17 Complications in Thyroid and Parathyroid Surgery

217

Andrea Frilling and Frank Weber

Contents Once death from thyroid operation became an exception, specific pitfalls of the procedure, namely, 17.1 Introduction . . . 217 injuries to the laryngeal nerves and damage to the 17.2 General Complications . . . 217 parathyroid glands, became obvious. While some sur- 17.3 General Surgical Complications . . . 218 geons, including Kocher, tried to prevent recurrent 17.3.1 Wound Infection . . . 218 laryngeal nerve injuries by avoiding any contact with 17.3.2 Edema . . . 218 the region of the nerve, others advocated routine iden- 17.3.3 Bleeding . . . 218 tification and dissection of the nerve. The importance 17.3.4 Malpositioning . . . 218 17.4 Specific Surgical Complications . . . 218 of the external branch of the superior laryngeal nerve 17.4.1 Unilateral Injury to the Recurrent was not appreciated until decades later. Halsted is Laryngeal Nerve . . . 218 credited for his studies of surgical anatomy and blood 17.4.2 Bilateral Recurrent supply of the parathyroid glands and the introduction Laryngeal Nerve Injury . . . 220 of the technique of capsular dissection that imple- 17.4.3 Injury to the Superior Laryngeal Nerve . . . 221 mented preservation of the vascular pedicle of a para- 17.4.4 Rare Neural, Vascular, thyroid gland and led to a safer approach to thyroid and Visceral Lesions . . . 221 and parathyroid surgery. Today morbidity remains a 17.4.5 Tracheal Instability . . . 222 subject of concern for surgeons performing thyroid 17.4.6 Injury to the Lymphatic Structures . . . 222 and parathyroid procedures. Injury of the recurrent 17.4.7 Hypoparathyroidism . . . 222 laryngeal nerve and hypoparathyroidism are the most 17.4.8 Thyroid Storm . . . 223 frequent complications. The key issue of an effective References . . . 223 and safe surgical approach is a profound knowledge of specific anatomy and pathophysiology in combination with meticulous handling and dissection of tissue. The overall permanent complication rate should 17.1 Introduction not exceed 1% in centers providing expertise [2–4]. The relationship between volume of operations and Mortality from thyroid and parathyroid surgery is outcome has been extensively examined by Sosa et virtually disregarded nowadays. During the eigh- al. in the State of Maryland [2]. They demonstrated teenth century, however, the mortality rate of thyroid a significant inverse relationship between the volume surgery was as high as 40% from bleeding and sepsis of thyroidectomies performed by individual surgeons [1]. As a consequence, in 1850 the French Academy and complication rates, postoperative length of stay, of Medicine recommended its routine use be aban- and hospital charges. Surgeons who performed more doned, and many leading surgeons would not per- than 100 thyroidectomies over a 6-year period had form it. The greatest advance in thyroid surgery is to the lowest hospital charges, compared with those per- be credited to Theodor Kocher who first recognized forming 30–100 cases, 10–29 cases, and between one the importance of anti- and aseptic handling, hemo- and nine cases. stasis, and precise operative technique. Within a de- cade, his overall operative mortality decreased from 15% to 2.4%. With the exclusion of complicated cases, 17.2 General Complications in 1898 he reported a mortality rate of only 0.18%. Following Kocher’s principles, William Halsted, Endocrine neck surgery is associated with general Charles Mayo, George Crile, and others contributed non-surgical morbidity in less than 1.5% of patients, further to the development of thyroid surgery. corresponding to respiratory (1.5%), urologic (0.9%), 218 Andrea Frilling and Frank Weber

