SPECIALIZATION IN OTORHINOLARYNGOLOGY
Supervisor:
Dr. Giuditta Mannelli ,
Author:
Dr. Federica Granato ,
ANNO ACCADEMICO 2017/2018
The surgical treatment of unilateral vocal cord paralysis:
qualitative review analysis and meta-analysis study
The surgical treatment of unilateral vocal cord paralysis: qualitative review analysis and meta-analysis study.
Tale of contest: 1. Introduction
2. Causes of vocal cord paralysis:
2.1 Viral/Idiopathic 2.2 Malignant lesions 2.3 Surgery
2.4 Others (i.e. trauma, RT, intubation history, drugs)
3. Diagnosis of vocal cord paralysis
3.1 Anamestic data, measures of the vocal handicap and auditory-perceptual evaluation
3.2 Stroboscopy 3.3 Laringoscopy 3.4 Imaging for UVFP
3.5 Laryngeal Elettromiography
4. Type of surgical treatment:
4.1 Trans-oral injection (materials, injection mode) 4.2 Vox implant
4.3 Thyroplasty type I (Montgomery, Gorotex), Arytenoid Adduction(AA) 4.4 Thyroplasty I + IV
4.5 Cricothyroid Subluxation 4.6 Laryngeal re-innervation
5. Objectives of the review 6. Methods
6.1 Study characteristics and quality assessment 6.2 Statistics 7. Results: 7.1 Trans-oral procedures 7.2 Open procedures 7.3 Open vs Transoral 8. Discussion 9. Limitations 10. Conclusions 11. References
1. Introduction.
Unilateral vocal fold paralysis (UVFP) is the complete immobility of one vocal fold due to nerve dysfunction and it is a major cause of dysphonia and of possible dysphagia.
Umpteen number of causes were attributed to its appearance and its etiology showed changing in trends from place-to-place and over time. It is of utmost importance to arrive at a correct diagnosis to plan its management and to determine each patient prognosis. Restricted vocal fold movements could be secondary to impaired laryngeal innervation or mechanical fixation of the crico-arytenoid joint 1. The former, could be due to a lesion in the motor cortex, the cortico-bulbar motor pathways, the nucleus ambiguus, the vagus nerve, or any part of the recurrent laryngeal nerve (RLN) 2. On the other hand, mechanical fixation of the crico-arytenoid joint could occur after crico-arytenoid dislocation, local inflammation or neoplastic invasion.As in the case with vocal fold paralysis, incomplete paralysis or paresis could be due to iatrogenic, neoplastic, neurologic, and idiopathic causes outlined in section. Idiopathic causes were much more common with vocal fold paresis, and could represent a viral neuropathic process 3. A high index of suspicion for an underlying progressive neurologic disease (e. g., amyotrophic lateral sclerosis, post-polio syndrome) must be maintained as well. Since the 1970s papers reported that the main causes of UVFP were malignancies (prevalence 25.2–38.1 %, including lung neoplasms in 8.7–22.4% of cases) , followed by surgery (10.4–24.4 %, with thyroid surgery accounting for 3.7–19.8 % of cases), and idiopathic causes (up to 26.8 %) 4. This trend continued during the 1980s and the first half of the 1990s, with malignancies being reported in 24.6–40.5 % of cases (lung neoplasms in 15.3–16.7 %), surgery in 23.9–34.5 % (including thyroid surgery in about 8.3 %) 5,6,7 , and an idiopathic origin in 10.7–19.6 %. However, trends in aetiology for UVFP started showing changes in papers published between 1990 and 2005, which described an increased prevalence of post-surgical cases (47.8–51.2 %, including 14.1–21.1 % after thyroid surgery), followed by malignancies (9.9–21.6 %, including lung neoplasms in about 6.3 %), and idiopathic causes (16.8–17.6 %). On the basis of these findings, it seems that over time there has been a decrease in prevalence of malignant neoplasms causing UVFP (mainly due to a progressive reduction in the occurrence of lung cancer), and a progressive increase in cases attributable to thyroid surgery 8,9. Cantarella et al. 10 published a retrospective study analyzing the etiology of UVFP between 1990 and 2015 by comparing a cohort of patients treated in 1990-1992 with a cohort treated in 2013-2015 documenting a changes in the aetiological pattern of UVFP over the last 25 years, with a considerable decrease in post-thyroidectomy UVFP, and a growing predominance of idiopathic and post-thoracic surgery UVFP. An increase in thyroidectomies, not surprisingly, had been associated with more postoperative complications. In fact, surgical manipulation were responsible for 46% and 56% cases of unilateral (UVFP) and bilateral vocal fold paralysis (BVFP), respectively, which often resulted in severe dysphonia, dysphagia, and dispnea 11.
Finally, it is important to remember that the literature shows a preponderance of the paralysis of the left side and the data relating to this finding date back to the 40s 12. According to Meurman et al. the left recurrent laryngeal nerve was more likely to be injured because the vagus nerve branches more caudally on the left side than the right side. In fact, after the beating of the vagus nerve, the recurrent laryngeal nerve on the left, unlike the right, flows under the aortic arch. It then runs upward in the groove between the trachea and the esophagus with a more medial course, closer to the thyroid gland than the right recurrent laryngeal nerve. Another reason for the increased frequency of left side palsy may be in the length of each nerve 13-14. On average, the left recurrent laryngeal nerve measures 12 cm, while the right laryngeal nerve measures 5 to 6 cm 15. The added length may explain the higher rate of paralysis of the left side making the nerve more vulnerable. The primary symptom of UVFP is dysphonia. The prevalence of voice disorders in the general population is 6.6% 16 and the incidence of UVFP among those with voice disorders has been calculated at 1.2% 17.Thus, the dysphonia is constant during unilateral laryngeal paralysis but its intensity is variable ranging from mild dysphonia (so slight that it can sometimes go unnoticed to listen for an untrained practitioner) to the whispered voice with breathlessness, passing through classical diplophony. The incidence of deglutination disorders estimated at 30% varies according to the etiology and the topography of the attack with a severity ranging from simple episodes of coughing during swallowing of liquids to genuine pneumopathies. Modern work highlights the intricacy of pathophysiological mechanisms generate these disorders of the swallowing with the defect of glottic closure especially at the level of the posterior glottis, the alteration of the hypopharyngeal and ipsilateral laryngeal sensitivity, the alteration of the peristalsis and mechanisms of pharyngeal propulsion of the alimentary bolus, the desynchronization different oropharyngeal times of swallowing and alteration of the reflex of cough. Dyspnea is rare, noted in less than 5% of cases. It occurs during physical exertion and is the result of syncinesies which testify to an aberrant re-innervation process in the paralyzed laryngeal muscles (additive nerve fibers re-innervate laryngeal muscles whose function is abductive and the other way around) 18. Effective management of the UVFP required accurate diagnostic and prognostic information in order to construct a clear therapeutic ration, always taking into account the needs and lifestyle of the patient and the real stated goals of intervention. A number of factors are likely to influence treatment selection, including onset of injury, cause, degree of glottal insufficiency, severity of dysphonia and prognosis. Obviously, in addition there were various factors that can give weight to the choice of treatment: age, co-morbidity, patient expectation, treatment facility, experience / ability of the clinician and availability of equipment. The problem was an increasing number of studies reporting the efficacy of treatments for UVFP, but most studies did not provide a clear clinical motivation for the choice of treatment program 19. The aim of treatment for UVFP is to restore functional voicing and improve glottal insufficiency.After a watchful waiting period of about 9–12 months and/or speech therapy (voice) exercises for patients with continued dysphonia is indicated a surgical approach either with injection augmentation of the vocal fold or laryngeal framework
