3 Approach-Related Complications Following Anterior Cervical Spine Surgery: Dysphagia, Dysphonia, and Esophageal Perforations

Bharat R. Dave, D. Devanand, and Gautam Zaveri

Introduction This chapter analyzes the problems of dysphagia, dysphonia, and esophageal tears during the Pathology involving the anterior subaxial anterior approach to the cervical spine and cervical spine is most commonly accessed suggests ways of prevention and management. through an anterior retropharyngeal approach (Fig. 3.1). While this approach uses tissue planes to access the anterior cervical spine, visceral Dysphagia structures such as the and esophagus and such as the recurrent laryngeal Dysphagia or difficulty in swallowing is a (RLN), superior laryngeal nerve (SLN), and symptom indicative of impairment in the ability pharyngeal plexus are vulnerable to direct or to swallow because of neurologic or structural traction injury (Table 3.1). Complaints such as problems that alter the normal swallowing dysphagia and dysphonia are not rare following process. Postoperative dysphagia is labeled as anterior cervical spine surgery. The treating acute if the patient presents with difficulty in surgeon must be aware of these possible swallowing within 1 week following surgery, complications,­ must actively look for them in intermediate if the presentation is within 1 to the postoperative period, and deal with them 6 weeks, and chronic if the presentation is longer expeditiously to avoid secondary complications. than 6 weeks after surgery.

Common carotid Vagus nerve Recurrent laryngeal nerve

Longus colli muscle Internal jugular artery

Anterior scalene muscle

Middle scalene muscle External jugular vein Posterior scalene muscle

Fig. 3.1 Anterior retropharyngeal approach to the cervical spine.

Table 3.1 Vulnerable nerves during ACDF

Glossopharyngeal, hypoglossal nerves C3 level or above—oral and pharyngeal phases of swallowing. Superior laryngeal nerve C3–4 level—laryngeal sensory impairment—aspiration, dysphagia. Recurrent laryngeal nerve C6 level or below—milder dysphagia, mainly during swallowing of liquids. Nerves of the pharyngeal plexus Vagus nerve (normally protected by the )—retractional injury at any subaxial cervical levels—C2 to C5—pharyngeal dysphagia.

Abbreviation: ACDF, anterior cervical decompression and fusion. 34 Complications in Spine Surgery CHAPTER 3 Approach-Related Complications Following Anterior Cervical Spine Surgery

Anatomy and Physiology of Swallowing dysfunction can be divided into four categories: an inability or excessive delay Deglutition in initiating pharyngeal swallowing, aspiration Normal swallowing involves more than 30 of ingested food, nasopharyngeal regurgitation, muscles and is performed up to 600 times a day. and residue of ingested food within the 1 It involves the following three phases (Fig. 3.2): pharyngeal cavity even after swallowing. 1. Oral phase begins with the entry of food into the oral cavity. It involves preparing Incidence the food for digestion by sucking, chewing, The incidence of postoperative dysphagia after and rolling, followed by transport of food anterior cervical decompression and fusion into the throat. Oral phase is voluntary (ACDF) varies widely in literature, ranging from and is mediated by the facial, hypoglossal, 5 to 69%.2–8 Recent prospective studies have and glossopharyngeal nerves. reported a higher incidence when compared 2. Pharyngeal phase starts when the leading with previous retrospective studies.9,10 Bazaz edge of the bolus of food goes past the et al prospectively studied 249 patients who faucial arch. The is elevated, and underwent anterior cervical spine surgery. They there is inversion of the epiglottis with reported difficulty in swallowing in 50.3%, 17.7%, closure of the true and false vocal cords, and 12.5% of their patients at 1, 6, and 12 months preventing aspiration of food or liquid. postsurgery, respectively.8 The wide variation The respiration temporarily ceases, in published incidence rates can be attributed while powerful contractions from the to differences in surgical technique, extent constrictor muscles clears the bolus of of surgery, and the size of the implant used. food from the pharynx. The pharyngeal Variations in the definition of dysphagia and its phase is involuntary and is mediated by measurement, as well as the time period when the SLN, RLN, and pharyngeal plexus. the patient is evaluated, also contributes to the 3. Esophageal phase begins with entry large variation in reported incidence. Although of food through the upper esophageal the incidence of postoperative dysphagia is high, sphincter and its exit through the lower most patients recover within 1 to 3 months esophageal sphincter into the stomach. It postsurgery. Yue et al reported that although 35% involves relaxation and tightening of the of 74 patients had varying degree of persistent esophageal sphincters and coordinated dysphagia when evaluated at 7.2 years following peristalsis of the esophageal musculature. anterior cervical surgery, only 1 patient reported The esophageal phase is mediated by the severe difficulty in swallowing.6 myenteric plexus of Auerbach, triggered by the vagus nerve.

