disorders of the pharynx

Disorders of the pharynx

Eileen K. Sullivan, DVMa,*, Eric J. Parente, DVMbaDepartment of Clinical Sciences, Colorado State University,

College of Veterinary Medicine and Biomedical Sciences,

James L. Voss Veterinary Teaching Hospital, Fort Collins, CO 805231620, USAbDepartment of Clinical Studies, University of Pennsylvania, School of Veterinary Medicine,

Kennett Square, PA, USA

Congenital disorders of the pharynx

Choanal atresia

Choanal atresia is a disorder resulting from failure of the bucconasalmembrane to perforate during embryologic development [1] and is rare inhorses [2]. The bucconasal membrane then forms a partial or completeseparation between the caudal nasal cavity and the pharynx [1]. Choanalatresia can occur as a unilateral or bilateral condition and is recognizedmost often in the neonate. Unlike what is reported in people and llamas, theobstruction in horses is not bony.

Clinical signs include severe dyspnea and decreased air movement fromeach aected nostril. When both nasal passages are aected, emergencytracheotomy is necessary shortly after birth to maintain airway patency.Endoscopic examination and contrast radiography can be used to dem-onstrate the imperforate septum. The bucconasal membrane can beexcised surgically through a nasal ap or transnasally using endoscopicguidance. Stents to minimize stricture should be considered after bucconasalmembrane excision [3], but, to date, there are no long-term reports of re-covery to athletic function, and it is presumed that stricture is common.More recently, the authors have used a technique of frequent bougienage,which seems promising.

Cleft palate (palate hypoplasia)

A cleft palate may be suspected when milk drains from a newborn foalsnostrils shortly after initial nursing eorts. Diagnosis is conrmed by either

Vet Clin Equine 19 (2003) 159167

* Corresponding author.

E-mail address: [email protected] (E.K. Sullivan).

0749-0739/03/$ - see front matter 2003, Elsevier Science (USA). All rights reserved.doi:10.1016/S0749-0739(02)00071-8

oral palpation of the defect or by endoscopic examination. The resultingoronasal defect can predispose the foal to failure of passive transfer,malnutrition, and aspiration pneumonia [4]. If the palate defect is small,foals may mature without denitive diagnosis from 6 weeks to 7 years ofage, although eventual soundness is jeopardized by the defect [58]. Whensevere, surgical repair is the necessary treatment and should be performedas early as possible to close the oronasal stula and prevent secondarycomplications. Mandibular symphysiotomy is the most common surgicalapproach to palate repair [4]. Complications after surgical repair includeaspiration pneumonia, mandibular osteitis or nonunion, and dehiscencefailure of the palatal repair [9]. Despite successful treatment of the oronasaldefect, pharyngeal function may still be compromised, precluding athleticfunction as an adult. Concurrent congenital facial deformities are knownto occur with cleft palate and include cyclops [10] and nasal septal devia-tion [6]. The presence of additional congenital abnormalities must alwaysbe investigated.

Pharyngeal cysts

Pharyngeal cysts have been identied in the dorsal pharyngeal walland soft palate but occur most commonly in the subepiglottic region.Subepiglottic cysts are thought to be embryologic remnants of the thy-roglossal duct [11], although a traumatic origin has been postulated [12].Cysts located on the dorsal pharyngeal wall may be congenital and resultfrom a persistent remnant of the craniopharyngeal duct or Rathkes pouch[11]. Cysts, usually evident at a young age, can occur in any breed and havebeen more commonly reported inmaale horses [13]. Clinical signs includeabnormal upper airway noise, cough, exercise intolerance, nasal discharge,dysphagia, and aspiration pneumonia. Foals with cysts involving thesoft palate may develop dorsal displacement of the soft palate (Fig. 1).A pharyngeal cyst may be suspected based on history and clinical signs,but endoscopic and radiographic examination is necessary to conrm thediagnosis. Contrast radiography after oral administration of barium sulfatecan be helpful is isolating pharyngeal cysts located on the soft palate [14].Surgical excision of the cyst can be accomplished through laryngotomy,pharyngotomy, or a transoral or transnasal approach. Noncontact laserablation can also be successful and obviate the need for a surgical incision.