surgery. One of the mainstays of surgical treatment of UVFP is the concept of medialization, in which the paralyzed vocal fold is displaced toward the midline to facilitate glottal closure. Injection medialization of the vocal fold was first performed in 1911 by Brunings via perioral injection using paraffin. This technique lost popularity until the development of other injectables that were thought to be less reactogenic; a variety of materials is now available for use in injection medialization : bovine gelatine, collagen-based products, hyaluronic acid gel, autologous fat , calcium hydroxylapatite (radiesse), teflon, goretex ecc.. Timing of injection medialization may affect long-term outcomes. In all comers, overall need for permanent medialization (eg, medialization thyroplasty) is approximately 20% to 30% after injection 20. There are now data to suggest that early injection medialization may be associated with a lower rate of eventual need for permanent medialization thyroplasty21,22. In unilateral vocal fold paralysis (UVFP), framework surgery was generally performed after a waiting period of 6–12 months to allow for spontaneous recovery. Medialization laryngo-plasty was indicated for those patients with moderate to severe glottic insufficiency manifested by weak, ventilated dysphonia and / or dysphagia. While most patients with minor degrees of glottic insufficiency (glottic gap <1-mm on phonation) who had minimal speech symptoms (eg speech fatigue) could be more likely to be candidates for voice injection and / or therapy. Medialization laryngoplasty could be performed with a variety of implant substances, including Silastic, gore-tex, hydroxyapatite and titanium. Arytenoid adduction (AA) was another technique used in the treatment of glottal insufficiency that acts through direct traction on the arytenoid cartilage at the muscular process, mimicking the action of the lateral cricoarytenoid muscle. AA was an important adjunct in selected cases of vocal fold paralysis such as patients who had a lack of vocal process contact during phonation (large posterior gap), short-ened immobile vocal fold, and those with vocal folds at different levels, AA should be considered in addition to medializzation laryngoplasty. Another technique used in addition to the medializzation laringoplasty and when there was a shortened vocal fold , frequently seen in unilateral vocal fold paralysis, is the Cricothyroid subluxation developed by Steve Zeitels 23 . This procedure consisted to increasing the distance from the cricoarytenoid joint to the anterior commissure (thyroid cartilage) by subluxating the cricothyroid joint on the side of the unilateral vocal fold paralysis. A further technique to be considered was the re-innervation of the primary intraoperative recurrent laryngeal nerve (RLNR) which had numerous advantages over thyroplasty and injection laringoplasty being performed during surgery ; a prospective study published in 2018 by Lee et al compared and assessed long-term voice outcomes when thyroidectomy-related unilateral vocal fold paralysis (VFP) was managed using injection laryngoplasty (IL) and recurrent laryngeal nerve re-innervation (RLNR) with the result of an improvement of the post-operative voice, after 36 months, greater if intra-operative re-innervation was performed compared to injective laryngoplasty alone 24.
This paper provides a review of the surgical treatment in laryngeal paralysis over the last decade in order to give a comprehensive overview of the most recent advances in treatment of laryngeal
paralysis and combined with all of the information needed to give correct diagnosis and individualised , right treatment of “early” unilateral vocal fold paralysis for each patient.
2. Causes of vocal cord paralysis
2.1 Viral/ Idiopathic :
Idiopathic vocal fold paralysis (IVFP) had been reported as the most common cause of unilateral vocal fold paralysis 25 . Diagnosis was based on exclusion of other etiologies, such as iatrogenic injury, neoplastic invasion, trauma, central nervous system lesions, and intubation 26.
The development of new diagnostic tools able to reveal the veridical diagnosis for a unilateral vocal fold paralysis, and the development of techniques that could cause iatrogenic trauma have caused over time the decreasing the incidence of unilateral IVFP while that of iatrogenic vocal fold paralysis has been increasing 27. The precise pathophysiology of IVFP remains debatable ; the most widely held theory is herpes simplex infection, so a post-viral phenomenon often seen in a healthy patient. It is assumed that the lesion is an inflammatory neuropathy, similar to the cranial neuritis observed with the Bell palsy 28.In comparison to the paralysis of the vocal cords of other causes it has a relatively good prognosis, with the majority of patients having a partial or complete recovery of the voice function. . Although this theory is widely regarded as true, few scientific data have been published to show that HSV neuritis is the causative agent in "idiopathic" UVFP.
2.2 Malignant Lesions :
Non-laryngeal neoplasms represented an additional serious cause related to laryngeal paralysis. In this condition the mechanisms that cause the paralysis of the vocal cord could be multiple. In malignant disease, recurrent laryngeal nerve paralysis (RLN) could be caused by the direct invasion of malignant cells or by tumour mass compression. In the case of benign disease, for example a voluminous thyroid nodule, compression and stretching of the nerve were possible etiologies. Important neoplasms to consider included bronchogenic carcinoma , thyroid and thymic malignancies, esopha- geal cancer, and neurogenic tumors such as para- gangliomas and schwannomas. Malignant tumor progression could also be heralded by the development of vocal fold paralysis . Of particular importance was the fact that new VCP in a patient with a known intrathoracic malignancy could suggest a more advanced disease stage by indicating previously unrecognized mediastinal invasion or compressive adenopathy. Lymphoma was another of the possible tumor causes of VCP and could produce VCP by compression, rather than by invasion, of the RLN 29. O’Duffy et al 30 reported in their study an incidence of thyroid disease with
recurrent laryngeal nerve paralysis of 1.7 percent in this series comparable to other 1.2 percent series.
Paralysis of the recurrent laryngeal nerve in the presence of thyroid disease wasn’t pathognomonic due to neoplasm. The current literature could underestimate the association between paralysis of the vocal cords and benign thyroid pathology indeed the paralysis could manifest itself both as an expression of a malignant pathology and a benign thyroid disease (cysts, multinodular goiter, thyroiditis, etc.)