Valleculae

Pharynx Vellum Hard palate Bolus Tongue

Hyoid

Vocal folds Epiglottis Trachea Esophagus a b c d Fig. 3.2 Phases of swallowing. (a) Oral preparatory phase. (b) Oral transport phase. (c) Pharyngeal phase. (d) Esophageal phase. Complications in Spine Surgery CHAPTER 3 Approach-Related Complications Following Anterior Cervical Spine Surgery 35

Causes that ipsilateral injury may be asymptomatic. Nerves of the pharyngeal plexus originate from Causes of dysphagia following anterior cervical the vagus nerve. A retraction injury at C2 to spine surgery can be divided into the following: C5 levels causes pharyngeal dysphagia with ••Intrinsic: Edema of the esophageal or difficulty in initiating swallowing, pooling of secretions in the throat, aspiration, choking pharyngeal wall due to excessive or sensation, and often severe dysphagia to both prolonged retraction at surgery or trauma solids and liquids. The glossopharyngeal and during intubation.11 Esophageal tears may hypoglossal nerves are vulnerable during also present with dysphagia. surgeries from C1 to C3. ••Extrinsic: Compression of the esophagus Patients undergoing revision surgery, multi­ or pharynx by a large retropharyngeal level procedures, prolonged surgery, female sex, hematoma (Fig. 3.3) and displaced bone and those in the older age group (> 60 years) are graft, cage, or plate (Fig. 3.4).12,13 at higher risk of dysphagia.11 Sixty-six percent ••Neurologic: Injury to the RLN, SLN, or of patients with cervical myelopathy have been nerves of pharyngeal plexus due to found to have subtle swallowing difficulties prolonged or forceful retraction, nerve on preoperative barium swallow. Spinal cord division, misplaced ligatures, or thermal compression can cause swallowing dysfunction injury due to aggressive use of monopolar by interfering with the preganglionic, sympa­ cautery. thetic outflow or spinal afferents that interrupt Extrinsic compression usually causes dysphagia local reflex mechanisms.16 These patients are to solids. Nerve injury usually results in dys­ more prone to developing worsening of dys­ phagia to both liquids and solids. Injury to phagia postoperatively. the RLN typically occurs at C6 or below. It can result in diminished closure of the glottis Investigations predisposing the patient to aspiration, coughing, and a gasping voice. Denervation of the inferior Radiography of the cervical spine gives the constrictor and cricopharyngeal muscles may initial clues in terms of increase in gas shadow, result in milder forms of dysphagia, especially prevertebral edema/hematoma, graft, and during swallowing of liquids.14,15 The SLN is implant position.17,18 Subjective assessment of vulnerable during anterior approach at C3–4. dys­phagia can be done with a questionnaire Sensory innervation is usually bilateral, such and represented semiquantitatively using the

a b

Fig. 3.3 (a) Postoperative radiograph showing increased Fig. 3.4 Delayed esophageal perf­ after surgery due to a large retropharyngeal oration due to backing out of plate hematoma. (b) Hematoma with plate impression removed and screws. during reexploration. 36 Complications in Spine Surgery CHAPTER 3 Approach-Related Complications Following Anterior Cervical Spine Surgery