gastrointestinal (0.8%), and cardiac (0.5%) complica- sels, can be performed prior to wound closure. Rou- tions. In addition, allergy, drug, or other abnormal tine use of suction drains does not prevent postopera- reactions are reported in 0.4% of patients [2]. tive cervical bleeding. In the majority of patients, symptomatic hemorrhage occurs between 6 and 12 hours after the initial 17.3 General Surgical Complications operation. Since in approximately 20% of cases the onset of hematoma symptoms is reported beyond 17.3.1 Wound Infection 24 hours postoperatively, ambulatory surgery with a 4- to 8-hour observation period might harbor risk Wound infections, usually caused by Staphylococ- of delayed intervention [7]. Once recognized, the cus or Streptococcus species are considered to be rare wound should be deliberately reopened and the he- events, occurring in 0.3% [5] to 0.8% [2] of cases. matoma evacuated. In case of significant respiratory Antibiotic prophylaxis is recommended only in im- distress emergency bedside hematoma evacuation, if munocompromised patients or in those with val- necessary in combination with endotracheal intuba- vular cardiac disorders. While mild neck cellulitis tion, is required. The requirement for tracheotomy frequently regresses under conservative treatment, either in the emergency setting or due to persisting abscesses require rapid incision and evacuation. De- airway obstruction after hematoma removal is gener- lay of invasive treatment can result in devastating me- ally a rare event. diastinitis. Clinically evident seromas respond well to percutaneous aspiration. 17.3.4 Malpositioning

17.3.2 Edema The brachial plexus and ulnar nerve may be at risk when a patient is malpositioned on the operating Laryngotracheal edema can be a cause of respiratory table. In order to avoid nerve paralysis both arms obstruction after extensive thyroid surgery. After bi- should be adducted and secured. Hyperextension of lateral lymphadenectomy, disturbances of lymphatic the head causes nausea and headache during the early flow may be the cause of edema. Pharyngolaryngeal postoperative course. edema, in addition, is a well-recognized complication caused by the endotracheal tube or laryngeal mask and can also occur in association with an anaphy- 17.4 Specific Surgical Complications lactoid reaction [6]. Steroid therapy, occasionally in combination with temporary reintubation, leads to 17.4.1 Unilateral Injury to the Recurrent rapid relief. Laryngeal Nerve

Recurrent laryngeal nerve (RLN) injury is one of the 17.3.3 Bleeding most serious complications in endocrine surgery. It is related to significant morbidity and frequent mal- The incidence of symptomatic hemorrhage requir- practice litigation [10]. The recurrent laryngeal nerve ing reintervention amounts to 0.1–1.5% [5–9]. Post- originates from the trunk of the vagus nerve. Upon operative bleeding will characteristically be prefaced reaching the larynx, it is renamed the inferior laryn- by respiratory distress, pain, or cervical pressure, geal nerve. It innervates all the intrinsic muscles of dysphagia, and increased blood drainage. No specific the same side with the exception of the cricothyroid perioperative risk factors that would allow identifica- muscles, and supplies sensory innervation to the la- tion of the high-risk patient population for this po- ryngeal mucosa below the true vocal folds. While as- tentially lethal complication are known. High surgical cending, the nerve on the right and on the left side volume does not reduce the incidence of hematoma delivers branches that supply the trachea and the formation. Consequently, the key issue of prevention esophagus. The morphologic appearance and course is attention to anatomic detail and careful hemosta- of the recurrent laryngeal nerve are subject to great sis during surgery. If the surgeon is uncertain about anatomic variability. In addition, it may often be over- the dryness of the operative field, a Valsalva maneu- looked that the nerve most frequently does not con- ver, which elevates the intrapulmonary pressure to sist only of a single trunk but exhibits a network of 40 cm H20 and facilitates recognition of bleeding ves- smaller branches. On the right side it usually loops 17 Complications in Thyroid and Parathyroid Surgery 219 around and behind the subclavian artery and then as- the posterior thyroid capsule near the cricoid cartilage cends into the neck in the tracheoesophageal groove and upper tracheal rings. In addition to visual identi- to enter the larynx distal to the inferior cornu of the fication, the nerve can be located by direct palpation thyroid cartilage. In instances of embryologic malfor- of the tracheal wall below the lower thyroid pole. mation of the aortic arch in terms of retroesophageal Considerable debate has long existed concerning the right subclavian artery, the nerve passes with a more necessity of deliberate exposure of the recurrent la- median course directly to the larynx (non-recurrent ryngeal nerve during thyroid surgery. Kocher com- laryngeal nerve) (Fig. 7.4). Although the reported in- mented on postoperative hoarseness and stated that, cidence of non-recurrent laryngeal nerve is less than following his technique of thyroid dissection, injury 1%, the surgeon has to be aware of the existence of to the nerve can with certainty be avoided without this rare anatomic condition [11,12]. The left recur- the direct exposure. The first surgeon who advocated rent laryngeal nerve courses upward around the liga- routine dissection and demonstration of the nerves in mentum arteriosum and the aortic arch and runs 1911 was August Bier of Berlin; he was followed by vertically toward the tracheoesophageal groove. On Frank Lahey of Boston in 1938 [13]. Others advocated their way to the cricothyroid muscle where they en- that exposure itself is a risk due to potential induction ter the larynx, both nerves run close to the capsule of local edema by dissection of adjacent tissues and of the lateral aspect of the thyroid and cross the infe- hemorrhage. Following these initial experiences, sev- rior thyroid artery. Several variations of the relation- eral studies revealed that depending upon the skill of ship between the nerve and the artery, particularly an individual surgeon principal identification of the on the right side, can be observed. The nerve may nerve reduces the risk of permanent laryngeal nerve pass superficially to the artery, deep to it, or between injuries from over 5% to less than 1% (Table 17.1) the branches of the vessel (Fig. 17.1). After running [2,5,14–18]. Nowadays, the practice of visual identifi- into the laryngeal wall the nerve separates into two cation of the nerve represents the gold standard. branches that supply the innervation of various laryn- To alleviate the visual identification of the nerve geal muscles, and a third branch that serves as a con- and to provide an intraoperative tool to prove its nection with the superior laryngeal nerve. functional integrity, diverse monitoring methods, During cervical exploration the recurrent laryn- i.e., intramuscular vocal cord electrodes inserted ei- geal nerve can be exposed at different levels; caudally, ther through the cricothyroid membrane or placed at the crossing with the common carotid artery, in endoscopically, endotracheal tube surface electrodes, the neighborhood of the inferior thyroid artery, and endoscopic visualization of the vocal cords in combi- cranially, at Berry’s ligament, a dense condensation of nation with nerve stimulation [19], and palpation of