2.3 Surgery :
The major cause of UVFP is lesion of the recurrent laryngeal nerve. A frequent cause of trauma to this nerve was iatrogenic, including thyroidectomy, thoracic, heart and cervical spine surgeries. Thyroidectomy was the principal cause of surgery-related paralysis 31 : vocal changes and swallowing impairment were usually well-known sequelae following thyroid surgery due to lesion of the laryngeal nerves. Permanent lesions to these nerves occured in 0.7-13.3% of cases for the RLN and in 5-30% of cases for the external branch of the superior laryngeal nerve after thyroid surgery. This rate varied greatly depending on the surgeon's experience32
In the literature, however, there were data that in recent years suggest that non-thyroid surgeries, including cardio-thoracic interventions, passed thyroid studies as the most common iatrogenic causes of UVFP 33,34. Some authors suggested that up to 26% of patients undergoing total aortic arch and descending surgery suffer complication with UVFP 35. Others suggest a post-operative paralysis of RLN in 10.8% of the patients undergoing thoracic surgery and in 31.5% of patients whose surgery was determined to place the "high risk" RLN 36.VFP was a complication also associated with esophagectomy interventions with an incidence reported from 2% to 80% 37 Among the main factors associated with post-esophagectomy VFP there was obviously the surgical approach 38-39. In their study Loochtan et al 40 found that the majority of patients (n = 56, 62%) who underwent esophagectomy using cervical mobilization had postoperative VFP (39%). When compared to other types of surgical exposure, transcervical dissection was significantly associated with postoperative VFP (P \ .0001). Paralytic cord paralysis also formed part of the frequent complications of open surgery of the aortic arch and the descending aorta and was associated with significant morbidity. Previous publications on the surgical repair of thoraco-abdominal aortic aneurysms have reported UVFP rates of between 20% and 40%, depending on the position of the aneurysm 41,42. Ishimoto and colleagues 43 examined the outcomes of 62 patients who had undergone thoracic aortic repair and described a 32% VCP incidence. Ishii and colleagues 44 reported that 9% of 156 patients had the complication after repairing the thoracic aortic aneurysm. Ohta and colleagues 45 have documented a 22% incidence of VCP in 183 patients who underwent aortic arch aneurysm repair and described the resulting pulmonary complications. Di Lisio and colleagues46 examined a series of 498 patients who underwent surgery for thoracic aortic aneurysm and found a 7.2% VCP incidence in the bow and descending aortic repair group. Lodewyks et al 47 suggest an incidence of VCP comparable to previously published reports and also highlight an increased risk of this complication in patients undergoing total arch and descending aortic procedures.
2.4 Others (drugs, trauma, RT, intubation history)
Vocal cord paralysis is one of the most serious complications associated with tracheal intubation, resulting in severe vocal disability and aspiration.
Several study48 have shown that the risk of vocal cord paralysis was found to be increased three-fold in patients aged older than 50 yr, two-three-fold in patients intubated 3 – 6 h, fifteen-three-fold in patients intubated 6 h or more, and two-fold in patients with a history of diabetes mellitus or hypertension. The endolaringeal soft tissue injury was usually caused by inappropriate (usually emergency) or prolonged intubation or by placing the tube too high or with a cuff too swollen or traction on the tube (eg passive movements of the head during the movement of the ducted patient ). The most common lesions were the edema of the subglottic mucosa, the hematoma or tears or even the intubation granulomas in correspondence with the vocal process, dislocation of an arytenoid cartilage and laceration of the vocal cords.
Vincristine is a vinca alkaloid widely used in the treatment of neoplastic diseases and is a potent agent in the group for the treatment of acute lymphoblastic leukemia. Its toxicity is dose-dependent and it is responsible for a neuropathy: peripheral nervous (motor / sensory), autonomic, cranial nerve or encephalopathy. The pathogenesis of vincristine-induced neurotoxicity is not well defined, but is thought to be related to its main mechanism of action as an inhibitor of the mitotic spindle thus inhibiting the rapid axonal transport by microtubules. The paralysis of the vocal cords may be the result of peripheral damage to the laryngeal nerve or to the processes of the central nervous system that affect the nuclei and the origin of the vagus nerve49. It may be unilateral (typically left-side) or bilateral and may require intubation or surgery, e.g. cordotomy to maintain airway pattern.
Several cases of external trauma of the larynx were reported in the literature, including several related to sport activity due to paralysis of the vocal cords. Less frequent, however, the literature reported cases of vocal fold fixation as a result of trauma caused by a foreign body; Guo et all 50 reported a unique case of vocal fold fixation caused by traumatic penetration of a shard of steel in a 31-year-old steelworker.Laryngeal and pharyngeal radiotherapy was known to cause direct lesions of laryngeal tissue, especially in the treatment of locally advanced head and neck carcinoma.
Radiation neuropathy was generally considered progressive and irreversible, occurs at least for months to years after discontinuation of therapy 51 with latency inversely related to the radiation dose 52,53. In peripheral nerves, radiation-induced damage occurred after exposure to local radiation and was the result of several factors including radioactive fibrosis caused by free radicals, especially reactive oxygen species, which promote it when the mechanics for their disposal was overwhelmed, a condition that persists in chronic inflammation or hypoxia 54. This damage was built up to produce neuropathy symptoms over the years. The main clinical feature of post-radiation laryngeal neuropathy was the high incidence of dysphagia associated with
dysphonia and had a minimal potential for spontaneous recovery. The increase or medialization should be considered not only for the altered tissue response when the larynx was in the irradiated field, but also for the potential for future deficits that develop in the contralateral nerve exposed to the same radiation 55.
3. Diagnosis of vocal cord paralysis
3.1 Anamestic data, measures of the vocal handicap and auditory-perceptual evaluation
The collection of anamnestic data and in particular of the symptoms is the first step for the evaluation of a patient with paralysis of the vocal cords. About 30 per cent of patients may be asymptomatic 56. The considerable effect on the quality of life of the patients affected has led to
the development of self-assessment methods whose purposed is to quantify the perceived severity of the disability of the patient's language.
In 1997, Jacobson et al. 57 proposed a measure of the vocal handicap known as the Voice Handicap Index (VHI). This self-assessment tool consisted of a short, self-administered questionnaire that quantifies the patients' perception of their vocal handicap on a scale from 0 to 40 (with higher values corresponding to a higher level of perceived handicap due to their voice ) .
The Voice Handicap Index (VHI-30) consisted of 30 questions divided into three groups : physical area functional area and emotional area. A new version of the VHI was then reformulated and reduced to 10 items (VHI-10) for clinical purposes; the 10 elements that maked up the VHI-10 were extracted from the VHI-30. Several studies have shown that the VHI-10 was a robust tool that can properly represent and replace the VHI-30 58.Later ,in 1999 Gliklich et al. 59 developed the Voice Outcome Survey (VOS) a short, reliable tool that was the most sensitive measure to clinical change after surgery. The auditory-perceptive evaluation of voice quality involved an experienced listener who judges a vocal sample based on various vocal parameters and marks the extent to which the voice differs from a perceived "normal" interval.
There are several formal assessment scales including the GRBAS scale (degree, roughness, breath, asthenia, stress) or more recently the perceptive evaluation of the object (CAPE-V) that incorporates the parameters of degree, roughness, breathability, asthenia and tension and also allows to add further dimensions; both show that patients with UVFP are assessed significantly worse than normal. In the literature there was no consensus on which vocal outcome indicators (VOIs) should be used to compare the merits of the various surgical treatments for unilateral paralysis of the vocal cords. Desuter et al 60 performed a literature review to identify which VOIs are most frequently used and most relevant in terms of significant change in pre- and post-operative measurements and to evaluate UVFP surgical treatments.For these most frequently used VOI’s, the number of studies that showed a statistically significant change in pre- and post-operative results were compared to the total number of studies found using that same VOI, this portion was expressed in percent. This percentage was defined as the “percentage of
significance” and used to assess changes of each VOI.The results indicate that between these maximum fonation time (MPTs) and GRBAS-I represent two of the most important VOIs in terms of "significance percentage" of 90% and 85% respectively while the VHI-30 showed a relatively low and low utilization rate “percentage of significance "of only 64%.