Bazaz-Yoo grading score (Table 3.2). Objective to be the main cause of postoperative assessment can be done with indirect and dysphagia, the trachea and esophagus direct laryngoscopy, video fluoroscopic swallow are manually mobilized by the patient evaluation (VSE), or fiberoptic endoscopic preoperatively. Using the thumb belly, evaluation of swallowing (FEES).8 Other tests the patient is asked to push the thyroid that may be useful include electromyography cartilage across the midline from right to (EMG) to record the electrical activity of the left multiple times a day. This exercise swallowing muscles, an ultrasound to observe started 3 to 4 days before surgery has movement of the swallowing muscles, and been shown to reduce the incidence of esophageal manometry. Indirect laryngoscopy swallowing difficulties after surgery.19 helps evaluate the position of the vocal cords in ••Atraumatic endotracheal intubation. patients with suspected RLN injury. The VSE is •• used to determine the presence, severity, and Gentle dissection with adequate release of timing of aspiration, and to detect and analyze the platysma and cervical . At C5 to functional impairment of the swallowing C7 levels, the may have mechanism. to be transected, to allow less forceful retraction (Fig. 3.5). Preventive Measures ••Retraction of the trachea and esophagus has to be gentle, applied for a short period ••Tracheoesophageal traction exercises (< 175 minutes) and relieved intermit­ (TTEs)—since prolonged/excessive traction tently. The authors prefer using handheld of the trachea and esophagus is postulated retractors in which the pressure can be controlled and released intermittently, as compared with static self-retaining Bazaz-Yoo dysphagia grading score Table 3.2 retractors.20 The retractor blades must be 0 No difficulty No difficulty with liquids or solids. placed below the longus colli (Fig. 3.6), 1 Mild No difficulty with liquids. and the pressure must be downward Rare with solids. rather than transversely. 2 Moderate No or rare difficulty with liquids. ••Reduction in endotracheal cuff pressures Occasional difficulty with specific (ETCPs) to 20 mm Hg after the placement solids. of retractors.14,15,21 In the anterior 3 Severe No or rare difficulty with liquids. cervical approach, the esophagus gets Frequent difficulty with majority com­pressed in between the unyielding of solids. cervical retractors and endotracheal tube.

Fig. 3.5 Omohyoid needs to be cut during Fig. 3.6 Retractors placed safely below the longus approaches to C6/7. colli. Complications in Spine Surgery CHAPTER 3 Approach-Related Complications Following Anterior Cervical Spine Surgery 37

By reducing the cuff pressure, there is ENT surgeon may be consulted to perform an less compression on the esophagus with indirect laryngoscopy to rule out RLN injury. In retraction. patients with persisting severe dysphagia, after ••Choosing a low-profile, small, and smooth the first week, consideration must be given to 25 cervical plate.20,22,23 Plate should sit flush introducing a PEG to rest the oropharynx. with the bone. Rapid progression of symptoms, especially ••Avoid routine use of rhBMP2. It results with accompanying inspiratory stridor, may in prolific and heterotopic bone forma­ be observed in patients with an expanding tion that may result in compression of hematoma. A radiograph may reveal widening esophagus. of the retropharyngeal space. This necessitates urgent exploration of the wound to drain the ••Meticulous hemostasis. Use of a post­ epidural hematoma. operative drain to prevent hematomas. Late presentations secondary to bone graft/ ••Application of local steroids (triamcin­ cage or plate failure need to be assessed for olone) into the retropharyngeal space to 26 limit edema. Intravenous (IV) adminis­ fusion status. Decision of hardware removal tration of methylprednisolone or hydro­ is based on symptomatic status of the patient cortisone reduces edema following and response to conservative means as shown prolonged surgeries. in algorithm. Patients with persistent dysphagia or with repeated aspiration suspected due to ••Application of icepacks over the wound coughing, choking, or atelectatic changes on postoperatively reduces bleeding as well chest radiographs should undergo speech path­ as edema of the soft tissue structures. ology evaluation and active swallow therapy. An algorithm for the management of postoperative Treatment dysphagia is proposed in Fig. 3.7.

