cricopharyngeal dysphagia

CE Article #1Cricopharyngeal Dysphagia in Dogs:The Lateral Approach for Surgical Management Lysimachos G. Papazoglou, DVM, PhD, MRCVS* F. A. Mann, DVM, MS, DACVS, DACVECC Jennifer J. Warnock, DVM Kug Ju Eddie Song, DVM University of Missouri–Columbia ABSTRACT: Cricopharyngeal dysphagia occurs in dogs when there is achalasia or asynchrony of the cricopharyngeal muscle. Differentiation of other causes of dysphagia and preoperative stabilization of the patient are essential for a successful outcome. Cricopharyngeal myectomy or myotomy using a lateral or ventral approach is the preferred treatment. he swallowing process may be divided into oropharyngeal, esophageal, and gastroesophageal phases.1 The oropharyngeal phase of swallowing may be further subdivided into oral, pharyngeal, and cricopharyngeal phases. Impairment of any part of the oropharyngeal phase of swallowing may result in dysphagia. 2 In the oral phase of swallowing, prehension and formation of a food bolus (which is moved to the tongue base) occur.1,2 Oral dysphagia is characterized by decreased tongue movements and difficulty in bolus accumulation.2 During the pharyngeal phase of swallowing, the bolus is delivered to the caudal pharynx by coordinated contraction of the pharyngeal muscles.1 Pharyngeal dysphagia is characterized by interrupted movement of the bolus from the oropharynx to the hypopharSend comments/questions via email to ynx and by impaired initiation [email protected] of the involuntary portion of or fax 800-556-3288. the swallowing reflex.2 During Visit CompendiumVet.com for full-text articles, CE testing, and CE test answers. T *Dr Papazoglou is now affiliated with Aristotle University of Thessaloniki, Greece. the cricopharyngeal phase of swallowing, the thyropharyngeal muscle contracts while the cricopharyngeal muscle relaxes, allowing passage of the bolus from the pharynx to the esophagus.1 At other times, and as soon as the bolus is completely transported into the esophagus, the cricopharyngeal muscle constricts continuously, thereby closing the proximal esophagus to prevent entrance of air into the esophagus during respiration and to prevent gastroesophageal reflux into the pharynx. Cricopharyngeal dysphagia (CPD) is an upper esophageal sphincter abnormality that occurs with inadequate relaxation of the cricopharyngeal muscle (achalasia) or failure of synchronization between pharyngeal contraction and cricopharyngeal relaxation (asynchrony) during swallowing. 2–5 Esophageal dysphagia occurs when there is difficulty transporting the bolus through the esophageal body.2 Gastroesophageal dysphagia results when there is a problem transporting the bolus through the caudal esophageal sphincter.2 CPD is uncommon in dogs, and its underlyOctober 2006 COMPENDIUM 696 Cricopharyngeal Dysphagia in Dogs: The Lateral Approach for Surgical Management CE 697 Case Report A 1-year-old castrated English cocker spaniel weighing 24.2 lb (11 kg) was referred to the Veterinary Medical Teaching Hospital, University of Missouri– Columbia, with a history of chronic coughing and regurgitation after eating. The dog had a low body condition score (i.e., 2 of 9). The complete blood count and serum biochemistry profile results included slight neutrophilia and lymphocytosis. The result of a serologic examination for Ehrlichia canis infection was positive. A neurologic examination disclosed no abnormalities. An acetylcholine antibody titer was within normal limits. Thoracic radiography detected a bronchial and interstitial pattern that was most evident in the left caudal lung lobe. Barium swallow videofluoroscopy showed normal movement of the barium from the oral cavity to the pharynx. Attempts to propel the bolus into the esophagus were unsuccessful because the upper esophageal sphincter was not adequately relaxed. A diagnosis of CPD was made, and the dog was prescribed doxycycline (50 mg PO bid for 3 weeks) and discharged from the