Current Concepts in the Management of Unilateral Recurrent ...

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The Journal of Clinical Endocrinology & Metabolism 90(5):3084 –3088 Copyright © 2005 by The Endocrine Society doi: 10.1210/jc.2004-2533

CLINICAL REVIEW: Current Concepts in the Management of Unilateral Recurrent Laryngeal Nerve Paralysis after Thyroid Surgery Dana M. Hartl, Jean-Paul Travagli, Sophie Leboulleux, Eric Baudin, Daniel F. Brasnu, and Martin Schlumberger Departments of Otolaryngology and Head and Neck Surgery (D.M.H.), Surgical Oncology (J.-P.T.), and Nuclear Medicine and Endocrine Tumors (S.L., E.B., M.S.), Institut Gustave Roussy, 94805 Villejuif, France; and Department of Otolaryngology and Head and Neck Surgery (D.F.B.), European Hospital Georges Pompidou, 75015 Paris, France Objective: This study was designed to provide an update on the pathophysiological concepts and patient management in a common complication of thyroid surgery, unilateral recurrent laryngeal nerve paralysis (URLNP). Method: Recent publications in physiology and head and neck surgery were reviewed. Results: Even for experienced surgeons, URLNP may occur after thyroid surgery, especially for thyroid cancer and in case of reoperation. URLNP is frequently well tolerated but may be life threatening by inducing aspiration pneumonia. Permanent URLNP may decrease quality of life by decreasing voice quality and increasing vocal effort. Spontaneous recovery of vocal function, with or without full recovery of vocal

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NILATERAL RECURRENT LARYNGEAL nerve paralysis (URLNP) is a known complication of thyroid surgery. Even for experienced surgeons, a number of patients will have temporary laryngeal paralysis or paresis, which for some will become permanent (after 12 months) (1). The incidence varies widely, but up to 3.5% of patients may have permanent URLNP (1). The risk is highest after surgery for thyroid cancer, especially in case of extensive local or paratracheal nodal disease or reoperation (1). URLNP is frequently well tolerated but in some patients can be life threatening: aspiration pneumonia can be fatal, especially in older patients or patients with impaired pulmonary function preoperatively (2). Permanent URLNP may decrease quality of life due to poor voice quality and increased vocal effort (3). Today there are several surgical techniques that improve patients’ voice quality and quality of life (3) and eliminate aspiration (1). This type of surgery is well tolerated with few complications, is easy to perform, and should be systematically proposed to patients with symptomatic URLNP. Physiopathology

Basic considerations

From a phylogenetic standpoint, the larynx is above all a sphincter, protecting the airway from aspiration and the First Published Online February 22, 2005 Abbreviation: URLNP, Unilateral recurrent laryngeal nerve paralysis. JCEM is published monthly by The Endocrine Society (http://www. endo-society.org), the foremost professional society serving the endocrine community.

fold motion, may occur due to spontaneous axonal regrowth or other neurological phenomena. In the last decade, several surgical techniques have been developed to treat aspiration and poor voice quality due to URLNP by medialization of the paralyzed vocal fold. These techniques are simple, have a low complication rate, and are highly efficient in eliminating aspiration and improving voice quality and quality of life. Conclusions: The voice and swallowing handicap caused by URLNP may be efficiently treated by safe and simple techniques. The possibility to improve the quality of life should be proposed to all patients with symptomatic URLNP. (J Clin Endocrinol Metab 90: 3084 –3088, 2005)