Rostral displacement of the palatopharyngeal arch

Typically, the larynx protrudes through the intrapharyngeal ostium, whichis bordered caudally by the palatopharyngeal arch. Rostral displacementof the palatopharyngeal arch is a congenital anomaly that induces pha-ryngeal dysfunction. Horses may display clinical signs of dysphagia, per-sistent cough, abnormal upper respiratory noise, and aspiration pneumonia

160 E.K. Sullivan, E.J. Parente / Vet Clin Equine 19 (2003) 159167

[15]. In some cases, the primary clinical sign is abnormal upper respiratorynoise [16]. Treatment options are limited, because concurrent anomalies,such as absence of the cricopharyngeal muscle, deformed thyroid cartilage,absence of the cricothyroid articulation, and degeneration of the recurrentlaryngeal nerve, can accompany the palatopharyngeal arch displacement[17]. Successful surgical laser ablation of the displaced palatal tissue hasbeen performed; however, the prognosis for athletic performance remainedpoor [18].

Pharyngeal trauma

Trauma to the pharynx may manifest as external swelling, dyspnea,dysphagia, or unusual upper respiratory noise. Diagnostic tools, such asastute physical examination, radiography, and upper airway endoscopy,may elucidate both the source of trauma and extent of pharyngeal damage.Potential origins of pharyngeal trauma include external lacerations, punc-ture wounds, and blunt trauma. Another potential origin of pharyngealtrauma is foreign body penetration. Pharyngeal foreign bodies are mostcommonly composed of wood or metal [19], although, historically, an-thelmintic boluses administered by a balling gun have been implicated[20]. Obligate anaerobic bacterial infections may result in foreign bodiespenetrating the mucosa, and anaerobic commensals may gain access todeeper pharyngeal tissues [21]. Radiographic examination is the diagnostictool of choice with metallic foreign bodies [22]. In most horses, surgicalremoval of pharyngeal foreign bodies is necessary before clinical signs canbe resolved [22].

Fig. 1. A lateral skull radiograph with persistent displacement of the soft palate. The epiglottis

can be seen below the cyst. An esophageal feeding tube is present.

161E.K. Sullivan, E.J. Parente / Vet Clin Equine 19 (2003) 159167

Iatrogenic causes of pharyngeal trauma include laceration secondary tonasogastric intubation. Trauma may be caused by forceful initial insertionor prolonged intubation and can result in signs of ptyalism, dysphagia, andcoughing [23]. It may be difcult to differentiate between pharyngeal andesophageal trauma based on clinical signs alone without the use of endo-scopic examination [23]. Clinical signs associated with pharyngeal perfora-tion may not be evident for several weeks after the initial trauma, whensecondary abscesses form [24]. Treatment regimens may include esoph-agostomy to allow enteral feeding or gastric decompression if required.

Although rare, iatrogenic laceration of the soft palate can occur whentransnasal approaches are used to correct epiglottic entrapment. Full-thickness lacerations of the soft palate have been repaired successfully inadult horses after inadvertent division [25].

Nasopharyngeal cicatrix may develop as a result of scarring and in-ammation secondary to pharyngeal trauma. In many horses, the underly-ing traumatic incident is not readily apparent at the time of endoscopicexamination, although other abnormalities seen concurrently include abnor-mal or deformed epiglottic and arytenoid cartilage [26]. Concurrent clinicalsigns include upper respiratory noise and exercise intolerance. Naso-pharyngeal cicatrix may not be the primary cause of respiratory impairment,although when it is implicated, surgical correction may be attempted [27].In more severe cases, permanent tracheostomy is recommended [24].