Dysphagia is the most common postoperative patient complaint following ACDF. In the vast Rehabilitation for Patients with majority of patients, it is temporary and resolves Persistent Dysphagia within 3 months.8 During the postoperative rounds following an anterior cervical spine The goals of treatment in patients with persistent surgery, it is vital to make the patient sit up difficulty in swallowing are to maximize food in bed and evaluate his/her ability to swallow. transfer and minimize or prevent aspiration. Mild difficulty in swallowing is not unexpected Compensatory strategies that can be used for and is usually due to edema of the esophageal facilitating the safe and effective passage of bolus wall due to prolonged retraction at surgery. In material include (1) modifying diet: controlling these patients, icepacks are placed over the neck bolus size or texture and avoiding certain foods; to limit bleeding and edema, and the patient is (2) heightening sensory input prior to or during kept on a liquid diet. swallowing; (3) applying voluntary control to If difficulty in swallowing is more severe the swallow (breath holding, effortful swallow); so that the patient is unable to even swallow (4) protecting the airway with postural adjust­ his/her own sputum and there is pooling ments to reduce risk of aspiration (e.g., chin tuck, of secretions in the throat, nerve injury or head tilt, head rotation, head lift, lying down); significant trauma to the pharynx/esophagus and (5) doing exercises to strengthen weak facial is suspected. The patient is kept nil by mouth, muscles, to improve range of oral or pharyngeal the pooled secretions are suctioned, and a Ryle’s structural movement, and/or to improve tube may be inserted.24 Icepacks are placed over coordi­nation.27 If the patient is still unable to the neck, and IV steroids may be administered to swallow safely despite rehabilitation, surgical reduce the edema. IV fluids are continued. The procedures such as Teflon augmentation, vocal patient must be nursed in the sitting position cord medialization, and palatal lifts can be used to reduce the risk of aspiration. If necessary, an to minimize risk of aspiration. 38 Complications in Spine Surgery CHAPTER 3 Approach-Related Complications Following Anterior Cervical Spine Surgery

Moderate or severe dysphagia

Investigate (X-ray/CT/MRI)

Soft tissue edema Hematoma Implant/graft displacement/ Plate displacement/new ossification/ Flexed occipito-cervical fusion

Steroids Drain and explore Reposition/removal of bone/posterior instrumentation if anterior not applicable

Fig. 3.7 Algorithm for management of postoperative dysphagia.

Key Points injury is detected and treated within the first 24 hours. Mortality rate increases to as high as 50% 28–30 ••Dysphagia is a self-resolving condition that when treatment is further delayed. is successfully managed nonoperatively in most patients. Anatomy ••Preoperative assessment for dysphagia The esophagus lies directly anterior to the especially in myelopathy cases and prior spine and requires to be retracted medially to repeat anterior cervical procedures. when performing an anterior retropharyngeal ••Predisposing factors for postoperative approach to the cervical spine. The esophagus dysphagia include older age, female sex, is separated from the spine by several layers revision surgery, multilevel procedures, of prevertebral fascia. This adventitious tissue prolonged operation, and cervical protects the esophagus during the anterior myelopathy. approach. However, there are two areas where ••Gentle handling of tissues and meticulous the esophagus is vulnerable to injury. The most hemostasis. vulnerable area called “Killian’s triangle” is anterior to the C5/6 disk and is formed by the ••Reduced endotracheal tube cuff pressure cricopharyngeus muscle along with the inferior and avoidance of prolonged, continuous constrictor muscle of the pharynx from either retraction. side. Here the posterior esophageal mucosa is ••Must specifically examine for dysphagia covered only by a thin layer of buccopharyngeal and dysphonia on postoperative rounds. fascia without any muscular layer in between. The second region is at the level of the thyrohyoid membrane laterally. The esophagus is made up Esophageal Injury of a mucosa, a submucosa, and a muscle layer made up of circular and longitudinal muscles. Esophageal injury during anterior cervical surgery is fortunately rare, but the risk of deep Incidence cervical or mediastinal infection and secondary airway compromise makes this injury serious The reported incidence of esophageal injuries and potentially life threatening. Mortality rates ranges from 0.2 to 4% in several large reported reaching 20% have been reported even when the studies.13,28,31–33 Hershman et al reported two Complications in Spine Surgery CHAPTER 3 Approach-Related Complications Following Anterior Cervical Spine Surgery 39