3.2 Stroboscopy:
The alterations of the vibration of the vocal cords may be the result of various diseases, the technique that allows us to evaluate this aspect is the videostroboscopy an important complement to the collection of clinical history and physical examination.
Quantitative characterization of the vibratory behavior of the vocal folds is a pivot task to add to the diagnostic step. In 10-30% of cases, the results of videostroboscopy lead to a change in the diagnosis and treatment of patients with dysphonia 61.A well-known drawback of video-laryngo-stroboscopy (VLS) is the reliance on quasi-periodic voice signals 62 when producing a real-time slow-motion stroboscopic effect. Objective measurements of the vocal fold vibration pattern date back to the initial high-speed cinematography recordings of vocal fold vibration from the works of Timcke, von Leden, and Moore 63-66.
Several indices, describing the glottal wave form, are usually used for the characterization. They provide mainly the ‘‘functional information’’ about the vibratory function of the vocal folds and the glottal closure, and when they are matched with direct endoscopic images, they provide together more detailed information about structural and morphological peculiarities which are both fundamental in making the correct diagnosis. In fact, this tool is able to reveal a number of abnormalities, including abnormalities of laryngeal structure, absence of vibration, and vibratory asymmetry. Flashing light is used to illuminate an object in stroboscopy. When the flashes are synchronized with the vocal fold vibrations, a stationary view of the vocal folds is obtained. However, the single-flash-timing laryngeal videostroboscopy has a limitation that it is effective only when vocal fold vibrations exhibit only one single fundamental frequency. The advent of high-speed videolaringoscopy (HSV) offered the opportunity to see the actual vibratory cycle of the vocal cords in detail through a high sampling rate of successive frames and adequate spatial resolution. The vibration parameters of the vocal cords evaluated by means of the stroboscopy are: glottal closure, vibrational symmetry, periodicity, mucosal wave, amplitude (Hz) and phases of the glottal cycle 67.
3.3 Laringoscopy:
Laryngoscopy is an important diagnostic technique and perhaps the first concrete step for clinical evaluation and to plan the type of intervention required in patients with unilateral paralysis of the vocal cords. While videostroboscopy offers better image quality, better magnification and can help to detect the subtle movements of the vocal fold, of the vocal process and of the arytenoid, flexible laryngoscopy provides a more “physiological” image that is to
visualize the mobility of the vocal cords in its natural state; therefore the two techniques are complementary to each other.
A paralyzed vocal fold can occupy a variety of positions, Hong and Jung 68 classified the position of vocal folds as adduced if positioned along the midline or paramedian, neutral if along the intermediate line and abducted or cadaveric if positioned laterally (Fig.1)
In the past it was thought that the position of the paralyzed vocal fold had some topognostic meaning , for example: the lateral position of the vocal fold indicated a complete paralysis of the vagal caranic nerve due to the involvement of RLN and SLN , but the theory was later disproved by from different authors 69 ; it is actually believed that the final position of the vocal fold following a nerve injury is due entirely to the degree of re-innervation and to the present synkinesis. Endoscopic laryngeal findings can also vary. In cases of unilateral VFP (UVFP), the most common laryngoscopic findings include bowing, incomplete glottal closure, and phase asymmetry on videostroboscopy. The paralyzed side tends to be shortened and the arytenoid is commonly anteriorly rotated 70. Istead, few studies have utilized laryngoscopy as a prognostic tool to predict recovery, Menon et al 71 have analyzed endoscopic results of the immobility of the unilateral vocal fold and determined the prognostic value of laryngoscopy in predicting recovery. Factors evaluated in the aforementioned study were muscle movement (anterior adductors, posterior cricoarytenoid, interarytenoid), position of the vocal cords and position of the arytenoid (normal, anteromedial inclination, lateral tilt, postero-lateral inclination).The statistycal analysis conducted to examine the associations between the three parameters above and the recovery revealed that those patients with paralysis of the arytenoids and postero-lateral inclination of the arithenoid had less chance of recovery while the position of the vocal fold did not have an association significant with recovery. Furthermore the compensatory movement of the healthy side guaranteed, if present, a better voice function even in the absence of recovery and without the need for any intervention.
3.4 Imaging for UVFP :
Imaging is essential when we are faced with paralysis without a known cause.
Approximately 30% of the unilateral paralysis of adult vocal cords without apparent cause is caused by subclinical tumors 72.
Chest radiography, chest CT scan with / without neck and magnetic resonance imaging from the from the skull base to the chest are the most commonly used imaging studies for the detection of subclinical tumors responsible for paralysis of the vocal cords.
Magnetic resonance imaging is effective in detecting tumors in the brainstem and cranial base, but taking into account that subclinical tumors in these regions ,responsible for paralysis of the unilateral vocal cords in adult patients ,are quite rare and that thyroid cancer is one of the most common neoplastic causes of paralysis in adults, magnetic resonance is not supported by the literature compared to CT 73 .
A chest CT scan can show lung and mediastinal tumors very well and appears to be supported by a moderate amount of literature 74; however, a CT scan of the neck is of questionable utility in the differential diagnosis of thyroid tumors and causes radiation exposure of patients 75.
So ultrasound is the most sensitive and accurate imaging study for the differential diagnosis of thyroid tumors compared to thyroid scintigraphy, CT and MRI and as suggested by other investigators 76,77 besides the thyroid gland ultrasonography can check the other neck regions, tracheo-esophageal sulcus, the entire jugular chain, the supra-clavicular regions and possible tumors of these areas.
Although PET is not among the diagnostic techniques routinely used during UVFP, it is important to remember that this can be responsible, if used, for false positives. Several studies have shown that in the presence of a unilateral paralysis of a vocal cord the normal contralateral side can have a high intake of fluorodeoxyglucose, considered secondary compared to the compensatory movement attempt, causing misleading doubts due to the presence of malignancy 78,79. These findings were more commonly described in patients with primary pulmonary neoplasms who had recurrent unilateral recurrent laryngeal nerve palsy. Other cases described in the literature of false positives due to the use of PET derive from the injective treatment of UVFP: granulomas that derive from the use of Teflon for the injection medialization can lead to false positive results on PET 80.
3.5 Laryngeal Elettromiografy :
The immobility of the vocal cords may be the result of multiple causes including nerve damage, fixation of the crico-arytenoid articulation, neuromuscular joint disorders and tumor infiltration 81. The most common causes are nerve damage (incomplete or complete) and mechanical
fixation. Complete patient assessment should provide a complete physical examination, including neurological evaluation, with optical and stroboscopic fibers. However, it is difficult to identify the cause exclusively from clinical manifestations and indirect laryngoscopy alone is insufficient for the etiological diagnosis of unilateral immobility of the vocal cords, giving false results in almost 30% of cases 82. Laryngeal electromyography (LEMG) was introduced in 1944 by Weddel, and the technique was improved in the '50s by Faaborg-Andersen and Buchthal, but its development as a diagnostic tool occurred mainly in the' 80s and '90s 83. Only through LEMG was it possible to know the physiological characteristics of nerves and laryngeal muscles. This technique was able to identify the normal innervation, the absence of innervation, the re-innervation and even the sinkynesis from characteristic electrical signals.