Fig. 17.1 Variations in the anatomy of the cervical course of the recurrent laryngeal nerve. a The nerve runs dorsally to the thyroid artery. b The nerve passes the vessel between its branches.c The nerve passes the vessel superficially to the thyroid artery. With permission of A. Zielke and M. Rothmund, Praxis der Viszeralchirurgie. Endokrine Chirurgie, Springer, 2000 220 Andrea Frilling and Frank Weber

Table 17.1 Incidence of transient and permanent recurrent laryngeal nerve palsy after thyroidectomy in large series. (RLN Recur- rent laryngeal nerve, N.R. not reported) Author Publication year Period Number of Transient RLN Permanent RLN patients palsy (%) palsy (%) Jatzko [15] 1994 1984–1991 803 3.6 0.5 Wagner [16] 1994 1983–1991 1,026 5.9 2.4 Sosa [2] 1998 1991–1996 5,860 N.R. 0.8 Hermann [14] 2002 1979–1990 9,385 N.R. 3.0 1991–1998 6,128 N.R. 2.0 1991 651 N.R. 1.3 Rosato [5] 2004 1995–2000 14,934 2.0 1.0 Goncalves [17] 2005 1990–2000 1,020 1.4 0.4

the cricoarytenoid muscle with simultaneous neural routine indirect laryngoscopy or videostroboscopy stimulation [20], have been developed. Although in- is performed, many cases of vocal cord paresis will traoperative neuromonitoring might be of use in the remain unrecognized. The authors recommend presence of extended thyroid surgery, particularly in a preoperative and postoperative laryngoscopic ex- patient with a preoperatively documented vocal cord amination of the vocal cord function, not only for paralysis or in difficult anatomic situations, it does medicolegal reasons but also to document potential not further reduce the low risk of permanent recur- preexisting pathologies and consecutively adapt the rent nerve lesions and it fails to reliably predict the surgical approach. If the paretic cord moves to the lat- outcome [21–23]. This experience has been found not eralized position, hoarseness or aspiration can occur. only in primary but also in reoperative thyroid and The prognosis considering gain of normal function is parathyroid procedures [24]. favorable in cases of delayed onset of symptoms. In Damage to the recurrent laryngeal nerve may be symptomatic patients either treatment by a speech caused by different mechanisms: cutting, clamping, and language pathologist or invasive interventions or stretching of the nerve, nerve skeletonization, local such as injection laryngoplasty or medialization la- compression of the nerve due to edema or hematoma, ryngoplasty are necessary. or thermal injury by electrocoagulation. Transient cord paresis, which is often caused by edema or axon damage by excessive nerve stretching, seldom 17.4.2 Bilateral Recurrent lasts more than 4–6 weeks. When no restitution of Laryngeal Nerve Injury function is notable within 6–12 months postoperatively, permanent damage should be assumed. Acci- This serious complication results in a near midline dental injury to the recurrent laryngeal nerve is not position of the vocal cords and variable degrees of air- recognized during surgery in most of the cases. If the way obstruction. As reported by Rosato et al., diplegia surgeon is aware of this complication intraoperatively, may occur in 0.4% of bilateral thyroidectomies [5]. primarily repair of the nerve using microsurgical Commonly, it will be diagnosed directly after extuba- techniques and epineural sutures or a cable graft from tion or during the early postoperative phase. The pa- the greater auricular nerve can be attempted. Even tient should be reintubated without delay and treated if the nerve is reanastomosed, the dysfunctioning systemically with corticosteroids. In the presence of vocal cord will probably never completely recover. reversible nerve injury, extubation under controlled Delayed nerve repairs are virtually always ineffective conditions is feasible in most cases after 24–72 hours in restoring cord function. When a paralyzed vocal and no further treatment is necessary. In case of per- cord stays in the paramedian position the patients sisting respiratory obstruction, reintubation and a frequently remain asymptomatic. This phenomenon tracheostomy must be carried out immediately. If the is due to compensatory overadduction of the intact vocal cords fail to recuperate after a waiting period cord and consecutive constriction of the glottic of 9–12 months, tracheostomy remains as a perma- chink. The majority of asymptomatic patients need nent solution or transverse laser cordotomy is per- no special treatment but close observation. Unless formed [25]. 