Reverse sneezing as a clinical manifestation of nasopharyngeal-oropharyngeal fistula in a dog

Abstract

A 6-year-old spayed female Labrador retriever was evaluated for a 3-month history of intermittent reverse sneezing and gagging episodes. Pertinent findings at evaluation included frequent reverse sneezing and non-productive retching. No pathology was visible on sedated oral examination. Contrast-enhanced computed tomography of the skull revealed a gas-filled defect within the left ventral aspect of the soft palate. A non-eroded defect was present in the left caudoventral nasopharyngeal wall on nasopharyngoscopy. Surgical exploration revealed a nasopharyngeal-oropharyngeal fistula within the left palatine tonsillar fossa. The dog had a witnessed oropharyngeal stick injury (OSI) 3 months previous in the location of the fistula. The OSI had been allowed to heal by secondary intention and was treated with an oral antibiotic and NSAID. However, the dog lacked characteristic signs of a chronic OSI such as nasal discharge or abscess formation. The defect in the soft palate was surgically debrided and closed, and the left palatine tonsil was excised. The dog recovered completely with cessation of reverse sneezing and retching episodes.

Reverse sneezing occurs when irritation to the nasopharyngeal mucosa triggers spasms of the pharyngeal muscles preventing air passage to the larynx. Instead, secretions and foreign material are transferred to the oropharynx for swallowing. Reverse sneezing also promotes mucociliary clearance of secretions and foreign material by triggering a coughing episode following a reverse sneezing episode.

In many small breed dogs, reverse sneezing paroxysms are idiopathic, nonpathological, and do not progress. Pathologic causes of reverse sneezing are commonly associated with space-occupying lesions within the nasopharynx including benign or malignant space-occupying masses, foreign bodies, and fungal mats/granulomas (e.g., sinonasal aspergillosis). Other nasopharyngeal irritants leading to increased secretions and reverse sneezing include viral infection, allergic rhinitis, or parasitic disease such as the nasal mite Pneumonyssoides caninum (1–4). Diagnosis of the underlying cause of pathologic reverse sneezing requires a thorough review of the history, as well as findings from a general physical examination, computed tomography (CT), rhinoscopy, and nasopharyngoscopy.

This case report is unique because it describes a dog in which chronic reverse sneezing was the primary clinical sign occurring secondary to a nasopharyngeal-oropharyngeal fistula. The goal for this case report is to describe the clinical presentation, diagnosis, management, and outcome of a nasopharyngeal-pharyngeal fistula that formed secondary to an oropharyngeal stick injury (OSI) in a dog.

Case description

A 6-year-old spayed female Labrador retriever was presented to the University of Wisconsin Veterinary Care for evaluation following an ~3-month history of persistent reverse sneezing, intermittent gagging, and recent onset halitosis. Three months before referral, the dog had been observed running with a stick, during which time she vocalized and began to extend her head and neck unable to further vocalize or bark. The dog was taken to a veterinarian that day for evaluation, where she was discovered to be febrile (39.6°C). The remainder of the physical examination was reportedly unremarkable. Radiographs of the cervical and thoracic regions were performed in addition to a sedated oral examination. Radiographic evaluation revealed a scant amount of gas striating the retropharyngeal space, dorsal to the larynx, spanning the level of the stylohyoid bones to the plane of the larynx. Sedated oral examination revealed trauma to the left caudal soft palate, with no foreign material observed. She was discharged with 5 d of carprofen (Rimadyl; Zoetis, New Jersey, USA), 2 mg/kg body weight (BW), PO, q12h, 2 d of maropitant (Cerenia; Zoetis, New Jersey, USA), 2.4 mg/kg, BW, PO, q24h, and 5 d of doxycycline (Wedgewood Pharmaceuticals, New Jersey, USA), 8 mg/kg, BW, PO, q12h as treatment for oropharyngeal trauma.

Three days after initial presentation, the dog was able to eat and drink normally, but she began to experience intermittent episodes of reverse sneezing and gagging. Four weeks after initial presentation, the dog returned to the primary veterinarian with the chief complaint of intermittent hacking and reverse sneezing. She had an inducible cough on tracheal palpation during physical examination. Sedated oral examination was repeated and an ~2 cm area of swelling along the left caudal soft palate, as well as an associated draining tract adjacent to the left palatine tonsil were noted. A small volume of fluid was aspirated from the draining tract, and cytology revealed neutrophilic inflammation and the presence of rod bacteria. Aerobic culture and susceptibility testing was submitted on the fluid obtained, and the dog was discharged with a 2-week course of clindamycin (Midwest Pharmaceuticals, Michigan, USA), 12 mg/kg, BW, PO, q24h. Culture results revealed significant growth of Enterobacter cloacae. Based on the bacterial antibiotic susceptibility profile, ciprofloxacin (Rising Pharmaceuticals, New Jersey, USA), 20 mg/kg, BW, PO, q24h was prescribed 7 d later and subsequently the owner reported some improvement in both reverse sneezing and gagging. Consideration of referral for additional diagnostics to address the reverse sneezing was recommended at that time.

