Canine-cricopharyngeal Achalasia In Dogs

Vol. 22, No. 8 August 2000

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Refereed Peer Review

FOCAL POINT

Cricopharyngeal Achalasia in Dogs

★Cricopharyngeal achalasia (CPA) in dogs can be treated effectively with cricopharyngeal myotomy.

University of London

Jane Ladlow, MA, VetMB Robert J. Hardie, DVM

KEY FACTS ■ The common clinical signs of CPA include dysphagia, regurgitation, coughing, aspiration pneumonia, and poor growth in young dogs. ■ Clinical signs of dysphagia can result from disruption of any part of the oropharyngeal phase of swallowing. ■ Contrast fluoroscopy is essential for evaluating swallowing function. ■ Improvement in swallowing function is seen immediately after cricopharyngeal myotomy. ■ Diagnosis of CPA depends on careful evaluation of swallowing function to exclude other oropharyngeal disorders.

ABSTRACT: Cricopharyngeal achalasia occurs in young dogs, causing both swallowing and respiratory signs. It occurs when the upper esophageal sphincter fails to open during swallowing, thereby preventing food from entering the proximal esophagus. Careful evaluation of swallowing function and exclusion of other causes of dysphagia are necessary for a diagnosis. Cricopharyngeal myotomy is an effective treatment with few complications.

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ricopharyngeal achalasia (CPA) is a disease of young dogs. It is caused by failure of the upper esophageal sphincter to open during swallowing, thereby preventing food from entering the proximal esophagus.1–3 Dysphagia, regurgitation, aspiration, coughing, and nasal reflux may occur during eating as a result of food being retained in the pharynx after swallowing. Similar clinical signs may be caused by other oropharyngeal or esophageal diseases. Diagnostic differentials should include cricopharyngeal asynchrony, pharyngeal dysphagia, cleft palate, congenital hypoplasia of the soft palate, congenital stenosis of the esophagus, vascular ring anomaly, esophageal foreign body, esophageal diverticulum, space-occupying masses, and megaesophagus.4–6 Determining the diagnosis requires thorough history taking and physical examination as well as careful evaluation of swallowing function. This article describes the relevant anatomy, the phases of swallowing, diagnosis, surgical treatment, and a review of reported cases; in addition, aspects of the disorder in dogs are compared with those in humans.

ANATOMY The cricopharyngeus and thyropharyngeus muscles compose the upper esophageal sphincter that surrounds the caudal pharynx and proximal esophagus.7 The cricopharyngeus muscle is the primary muscle controlling the passage of food into the esophagus (Figure 1). At rest, the cricopharyngeus muscle is contracted, thereby closing the proximal esophagus. Its function is to prevent air from entering the esophagus during respiration and to preclude gastroesophageal reflux from passing into the pharynx. During swallowing, the cricopharyngeus muscle relaxes and opens to allow food into the esophagus. Information regarding the anatomic structure of the cricopharyngeus muscle is conflicting. Previous information indicated that the muscle was paired, with

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each side originating from the tation, aspiration, and coughlateral surfaces of the cricoid ing. Repeated attempts to swalcartilage and inserting dorsallow eventually force some ly on the median raphe. 8 food through the upper esophaHowever, a more recent study geal sphincter, where it then involving normal dogs indipasses to the stomach. cated that the cricopharynDIAGNOSIS geus muscle is not paired and For any dog with dysphathat individual muscle fibers gia, a thorough history should originating from one side of the cricoid cartilage spread Figure 1—Lateral musculature of the laryngopharynx and be obtained to help determine over the dorsal surface of the upper esophageal sphincter. (CH = ceratohyoideus; CP = the underlying cause (see Imesophagus and either termi- cricopharyngeus; E = esophagus; MH = myohyoideus; SH portant Questions to Ask When nate within the body of the = sternohyoideus; SM = sternomastoideus; ST = ster- Taking the History of a Dog Suspected to Have Cricophamuscle or insert on the oppo- nothyroideus; TP = thyropharyngeus) ryngeal Achalasia). Dogs with site side of the cricoid cartiCPA usually develop clinical signs (e.g., various degrees lage.9 This study also identified differences between the of gagging, regurgitation, coughing, nasal reflux, and cricopharyngeus and thyropharyngeus muscles. The possibly aspiration pneumonia) at the time of weaning. cricopharyngeus muscle was found to be composed The signs are usually static unless complicated by pneupredominately of type 1 fibers, whereas the thyrophamonia. Prehension in these dogs is normal, and they ryngeus muscle was found to comprise predominately are able to form a bolus of food but are unable to swaltype 2 fibers. A difference was also found in the distrilow. Regurgitation occurs immediately after attempted bution of the motor end-plates within the muscles, and swallowing. Liquids are sometimes swallowed better the diameter of the muscle fibers was significantly than solids are but may be associated with nasal reflux. smaller in the cricopharyngeus muscle than in the thyOwners may describe lack of weight gain or failure to ropharyngeus muscle.9 The blood supply to the cricothrive despite a ravenous appetite. pharyngeus muscle comes primarily from the branches Differentiating the various causes of dysphagia reof the cranial thyroid artery, and the innervation is quires a thorough oral examination and observation of from the glossopharyngeal nerve and the pharyngeal the dog while it eats. Watching the dog eat helps deterbranches of the vagus nerve.7

