DEFINITION/OVERVIEW
- A pathological pathway between the mucosal surface of the oral and nasal cavities (Fig. 28-1)
- Communication between the mouth and nasal cavity can occur from lesions around any of the maxillary teeth; the canine teeth are most commonly affected; defects are vertical
Figure 28-1 This chronic oronasal fistula with canine tooth already lost maintains a large opening into the nasal cavity.
ETIOLOGY/PATHOPHYSIOLOGY
- Can be caused by trauma, penetration of a foreign body, bite wounds, traumatic tooth extraction, electrical shock, or oral cancer
- Usually associated with advanced periodontitis of the maxillary canine tooth leading to destruction of the bone separating the nasal and oral cavities
- Fistula width is related to the size of the dog; fistula depth to the chronicity of the periodontal infection
- Dogs with uncorrected lingually displaced (base-narrow) canines and those with mandibular distocclusion (prognathic or overbite) malocclusions causing the mandibular canines to penetrate the hard palate are predisposed
SIGNALMENT/HISTORY
- Dog: dolichocephalic head types are affected most often, especially dachshunds
- Can occur in cats but is rare
CLINICAL FEATURES
- Chronic rhinitis, with or without blood
- Sneezing also common, especially when the maxillary canines are digitally palpated
DIFFERENTIAL DIAGNOSIS
- Periodontal disease
- Neoplasia
- Trauma
- Foreign body penetration
DIAGNOSTICS
- Maxillary canines are most commonly affected
- The palatal root of the maxillary fourth premolar is the next most common
- Inserting a periodontal probe into the pocket along the palatine surface of the maxillary canine tooth often causes hemorrhage from the ipsilateral nostril, confirming an oronasal fistula
- Radiographs rarely diagnose oronasal fistula because the lesions are generally isolated to the medial surface
- Radiographs may show foreign body entrapment, or lysis consistent with neoplasia
- Cytology of nasal discharge
- Culture and sensitivity of discharge
- Appropriate preoperative diagnostics when indicated prior to procedure
THERAPEUTICS
Procedures
- Appropriate antimicrobial and pain management therapy when indicated
- Appropriate patient monitoring and support during anesthetic procedures
- Repair to prevent foreign material and infection from passing from the mouth into the nose causing rhinitis, sinusitis, and possibly pneumonia
- Extract the tooth and close the defect; after extraction, the goal of surgical closure is to place an epithelial layer in both the oral and nasal cavities
- Full-thickness flap: after tooth extraction, a mucoperiosteal pedical flap may be elevated from the dorsal aspect of the fistula, released, advanced to cover the defect, and sutured in place; a successful full-thickness flap requires some attached gingiva above the defect, sutures at the edge of the defect (not over the void), and no tension on the suture line (Fig. 28-2)
- Double reposition flap: used for large fistulas or repair failures where no attached gingiva remains or where periosteal tissue cannot be included; after extraction, the first flap is harvested from the hard palate and inverted so that the oral epithelium is toward the nasal passage (Figs. 28-3 and 28-4); the second flap is mucobuccal and harvested from the alveolar mucosa and underside of the lip rostral to the fistula (Fig. 28-5); it is sutured over the first flap and donor site (Fig. 28-6)
- Guided tissue regeneration of the maxillary canine may be used for repair of a deep palatal pocket if not yet fistulated; a palatal flap is elevated to approach the infrabony defect; soft tissue and calculus are removed from the defect with a curette
- Bone grafts such as Consil (Nutramax Laboratories, Edgewood, MD), OsteoAllograft (Veterinary Transplant Services Inc., Kent, WA) synthetic and natural hydroxyapatite, autogenous and heterologous bone, polylactic acid, and calcium disulfate have been used to exclude regrowth of gingival connective tissue and epithelium, promoting regeneration of bone and periodontal ligament; the use of bone grafts is not indicated in cases where the fistula extends into the nasal cavity
- Can surgically repair oronasal fistulas located in the central portion of the hard palate with a transposition flap of the hard palate mucoperiosteum from tissue adjacent to the defect
Figure 28-2 When utilizing a full-thickness mucoperiosteal flap, the fibers of the inelastic periosteum on the inner layer of the flap must be excised to release tension.
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