Pharyngeal dysfunction

Dorsal displacement of the soft palate

Dorsal displacement of the soft palate (DDSP) can be intermittent orpersistent. Horses with persistent DDSP exhibit exercise intolerance andupper respiratory noise and may or may not cough and be dysphagic.Diagnosis is conrmed on endoscopic examination after failure to see theepiglottis during a prolonged examination and frequent attempts to correctthe displacement after swallowing. The etiology of persistent displacementversus intermittent displacement seems to be dierent and therefore shouldbe addressed accordingly. Occasionally, persistent displacement is observedwith concurrent epiglottic entrapment. This should be suspected if there isbulging of the palate from the epiglottis, minimal dysphagia, and no otherneurologic decits. Infrequently, the edge of the entrapment can be rec-ognized separate from the edge of the palate (Fig. 2). Radiographs mayconrm this diagnosis, and resolving the entrapment surgically resolves thedisplacement problem. Persistent displacement associated with moresignicant dysphagia and neurologic problems has a poorer prognosis,and therapy is aimed at resolving the underlying neurologic dysfunction.

Intermittent DDSP (IDDSP) is a signicant performance-limitingproblem in horses that is only evident during exercise. Often, a presumptive


diagnosis and treatment are based on historical information of poor per-formance, abnormal respiratory noise, resting or postexercise endoscopicexamination, and lack of other clinical ndings. Although the cause of thisdisorder is unknown, epiglottic hypoplasia, malformation, and neuromus-cular dysfunction have been proposed [28]. More recent information froma study of IDDSP during high-speed treadmill endoscopy provides evidencethat IDDSP occurs in multiple forms and can be associated with otherdynamic respiratory abnormalities [19]. Furthermore, many horses had nostructural abnormalities noted on resting endoscopic examination and nohistory of making an abnormal respiratory noise [19]. Although thediagnosis of IDDSP is not easy, IDDSP may be suspected if the epiglottisappears small or accid on endoscopic examination and the upper airwaynoise reported during exercise is consistent with this diagnosis. Transientdisplacement of the soft palate during resting endoscopic examination is anincidental and insignicant nding if DDSP is not suggested in the history[19,29]. Horses that are predisposed to IDDSP may develop palatedisplacement on occlusion of the external nares during a standingexamination, because this maneuver mimics the exercise examination bycreating negative pressure in the pharynx [30]. It has long been suspected

Fig. 2. Concurrent displacement of the soft palate and epiglottic entrapment. Both the edge of

the entrapment and the edge of the palate can be discerned.


that horses affected with IDDSP develop an ulcer on the free border of thesoft palate as a result of the frequent displacement and replacement thatis evident on standing endoscopic examination [31], but a signicantcorrelation between ulceration of the palate and displacement during high-speed treadmill endoscopy has not been supported [19].

Given the diculty in diagnosing and dierentiating the cause of IDDSP,moderate success with numerous treatments is not surprising. Use of atongue tie can be benecial to prevent caudal retraction of the larynx,thereby increasing palate contact with the epiglottis [29]. Surgical treatmentsof DDSP also target caudal retraction of the larynx by excising muscles thatapply caudal retracting forces. The sternothyrothoideus myectomy provideda successful outcome in 58% [32] and 60% [33] of horses in two popula-tions. Staphylectomy, thought either to stiffen the free edge of the palate orto enlarge the pharyngeal ostium physically, improved 60% of horses ina similar population [33]. Neodymium:yttrium (Nd:Yag) laser augmentationof the free border of the soft palate has also been used to induce scar tissueand discourage palatal displacement [34]. When applicable, augmentation ofa accid epiglottis can improve an individual horses airway dynamics, anda 66% success rate is reported [31]. Younger horses that are suspected ofhaving a primary neurogenic cause can also improve with rest and anti-inammatory treatment [19].

Pharyngeal collapse

Collapse of the dorsal pharyngeal wall during exercise is a performance-limiting problem causing upper airway noise during peak expiration.Although the etiology of pharyngeal collapse during exercise is unknown,pharyngeal neuromuscular paresis and other adjacent dynamic abnormal-ities, such as mild guttural pouch tympany, have been proposed [35,36].When suspected, denitive diagnosis of pharyngeal collapse is made throughuse of videoendoscopic examination during treadmill exercise. In threepopulations of horses undergoing treadmill evaluation for poor perfor-mance or upper airway noise, the incidence of pharyngeal collapse was 3%[37], 8% [38], and 12% [39]. Because there is no known treatment for thisdisorder, the prognosis for athletic function is guarded [35].