17 Complications in Thyroid and Parathyroid Surgery 221

17.4.3 Injury to the Superior tensor of the vocal cord, injury to the external branch Laryngeal Nerve of the superior laryngeal nerve often results in detri- mental voice changes and inability to perform high- Although the risk of injury to the superior laryngeal pitch phonation. For those patients who rely on their nerve during thyroid surgery is significant, this com- voice quality professionally this may be of essential plication is less reported, probably because of the dif- consequence. ficulty to asses its manifestation [26]. Laryngeal elec- It should be pointed out that not every vocal cord tromyography provides the most accurate diagnosis. dysfunction following thyroid or parathyroid surgery The superior laryngeal nerve separates from the main is caused by the surgical procedure itself. Most prob- trunk of the vagus nerve outside the jugular foramen. ably, 0.3% of patients exhibit laryngeal injury as a re- It passes anteromedially on the thyrohyoid membrane sult of the intubation technique or use of the laryn- where it is joined by the superior thyroid artery and geal mask [28]. vein. At about the level of the hyoid bone it divides into two branches. The external laryngeal nerve innervates the cricothyroid muscle and the internal 17.4.4 Rare Neural, Vascular, branch provides sensory innervation of the supra- and Visceral Lesions glottic larynx. The internal laryngeal nerve separates into three branches that communicate with the recur- The cervical sympathetic trunk is injured on rare rent laryngeal nerve posterior to the cricoid cartilage. occasions (1:5,000 cases) when for instance a retro- Injuries to the internal branch are rare during thyroid esophageal extension of a goiter is being dissected or parathyroid surgery. The most common position [29]. Therefore, care should be taken over the pres- of the external branch in relation to the superior thy- pinal surface when mobilizing the carotid sheath. In- roid artery is medial to it (Fig. 17.2). In about 20–30% jury to the cervical sympathetic trunk causes Horn- of cases the nerve crosses the upper thyroid vessels er’s syndrome, characterized by a constricted pupil, below the upper border of the superior thyroid pole. drooping eyelid, and facial dryness. This condition places the nerve at high risk of dam- Damage to the phrenic nerves, inducing hemi- age during mobilization and division of the superior diaphragmatic elevation, or to the spinal accessory thyroid vessels [27]. In order to avoid damage during nerve, causing dropping of the shoulder, muscle at- ligation of the superior thyroid pedicle, meticulous rophy, and weakened or limited elevation of the arm dissection of the adventitial tissue between the upper and shoulder, can occur during lymph node dissec- thyroid pole, which should be retracted laterally, and tion for thyroid carcinoma. These rare injuries may the laryngeal wall is necessary. Electrocautery should especially occur after extensive cervical lymphad- be omitted if bleeding within the cricothyroid muscle enectomy. In the presence of a large substernal goiter occurs. Neuromonitoring may facilitate the identifi- or mediastinal lymph node metastases which neces- cation of the nerve. Since the cricothyroid muscle is a sitate dissection toward the upper thoracic aperture,