PHASES OF SWALLOWING Swallowing is the coordinated process of moving a bolus of food from the mouth to the stomach. The process can be divided into oropharyngeal, esophageal, and gastroesophageal phases. The oropharyngeal phase of swallowing can be further divided into three separate phases—oral, pharyngeal, and cricopharyngeal. In the oral phase, prehension takes place and the bolus of food is formed at the base of the tongue. In the pharyngeal phase, the bolus is propelled to the caudal pharynx by coordinated contractions of the rostral and caudal pharyngeal muscles. In the cricopharyngeal phase, the cricopharyngeal muscle relaxes and opens in coordination with the pharyngeal contraction, allowing the bolus of food to pass into the proximal esophagus.10 Disruption to any part of the oropharyngeal phase of swallowing can cause signs of dysphagia.4,6 In dogs with CPA, failure of the cricopharyngeus muscle to relax during pharyngeal contraction disrupts the cricopharyngeal phase of swallowing. Consequently, food remains in the pharynx, which causes gagging, regurgi-

Important Questions to Ask When Taking the History of a Dog Suspected to Have Cricopharyngeal Achalasia ■ What was the dog’s age at the onset of clinical signs? ■ Was onset acute or chronic? ■ Are the signs static or progressive? ■ When does regurgitation occur? What is the condition of the regurgitated food? ■ Does the dog have any difficulty chewing or swallowing or does food drop from its mouth? ■ Are liquids swallowed more easily than solids? ■ Is there any coughing, nasal reflux, or signs of aspiration pneumonia? ■ How is the dog’s appetite? ■ Has there been any weight loss or other concurrent problems?

