rupture, or laryngeal oedema) were seen a few weeks after the surgery and hence carried with them additional potential risk. Taken together, we still believe that laterofixation is be a good option for more traumatic tracheotomy, but it requires attentive follow-up. However, other authors consider this technique to be more valuable [25]. The weakness of our laterofixation efforts may be that we were able of try only a limited number of materials like threads etc. It has to be mentioned that the use of other, perhaps dedicated, materials could decrease the complication rate of this technique. East year onabotulinum toxin A injection into the cricothyroid muscles was proposed for bilateral VCP treatment as an alternative for surgery [26]. The idea seems to be interesting but controversial and requires further investigation.

Between the years 1998 and 2014 we used four laser-assisted techniques of laryngeal widening in the case of bilateral vocal cord paralysis: according to Denis and Kashima [15]; Crumley [16]; Pia et al. [17]; and Ossoff et al. [18, 19]. In our results, it can be seen that laser-assisted total arytenoidectomy with posterior cordectomy presented by Ossoff et al. is the most accepted surgical technique by our team. Two thirds of our studied group underwent this kind of surgery. The operation gives good ventilation results, presented as the percentage of successful decannulation in tracheotomised patients (62.9% after first surgery; 97.6% final rate) and substantial or average subjective ventilation improvement assessed in 96% of patients (51.5% and 44.4%, respectively). Most of our patients reported acceptable quality of life and many of them carried on with their intellectual work. These results agree with those previously presented both by our team [24, 27, 28] and other authors [10, 29]. Moreover, Ossoff’s surgery appeared to be a reasonably safe technique with only about 7% of minor unwanted effects (mainly granulation) [30]. Furthermore, the results of mitomycin-C application are very promising, although our studied group needs further investigation. The protective role in laryngeal wound healing was described previously [14].

Although we did not manage to present significant results concerning the impact of surgeon’s experience or the accessibility of modern anaesthesiological or surgical equipment on the results of our operations, a clear trend could be seen. Surgeon’s experience seemed to play the most important role in the success of the treatment, yet the accessibility of modern anaesthesiological equipment (i.e. jet ventilation, mitomycin-C) or modernised surgical instruments improved both surgical and follow-up patients’ safety. These results seem to be obvious nowadays.

Conclusions

Surgery of the thyroid gland remains the main cause of bilateral VCP. However, there are surgical procedures allowing the correction of the glottis. One of them is laser-assisted total arytenoidectomy with posterior cordectomy. The procedure is safe and provides acceptable ventilation improvement that gives patients satisfactory quality of life and the possibility of returning to active professional life. In our opinion, laterofixation should be considered as an alternative for temporary tracheotomy rather than permanent procedure.