hospital. Seven days later, the dog was readmitted to the hospital to undergo surgery for CPD. Results of a clinical examination of the oral cavity and larynx, with the patient under light anesthesia, were normal. Results of an intraoperative electromyographic examination of the left pelvic limb and pharyngeal muscles were within normal limits. A percutaneous endoscopic gastrostomy tube was placed on the left side, and the dog underwent left lateral cricopharyngeal myectomy as already described.10,20 The resected cricopharyngeal muscle was submitted for histopathologic examination. The specimen was stained with hematoxylin–eosin, modified trichrome, periodic acid–Schiff, ATPase at pH levels of 9.8 and 4.3, esterase, nicotinamide adenine dinucleotide–tetrazolium reductase, acid phosphatase, alkaline phosphatase, oil red O, and staphylococcal protein A conjugated with horseradish peroxidase. The results of histopathology showed moderate variability in myofiber size, with scattered, round atrophic fibers. Abundant endomysial, perimysial, and adipose connective tissues were seen. Necrotic fibers were also present, and intramuscular nerve branches moderately depleted of myelinated fibers were seen. The dog recovered uneventfully from anesthesia and started enteral feeding via the gastrostomy tube. The dog was offered ice cubes 12 days after surgery and had canned food and water 14 days after surgery without showing signs of regurgitation. Forty-five days after surgery, the owner reported that the dog was eating canned and dry food normally, without regurgitation or coughing. ing causes have been attributed to neuromuscular dysfunctions.6–10 The following should be included in the differential diagnosis of dysphagia: space-occupying masses, foreign bodies, cleft palate, strictures, traumatic lesions, and neuromuscular diseases.11 Pharyngeal dysphagia has clinical signs similar to those of CPD, and differentiation between these two types of dysphagia is very important because surgical intervention for CPD may worsen pharyngeal dysphagia.12 Positive-contrast videofluoroscopy is reliable in confirming the diagnosis of CPD and in differentiating the condition from other causes of dysphagia.8,13 According to the literature, 45 dogs ranging in age from 5 weeks to 10 years have reportedly had surgery for CPD. 1,6,8–10,14–20 The disorder has reportedly affected mostly young dogs, but cases of older dogs with CPD have also been reported.8,21 In a recent study21 of 14 dogs undergoing surgery for CPD, the median age was 15 months at initial evaluation compared with a median age of 5.5 months for dogs in previous reports.1,6,8–10,14–20 This age difference as described in the study has been attributed to the concurrent existence of acquired disorders, October 2006 including myasthenia gravis, laryngeal paralysis, and esophageal stricture.21 Of the 45 dogs reported on to date, 65% were female and 35% were male. The most common breeds identified included the cocker spaniel (20%), springer spaniel (9%), Bouvier des Flandres (9%), golden retriever (6.5%), miniature poodle (4%), and standard poodle (4%). A genetic component of CPD has been identified in golden retrievers22 and has been suggested to exist in cocker spaniels.8,18 In addition, muscular dystrophy of hereditary origin has been proposed as a cause of dysphagia in Bouvier des Flandres.9 SURGICAL ANATOMY The cranial esophagus is dorsal to the larynx and left of the midline. The upper esophageal sphincter is formed by the thyropharyngeal and cricopharyngeal muscles. The thyropharyngeal muscles originate from the lateral surface of the thyroid cartilage lamina and course dorsally and cranially over the dorsal border of the thyroid lamina and insert on the median dorsal surface of the pharynx in a bilaterally symmetric fashion. The cricopharyngeal muscle originates from the lateral COMPENDIUM 698 CE Cricopharyngeal Dysphagia in Dogs: The Lateral Approach for Surgical Management