An important question is : when the EMG must be done?
Wang and al 84 recommend 2 months, but the time set by neurologists for EMG is 3 weeks. At 3 weeks, the type of disease can be assessed, while at 2 months it is possible to see the presence of re-innervation, which is related to the prognosis.
The value, both diagnostic and prognostic , has been established in several studies 85-87,
and in particular the predictive ability on the prognosis of patients with cordal paralysis due to different causes and with varying degrees of severity at presentation of the disease was evaluated.Statham and colleagues 88 showed that the presence of synkinesis in patients with vocal fold paralysis has improved the negative predictive value (NPV) of LEMG from 53% to 100% and sensitivity from 56% to 100%. Rickert and colleagues 89 published a meta-analysis in 2012 of studies reporting LEMG results and clinical outcomes, out off 503 patients, reporting a positive predictive value (VPP) of 90.9% and an negative predictive value (NPV) of 55.6%. Similar results were published in 2014 by Wang and colleagues90 who performed a prospective study using LEMG to predict the long-term prognosis of UVFP, including 85 patients, reporting a 93% PPV and a 40% NPV and when LEMG was performed more than 2 months after the onset of symptoms, the PPV was 97.9%.
Pardomaza et al. 91 in their study published in 2017 and conducted on 80 patients, they performed LEMG at least 3 weeks after the injury in order to evaluate the link between the degree of injury and the prognosis of the recovery of the vocal movement, resulting in 88.2% of the positive predictive value and 35.7% of the negative predictive value. The results were therefore comparable with those published previously in the literature.
Laryngeal electromyography therefore has a high positive predictive value in predicting the long-term outcome of patients with UVFP with poor prognosis.
Despite it is relatively easy to perform and with few side effects 92 it requires an ENT physician and a neurophysiologist to perform the exam and interpret the results making it unused in routine practice 93.
4. Type of surgical treatment:
The principle behind the surgery of unilateral laryngeal paralysis is the medialization of the paralytic vocal cord to restore the correct coping of the vocal chords during the phonation and restoring the swallowing sphincter.
Medialization can be obtained by increasing the volume of the vocal cord by injecting endoscopically or trans-cutaneously opposed surgically open: thyroplasty or by keeping the arytenoid in adduction with a pexy.
In the past it was a common opinion that the use of temporary materials for medialization offered only short-term benefits. To date there are numerous studies showing a statistically significant association between the temporary injection of a paralyzed vocal cord and the reduced need for permanent medialization with laryngoplasty 94.
In particular, the data demonstrate 95 that UVFP patients undergoing vocal fold injection with a temporary agent have better measures of the perceptual quality of the voice and glottic insufficiency than those managed conservatively over the period of time when temporary agents are reabsorbed.
Furthermore, it was documented that earlier medialization occurred by injection was less probable for patients to undergo definitive surgery compared to patients who had been treated with conservative treatment alone or who had delayed treatment after 6 months 96.
4.1 Injection :
The fundamental premise when it comes to increasing the vocal cords by injection is surely the fact that we are talking about a minimally invasive approach that can be performed in a clinical context compared to surgery of the laryngeal structure that is performed in the operating room, under general anaesthesia burdened from the risk of reactive airway oedema after surgery. Because of these limitations, many patients with acute / sub acute UVFP may not be good candidates for laryngeal surgery; in addition, the patient with unilateral iatrogenic paralysis may not be willing to return to the operating room for another surgery, but could more easily accept the idea of an increase in vocal cords in an outpatient setting and especially under local anaesthesia.
In fact, local anaesthesia is generally preferred for performing this technique (oral or percutaneous approach) so that the patient's voice can be used as a constant source of feedback during the procedure.
• Materials:
The first descriptions of laryngoplasty by injection date back to 1911 by Brünings who described paraffin injection in vocal plica, this substance was effectively abandoned for several years due to poor tolerance and complications related to paraffin.
The ideal material for vocal injection should have the following properties: biocompatible, non-reactive, non-volatile and non-carcinogenic; also maintaining its volume and its position over time together with the ease of preparation and injection would be important features.
There are now many materials by increasing the volume of the paralyzed vocal cord and it is possible to divide them according to their characteristics : temporary injection substances ( 2 – 6 months) or long-lasting substances (2 years or more), materials used for deep vocal cords injection or for superficial vocal cords injection , exogenous materials and autologous materials. Among the autologous materials most frequently used the fat is theoretically the best material to implant thanks to its biocompatibility and its viscosity properties that are similar to those of Reinke's space.
Withdrawals from various donor fat sites are possible: abdominal fat 97, postero-lateral thigh fat, submental fat 98 , adipose body of the cheek (Bichat bubble) 99
The problem related to the use of this material is a degree of variable resorption therefore a progressive degradation of the adipose graft causes a deterioration over time of the vocal properties and the need for a second late intervention (in the five years after the first procedure) in 20-40% of cases 100,97,98. These findings mean that fat injection seems ideal in situations situations where a short recovery is expected or in patients with a reduced life expectancy.
Lipoinjection of the vocal fold must be performed with the objective of a substantial over-injection of the vocal cord, considering the loss of fat expected during the transplantation process. After lipo-injection of the vocal fold, 3-6 days of resting of the voice and a cycle of oral steroids are recommended.
Deep fat injection complications in the vocal cords include: over-correction can be responsible for dyspnoea or dysphonia 101, sub-injection, fat loss injected through the injection site and
granuloma formation or a pseudo-polype at the site injection 102,103, injection site infection,
allergic reaction and accidental injection of excessively superficial material. This last event occurs when a zero-measuring needle is used and the injection depth is not controlled, in which case the material must be removed as soon as possible. It usually takes about 3-6 months for the injected material to stabilize completely before deciding whether an excessive vocal fold injection material has been deposited.
Among the autologous materials used to inject into the vocal cord there is also a muscle fascia usually taken on the lata fascia 104 or on the temporal fascia taken from the retro-auricular way 105. Free fascial grafts have been used for a century in various surgical fields 106 because they are considered stable and predictable materials safe from risks arising from allergic or other foreign body adverse reactions 107 .
In the larynx, the autologous fascia was presented by Rihkanen in 1998 108 and then reproposed by various authors 109,110 with the following technique: the chopped band, taken from the lata fascia on the lateral aspect of the thigh, is diluted and rolled up cylinders. The cylinders were inserted into the suspended micro-laryngoscope and through an upper cordotomy (sutured later at the end of the procedure) into the lamina propria for the entire length of the vocal fold, from the anterior commissure to the lateral side of the vocal process. If necessary, it was possible to use different cylinders. In this case the recommended postoperative vocal rest was about a dozen days. The fascia carries fibrocytes and collagen and did not pose problems of resorption; short-term (7-9 months) and long-short-term results have been satisfactory.