passage of food, liquids, or saliva into the airway (4). URLNP causes insufficient laryngeal closure during swallowing, cough, and phonation and may cause dyspnea during exertion. The glottal air leak on phonation causes a breathy and rough voice quality. One must note that dyspnea at rest occurs only for bilateral vocal fold paralysis, in which physiopathology, symptoms, and treatment differ greatly from URLNP. The recurrent laryngeal nerve is a branch of the vagus nerve and is a mixed motor, sensate, and autonomous nerve. It innervates both adductor muscles and abductor muscles. However, the action of these muscles is not quite as distinct as it may seem. In normal larynges, for example, the principal abductor muscle (the posterior cricoarytenoid muscle) shows activity that is simultaneous with adductor muscles during certain laryngeal gestures in speech and song (5). Thus, the adjustments of laryngeal configuration during phonation are complex and the variability of the position of the paralyzed vocal fold seems to be due in part to this complexity. The external branch of the superior laryngeal nerve, also a branch of the vagus nerve, passes among the vascular elements of the superior thyroid pedicle and can be injured during thyroid surgery. This nerve provides motor innervation to only one muscle, the cricothyroid muscle, typically considered as a tensor for the vocal fold, with an adductory component. An isolated lesion of this nerve does not produce laryngeal paralysis but may impair certain laryngeal gestures, especially in singers. It has been shown that the cricothyroid muscle does not influence the functional prognosis

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Hartl et al. • Recurrent Laryngeal Nerve Paralysis after Thyroid Surgery

FIG. 1. Schematic representation of vocal fold medialization by endoscopic injection. [Reproduced with permission from The Larynx, 2nd ed. (edited by M. P. Fried), St. Louis, MO, (Mosby) Elsevier, 1996, p 211 (24).]

or the position of the vocal fold in recurrent nerve paralysis (6). Risk factors

The risk of lesion to the recurrent laryngeal nerve exists in all cases of thyroid surgery. The physical mechanisms involve stretch, crush, thermal, and electric injuries and nerve transsection (1). The risk is increased in cases of thyroid cancer, especially during the paratracheal lymph node dissection or in case of extrathyroidal extension of the tumor. Reoperation of the thyroid bed or of the paratracheal lymph nodes or previous external beam radiation therapy increase the risk of URLNP. In large, intrathoracic multinodular goiter, the nerve may already be stretched by the goiter and is at an increased risk of paralysis during surgery. Small-caliber nerves or nerves with extralaryngeal branching may be more susceptible to injury during thyroid surgery (1). Nerve regrowth or spontaneous recovery of URLNP may be of poorer quality in elderly patients, heavy smokers, diabetic patients, or patients with other severe associated diseases. Radioiodine therapy does not seem to have an effect on the incidence or outcome of URLNP. Pathophysiology

There are several different mechanisms of nerve injury and means of nerve regrowth (7). This explains the varying func-

J Clin Endocrinol Metab, May 2005, 90(5):3084 –3088

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tional outcomes in terms of swallowing and voice that are observed after spontaneous recovery of URLNP after thyroid surgery. A temporary blockage of nerve conduction (neurapraxia) can occur despite careful dissection but generally recovers completely and spontaneously after several weeks. Also despite careful dissection, the myelin sheath may be injured, with a macroscopically intact nerve (axonotmesis). Axonal regrowth is spontaneous after a phase of retrograde degenerescence, but the resulting muscular contractions may be of poor quality and thus the voice of poor quality as well. More violent stretch injury may result in an interruption of the endoneurial, perineurial, and/or epineurial sheaths (neurotmesis). Nerve regrowth does not follow the normal route and axons may be rerouted to different muscles. These new axons tend to have a small diameter and a low-quality myelin sheath, and muscular contractions are of poor quality or absent. The association of these three types of injury and the different types of neural regrowth and contractile qualities have been incriminated in the variability of the position of the paralyzed vocal fold and the impossibility to predict outcome after paralysis, especially if the nerve is macroscopically preserved during surgery. Axonal regrowth is a slow process and is considered complete, without hope for improvement, only after a 12-month period (8, 9). One hypothesis in the physiopathology of recurrent nerve paralysis is based on the phenomena of synkinesis, (10) in which axons are rerouted during their growth after injury in such a way that axons initially innervating adductor muscles end up innervating an abductor muscle and vice versa. The resulting vector of mobility of the vocal fold is zero because the antagonistic muscles are contracting at the same time. Thus, one may observe small movements of the paralyzed vocal fold without an effective voice. Other mechanisms are thought to play a role in the ultimate configuration of the larynx after URLNP and thus in ultimate voice quality. The interarytenoid muscle may continue to function due to its bilateral innervation. The paralyzed larynx may be spontaneously reinnervated from the contralateral side via endolaryngeal neural anastomoses (11). Reoccupation of vacant motor endplates by autonomous nerves has been shown to occur (12). Vocal muscle atrophy and periarticular fibrosis can cause lateral retraction of the paralyzed vocal fold. Other laryngeal structures such as the ventricular folds and the epiglottis may show compensatory motion during phonation (13). Finally, laryngeal spasms with consequences on voice and breathing have been shown to occur after URLNP (14). Spontaneous outcome can thus be favorable, with a good voice and the paralyzed vocal fold in a paramedian or median position, preserved muscle tone, and compensation by the contralateral vocal fold or unfavorable, with poor voice quality and the paralyzed vocal fold in a more abducted position or with abnormal motion. Early electromyographic analysis of the laryngeal muscles does not allow one to predict the ultimate outcome. Clinical Consequences