Figure 1. Positioning for the left lateral approach for cricopharyngeal myectomy or myotomy. The dog is placed in right lateral recumbency with a rolled towel under its neck. The dog’s head is to the left in this figure.The arrows indicate the jugular vein, and the dotted line indicates the proposed skin incision just ventral to the jugular vein. Figure 2. The sternocephalicus muscle (SC) and the jugular vein (arrow) are retracted dorsally. The sternothyroideus muscle (ST) can be visualized in the ventral part of the incision. surface of the cricoid cartilage and spreads over the dorsal surface of the esophagus across the midline and ends by narrowing its belly to the contralateral aspect of the cricoid cartilage. The borders of the cricopharyngeal and thyropharyngeal muscles are obscured as the fibers blend together. 5,23 In contrast to what has been reported,23 recent studies5 in normal puppies and adult dogs have shown that the cricopharyngeal muscle is unpaired (i.e., single). The cricopharyngeal muscle is innervated by the glossopharyngeal nerve and the pharyngeal branch of the vagus nerve.24 The cricopharyngeal muscle receives its blood supply primarily from branches of the cranial thyroid artery. dres with muscular dystrophy undergoing surgery for CPD showed incoordination in the pharyngeal phase of swallowing in addition to CPD.9 Aspiration pneumonia and/or bronchitis has been reported in 46% of the 45 dogs that underwent surgery for CPD.1,8,10,15–18,21 Laryngeal paralysis and masticatory myositis have also been reported preoperatively in dogs with CPD.21 SURGICAL MANAGEMENT Preoperative Considerations and Care Preoperative stabilization of dehydrated and debilitated patients is mandatory for a successful outcome4 and includes administration of intravenous fluids and electrolytes as well as antimicrobials to prevent aspiration pneumonia. To obtain optimal nutritional status, a percutaneous endoscopic gastrostomy tube should be placed in dogs with persistent dysphagia. Electromyography of the pharyngeal and laryngeal muscles is useful in excluding other abnormalities associated with the pharyngeal phase of swallowing or laryngeal paralysis that may adversely affect the outcome.9,21 Preoperative electromyographic recordings in four Bouvier des FlanCOMPENDIUM Surgical Technique Cricopharyngeal myotomy or myectomy, alone or combined with thyropharyngeal myotomy or myectomy, is the definitive treatment of dogs with CPD to relieve clinical signs and facilitate swallowing. 3,4,6,10,16,21,25,26 During cricopharyngeal myotomy, the muscle is transected along the dorsal midline to the esophageal muscularis.4,6 Cricopharyngeal myectomy involves partial excision of the cricopharyngeal muscle after elevating the muscle fibers from the esophageal muscularis. 3 Cricopharyngeal surgery may be performed using the standard ventral midline approach. 3,4,6 A lateral approach has recently been described for myotomy or myectomy of the cricopharyngeal muscle.10,20,21,26 This approach is similar to that used for cricoarytenoid laryngoplasty in dogs with laryngeal paralysis.27 Of the 45 dogs receiving surgical treatment of CPD,1,6,8–10,14–21 53% had cricopharyngeal myotomy, 25% had cricopharyngeal myectomy, 9% had cricopharyngeal and thyropharyngeal myotomy, and 13% had cricophaOctober 2006 Cricopharyngeal Dysphagia in Dogs: The Lateral Approach for Surgical Management CE 699 Figure 3. The thyroid cartilage is identified (grasped with forceps). Figure 4. The thyropharyngeal muscle (grasped with forceps) and cricopharyngeal muscle (CP) can be easily identified by dissection of the loose connective tissue around the thyroid cartilage. Figure 5. Cricopharyngeal myectomy by dissection of the muscle laterally and dorsally to the midline. The cricopharyngeal muscle has been incised dorsally and is grasped with hemostats to facilitate further dissection and final incision (dotted line) laterally. ryngeal and thyropharyngeal