Nagai et al. 111 published a study in 2016 reporting the effects of autologous fascia vocal cord transplantation in addition to controlled release of fibroblast growth factor (bFGF) and using an animal model (rats) of UVFP. Two groups of the same animals were transplanted , one were implanted with autologous fascia only and one group received also controlled release of b-FGF. Normalized laryngeal volume, fat volume, and lateral thyro-arytenoid muscle volume were significantly increased in the fascia implantation with bFGF groups.
Therefore, the increased laryngeal volume on the treated side was due to a factor in addition to the implanted material. These results suggest that ATFV with controlled release of bFGF improves lost laryngeal function due to long-term denervation in UVFP.
Teflon was the first material used, but its use was then abandoned due to numerous complications. The injection was performed by direct laryngoscopy deep into the thyro-aritenoid muscle, the injection should not be too superficial to minimize the risk of inflammation of the Reinke space and alteration of the mucous vibration. Usually when an injection of Teflon is performed there is always an inflammatory response that in most cases is localized and has no significant clinical complications. However, there is a risk of clinically apparent granuloma expansion in these patients after the initial injection after a period of good voice. This granuloma appears as a submucosal mass that causes a swelling in the false vocal cord, in the ventricular mucosa and / or in the true voca; it can develop inferiorly with consequent subglottic bulge. The videostroboscopy reveals a mass of rigid and non-vibrating vocal cord that is due to the mass effect (stretching of the vocal fold with the damping of the wave) or, more commonly, to the infiltration of the granuloma into the lamina propria and / or mucosa. Occasionally, the airway in this case is useful to perform a CT scan of the neck with contrast to evaluate the position of the Teflon and the extension of the granuloma to make differential diagnosis with granulomas due to another cause. In literature cases of granulomas from foreign bodies and extrusion migration have been described 112-113. The surgical indication for the removal of the granuloma, in the case in which there are no co-morbidities or difficulties in the endoscopic intervention, is linked to the cases in which this slowly worsening dysphonia may progress towards the difficulties of the airways. However finally due to this significant complication this substance has currently a very limited utility. The most common injectable products based on gelatine and collagen of bovine origin are known as Gelfoam, Surgifoam, Zyplast and Zyderm.
The first products based on collagen used to increase the vocal cords have been used for over 20 years and in particular gelfoam with good results for 25 years. Although no serious adverse reactions have been reported to the use of bovine collagen in the larynx, hypersensitivity has been reported in approximately 3% of the population 114, presumably because of dietary sensitization.
A small test dose of bovine collagen is recommended placed in the arm 1 month prior to injection to monitor for hyper- sensitivity. Occasional systemic reactions also have been observed after bovine collagen administration include arthalgias, arthritis, fever, urticaria, and generalized swelling 115. In the case of products based on bovine gelatin the material is quite viscous since before being injected must be mixed with a saline solution forming a paste which is then injected with a large diameter injection needle and a pressurized injection device.
The most recent collagen-based products include Cymetra (micronized cadaveric skin tissue) and Cosmoplast / Cosmoderm (laboratory-engineered collagen). No complications such as hypersensitivity reaction has been reported and in addition contains intact dermal collagen fibers that may be more stable than those found in previous bovine collagen preparations 116. Although Cymetra has the potential for infective transmission due to the use of cadaveric tissue as a source; the expected resorption time of this material is about 9 months or more, but many authors believe that 2-3 months are more accurate. There are several types of hyaluronic acid available in an injectable form including those most used in aesthetic medicine such as perlane, hylaform and restylane. Hyaluronic acid (HA) is a naturally occurring polysaccharide in the extracellular matrix of human cells 117-118 and also identified in vocal lamina 119.
Restylane is a commercially available form of cross-linked hyaluronic acid and is used by otolaryngologists in an off-label manner for injection medialization. The incidence of adverse reactions to fillers was previously recorded between 0.06% and 0.8% and correlated with low levels of protein impurities in the production of the product.This incidence decreased with the availability of more purified forms of HA 120. Aside from minor cases of temporary inflammation that resolved without sequelae, only three cases of serious adverse reaction to hyaluronic acid resulting have been reported in the literature 121-123. Shamanna et al 124 reported the case of a 53-year-old woman (previously undergone nine injection medializations without adverse sequelae) with previous radiation therapy to the larynx who developed a severe compartment syndrome-like reaction following IL with HA with inflammation, ulceration, necrosis, and subsequent tracheostomy dependence. Halderman et al 125 reported five patients out of 82 had adverse reaction to Restylane injection, and only one had respiratory symptoms, with laryngeal findings of edema of the false and true cords. Similarly, Rudolf and Sibylle 126 have reported one case out of 19 who had shortness of breath secondary to edema of the false cord and aryepiglottic fold at the site of injection managed successfully by corticoids therapy.The duration of these products is comparable to products based on collagen, usually 4-6 months.
Radiesse Voice is considered an effective soft tissue filler characterized by longevity, biocompatibility and low rate of side effects. There are several compositions of it including the Voice and the Voice gel; the latter contains microspheres of synthetic calcium hydroxyapathite,
with a diameter between 25 and 45 mm, suspended in an aqueous gel carrier. The Radiesse vocal gel usually lasts 2-3 months while the Radiesse Voice Gel has a duration that lasts up to 12 months. The voice gel has another carrier substance, carboxymethyl-cellulose, and is an injectable implant containing synthetically derived polymers that does not require preparation and above all does not present risks of transmission of biological infections 127. This material has been widely used for a variety of disorders including vocal fold paresis and paralysis, vocal fold scars and presbilarinx 128,129. In 2013, the effect of Radiesse Voice was directly compared with the throatoplasty medialization by Cantillo-Banos et al, the effects of thyreoplasty and this injectable implant seem comparable after 6 and 24 months of follow-up 130.
• Injection mode :
The increase in the vocal cords can be performed by micronolaringoscopy under general anaesthesia or endoscopically with local anaesthesia.
Suspended trans-oral microlaryngoscopy is the most commonly used classical route of injection or under general anaesthesia or under sedation and local anaesthesia. It allows a better control of the injection site and of the distribution of the injected product. The injection is carried out in the vocal muscle (tiroaritenoideo) laterally, ie in the depth of the muscle, at least at two injection points: at the middle third of the vocal plica and outside the vocal tract of the arithenoid 131. The injection should not be too far forward, to avoid creating an iatrogenic posterior glottic loss, responsible for a mediocre vocal result. Care must be taken not to suck up at the injection hole, in order not to favor the exit of the material through this route.
When the injected material is resorbable, in particular for the fat, an overcorrection is necessary: the vocal plica presents, at the end of the injection, a convex appearance surfacing on the midline on its middle third, witness of this overcorrection.
This pathway presents the risks of complication of any suspended laryngoscopy, in particular of mucous and dental complications 132,133.