Pharyngitis

Pharyngeal lymphoid hyperplasia is commonly recognized in younghorses. Many attribute pharyngeal lymphoid hyperplasia to a local immuneresponse to inhaled or ingested antigens [40], because it increases onchallenge to both acute bacterial and viral infections [41] and stabling [42].Diagnosis is obtained through pharyngeal endoscopic examination. Surveysof endoscopic ndings within the upper respiratory tract of racehorses


estimate the prevalence to be from 34.2% [43] in one population to as highas 89% [2] in another population. Multiple studies correlate prevalence andage, with younger horses having a higher incidence and severity [40,43,44].Some authors have implicated pharyngeal lymphoid hyperplasia as aperformance-limiting entity [11,41], although most now agree that thiscondition has little if any impact on the athletic ability of the horse orfunction of the upper respiratory tract, unless severe [4547].

The pharynx may play a role in both harboring and detecting etiologicagents of subclinical upper respiratory tract infection. The soft palateepithelium and tonsillar tissue have been implicated as sites of both initialpenetration and maintenance of Streptococcus equi infections, serving asa reservoir for future transmission [43]. Equine herpesvirus and inuenzavirus have been implicated in horses developing acute signs of infectiousupper respiratory disease [48]. Nasopharyngeal swab samples are helpful inidentication of the causative organism in acute upper respiratory tractinfections. Organisms isolated from pharyngeal mucosa have also beenimplicated as etiologic agents in lower respiratory tract disease [49,50].Fungal infections caused by Conidiobolus coronatus are also reported asetiologic agents in equine pharyngitis [51]. Topical antifungal and systemicfungal treatment is indicated in these cases.

Neoplasia

Although rare, primary pharyngeal neoplasia occurs in the horse. Clinicalsigns include nasal discharge, increased upper respiratory noise, exerciseintolerance, dysphagia, and generalized wasting. Lymphosarcoma andsquamous cell carcinoma are the most common tumors identied. Althoughprimary pharyngeal neoplasia is rare, extension of masses from neighboringanatomic regions, such as the oral cavity and sinus regions, occurs morefrequently. Diagnosis of pharyngeal neoplasia is based on clinical signs,endoscopy, and pharyngeal radiography. Many times, masses are severelyenlarged and tissue invasion is extensive at the time of diagnosis because ofslow onset of clinical signs [52]. For this reason, medical and surgicaltreatment options are limited and are not attempted many times [52].Treatment by intralesional injection or laser excision can be attempted.

References

[1] Freeman D. Nasal passages. In: Beech J, editor. Equine respiratory disorders. Philadelphia:

Lea & Febiger; 1991. p. 25374.

[2] Raphel C. Endoscopic ndings in the upper respiratory tract of 479 horses. JAVMA

1982;181:4703.

[3] Hogan PM, Embertson RM, Hunt RJ. Unilateral choanal atresia in a foal. JAVMA

1995;207:4713.


[4] Gaughan E, DeBowes R. Congenital diseases of the equine head. Vet Clin North Am

Equine Pract 1993;9:93110.

[5] Bertone J, Traub-Dargatz JL, Trotter G. Bilateral hypoplasia of the soft palate and

aryepiglottic entrapment in a horse. JAVMA 1986;188:7278.

[6] Haynes P, Qualls W. Cleft soft palate, nasal septal deviation, and epiglottic entrapment in

a Thoroughbred lly. JAVMA 1981;179:9103.

[7] Mason T, Speirs V, Maclean A, et al. Surgical repair of cleft soft palate in the horse. Vet

Rec 1977;100:68.

[8] Pouret E. Practical aspects of the treatment of difcult wound. Equine Vet J 1973;5:525.