esophageal perforations among 9,591 (0.02%) comes to light during routine radiographs, eso­ patients who underwent anterior cervical spine phagoscopy, and rarely when a patient coughs up surgery.34 Both the cases were detected and or passes out a screw in stools. More commonly treated in the acute postoperative period. One patients complain of dysphagia, neck pain or patient was successfully treated with debride­ fullness, odynophagia, fever or subcutaneous ment and primary closure, whereas the other one emphysema, chest pain, and vomiting. There died despite multiple debridements. Gaudinez may be deep wound infection with drainage et al reported 44 esophageal perforations­ among from the wound along with redness and 2,496 patients treated for spinal cord injury over swelling. If injury remains undetected, the a period of 25 years. Approximately 95% of the patient goes on to develop florid sepsis with patients with esophageal injuries underwent abscess, osteomyelitis,­ mediastinitis, pleuritis, direct repair.13 and pericarditis. Incidence of mediastinitis is less common with injuries to the cervical Causes esophagus as compared with injuries to the thoracic esophagus. Most cases of esophageal perforations are direct iatrogenic injuries due to improper handling Investigations of sharp instruments during various stages of surgery.13,28,35 During anterior cervical spine Plain radiographs are assessed for presence surgery, aggressive use of monopolar cautery, of air in the anterior cervical area (Fig. 3.9), improper placement of retractors, slippage of subcutaneous emphysema, paravertebral air, sharp instruments, or entanglement of soft tissue widening of retro-pharyngoesophageal space, in a high-speed drill can result in esophageal or migration of bone graft or hardware.17,18,41 injury. Such injuries are usually identified Cervical CT and MRI would be helpful for during surgery. Esophageal perforations can detailed assessment. Esophagoscopy and con­ also occur later, as a result of bone graft/cage trast esophageal study (Fig. 3.10) should be or plate/screw displacement. Pressure necrosis performed to identify the size and location of can also occur due to repeated microtrauma by injury whenever necessary.13,28,30,37 Use of water- proud metallic hardware (Fig. 3.8).13,15,36–39 soluble contrast should be encouraged instead of barium contrast to prevent barium-related 42 Clinical Presentation inflammation of . The clinical presentation of patients with eso­ Preventive Measures phageal perforation is highly variable. Reports by Yee and Terry40 and Pompili et al29 suggest ••Careful dissection with adequate soft that occasionally patients may be completely tissue mobilization. Special care with asymptomatic. In such cases, the perforation cautery.

a b c d Fig. 3.8 Three years following anterior cervical decompression and fusion (ACDF). Patient was asymptomatic. (a, b) Screw was observed to be missing during routine follow-up radiographs. (c, d) Esophagoscopy demonstrated a delayed pharyngoesophageal perforation. Plate and screw seen on esophagoscopy. 40 Complications in Spine Surgery CHAPTER 3 Approach-Related Complications Following Anterior Cervical Spine Surgery

Fig. 3.9 X-ray demonstrating air in the retrophary­ ­ Fig. 3.10 Contrast CT showing gas, fluid, and ngeal space, indicating esophageal perforation. debris within the retropharyngeal space due to undetected intraoperative esophageal tear.