In the literature, injection procedures performed under the control of the rinofibroscope are poorly described both with regard to this technique and its results; it is performed under local anaesthesia with nasal fossa load associated with a vasoconstrictor plus a pharyngeal laryngeal anaesthesia by instilling xylocaine through the rinofibroscope operator channel. The injection is performed with an endoscopic needle of 23G, introduced on the upper face of the vocal plica with the same experiences of suspension laryngoscopy (middle third of the vocal plica and lateral slope of the vito-arithenoid process).
Indications for this approach include difficult intubation, problems with vocal tract alignment such as cases of anterior larynx, limited mouth opening, patients with severe vomiting and those with general health problems.
Trask et al. 134 described this technique in 2005, reporting its ease of execution and excellent patient tolerability, especially in cases where anatomical or physiological barriers exist that could interrupt the procedure.
Hamdan et al 135 in 2005 published a study of sixteen patients who were injected with hyaluronic acid via the trans-nasal route, according to which the procedure was well tolerated by all patients with improved symptoms and voice aspiration in 66.66% and in 50% of patients, respectively. Injecion can also be performed via trans-cutaneously. The injected substance is conveyed by a needle introduced into the paraglottic space by cricothyroid route, with or without electromyographic control and with or without rhinofibroscopic control. The gesture can be performed in a patient in a sitting position and does not require any other local anaesthesia in addition to the anaesthesia of the nasal cavities associated with a vasoconstrictor.
This treatment technique has indications in the most fragile patients, with contraindications for a general anaesthesia, as an alternative to thyroplasty and requires only an outpatient management. The anatomical landmarks of injection by cryco-thyroid route, according to Jin et al. 136 are: the back third of the vocal cord. with a depth of the injection target is 15.75mm for men and 13.91mm for women. The entry point is 7mm from the middle line. The needle is directed from inside to outside at an angle of 10-11◦ for men and 12-13◦ for women. It is also directed from the bottom up at an angle of 47-48◦ for men and women.
For the transcutaneous route, there are various alternatives beyond the cricothyroid (CT) path, ie through the thyroid membrane (TH), or directly through the thyroid cartilage.
The CT membrane approach is favoured by some laryngologists because it causes less dead space and there are no losses from the needle puncture site but in reality the TH approach is a simpler method to control the depth and position of the vocal fold targeted as the operator can see from the tip of the needle to the vocal fold and this allows the surgeon to access all areas of the larynx that are not normally reachable using the trans-cartilagineous approaches. Secondly, with the TH approach, the needle enters the larynx intra-luminal (unlike the submucosa) through the thyroid incisor and passes through the epiglottis to penetrate the upper face of the vocal fold allowing better visualisation and guidance. ensuring a more precise positioning of the injectable material and this is particularly useful when using not reabsorbable materials such as CaHA 137. Regarding the trans-thyroid path is rarely indicated as it is reserved for the young person who does not yet have a calcification of the thyroid cartilage.
4.2 Vox Implant :
Vox Implant is defined as a solid silicone polymer composed of voluminous silicone particles whose size and consistency make it impossible or at least improbable their migration and their phagocytosis by macrophages; this biocompatible material has been implanted without major side effects for over 40 years and allows a permanent medialization.
All studies of local tissue reactions after the use of vox implant contained reports of moderate inflammatory reactions and the presence of giant cells (reaction to a foreign body) with the reception of particles by a fibrous matrix 138,139 . Because of this inflamed appearance of the vocal cords after the injection is not known, it could be the persistence of forcing the patient's voice or a reaction to the silicone itself. However, unlike the reaction obtained after using Teflon
the persistence of mucosal waves on videostroboscopy despite the postoperative inflammation of the vocal cords suggests that this material does little or nothing to alter the structure of the mucosa or the Reinke space ,therefore the inflammation it does not have functional repercussions on the mucosa of the vocal cords after injection.
4.3 Thyroplasty type I (Montgomery, Gorotex)
The ideal candidate for laryngoplasty medialization is a patient with moderate to severe glottic insufficiency that manifests as weak and respiratory dysphonia and / or dysphagia. Conversely, for patients with minor degrees of glottic insufficiency and minimal vocal symptoms such as speech fatigue, they may be more suitable for voice therapy and / or injection medialization surgery is usually delayed for up to 6-12 months to allow for spontaneous recovery in the patient. The patient with troublesome symptoms can be treated with a series of temporary measures that are primarily the injection increase.
Only in selected cases medialization between 3 and 9 months may be considered, especially if electromyography shows severe neuronal degeneration without evidence of neuronal recovery or history strongly suggests nerve transection.
The thyroplasty used for laryngeal paralysis is the type I which consists in creating a window in the thyroid wing and placing the cartilage inside the thyroid wing to keep the vocal cord inward 140. This technique allows a significant reduction of the posterior glottic loss, an increase in the closing quotient and an improvement in the amplitude of the mucous vibration 141.
Several variations of techniques have been described since Isshiki 142 has revalued the tyroplasty in 1974 related to the use of implants, to the reduction of the trans-thyroid access path and to the association of an arytenoid addition process and / or ipsilateral crico-thyroid subluxation.
However the principle remains the same : project the vocal cord paralyzed towards the midline without mucosal effraction without damaging the mucosa to avoid post-operative vibrations. With regard to the Isshiki technique 142,143 the skin incision is made laterally at the thyroid wing, at half height of the thyroid cartilage horizontally
The sterno-cleido-ioideo muscle is sectioned and reclined upwards while the thyroid muscle is slightly slanted and reclined backwards. Thus, the thyroid wing is exposed in its purely laryngeal part between the forward anterior angle, the upper and lower margins up and down, and the oblique ridge posteriorly.
The cartilaginous window is packaged in a rectangular shape with a large horizontal axis and is drawn on a half-height zone between the angle of the thyroid and the lower edge of the cartilage. Its anterior limit is located between 5 and 7mm from the midline. Its dimensions are, in humans, 5 mm vertically and 12 mm horizontally and, in women, 4 mm vertically and 10 mm horizontally. The upper edge of the window is then positioned at the top edge of the vocal string. Once the flap is completely removed, the internal perichondrium is detached from the thyroid cartilage, to prepare a bed to accommodate the cartilaginous fragments. The thyroid lapel is impacted inside and, therefore, is maintained with a fragment of silicone 144.
The thyroplasty according to Guerrier 145 differs from the previous technique because involves the removal of one or two cartilaginous pieces (about 15 mm long and 3 mm wide) on the upper edge of the thyroid wing, which are then vertically inserted upwards between the margin and the impacted cartilaginous fragment, until their lower end is fixed, then they are made to fall down to be vertically included, blocking the impacted wing thyroid fragment. The posterior fragment is slightly larger to create an arytenoid adduction by medializzation the vocal process (Fig 2).
Figure 2 : Guerrier thyroplasty technique: 1. Cartilaginous fragments; 2. Impactate thyroid ala
A. Tracing of cartilage incisions and thyroid wing withdrawal B. Cartilaginous fragments in place (1).
D. Cross-section.
Medialization by thyroplasty also includes techniques that provide for the placement of an implant that performs the medialization alone without the creation and insertion of cartilaginous fragments. The shape and volume of the implant are adapted by the surgeon according to the quality of the voice during the intervention that is performed under local anesthesia.