[9] Bowman K, Tate L, Evans L, et al. Complications of cleft palate repair in large animals.

JAVMA 1982;180:6527.

[10] Crowe W, Swerczek T. Equine congenital defects. Am J Vet Res 1985;46:3538.

[11] Proudman C, Knottenbelt D, May S, et al. Soft palate hypoplasia in a horse. Vet Rec

1991;129:2846.

[12] Richardson J, Lane J, Day M. Congenital choanal restriction in 3 horses. Equine Vet J

1994;26:1625.

[13] Koch D, Tate L. Pharyngeal cysts in horses. JAVMA 1978;173:8602.

[14] Haynes P, Beadle R, McClure J, et al. Soft palate cysts as a cause of pharyngeal

dysfunction in two horses. Equine Vet J 1990;22:36971.

[15] Cook W. Some observations on diseases of the ear, nose, and throat in the horse, and

endoscopy using a exible beroptic endoscope. Vet Rec 1974;94:53341.

[16] Goulden B, Anderson L, Davies A, et al. Rostral displacement of the palatopharyngeal

arch: a case report. Equine Vet J 1976;8:958.

[17] Klein H, Deegen E, Stockhofe N, et al. Rostral displacement of the palatopharyngeal arch

in a seven-month-old Hanoverian colt. Equine Vet J 1989;21:3823.

[18] Blikslager A, Tate L, Tudor R. Transendoscopic laser treatment of rostral displacement of

the palatopharyngeal arch in four horses. J Clin Laser Med Surg 1999;17:4952.

[19] Parente EJ, Martin BB, Tulleners EP, et al. Dorsal displacement of the soft palate

in 92 horses during high-speed treadmill examination (19931998). Vet Surg 2002;31:

50712.

[20] Hamilton DP. Pharyngeal rupture in a horse. JAVMA 1973;162:466.

[21] Moore R. Pathogenesis of obligate anaerobic bacterial infections in horses. Compend

Contin Educ Pract Vet 1993;15:27886.

[22] Kiper M, Wrigley R, Traub-Dargatz J, et al. Metallic foreign bodies in the mouth or

pharynx of horses: seven cases (19831989). JAVMA 1992;200:913.

[23] Hardy J, Stewart R, Beard W, et al. Complications of nasogastric intubation in horses: nine

cases (19871989). JAVMA 1992;201:4836.

[24] Rakestraw PC, Eastman TG, Taylor TS, Schumacher J, Wright L. Long-term outcome of

horses undergoing permanent tracheostomy: 42 cases. In: 46th Annual Convention

Proceedings of the American Association of Equine Practitioners. 2000. p. 1112

[25] Holcombe S, Robertson J, Richardson L. Surgical repair of iatrogenic soft palate defects in

two horses. JAVMA 1994;205:13157.

[26] Rashmir-Raven A, DeBowes R, Douglas J, et al. What is your diagnosis? JAVMA

1991;198:19912.

[27] McClure S, Schumacher J, Snyder J. Transnasal incision of restrictive nasopharyngeal

cicatrix in three horses. JAVMA 1994;205:4613.

[28] Holcome S, Derkson F, Stick J, et al. Pathophysiology of dorsal displacement of the soft

palate in horses. Equine Vet J Suppl 1999;30:458.

[29] Haynes P. Dorsal displacement of the soft palate and epiglottic entrapment: diagnosis,

management, and interrelationship. Compend Contin Educ Pract Vet 1983;5(Suppl):

S37989.

[30] Heffron C, Baker G. Observations on the mechanism of functional obstruction of the

nasopharyngeal airway in the horse. Equine Vet J 1979;11:1427.


[31] Tate LP, Sweeney CL, Bowman KF, et al. Transendoscopic Nd:YAG laser surgery for

treatment of epiglottal entrapment and dorsal displacement of the soft palate in the horse.

Vet Surg 1990;19:35663.

[32] Harrison I, Raker C. Sternothyrothoideus myectomy in horses: 17 cases (19841985).

JAVMA 1988;193:1299302.