myectomy. Of dogs undergoing myotomy or myectomy of both muscles, three had partial myotomy and four had partial myectomy. The ventral midline approach was performed in 82% of the dogs1,6,8,10,14–21 and the lateral approach in 18%.10,20,21 In one report,19 a ventral approach with 45° rotation to the right was used. In the lateral approach, the dog is placed in lateral recumbency, and a rolled towel is placed under its neck to elevate the cricopharynx toward the surgeon (Figure 1). An orogastric tube is preplaced to aid identification of the October 2006 esophagus. The head is stabilized on the table by placing adhesive tape on the nose. An 8- to 10-cm left lateral incision is made dorsal to the larynx and ventral to the jugular vein starting at the cranial aspect of the cricoid cartilage (Figure 1). The platysma muscle and subcutaneous tissue are incised. With the use of Gelpi retractors, the sternocephalicus muscle and jugular vein are retracted dorsally and the sternohyoideus muscle is retracted ventrally to allow identification of the thyroid cartilage (Figures 2 and 3). The loose connective tissue around the thyroid cartilage is dissected free to expose the thyropharyngeal muscle, the cricopharyngeal muscle caudal to it, and the esophagus (Figure 4). The thyroid gland may become visible between the trachea and the sternohyoideus muscle. The cricopharyngeal muscle is dissected free laterally and dorsally down to the midline (Figure 5). Small branches of the cranial thyroid artery are ligated or electrocoagulated to control bleeding. Perforation of the esophageal wall is avoided. A 2- to 2.5-cm portion of the cricopharyngeal muscle is removed and placed in 10% buffered neutral formalin for histopathologic examination. Connective tissue is apposed with a continuous pattern of 3-0 absorbable suture. Skin closure may be accomplished with a continuous intradermal pattern using 3-0 absorbable suture, or the skin may be closed with nylon suture or staples. Postoperative Care and Complications The day after surgery, patients should be fed canned or blenderized food for the first 2 days and gradually returned to a normal diet over the next 3 to 4 days.28 COMPENDIUM 700 CE Cricopharyngeal Dysphagia in Dogs: The Lateral Approach for Surgical Management Table 1. Outcome and Follow-up of 45 Dogs Following Surgery for Cricopharyngeal Dysphagia Number of Dogs Outcome Follow-up Studies 22 Complete resolution of clinical signs 1 wk–8 yr (21 dogs) Ladlow and Hardie,1 Sokolovsky,6 Watrous and Suter,8 Peeters et al,9 Niles et al,10 Rosin and Hanlon,14 Shaw and Dodd,15 Quick et al,16 Carlisle and Egger,17 Weaver,18 Allen,19 Pfeifer,20 Warnock et al21 Ladlow and Hardie1 Watrous and Suter,8 Weaver,18 Warnock et al21 Warnock et al21 Peeters et al9 Watrous and Suter8 Rosin and Hanlon14 Warnock et al21 1 8 3 3 1 1 6 The dog was normal besides an occasional cough Improvement of clinical signs Transient resolution of clinical signs (two dogs were euthanized) Died from aspiration pneumonia and concurrent pharyngeal-phase dysphagia Euthanized; aspiration pneumonia, anesthetic stress, exacerbation of dysphagia after surgery Euthanized; persistent dysphagia due to fibrosis and contracture Persistent dysphagia associated with concurrent esophageal sphincter structural disease, laryngeal paralysis, neuromuscular disorders, pharyngeal disorders, and poor nutritional support 3 mo 1 wk–5 yr (five dogs) 2–36 wk 2 days 1 wk 2 wk 12 hr–1 mo (three dogs) Tube gastrostomy should be considered in patients that fail to maintain their body weight after surgery and that have persistent dysphagia.21 Fluid therapy and antimicrobials may be continued in the presence of aspiration pneumonia. 