CRICOPHARYNGEUS MUSCLE ■ OROPHARYNGEAL SWALLOWING PHASE ■ CLINICAL SIGNS

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mine which phase of swallowline. Care must be taken to ing is abnormal and aids in ensure that all of the muscle further localizing the probfibers are cut and no longer lem. Survey radiographs of constrict the esophagus. The the pharyngeal area and thoesophagus should be carefully rax are usually normal but inspected for evidence of permay reveal signs of aspiration foration before the stay suture pneumonia caused by chronic is removed and the esophagus dysphagia. Contrast fluoand trachea are returned to roscopy is essential for evalutheir normal position. The ating the phases of swallow- Figure 2—Preoperative fluoroscopic spot film showing sternohyoideus muscles and ing and observing the passage contrast medium distending the caudal pharynx and aspi- subcutaneous tissue are closed of food from the esophagus rating into the trachea in a dog with cricopharyngeal acha- with absorbable suture mateto the stomach. Barium sul- lasia. Only a very small amount of medium passed through rial in a simple continuous or fate preparations are the most the upper esophageal sphincter during swallowing. simple interrupted pattern. commonly used contrast meThe skin is closed routinely. dia to examine swallowing. Postoperative care involves Contrast media should be given in liquid or paste form providing necessary supportive care and analgesia and and mixed with food to obtain the maximum amount monitoring the incision for complications. Once the of information on bolus formation and swallowing dog has recovered, swallowing function can be evaluatfunction. For cases in which aspiration is likely, noned by feeding a small amount of soft food. Function ionic, water-soluble, iodine-based contrast medium improves immediately after cricopharyngeal myotomy.1 Potential postoperative complications include recurrent may be advisable to avoid potential complications with laryngeal paralysis, esophageal perforation, recurrence inhaled barium. of dysphagia, and pharyngocutaneous fistula.8 Findings on endoscopic examination of the pharynx and upper esophageal sphincter are normal, and there is CASE REPORT no obvious obstruction to the passage of an endoscope or History stomach tube in dogs with CPA. A presumptive diagnoA 6.5-month-old female English cocker spaniel was sis of CPA can be made if a dog is able to form a bolus referred to the Royal Veterinary College at the Univerand move it to the caudal pharynx in the normal manner sity of London with a 5-month history of dysphagia, but is unable to pass it into the esophagus because the regurgitation, and aspiration. The owner reported that cricopharyngeus muscle fails to dilate during swallowing. the first signs occurred at weaning when the dog regurA diagnosis of CPA is confirmed by response to such gitated through the nares. The dog would occasionally treatment as cricopharyngeal myotomy.6,11 cough and become cyanotic when eating. Hand-feedSURGICAL TREATMENT ing small meals improved the dysphagia, although Surgical treatment for CPA involves transection of episodes of regurgitation and coughing still occurred. the cricopharyngeus muscle to prevent further obstrucAt the time of presentation, the dog was notably smalltion during swallowing.6,8 The procedure is performed er than its littermates. by using a ventral approach to the larynx and proximal Clinical Signs and Diagnosis esophagus.1 A ventral midline incision should be made Physical examination revealed a dog of small stature cranial to the larynx to the midcervical region. The weighing 6.2 kg. Vital signs were normal, but increased sternohyoideus muscles are separated to expose the larlower respiratory sounds were noted on thoracic ausculynx. The larynx and proximal esophagus are identified tation. Neurologic examination, which included testing and rotated, avoiding injury to the recurrent laryngeal cranial nerve reflexes, was normal. Complete blood nerve on the lateral aspect of the trachea. Rotation can count and serum biochemistry profiles were within be maintained with a stay suture placed through the normal limits, except for an increased total leukocyte lamina of the thyroid cartilage. An appropriately sized count and mature neutrophilia. A lateral radiograph of tube placed down the esophagus aids identification of the thorax revealed an alveolar pattern in the ventral the upper esophageal sphincter. lung lobes. Regurgitation was seen during feeding deThe cricopharyngeus muscle, which surrounds the spite normal prehension and swallowing efforts. proximal esophagus immediately caudal to the thySwallowing function was examined using fluoroscopy ropharyngeus muscle, is transected on the dorsal midSURVEY RADIOGRAPHS ■ CONTRAST FLUOROSCOPY ■ CRICOPHARYNGEAL MYOTOMY

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while the dog was fed a soft food–barium sulfate mixture. Fluoroscopy showed normal prehension and bolus formation with strong contractions of the pharyngeal muscles, which pushed the bolus toward the upper esophageal sphincter and distorted the pharynx. The sphincter did not relax and open synchronously with pharyngeal contraction, and thus food remained in the pharynx. Food was aspirated into the trachea during inspiration and then coughed up. A small amount of contrast medium passed through the upper esophageal sphincter and into the stomach (Figure 2). The clinical examination and radiographic and fluoroscopic findings were consistent with CPA and secondary aspiration pneumonia. The other diagnostic differential was severe pharyngeal–cricopharyngeal asynchrony.

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pH 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 size of the myofibers varied moderately but seemed to be within the Figure 3—Interoperative photograph of the transected cri- normal range for the muscle. Type 1 and 2 muscle fibers copharyngeus muscle and the underlying esophagus. were present, and no specific abnormalities were noted during enzyme reactions or with any of the staining methods.