Fig. 17.2 Most common variations of the external branch of the superior laryngeal nerve. 1 Internal branch of the superior laryngeal nerve, 2 external branch of the superior laryngeal nerve, 3 superior thyroid artery. With permission of A. Zielke and M. Rothmund, Praxis der Viszeralchirurgie. En- dokrine Chirurgie, Springer, 2000 222 Andrea Frilling and Frank Weber

complications such as pneumothorax or transection correction with an aim to ligate the fistula should be of the subclavian artery or vein can occur. Clinically considered. significant pneumothoraces require air evacuation via an inserted needle or placement of a thoracic drain. The carotid artery is rarely at risk during thyroid- 17.4.7 Hypoparathyroidism ectomy, although excessive lateral retraction of a dis- eased artery with arteriosclerosis during mobilization The reported rate of hypocalcemia after thyroid sur- of an enlarged thyroid gland may injure the vessel gery varies from 1% to over 50% [29–31]. While the wall or damage the blood flow to the cerebrum. This majority of instances of postoperative hypocalcemia complication is avoidable if assistants are carefully in- are transient, permanent hypoparathyroidism is de- structed by the surgeon with regard to the handling of cidedly unusual and should amount to less than 1%. retractors. Arteriovenous fistula may occur at supe- Although the pathogenesis of postthyroidectomy hy- rior pole vessels. This complication can be prevented pocalcemia is multifactorial, damage to the parathy- by ligating the superior pole vessels at the end of the roid glands in the form of direct injury, unrecognized surgery and by isolating arteries and veins and ligat- inadvertent removal, or indirectly by devasculariza- ing them independently. This maneuver also helps in tion of the gland are the most common causes. Other the prevention of injury to the external branch of the causative factors are negative calcium balance due to superior laryngeal nerve. calcium absorption by bones in repair of osteodys- In the course of surgery for extended thyroid dis- trophy in hyperthyroid patients, decreased serum ease, injury to the anterolateral esophageal wall can albumin levels caused by hemodilution, increased se- be observed occasionally. This risk is greater if the cretion of calcitonin during thyroid mobilization, or surgeon has difficulty locating the recurrent laryngeal conditions associated with increased renal excretion nerve in the presence of an altered anatomy which of calcium [32]. can occur in large multinodular goiters. The manage- Knowledge of the specific anatomic details and ment of this rare condition includes direct suturing meticulous surgical technique are prerequisite condi- and total parenteral nutrition (TPN) for 2–3 days. tions for successful restriction of the risk of hypocalcemia. The superior parathyroid glands are derived from the fourth branchial pouch and descend along 17.4.5 Tracheal Instability the posterior surface of the upper thyroid pole toward the inferior thyroid artery. Usually, the gland lies lat- Tracheomalacia resulting in tracheal collapse rarely erally to the recurrent laryngeal nerve. The inferior occurs after removal of a large goiter. In such an event, parathyroid glands, derived from the third branchial endoluminal stenting in order to regain tracheal sta- pouch, migrate along the lower thyroid pole toward bility may be necessary. External splinting by custom- the mediastinum in close relation to the thyrothymic made rings or Marlex mesh has also been tried. How- pole. In the majority of cases they can be found su- ever, tracheostomy remains the ultimate treatment if perficially to the recurrent laryngeal nerve below the the above-mentioned measures fail. crossing of the nerve with the inferior thyroid artery. Although the number and localization of the parathyroid glands may vary, symmetric position, par- 17.4.6 Injury to the Lymphatic Structures ticularly of the superior glands, can be expected in the majority of patients. The arterial blood supply to the Patients in whom lymph node dissection is a compo- parathyroid glands is provided by a single terminal nent of thyroid surgery are at risk for injury to the artery in 80% of cases. In 20%, two to four separate thoracic duct on the left side and to the lymphatic arteries can be found. Most frequently superior and duct on the right side. Development of chyloma is the inferior glands are supplied by the inferior thyroid hallmark of this complication. If the injury is evident artery. To preserve the blood supply to the parathy- during surgery, ligation of the duct should be per- roid glands during thyroid resection, the technique of formed. In cases of delayed diagnosis a conservative individual ligation of peripheral branches of the in- management by continuous drainage and reduction ferior thyroid artery rather than ligation of the main of chyle production by TPN or by oral administra- trunk of the vessel should be followed. In 15% of pa- tion of a low fat, high carbohydrate, and high protein tients, the superior parathyroid gland may receive its diet may be carried out. In our experience additional blood from the superior thyroid artery and in 10% an systemic administration of somatostatin proved ex- anastomotic communication of both systems can be tremely efficient. If the chyle leak persists, surgical found. 17 Complications in Thyroid and Parathyroid Surgery 223