••Placement of the retractor blades beneath and surgery is completed with fresh uncon­ the longus-colli muscles. Intermittent taminated instruments. If possible, insertion release of retraction. of metallic hardware is avoided. The wound is ••Care in handling sharp instruments and closed over a suction drain. A nasogastric tube drills. The esophagus must be protected must be inserted, the patient must be kept nil during placement of screws and plates. by mouth for 2 to 3 weeks, and wide-spectrum antibiotics that also provide anaerobic cover ••Use of smooth, low profile, well-contoured must be started. No specific recommendation locking plates. for the length of time of wound drainage or antibiotic therapy has been mentioned in Treatment literature.33 At 2 to 3 weeks, repeat imaging is performed to see whether there is any If the esophageal tear is detected intra­opera­ residual leak from the esophagus. If there is no tively, the tear must be isolated from surround­­ leakage, patient can be started on oral feeds. ing structures, edges freshened, and sutured However, if there is some residual leakage, it is using interrupted or imbricating absorbable recommended that a percutaneous endoscopic sutures, without any tension on the suture line gastrostomy tube be placed for feeding and a (Fig. 3.11). The wound needs to be thoroughly repeat wound exploration be performed. Use of irrigated and debrided, following which the a sternocleidomastoid or omental flap must also instru­ments used must be preferably discarded, be considered to reconstruct the esophageal

Intercostal muscle pedicle

Fig. 3.11 Suturing an esophageal tear in layers ab cd e without tension. Complications in Spine Surgery CHAPTER 3 Approach-Related Complications Following Anterior Cervical Spine Surgery 41

wall. Local sternomastoid flap is often used in are recommended. The esophageal wall may view of its proximity and ease of mobility.43 be friable and difficult to suture. In such cases, Flap cover helps in improving antibiotic deli­ a flap may be used to reconstruct it. The role very, wound healing, controlling leaks, and of hardware in maintaining the spinal stability 44 in stopping further erosion. The wound can needs to be assessed and managed accordingly also be left open and a negative suction drain as discussed in Fig. 3.12. Missed cases, poor applied till the leak seals, wound is healthy, blood supply, relatively thin wall, and leakage of and can be closed secondarily. An algorithm digestive juices pose challenges in the treatment for management of esophageal perforations is of esophageal injury.28,30,37,43 depicted in Fig. 3.12. Postoperatively, an esophageal injury is suspected if there is subcutaneous emphysema, Key Points drainage from the wound, and chest pain with vomiting. The injury is confirmed with plain ••Adequate exposure and proper use of X-rays, or a CT scan that may show presence of retrac­tors, especially in long-duration prevertebral air or subcutaneous emphysema surgery. Retractors must protect the and soft tissue swelling. Contrast swallow esophagus all the time. studies may be used to confirm the diagnosis. Although nonoperative treatment has been ••In redo surgery, Ryle’s tube may be described, in patients with suspected or con­ inserted preoperatively. Approach should firmed tears, surgical debridement and an be from the opposite side, if possible. attempt at closing the esophageal rent directly Extra care during retraction.

Established injury

Status of implants

Good position Malposition Infected

Ryle's tube (3 weeks) Change Remove/reinsertion of implant/ change to posterior fixation/Tong traction and secondary procedures later on after healing

Watch/observe Intraoperative finding

Heals Does not heal > 1 cm tear < 1 cm tear

OK Direct repair Ryle’s tube (3 weeks) (stemomastoid flap) + Conservative treatment

Fig. 3.12 Algorithm for management of esophageal perforations. 42 Complications in Spine Surgery CHAPTER 3 Approach-Related Complications Following Anterior Cervical Spine Surgery