Three months after the initial date of injury the dog was presented to the University of Wisconsin Veterinary Care. During the physical examination, the dog experienced frequent episodes of reverse sneezing, gagging, and non-productive retching when excited. Additional examination findings included marked halitosis and a mild left submandibular lymph node enlargement. The dog was non-painful upon opening the mouth and during palpation of the laryngeal region and temporomandibular joint. The remainder of the dog’s physical examination was unremarkable. Routine laboratory testing [complete blood (cell) count, chemistry profile] was unremarkable. Sedation for an oral examination was achieved using intramuscular methadone (Akorn Pharmaceuticals, Illinois, USA), 0.5 mg/kg, BW, IM and dexmedetomidine (Dexdomitor, Zoetis, New Jersey, USA), 0.005 mg/kg, BW, IM followed by intravenous propofol administered to effect through a 20-gauge IV catheter placed in the left cephalic vein. The sedated oral examination revealed no marked abnormalities. A contrast enhanced CT scan of the head was then taken under general anesthesia. The imaging revealed a cone-shaped gas-containing defect in the left dorsolateral soft palate with mild peripheral contrast enhancement, tapering at the apex of the defect approaching the tonsillar region (Figure 1) and incidental right otitis media.

Figure 1.

Contrast-enhanced and plain computed tomography (CT), transverse plane; right to left. A — At the level of the cone-shaped gas containing defect in the left dorsolateral soft palate (white arrow). B — A clinically normal patient at approximately the same anatomic location, with a smooth typical ovoid shape to the nasopharynx.

Following review of the dog’s CT images, retroflexed nasopharyngoscopy revealed a non-eroded defect within the wall of the left caudoventral nasopharynx (Figure 2). On further oral examination, an area of mild erythema was noted within the left palatine tonsillar crypt. Probing of the tonsillar crypt with a 20-gauge peripheral intravenous catheter documented a small, healed fistula without obvious abscessation between the oral cavity and the left caudal nasopharynx. This region of this lesion corresponded to the defect noted on nasopharyngoscopy (Figure 3 A). The fistula was flushed with sterile saline using a curved tip dental oral irrigation syringe. The decision was made to conduct a left tonsillectomy with resection of the fistulous tract. An elliptical incision was made around the left tonsil with a scalpel blade. The left tonsil and tonsillar crypt were then sharply excised along with the fistulous tract and associated scar tissue (Figure 3 B). The defect in the soft palate was closed with 3-0 glycomer 631 in a simple continuous pattern (Figure 3 C). The palate was inspected to ensure there was no longer communication between the nasopharynx and oral cavity after surgical repair. The excised tissue was submitted for histopathology, which revealed lymphoid hyperplasia as well as abundant granulation tissue formation. No foreign material was identified grossly, during flushing, or histologically.

Figure 2.

Retroflexed nasopharyngoscopy image of the reported dog’s nasopharynx (*) and defect in the left ventrolateral nasopharyngeal wall (^).

Figure 3.

Images of the dog’s oral cavity with the patient in dorsal recumbency under general anesthesia. A — A 20-gauge IV catheter is passed through nasopharyngeal-oropharyngeal fistula noted in left palatine tonsillar fossa. B — The nasopharyngeal-oropharyngeal fistula, as well as adjacent left palatine tonsil after surgical debridement. C — Sutures in the place of the previous nasopharyngeal-oropharyngeal fistula following surgical repair.

The dog had an uneventful recovery from general anesthesia with cessation of reverse sneezing and gagging episodes, and was later discharged with 10 d of fluconazole (Glenmark Pharmaceuticals, Mumbai, India), 5 mg/kg, BW, PO, q12h and 14 d of mometasone (Perrigo pharmaceuticals, Dublin, Ireland), in the right ear, q24h as treatment to address fungal otitis suspected to be un-related to the chronic nasopharyngeal-oropharyngeal fistula. No additional antimicrobials were prescribed, and the dog was given 3 d carprofen (Rimadyl; Zoetis, New Jersey, USA), 2 mg/kg BW, PO, q12h. Five months following surgical repair of the nasopharyngeal-oropharyngeal fistula, the dog’s owners reported continued complete resolution of her reverse sneezing and gagging episodes.

Discussion

A diagnosis of nasopharyngeal-oropharyngeal fistula secondary to a chronic oropharyngeal stick injury (OSI) was made in this dog based on a combination of history, advanced imaging findings, and thorough oral examination. This dog’s predominant presenting complaint was frequent episodes of reverse sneezing, which has not been a previously reported clinical sign in dogs with chronic OSI or oronasal fistulae.

Oropharyngeal stick injury is a relatively common cause of oropharyngeal trauma, and is typically the result of impalement during stick chasing or stick chewing in medium to large breed dogs (5). Common breeds presenting with OSI include border collies, collies, German shepherds, mixed breeds, English springer spaniels, and Labrador retrievers (6,7). Oropharyngeal stick injuries are generally categorized as acute (< 7 d) or chronic (> 7 d), with differences in both clinical presentation, treatment, and prognosis based on type (6,8).