A controversial debate exists about the number sociated with significant impairment of life quality, of parathyroid glands that should be identified and chronic gastrointestinal discomfort, changes in bone preserved during thyroid surgery in order to avoid metabolism, and development of cataracts. Single re- postoperative hypocalcemia. While some argue that ports on heterologous transplantation of parathyroid preservation of a singular intact parathyroid gland is tissue after microencapsulation with amitogenic algi- sufficient for normal homeostasis, others recommend nate exist, however, reliable clinical systems are not the identification and in situ preservation of at least yet widely available [38]. three glands [33]. If it becomes evident that a safe dissection of a parathyroid gland is technically not feasible or that its viability has been compromised, the 17.4.8 Thyroid Storm gland should be removed from the thyroid capsule, cut into small fragments, and implanted into a muscle Postoperative thyroid crisis as a complication of pocket in the sternocleidomastoid muscle (orthotopic thyroidectomy was once fairly common, but is now autotransplantation). The site of autotransplantation rarely seen. At the beginning of this century, the should be marked in case the tissue transplanted sub- mortality from thyroidectomy in patients with toxic sequently becomes pathologic. With an exception goiter was at least 5% due to the frequent occurrence of one older report [34], several studies reported a of thyroid crisis after goiter resection. The symptoms decrease of the risk of permanent hypoparathyroid- that may be seen are tachycardia, fever, nausea and ism to less than 1% when this approach is practiced vomiting, restlessness, mental stimulation, and fre- [35,36]. Biopsies of normal parathyroid glands should quently coma. Today, no patient should be subjected be omitted during thyroid procedures since they con- to elective thyroid surgery if not euthyroid, either as a tribute significantly to postoperative parathyroid dys- result of his or her own thyroid function or after ap- function. propriate preoperative medical treatment. Medical A mild case of postoperative hypocalcemia is self- therapy includes antithyroid drugs (propylthiouracil, limiting and may not be recognized unless routine metimazole), β-adrenergic blockers (propranolol), calcium determination is carried out. Nevertheless we and administration of iodine (saturated solution of would recommend measurement of serum calcium potassium iodide). levels routinely in every patient prior to and after bilateral thyroid surgery. After an uncomplicated unilateral thyroid resection, hypocalcemia will virtually References never be observed. Recently it was shown that intraoperative parathyroid hormone (PTH) determina- 1. Becker WF (1977) Pioneers in thyroid surgery. Ann Surg tion allows prediction of postoperative hypocalcemia 185:493–504 (PTH <10 pg/ml) and the necessity of early vitamin D 2. Sosa JA, et al (1998) The importance of surgeon experi- supplementation in order to reduce the risk of post- ence for clinical and economic outcomes from thyroidec- operative symptomatic hypocalcemia [37]. Intraoper- tomy. Ann Surg 228:320–330 ative PTH monitoring facilitates early discharge and 3. 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