DOCUMENTATION Cricopharyngeal achalasia has been documented in only eight other dogs (Table I).2,3,5,6,11 Six of the eight dogs were treated surgically with Figure 4—Radiograph showing contrast medium in the cricopharyngeal myotomy, upper esophagus after cricopharyngeal myotomy. Note and clinical signs were permathe bolus of food in the region of the cricopharyngeal my- nently eliminated in five. In otomy. There is no evidence of tracheal aspiration (com- the sixth dog, regurgitation recurred within 2 weeks, prepare with Figure 2). Surgical Procedure sumably because of fibrosis at Cricopharyngeal myotomy the previous myotomy inciwas performed using the ventral approach described sion, and further treatment was not pursued.2 Treatment and outcome were not recorded for the other two previously.1,6 The cricopharyngeus muscle was elevated off the esophagus and transected along the dorsal middogs. line. The transected muscle fibers contracted, leaving a COMPARISON WITH THE DISORDER IN HUMANS gap of approximately 1 cm between the cut edges (FigDepending on the cause, CPA in humans is classified ure 3). A section of the cricopharyngeus muscle was reas primary or secondary. Primary CPA includes congenmoved for histopathologic examination. The esophagus ital or idiopathic cases that are not associated with other was inspected for perforation and returned to its nordiseases. Secondary CPA is associated with other dismal position. The rest of the closure was routine. eases, including central neurologic disease; cerebrovascuPostoperative Results lar accidents; diffuse neuromuscular disorders; or such Twelve hours after surgery, the dog was fed a small local lesions as pharyngoesophageal stenosis, esophageal amount of soft food. It ate rapidly with no evidence of asdiverticulum, pharyngeal tumors, or external comprespiration or regurgitation. Fluoroscopic examination the sive lesions.12,13 Confirming the diagnosis of CPA in humans is simiday after surgery demonstrated normal passage of food lar to that in dogs. A thorough oral examination is perthrough the upper esophageal sphincter into the cranial formed, and the patient is observed while eating. Diagesophagus (Figure 4). At 1 and 3 months after surgery, the nostic tests include laryngoscopic examination, contrast owner reported that the dog was eating well, had no regurfluoroscopic examination of swallowing and esophageal gitation or aspiration, and coughed only occasionally. function, manometric studies of the upper and lower Histopathologic examination of the cricopharyngeus esophageal sphincters, and possibly endoscopic examimuscle involved staining with hematoxylin and eosin, nation of the esophagus.8,12 modified trichrome, periodic acid–Schiff, ATPase at HISTOPATHOLOGY ■ PRIMARY VS. SECONDARY CPA ■ DIAGNOSTIC TESTS IN HUMANS

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TABLE I Cases of Cricopharyngeal Achalasia Reported in the Literature Authors

Signalment

Clinical Signs

Diagnostic Test

Treatment

Outcome

Allen6

18-wk-old male miniature poodle

Regurgitation

Fluoroscopy

Cricopharyngeal myotomy

Clinically normal 1 yr after surgery

Shaw and Dodd11

10-wk-old female mixed-breed

Regurgitation and aspiration pneumonia

Contrast radiography

Cricopharyngeal myotomy

Clinically normal 2 mo after surgery

Rosin and Hanlon2

5.5-mo-old male terrier cross

Dysphagia

Fluoroscopy

Cricopharyngeal myotomy

Recurrence of dysphagia 2 wk after surgery; euthanized at owner’s request

5-mo-old male cocker spaniel

Dysphagia and aspiration pneumonia

Fluoroscopy

Cricopharyngeal myotomy

Clinically normal 4 yr after surgery

4-mo-old female miniature poodle

Dysphagia

Fluoroscopy

Conservative therapy followed by cricopharyngeal myotomy

Occasional cough and nasal discharge; clinically normal 2 yr after surgery

15-mo-old boxer

Regurgitation

Contrast radiography

Not reported

Not reported

12-mo-old foxhound

Regurgitation

Contrast radiography

Not reported

Not reported

Regurgitation

Contrast radiography

Cricopharyngeal myotomy

Clinically normal 3.5 mo after surgery

Pearson5

Sokolovsky3 13-wk-old female mixed-breed

Treatment for CPA in humans is also similar to that in dogs, although other nonsurgical approaches have been described; spontaneous improvement has occurred in some patients.8,12–15 Some infants with CPA may be fed more efficiently by placing them in a semirecumbent position (i.e., by using a “chalasia chair”) to improve their ability to swallow. More severely affected infants require intermittent gavage feeding or a gastrostomy tube to maintain adequate nutrition.12 Balloon dilation or bouginage of the upper esophageal sphincter has been attempted but has not proved to be effective in the long term.8,16 The use of botulinum toxin for the diagnosis and treatment of CPA has been reported.15 This technique uses percutaneous electromyography to guide an injection of botulinum toxin into the cricopharyngeus muscle. The botulinum toxin causes a graded muscle weakness and temporarily relieves dysphagia. The technique can be used as part of the diagnostic evaluation to determine the extent to which the dysphagia is caused by