28 Postoperative complications following cricopharyngeal myotomy or myectomy may include laryngeal paralysis, fibrosis, esophageal wall perforation, recurrence of dysphagia, and pharyngocutaneous fistulation.29 Persistent or recurrent dysphagia and aspiration pneumonia were the most common short- and longterm postoperative complications reported in 23 of the 45 dogs that underwent surgery for CPD.8,9,14,18,21 The management of aspiration pneumonia may include administration of intravenous fluids and/or antimicrobials, positive-pressure ventilation via tracheostomy tube or oxygen support via nasal tube, nebulization, and coupage.21 Aspiration pneumonia has been diagnosed in 12 dogs, 10 of which died or were euthanatized as a result of the complication 12 hours to 4 years after surgery; two dogs survived.8,9,18,21 Aspiration pneumonia COMPENDIUM may be difficult to manage effectively in the presence of esophageal hypomotility and megaesophagus. 21 In a study9 of 24 Bouvier des Flandres with dysphagia associated with muscular dystrophy, four had surgery for CPD and three died 2 days after surgery because of aspiration pneumonia. The concurrent presence of pharyngeal dysphagia in those three dogs may have been responsible for the unfavorable outcome. One dog experienced dysphagia attributed to fibrosis and contracture after undergoing cricopharyngeal myotomy for CPD. The dog underwent endoscopic bougienage without much success and was euthanized. 14 Thus some authors 3,5,18 support performing myectomy rather than myotomy to ensure complete removal of the muscle fibers and prevent the previously described complication. However, others4 favor myotomy as long as muscle fibers are all recognized and transected. Two dogs have had revision of previous CPD surgery because of partial or transient resolution of dysphagia. One dog underwent cricopharyngeal, thyropharyngeal, and hyopharynOctober 2006 702 CE Cricopharyngeal Dysphagia in Dogs: The Lateral Approach for Surgical Management Key Points • Diagnosis of cricopharyngeal dysphagia is made with positive-contrast videofluoroscopy. • Cricopharyngeal myectomy via a lateral approach provides more rapid and easier access than does a ventral approach for surgical management of cricopharyngeal dysphagia. • Accurate preoperative differentiation of cricopharyngeal dysphagia from pharyngeal dysphagia and esophageal hypomotility may decrease the possibility of surgical failure and aspiration pneumonia. and excised without difficulty if the esophageal wall is not traumatized. Five dogs with CPD that had cricopharyngeal muscle myectomy through the lateral approach had complete resolution of clinical signs for 2 to 8 years after surgery.10 Before surgery, CPD should be accurately differentiated from other causes of dysphagia (e.g., oral or pharyngeal-phase dysphagia and esophageal hypomotility) to eliminate the possibility of surgical failure and to decrease the chance of aspiration pneumonia.8,9,21,30 Preoperative stabilization of the patient and enteral feeding with a percutaneous endoscopic gastrostomy tube are essential for a favorable outcome. REFERENCES geal myectomy after previously having cricopharyngeal and thyropharyngeal myotomy with partial resolution of dysphagia, and the other dog had cricopharyngeal myotomy twice but experienced recurrent dysphagia 9 months after the second surgery.21 Other reported18,21 complications have included seroma in two dogs, incisional swelling in two dogs, and pharyngeal swelling and stridor in one dog. 1. Ladlow J, Hardie RJ: Cricopharyngeal achalasia in dogs. Compend Contin Educ Pract Vet 22:750–755, 2000. 2. Watrous BJ: Clinical presentation and diagnosis of dysphagia. Vet Clin North Am 13:437–453, 1993. 3. Rosin E: Cricopharyngeal dysphagia, in Bojrab MJ (ed): Current Techniques in Small Animal Surgery, ed 4. Baltimore, Williams & Wilkins, 1998, pp 145–147. 4. Goring RL, Kagan KG: Cricopharyngeal achalasia in the dog: Radiographic evaluation and surgical management. Compend Contin Educ Pract Vet 4:438– 447, 1982. 5. Hyodo M, Aibara R, Kawakita S, Yumoto E: Histochemical study of the canine inferior pharyngeal constrictor muscle: Implications for its function. Acta Otolaryngol 118:272–279, 1998. 