[33] Anderson J, Tulleners EP, Johnston JJ, et al. Sternothyrothoideus myectomy or

staphylectomy for treatment of intermittent dorsal displacement of the soft palate in

racehorses: 209 cases (19861991). JAVMA 1995;206:190912.

[34] Strand E, Staempi HR. Dynamic collapse of the roof of the nasopharynx as a cause of

poor performance in a Standardbred colt. Equine Vet J 1993;25:2524.

[35] Holcome S, Ducharme N. Pharynx. In: Auer JA, Stick JA, editors. Equine surgery. 2nd

edition. Philadelphia: WB Saunders; 1999. p. 33749.

[36] Stick J, Boles C. Subepiglottic cyst in three foals. JAVMA 1980;177:624.

[37] Kannegieter N, Dore M. Endoscopy of the upper respiratory tract during treadmill

exercise: a clinical study of 100 horses. Aust Vet J 1995;72:1017.

[38] Dart A, Dowling B, Hodgson D, et al. Evaluation of high-speed treadmill videoendo-

scopy for diagnosis of upper respiratory tract dysfunction in horses. Aust Vet J 2001;

79:10912.

[39] Martin B, Reef V, Parente E, et al. Causes of poor performance of horses during training,

racing, or showing: 348 cases (19921996). JAVMA 2000;216:5548.

[40] Ahern T. Tonsillitis and tonsillar hypertrophy predisposing to pharyngeal dysfunction in

the horse. J Equine Vet Sci 1997;17:2324.

[41] McAllister E, Blakeslee J. Clinical observations of pharyngitis in the horse. JAVMA

1977;170:73941.

[42] Holcome S, Jackson C, Gerber V, et al. Stabling is associated with airway inammation in

young Arabian horses. Equine Vet J 2001;33:2449.

[43] Stick J, Derkson F, Nickels F, et al. Upper airway videoendoscopy during exercise in

poorly performing horses. In: Proceedings of the Annual Convention of the American

Association of Equine Practitioners, 1991;36:4318

[44] Raker C. Diseases of the pharynx. Mod Vet Pract 1976;57:396400.

[45] Bayly W, Slocombe R. Airow mechanics in models of equine obstructive airway disease

under conditions simulating exercise. Res Vet Sci 1997;62:20511.

[46] King C, Evans D, Rose R. Cardiorespiratory and metabolic responses to exercise in horses

with various abnormalities of the upper respiratory tract. Equine Vet J 1994;26:2205.

[47] Timoney J. Shedding and maintenance of Streptococcus equi in typical and atypical

strangles. In Proceedings of the Fifth International Conference. Lexington: University

Press of Kentucky; Lexington, 1988. p. 2833

[48] Mumford E, Traub-Dargatz J, Salman M, et al. Monitoring and detection of acute viral

respiratory tract disease in horses. JAVMA 1998;213:38590.

[49] Bailey G, Love D. Oral associated bacterial infection in horses: studies on the normal

anaerobic ora from the pharyngeal tonsillar surface and its association with lower

respiratory tract and paraoral infections. Vet Microbiol 1991;26:36779.

[50] Del Piero F, Wilkins P, Timoney J, et al. Fatal nonneurological EHV-1 infection in

a yearling lly. Vet Pathol 2000;37:6726.

[51] Tulleners E, Stick JA, Leitch M, et al. Epiglottic augmentation for treatment of dorsal

displacement of the soft palate in racehorses: 59 cases (19851994). JAVMA 1997;221:

10228.

[52] Jones D. Squamous cell carcinoma of the larynx and pharynx in horses. Cornell Vet

1994;84:1524.


Disorders of the pharynxCongenital disorders of the pharynxChoanal atresiaCleft palate (palate hypoplasia)Pharyngeal cystsRostral displacement of the palatopharyngeal arch

Pharyngeal traumaPharyngeal dysfunctionDorsal displacement of the soft palatePharyngeal collapse

PharyngitisNeoplasiaReferences

disorders of the pharynx

Documents