the cricopharyngeus muscle, to treat patients that are unsuitable for surgery, or to provide temporary relief while managing the primary disease.15 Cricopharyngeal myotomy remains the principal treatment for humans with CPA. The procedure has been performed through an external approach similar to that described in dogs as well as an endoscopic approach that uses a rigid endoscope and carbon dioxide laser to incise the cricopharyngeus muscle.8,12,14 The overall prognosis for patients with CPA depends on the primary cause, but significant long-term improvement has been achieved with cricopharyngeal myotomy in patients without other problems. 8,12

CONCLUSION The signalment, history, and clinical signs for dogs with CPA are uniformly similar. All reported cases have occurred in young dogs, suggesting a congenital or primary abnormality. Careful evaluation of swallowing function is necessary to differentiate among other oro-

GAVAGE FEEDING ■ BALLOON DILATION ■ BOTULINUM TOXIN

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pharyngeal disorders that cause similar signs. Cricopharyngeal myotomy is an effective treatment with minimal morbidity; however, other nonsurgical forms of treatment may warrant further investigation.

REFERENCES 1. Goring RL, Kagan KG: Cricopharyngeal achalasia in the dog: Radiographic evaluation and surgical management. Compend Contin Educ Pract Vet 4(5):438–444, 1982. 2. Rosin E, Hanlon GF: Canine cricopharyngeal achalasia. JAVMA 160:1496–1499, 1972. 3. Sokolovsky V: Cricopharyngeal achalasia in a dog. JAVMA 150:281–284, 1967. 4. Suter PF, Watrous BJ: Oropharyngeal dysphagias in the dog: A cinefluorographic analysis of experimentally induced and spontaneously occurring swallowing disorders. Vet Radiol 21:24–39, 1980. 5. Pearson H: The differential diagnosis of persistent vomiting in the young dog. J Small Anim Pract 11:403–415, 1970. 6. Allen SW: Surgical management of pharyngeal disorders in the dog and cat. Prob Vet Med Head Neck Surg 3:290–297, 1991. 7. Hermanson JW, Evans HE: The muscular system, in Evans HE (ed): Miller’s Anatomy of the Dog, ed 3. Philadelphia, WB Saunders, 1993, pp 296–297. 8. McKenna JA, Dedo HH: Cricopharyngeal myotomy: Indications and technique. Ann Otol Rhinol Laryngol 101:216– 221, 1992.

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9. Hyodo M, Aibara R, Kawakita S, Yumoto E: Histochemical study of the canine inferior pharyngeal constrictor muscle: Implications for its function. Acta Otolaryngol (Stockh) 118:272–279, 1998. 10. Watrous BJ, Suter PF: Normal swallowing in the dog: A cineradiographic study. Vet Radiol 20:99–109, 1979. 11. Shaw DG, Dodd RR: Cricopharyngeal achalasia. Canine Pract 4:33–34, 1977. 12. Mitchell RL, Armanini GB: Cricopharyngeal myotomy: Treatment of dysphagia. Ann Surg 181:262–266, 1975. 13. Reichert TJ, Bluestone CD, Stool SE, et al: Congenital cricopharyngeal achalasia. Ann Otolaryngol 86:603–610, 1977. 14. Herberhold C, Walther EK: Endoscopic laser myotomy in cricopharyngeal achalasia. Adv Otorhinolaryngol 49:144–147, 1995. 15. Blitzer A, Brin MF: Use of botulinum toxin for diagnosis and management of cricopharyngeal achalasia. Otolaryngol Head Neck Surg 116:328–330, 1997. 16. Mihailovic T, Perisic VN: Balloon dilatation of cricopharyngeal achalasia. Pediatr Radiol 22:522–524, 1992.

About the Authors Ms. Ladlow and Dr. Hardie are affiliated with the Department of Small Animal Medicine and Surgery, the Royal Veterinary College, University of London, United Kingdom. Dr. Hardie is a Diplomate of the American College of Veterinary Surgeons and the European College of Veterinary Surgeons.