6. Sokolovsky V: Cricopharyngeal achalasia in a dog. JAVMA 150:281–285, 1967. 7. Pearson H: The differential diagnosis of persistent vomiting in the dog. J Small Anim Pract 11:403–415, 1970. 8. Watrous BJ, Suter PF: Oropharyngeal dysphagias in the dog: A cinefluorographic analysis of experimentally induced and spontaneously occurring swallowing disorders. Vet Radiol 24:11–24, 1983. 9. Peeters ME, Venker-van Haagen AJ, Goedegebuure SA, Wolvekamp WT: Dysphagia in Bouviers associated with muscular dystrophy; evaluation of 24 cases. Vet Q 13:65–73, 1991. 10. Niles JD, Williams JM, Sullivan M, et al: Resolution of dysphagia following cricopharyngeal myectomy in six dogs. J Small Anim Pract 42:32–35, 2001. 11. Shelton GD: Swallowing disorders in the dog. Compend Contin Educ Pract Vet 4:607–613, 1982. 12. Willard MD: Dysphagia and swallowing disorders, in Kirk RW (ed): Current Veterinary Therapy XI. Philadelphia, WB Saunders, 1992, pp 572–577. 13. Pollard RE, Marks SL, Davidson A, et al: Quantitative videofluoroscopic evaluation of pharyngeal function in the dog. Vet Radiol Ultrasound 41:409–412, 2000. 14. Rosin E, Hanlon GF: Canine cricopharyngeal achalasia. JAVMA 160:1496– 1499, 1972. 15. Shaw DG, Dodd RR: Cricopharyngeal achalasia. Canine Pract 4:33–34, 1977. 16. Quick CB, Hankes G, Womer R, et al: Cricopharyngeal achalasia. Auburn Vet 33:90–98, 1977. 17. Carlisle WT, Egger EL: Differential diagnosis of persistent dysphagia and regurgitation in the young. Iowa State Vet 42:14–18, 1980. 18. Weaver AD: Cricopharyngeal achalasia in cocker spaniels. J Small Anim Pract 24:209–214, 1983. 19. Allen SW: Surgical management of pharyngeal disorders in the dog and cat. Probl Vet Med 3:290–297, 1991. OUTCOME Of the 45 dogs that had surgery for CPD, 49% showed complete resolution of clinical signs of dysphagia; follow-up was available for 38 dogs and ranged from 12 hours to 8 years.1,6,8–10,14–21 The outcome and follow-up of 45 dogs are presented in Table 1. Myotomy achieved complete resolution of clinical signs in 12 dogs and myectomy in 11 dogs. However, the type of surgical procedure (myotomy versus myectomy) has reportedly not had an effect on the outcome,21 nor has surgeon experience (diplomates versus residents).21 CONCLUSION Surgery is the preferred treatment of dogs with CPD, and several techniques to resolve clinical signs of CPD have been discussed in the literature. A lateral approach has been described for myotomy26 and myectomy10,20,21 of the cricopharyngeal muscle. With the lateral approach, identification of the cricopharyngeal muscle is straightforward and the procedure is quicker and easier compared with the ventral approach, in which rotation of the larynx by 180˚ and placement of stay sutures to maintain rotation are necessary to identify the cricopharyngeal muscle. In addition, with the lateral approach, access to the dorsal midline of the muscle can be easily achieved and the muscle can be laterally and dorsally undermined COMPENDIUM October 2006 704 CE Cricopharyngeal Dysphagia in Dogs 20. Pfeifer RM: Cricopharyngeal achalasia in a dog. Can Vet J 44:993–995, 2003. 21. Warnock JJ, Pollard R, Kyles AE, et al: Surgical management of cricopharyngeal dysphagia in dogs: 14 cases (1989–2001). JAVMA 223:1462–1468, 2003. 22. Davidson AP, Pollard RE, Bannasch DL, et al: Inheritance of cricopharyngeal dysfunction in golden retrievers. Am J Vet Res 65:344–349, 2004. 23. Hermanson JW, Evans HE: The muscular system, in Evans HE (ed): Miller’s Anatomy of the Dog, ed 3. Philadelphia, WB Saunders, 1993, pp 258–384. 24. Venker-van Haagen AJ, Hartman W, Wolvekamp WT: Contributions of the glossopharyngeal nerve and the pharyngeal branch of the vagus nerve to the swallowing process in dogs. Am J Vet Res 47:1300–1307, 1986. 25. Gourley IM, Leighton RL: Surgical treatment for cricopharyngeal achalasia in the dog. Pract Vet 44:11–14, 1972. 26. Smith MM, Waldron DR: Head and neck surgery, in Smith MM, Waldron DR (eds): Atlas of Approaches for General Surgery of the Dog and Cat. Philadelphia, WB Saunders, 1993, pp 77–121. 