Acute OSIs are usually diagnosed based on eyewitness accounts of the accident. The most common clinical signs associated with acute OSI are oropharyngeal or cervical pain, oral bleeding, ptyalism, swelling, or the presence of subcutaneous emphysema, although some dogs may present with more subtle symptoms such as inappetence, pyrexia, dyspnea, lethargy, dysphagia, gagging, and halitosis (5–8). Chronic OSI is often more difficult to diagnose due to lack of an eyewitness account and has been associated with signs including abscess formation secondary to the presence of foreign material, draining tracts, chronic nonhealing wounds, nasal discharge, swelling, and halitosis (5,6). Importantly, the presence of draining tracts may or may not be reported by owners, as 69% failed to note them in one study evaluating chronic OSI (6).

Diagnosis of OSI is based on history, physical examination findings, and imaging findings. Routine laboratory testing (CBC, blood chemistry profile, urinalysis) is typically unremarkable. Plain and contrast radiography, ultrasonography, CT, and magnetic resonance imaging (MRI) are diagnostic imaging modalities that have been described in the diagnosis of OSI (5,8–11). Cervical emphysema seen on plain radiographs is a frequent clinical finding in acute OSI and in one study was associated with the presence of blunt trauma tracts in all dogs, making it a useful initial diagnostic test in dogs suspected of acute OSI (7). In contrast, plain radiography is unlikely to be helpful in dogs with chronic OSI as emphysema has likely resolved and wooden foreign material has absorbed fluids leaving it a similar radiopacity to the surrounding tissues (6).

The goals of treatment differ between acute and chronic OSI. With acute OSI, stabilization may be necessary depending on the location of the penetration and degree of swelling present. For acute OSI, definitive treatment is aimed at removal of any residual foreign material, repair of damaged soft tissue structures, and lavage of the affected tissues, often with surgical exploration under general anesthesia (7). Early surgical exploration is the best course of action to optimize outcome. Suggested antimicrobial prophylaxis with amoxicillin-clavulanate and metronidazole is aimed at organisms commonly seen in the dog oropharynx or with wounds contaminated with bacteria that have been recovered; such as, Staphylococcus aureus, Streptococcus spp., Escherichia coli, and Clostridium spp. (7). The prognosis following appropriate treatment of dogs with acute, non-life threatening OSI is favorable (5–7). In one study, all dogs with acute OSI (n = 6) survived; in another study, all 24 dogs with pharyngeal penetration survived, whereas 64% with esophageal penetration survived (6,7).

When chronic OSI is diagnosed, treatment is focused on removal of any residual foreign material, aggressive surgical debridement of abscesses and chronic inflammatory tissue, and exploration of all draining tracts (6). In the largest case series of chronic OSI to date, the initial injury site was identified in fewer than half of dogs, necessitating thorough evaluation. Historically, the prognosis associated with chronic OSI is poorer, with a previous case series describing an approximate 60% success rate for resolution of clinical signs within a 6-week follow-up period (6). Patients in that case series were considered to have failed therapy if clinical signs of dysphagia, ptyalism, abscess formation, or oral bleeding recurred within the follow-up period. The poor prognosis associated with chronic oropharyngeal stick injuries is related to the risk of aberrant migration of any remaining foreign material, thus making it more difficult to locate and successfully remove, recurrent abscessation, and granulation tissue formation (5,6).

Aside from a newly noted halitosis, the dog reported here lacked classic clinical signs of chronic OSI, with the primary presenting complaint of reverse sneezing. On initial sedated oral examination, no draining tracts or swelling were observed. Computed tomography was used to evaluate this dog for the presence of nasopharyngeal foreign material or masses as causes of its reverse sneezing. No foreign material was observed on CT examination of this dog’s head, or upon oral examination. Only the small nasopharyngeal-oropharyngeal fistula was noted. In this dog, small fragments of wood or other soft tissue attenuating foreign material may have been overlooked as this is a known limitation of advanced imaging modalities including CT and MRI (5). Despite these drawbacks, CT and MRI are the preferred imaging modalities as they allow for better inspection of the entire pharyngeal area and surrounding soft tissue and boney structures, thus allowing for more accurate lesion localization (1,8,10). In this dog, the combination of CT scan and nasopharyngoscopy provided the necessary direction to diagnose the nasopharyngeal-oropharyngeal fistula by probing of the left palatine tonsillar fossa.

Given the location of the fistula and the previously reported OSI, it seems likely that fistula formation was secondary to a healed OSI tract and the dog’s reverse sneezing was the result of oral material traversing the fistula and irritating the nasopharynx. This dog completely recovered without complication following surgical debridement and closure of the fistula noted on examination, despite poorer reported prognoses for chronic OSI, potentially due to the unique manifestation reported here (6).

This is the first report describing intermittent periods of reverse sneezing as a clinical manifestation of chronic OSI. Reverse sneezing is not a previously reported clinical sign in acute or chronic cases of OSI or nasopharyngeal-oropharyngeal fistula. This report highlights the importance of considering oropharyngeal penetrating injury or nasopharyngeal-oropharyngeal fistulae as a differential when acute onset reverse sneezing is reported. CVJ