••When esophageal tear is suspected, do not in a transverse trajectory inferior to the hyoid procrastinate. bone. It pierces the thyrohyoid membrane and ••High index of suspicion. An oropharyngeal culminates into three branches. The internal branch provides sensory and parasympathetic bypass is primary treatment. innervation to the laryngeal vestibule and glottis, up to the level of the vocal cords. It also Dysphonia sends a motor branch to the interarytenoid muscle. Because of bilateral nerve supply, a unilateral injury that may occur during anterior Dysphonia is defined as a dysfunction in the cervical spine surgery is usually asymptomatic. ability to produce voice. For voice to be classified A bilateral injury would result in complete loss as “dysphonic,” abnormalities must be present in of sensations within the larynx and decreased one or more vocal parameters: pitch, loudness, laryngeal cough reflex resulting in aspiration quality, or variability. Perceptually, dysphonia and choking. The smaller external branch of can be characterized by hoarse, breathy, harsh, the SLN travels caudally, medial to the carotid or rough vocal qualities, but some kind of , along with the superior thyroid artery. phonation remains. Besides supplying innervation to the inferior pharyngeal constrictor muscles, it innervates Anatomy the that plays an important role in phonation by regulating tension of the The larynx, commonly called the “voice box,” vocal folds. Injury to the external branch results is the organ in the neck that is involved in in impairment of both high and low frequencies breathing, sound production, and protecting of sound and easy fatigability of voice, besides the trachea against food aspiration. The larynx dysphagia. is innervated by branches of the vagus nerve on The RLNs branch off from the vagus nerve, each side (Fig. 3.13). the left at the aortic arch, and the right at the The SLN arises from the vagus nerve, within right . After branching, the the carotid sheath midway between the jugular nerves typically ascend toward the larynx in foramen and the carotid bifurcation at C2. It then a groove between the trachea and esophagus. runs medially and caudally for 1.5 cm, before They then pass behind the outer lobes of the dividing into the internal and external branches. thyroid gland and enter the larynx underneath The internal branch of the SLN courses along the inferior constrictor muscle, passing into the with the superior laryngeal artery medially and larynx just posterior to the cricothyroid joint.

Vagus nerve External carotid artery Superior laryngeal nerve

Internal branch of Superior thyroid artery superior laryngeal nerve

External branch of superior laryngeal nerve

Inferior thyroid artery Thyrocervical trunk

Right recurrent laryngeal nerve

Left recurrent laryngeal nerve

Fig. 3.13 Nerve supply of the larynx. Complications in Spine Surgery CHAPTER 3 Approach-Related Complications Following Anterior Cervical Spine Surgery 43

The left RLN loops around the arch of aorta Causes before entering the tracheoesophageal groove, and hence it is longer than the right, making it Dysphonia results either from impairment less susceptible to stretch injuries than the right. in vocal cord vibration or from injury to the The RLN supplies sensations to the larynx below nerve supply of the larynx.48,49,55,56 Impairment the vocal cords. It innervates all the intrinsic in vocal cord vibration can occur due to direct muscles of the larynx except the cricothyroid. vocal cord trauma occurring during intubation, The posterior cricoarytenoid muscles, which are postoperative acid reflux, and laryngeal and the only muscles that can open the vocal cords, vocal fold edema.14,50,55,57 Excessive and forceful are innervated by the RLN. Unilateral RLN paresis retraction of the trachea and esophagus can causes unilateral paralysis of the vocal cord so also cause swelling of the pharyngeal and that it lies in the paramedian position, unable to laryngeal musculature and, rarely, even fracture adduct or abduct. Insufficient laryngeal closure or dislocation of the arytenoid cartilage. During during phonation causes a breathy and rough surgery at the C2 to C5 levels, traction and voice quality (hoarseness), with increased vocal compression injuries to the SLN have also been effort and fatigue and dyspnea on exertion. reported. However, the most common cause of Because of loss of sensations in the glottis and dysphonia following anterior cervical surgery is the lack of complete closure of the vocal cord, injury to the RLN.14 there is a higher risk of aspiration. Injury to the RLN can occur due to compres­ sion, contusion, traction, thermal damage, nerve Incidence division or misplaced ligature, and postoperative edema.31,45–47 One of the main causes is com­ Laryngeal complications are not uncommon pression of the RLN during retraction of the 45–49 after anterior cervical spine surgery. The trachea and esophagus, between the retractor reported incidence of dysphonia in the early blade and the inflated cuff of the endotracheal postoperative period varies between 2 and tube. Apfelbaum et al found that laryngeal tissues 30%.46,50,51 Some authors have reported the rates adjacent to the endotracheal tube were subject of clinical dysphonia due to any cause, whereas to significant compression and displacement. others have specifically studied vocal cord There is approximately threefold increase in paralysis secondary to RLN palsy. Ziedman et al endotracheal tube cuff pressure during deep studied the Cervical Spine Research Society retractor placement.14 Reducing the cuff pressure database and reported a 0.2% incidence of RLN below 20 mm Hg allows the endotracheal tube palsy among 4,589 patients.7 A more recent to shift away from the endolaryngeal wall. This systematic review of literature by Tan et al limits compression of the RLN and reduces the revealed that the incidence of RLN palsy with rate of symptomatic palsy from 2.2 to 0.7%.57 vocal cord paralysis following anterior cervical This movement of the tube has been noted spine surgery is between 0.2 and 24.2%.52 More fluoro­scopically when retraction was briefly recently Gokaslan et al, from the AO Spine eased and the cuff deflated. Deflating the cuff North America Clinical Research Network, of the endotracheal tube after positioning of conducted a multicenter study and reported the retractors also allows the RLN to slip down that the incidence of RLN palsy ranged from 0.6 within the tracheaesophageal groove so that to 2.9% between centers. Seventy-four percent it is unaffected by subsequent retraction. of the patients in their study showed complete Thereafter, the cuff pressure is again elevated resolution of symptoms and 16% had partial up to 20 mm Hg. resolution with residual effects.53 The reported rate of persistent (> 12 months) symptomatic Controversy remains as to whether the vocal fold paresis varies from 0.33 to 2.5%.14,45 approach to the anterior cervical spine should Because SLN palsy is often subclinical, the data be from the right or the left to minimize the on the incidence of SLN palsy are limited. A risk of RLN injury. A retrospective study in the recent multicenter study identified one patient otolaryngology literature indicated that 15 of with SLN palsy from among 8,887 anterior 16 patients who presented to one clinic with cervical spine surgeries.54 aspiration and dysphagia following anterior 44 Complications in Spine Surgery CHAPTER 3 Approach-Related Complications Following Anterior Cervical Spine Surgery