Montgomery proposed the use of a calcium hydroxylapatite implant that has a flexibility closer to that of the glottic tissue. The implant is "clipped" on the margins of the thyroid window; it is thus set without the need for suturing, which avoids secondary migrations. It is easily removed, if necessary, even at a distance from the placement 146.The intervention should be performed in intra-operative endoscopy since quality control of the patient's phonation is very important. The incision is horizontal, halfway between the incisor of the thyroid and the cricothyroid membrane, extending laterally from an anterior edge of the sternoioid muscle to the other. The dissection identifies the superficial plane and the superficial cervical fascia. The sternoioid are reclined
laterally. The thyroid muscle is sectioned at half height. Through certain reference points, the cartilage window is created which is resected (Figure 3). The internal perichondrium is etched, leaving the deep band in place. The implant is inserted and "cut" into the window. The closure is made with the suture of the muscular, subcutaneous and cutaneous plan with or without suction drainage. With Montgomery implants, intraoperative complications such as the impossibility of stabilizing the posterior part of the implant or cartilage fracture located under the cartilage window have been encountered. Postoperatively, cases of posterior dislodgement of the implant have been noted 147.
Figure 3 : A - Technical principle on a transversal cut :
1-Tensionary-thyroid tissue, lateral band;
2-vocal muscle; 3-vocal ligation. B - Repairs of the cartilage window.
1-Lower tubercle
In 1999 Friedrich 148 conducted experimental and clinical research with the aim of replacing the silicone with a safer material and simplifying the surgical procedure, in particular excluding the risk of dislocation of the implant. The material chosen was titanium considered relatively safe with excellent biocompatibility with a simple and fast implantation and handling technique, and this material is easy to shape and adapt to the individual situation without the need for expensive tools. The main advantage was a significant reduction in operating time due to the preformed implant that is convenient both for the surgeon and for the patient, but it is also essential for obtaining optimal results thanks to the reduced swelling and intralaringeal hematoma. The tyrotomy technique is the same as for the Montgomery implant and the implant is "clipped" in the cartilage line. Devos et al 149 later, described a porous titanium implants (T40) , assessing their tolerance and effectiveness with less risk of extrusion, easy positioning and adjustment, adapted to each patient, with a simplified surgical revision.
Indeed the chosen material, the porous titanium, as it results from their studies perfectly integrated into the surrounding environment and allows the implant to be colonized by the surrounding cells, which should gradually fill the micropores. Better fixation is achieved, healing time is shorter and cell adhesion is better than solid titanium.
Among the other implants used for the medialization there is expanded polytetrafluoroethylene (Gore-Tex) a material that provides an alternative to silicone and cartilage. Its biocompatibility has been demonstrated during more than two decades of clinical use in vascular, cardiac and reconstructive surgery. The material was developed in the late 1960s by W. L. Gore and Associates, with the first human vessel implants in 1971150.
The use of Gore-tex as an implant material for laryngoplasty (ML) was reported for the first time by McCulloch and Hoffman 151 in 1998; this semi-porous material allows a minimal amount of growing tissue without significant surrounding inflammation conditions 152. The material has the advantage of a very low extrusion rate, while maintaining the capacity for easy removal, if necessary. The surgical technique used for the aforementioned implant involves a 3 cm skin incision of thyroid wing exposure and formation with a diamond bur of a small 5 × 5 mm cartilage window, located 5 mm from the midline, half-height of the thyroid cartilage, which allows a plant like a Goretex leaf to slide between the cartilage and the internal leaflet of the perichondrium 153,154 . The implant material consists of an ePTFE cardiac patch (5 x 7.5 x 0.6 cm). The patch material is removed from the sterile package and fashioned into a single 6-7 mm tape to improve ease of implantation. With guidance from both the visual feedback of fiberoptic video endoscopy and the auditory feedback from the patient's phonation, the ePTFE material is progressively positioned in the window with a blunt elevator. The rest of the tape is then judiciously positioned through the window, as needed, incrementally to obtain the optimal glottal configuration, identified by flexible endoscopy and vocal quality. The implant is then fixed with one or two permanent nylon or 4-0 Prolene sutures positioned through the ePTFE and circumferentially around the lower upright (Fig. 4).
Figure 4: A. Exposure of the thyroid wing (1) and formation of a small window of 5 × 5 mm C. Schematic aspect of the procedure
AA- Arytenoid Adduction
In patients with vocal cord paralysis who have a lack of contact with the vocal process during phonation (large posterior glottal space), a lateralized vocal fold during phonation, vertical differences in height (generally the paralyzed vocal fold is located in position superior) or simply inability to obtain a good intraoperative voice by medialization alone, the arytenoid adduction (AA) must be considered in addition to the medialization (ML).
Videostroboscopy provides valuable information on the contact of the vocal process, the height of the vocal cords and the length, and is therefore useful preoperatively in assessing whether a patient may need an AA while a maximum phonation time (MPT) of less than 5 seconds has been identified as a predictor of the need for AA in the event of paralysis of the vocal cords. The principle of this framework surgery is to recreate the traction of the posterior crico-aritenoid muscle (PCA) to obtain the repositioning of the vocal cords 155 ( Fig. 5) .The incision has the same position as for a classic tyroplasty, but is prolonged laterally by 3 cm in order to expose the posterior edge of the thyroid wing. After exposure of the thyroid cartilage and the creation of the tyroplasty window respecting the internal perichondrium, the dissection is extended behind the window up to the insertion of the posterior crico-arithenoid muscle on the arytenoid. Here a point has passed through the window, then through the muscular process of the arithenoid (it is found in the prolongation of the vocal cord, 1cm above the crico-thyroid joint, at the upper edge of the cricoid, at the convergence of the muscle fibers of the lateral and posterior crico-aritenoid muscles) before returning to the window . Two points are made on the thyroid blade in front of the window. The wire of Prolene has passed through the window, so it is made to escape through these points and is finally brought back to the cartilage window. The implant of calcium hydroxylapatite is positioned in the orifice of the tiroplasty, then the point is tightened progressively under the control of the voice, the suture thread is exteriorized through the front holes. The implant is positioned in the orifice of the tiroplasty, then the point is tightened progressively under the control of the voice.
Therefore the classical aritenoid adduction technique simulates contraction of the lateral crico-arytharoid muscle, however, the force vector for repositioning the suture is different. In fact, in this procedure, the origin of the suture tension is from the approximate level of the vocal fold (anterior thyroid plate) rather than from the natural caudal point of origin, the cricoid.
Zeitels e al156 described a new modified arithenopexy procedure, designed to provide a more normal arytenoid physiologic closure pattern that simulated agonist-antagonist contractile activity of the combined effects of inter-arytenoid, lateral crico-arytenoid, lateral thyro-arytenoid, and posterior crico-arytenoid muscles.
In this technique, the paralyzed arytenoid is fixed in an enhanced phonatory position ie the body of the arytenoid is positioned on the medial aspect of the cricoid facet, which simulates the natural sliding function and the inward oscillation which occurs with normal adduction.