27. Lahue TR: Treatment of laryngeal paralysis in dogs by unilateral cricoarytenoid laryngoplasty. JAAHA 25:317–324, 1989. 28. Fossum TW: Surgery of the digestive system, in Fossum TW, Hedlund CS, Hulse DA, et al (eds): Small Animal Surgery, ed 2. St Louis, Mosby, 2002, pp 274–449. 29. McKenna JA, Dedo HH: Cricopharyngeal myotomy: Indications and technique. Ann Otol Rhinol Laryngol 101:216–221, 1992. 30. Mason RJ, Bremner CG, DeMeester TR, et al: Pharyngeal swallowing disorders: Selection for and outcome after myotomy. Ann Surg 228:598–608, 1998. ARTICLE #1 CE TEST This article qualifies for 2 contact hours of continuing education credit from the Auburn University College of Veterinary Medicine. Paid subscribers may purchase individual CE tests or sign up for our annual CE program. Those who wish to apply this credit to fulfill state relicensure requirements should consult their respective state authorities regarding the applicability of this program. To participate, fill out the test form inserted in this issue or take CE tests online and get real-time scores at CompendiumVet.com.Test answers are available online free to paid subscribers as well. 1. Achalasia refers to a. failure of the cricopharyngeal muscle to relax. b. asynchrony of the cricopharyngeal and thyropharyngeal muscles. c. failure of the cricopharyngeal muscle to contract. d. failure of the thyropharyngeal muscle to relax. 2. CPD is an abnormality of the a. upper esophageal sphincter. b. lower esophageal sphincter. c. upper pharyngeal sphincter. d. esophageal muscle. 3. Which is an unpaired muscle? a. sternohyoideus c. sternocephalicus b. thyropharyngeus d. cricopharyngeus CE 4. Which breed has been identified as having a genetic component to CPD? c. golden retriever a. Labrador retriever b. boxer d. standard poodle COMPENDIUM October 2006 Cricopharyngeal Dysphagia in Dogs: The Lateral Approach for Surgical Management CE 705 5. Which statement regarding diagnosis of CPD is incorrect? a. A diagnosis of CPD can be confirmed by positivecontrast videofluoroscopy. b. Positive-contrast videofluoroscopy is not a reliable method of differentiating CPD from other causes of dysphagia. c. Electromyography of pharyngeal muscles may aid in differentiating CPD from other abnormalities associated with pharyngeal dysphagia. d. Electromyography of the laryngeal muscles in dogs with CPD is useful in excluding laryngeal paralysis, which may adversely affect patient outcome. 6. The cricopharyngeal muscle originates from the a. lateral surface of the thyroid cartilage. b. lateral surface of the cricoid cartilage. c. medial surface of the thyroid cartilage. d. medial surface of the cricoid cartilage. 7. Which complication has not been reported in dogs after surgery for CPD? a. aspiration pneumonia b. persistent dysphagia c. incisional seroma d. megaesophagus 8. Which statement regarding surgical treatment of CPD is incorrect? a. Cricopharyngeal myectomy via a lateral approach has been reported. b. Cricopharyngeal myectomy involves resection of the esophageal mucosa. c. During cricopharyngeal myotomy, the muscle is transected along the dorsal midline to the esophageal muscularis. d. Thyropharyngeal myotomy has been reported in conjunction with cricopharyngeal myotomy. 9. Which statement regarding surgical treatment of CPD is correct? a. Cricopharyngeal myotomy is more effective than cricopharyngeal myectomy. b. Surgeon experience has not been associated with patient outcome following surgery. c. Success after surgery is better with Bouvier de Flandres than with cocker spaniels. d. In dogs, long-term success after surgery is better with males than with females. 10. During the lateral approach for cricopharyngeal myectomy or myotomy, which muscle is retracted dorsally for exposure? c. sternothyroideus a. sternocephalicus b. sternohyoideus d. thyropharyngeus October 2006 COMPENDIUM