cervical spine surgery had right-sided, unilateral laryngeal muscles. The interpretation of vocal fold paralysis.45 However, Kilburg et al findings, however, is subjective, and accuracy is found no statistical difference in the rate of dependent on experience. RLN injury based on side of approach in their retrospective comparison of 418 patients Preventive Measures treated for one- or two-level instrumented 58 ant­erior cervical discectomy and fusion. ••Left-sided approach to the cervical spine. Other studies too have reported low rates of ••Careful dissection and adequate soft tissue RLN injury following procedures using a right- mobilization. Use of bipolar cautery. sided approach.46,59 It is difficult to advocate one approach over the other on the basis of the ••Placement of the retractor blades beneath current clinical literature. The authors prefer the longus-colli muscles, away from the the left-sided approach, irrespective of the side tracheoesophageal groove. of pathology. ••Avoid opening the retractor excessively Several factors have been identified as being wide. associated with a higher risk of RLN palsy, ••Intermittent release of retraction. including right-sided surgery, revision surgery, ••Deflating the cuff of the endotracheal tube multilevel procedures, duration of surgery, and after placement of retractors, followed by type surgery. Only repeat spine surgery has reinflation to less than 20 mm Hg. been shown to have a strong association with RLN palsy. ••In patients with previous anterior cervical spine surgery, thyroidectomy, radical neck dissection, and previous radiation therapy, Investigations an indirect laryngoscopy should be done Indirect laryngoscopy, direct laryngoscopy, preoperatively to assess the status of the or videostroboscopy with high-speed camera vocal cords. If the vocal cord on the side of can be used for visualization of vocal fold the previous surgery is nonfunctional, it is mobility (Fig. 3.14) and differentiation of preferable to approach the cervical spine vocal fold paralysis from paresis, hypo- and from the same side during repeat surgery. hyperfunctional vocal fold behavior. Laryngeal ••Use of intraoperative laryngeal EMG. EMG is the gold standard in diagnosis and Dimopoulos et al used this modality may be used to look for evidence of chronic to predict development of RLN palsy denervation or reinnervation of the intrinsic in 298 patients who underwent ACDF.

Respiration

Phonation

without paralysis unilateral paralysis bilateral paralysis

Fig. 3.14 Indirect laryngoscopic picture of vocal cords in health and diseases. Complications in Spine Surgery CHAPTER 3 Approach-Related Complications Following Anterior Cervical Spine Surgery 45

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