FIG. 2. Schematic representation of medialization thyroplasty with an implant placed through a window thyrotomy. [Reproduced with permission from The Larynx, 2nd ed. (edited by M. P. Fried), St. Louis, MO, (Mosby) Elsevier, 1996, p 213 (25).]

A favorable functional outcome is defined as serviceable voice or good voice quality, no aspiration, and good voicerelated subjective quality of life. Unfavorable functional out-

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FIG. 3. Algorithm for management of URLNP after thyroid surgery.

comes are the persistence of a breathy, bitonal, or rough voice; an increased vocal effort; dyspnea on exertion; aspiration; laryngeal spasms; and/or altered voice-related quality of life.

tenoid adduction technique) (Table 1). Laryngeal reinnervation techniques in general do not improve laryngeal mobility and are not employed routinely. Intravocal Fold Injection

Surgical Treatment of URLNP

The physiological basis of surgery for URLNP is the medialization of the paralyzed vocal fold to close the glottal gap on phonation so that the normal vocal fold can make contact with the paralyzed side. The aerodynamic function of the larynx is reestablished and vibration of both vocal folds can occur. The indications for surgery are basically 2-fold. First, aspiration is an absolute indication, in that aspiration pneumonia can be fatal (2). Then, in the absence of aspiration, the patient’s desire to improve voice quality and thus improve his or her voice-related quality of life should be an indication for surgery. There are no absolute contraindications to vocal fold medialization, especially in treating aspiration caused by URLNP. In general, the vocal fold can be medialized via an endoscopic approach (injection techniques) or by an external approach (cervicotomy to insert an implant) or displacing it medially by pulling on the muscular process of the arytenoid (which is what happens in normal phonation and the ary-

Intracordal injection (Fig. 1) is generally performed endoscopically under general anesthesia but may be done under local anesthesia by experienced physicians. Techniques vary in the type of material injected: autologous fat, minced autologous fascia lata, collagen, acellular heterologous dermis, and other materials. Autologous materials eliminate the risk of infection (as opposed to heterologous materials), their biocompatibility is unquestionable, and the cost is low. Resorbable materials (fat, collagen, and others) can be used before the end of the 12-month waiting period because their use will not impair a favorable spontaneous evolution (2, 15). Injection techniques are highly efficient in eliminating aspiration (2) and improving voice quality (17). Resorption of the material, however, often causes a secondary decrease in vocal quality unless spontaneous recovery occurs, and a more permanent technique is often required (18). Complications are rare and occur primarily at the site of harvest of autologous tissues (hematoma, infection) (16). Undercorrection may occur, especially if the posterior glottal leak during phonation is large.



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TABLE 1. Review of surgical techniques for the treatment of URLNP (2, 3, 16, 17, 21–23)

Duration of surgery Anesthesia Ease of operation Reversibility Indications Complications Dyspnea/edema Hematoma, sepsis Implant extrusion Patient satisfaction Voice improvement Resolution of aspiration Cost

Thyroplasty

Autologous fat

Arytenoid adduction

30 – 60 min Local Yes Variable Definitive paralysis

15–30 min General Yes Yes Any paralysis

30 min–2 h General Variable No Definitive paralysis

⬍1% ⬍2% ⬍2% 95–100% 70 –100% 95% Moderate

⬍1% ⬍2% 0 95–100% 70 –100% 95% Low

1–3.5% ⬍2% 0 95–100% 70 –100% 95% Moderate to high (length of surgery and hospitalization)

Medialization Thyroplasty

Through a short horizontal incision in the neck, a window is drilled in the cartilage of the thyroid ala for insertion of an implant (silicone, GoreTex, hydroxylapatite) (Fig. 2). This is considered as a definitive treatment for paralysis without spontaneous favorable outcome. These implants have been shown to have good biocompatibility. Thyroplasty is relatively easy to perform. Subjective voice quality is good or excellent in over 70% of cases and can be revised by reintervention for adjustment of the size of the implant for an excellent result in over 90% of cases (19). Cost may be a limiting factor for some types of implants. Complications are rare: laryngeal edema or hematoma may cause dyspnea within the first postoperative week (16, 19, 20). Arytenoid Adduction

This technique involves placing a suture in the muscular process of the arytenoid to pull it forward, effectively medializing the vocal process of the arytenoid tension to place on the suture. Laryngeal edema occurs more frequently after arytenoid adduction than after thyroplasty. Some authors have found a subjective vocal advantage to combining arytenoid adduction and thyroplasty (21), but no objective difference, compared with thyroplasty alone, has been found. Algorithm for Management of URLNP after Thyroid Surgery

First, one must evaluate the degree and the tolerance of the symptoms associated with URLNP: aspiration, increased vocal effort, altered voice quality, dyspnea on exertion, and decreased quality of life (Fig. 3). Medialization is urgent if aspiration pneumonia occurs or if aspiration is such that oral feeding is considered dangerous (patients with altered pulmonary function). Medialization is indicated (although not necessarily urgent) if dysphonia is poorly tolerated, i.e. in voice professionals. Vocal fold injection of autologous fat does not compromise spontaneous recuperation of nerve function and does not interfere with ulterior medialization using other techniques. This is the technique of choice if the type of nerve injury, i.e. a macroscopically intact nerve, allows one to believe that a favorable spontaneous recovery of laryngeal function may occur. If the URLNP is well tolerated, a waiting period is rec-

ommended, followed by evaluation of the quality of the spontaneous recovery. We have seen that a spontaneous favorable outcome can occur but may take 6 –12 months. Patients should be evaluated by a specialist using fiberoptic laryngoscopy, generally 3– 6 months after diagnosis of URLNP and then at 12 months. Many cases of URLNP will recover serviceable voice and swallowing. Speech therapy is controversial in URLNP (9, 10). It does not hasten reinnervation, although it may help patients with breath support and provides psychological support. Vocal forcing, however, may lead to hyperactive compensatory mechanisms that can compromise vocal outcome after vocal fold medialization. For minor aspiration in patients without underlying pulmonary disease, swallowing therapy can favor compensation with the tongue base and supraglottic structures, although liquids may need to be thickened. In case of persistent URLNP after 12 months with poor voice quality, definitive vocal fold medialization by a simple technique (injection or thyroplasty) is recommended. The choice of the technique is a matter of the surgeon’s habits and experience and depends on the glottal configuration on phonation (the size of the glottal gap). All of the techniques provide an excellent voice, eliminate aspiration, and improve quality of life. Conclusions

Surgical treatment of URLNP is beneficial for patients with aspiration, poor voice quality, increased vocal effort, or decreased quality of life due to these symptoms. Surgery is easy to perform, with a low complication rate, and should be proposed to patients with symptoms related to URLNP. Acknowledgments Received December 23, 2004. Accepted February 13, 2005. Address all correspondence and requests for reprints to: Dana M. Hartl, Department of Otolaryngology and Head and Neck Surgery, Institut Gustave Roussy, rue Camille Desmoulins, 94805 Villejuif Ce´dex, France. E-mail: [email protected].

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JCEM is published monthly by The Endocrine Society (http://www.endo-society.org), the foremost professional society serving the endocrine community.