A 6 years-old male neutered pit bull terrier was presented for chronic infection and multiple draining tracts of the craniofacial region. The clients reported that the clinical signs including open wounds on the face, a foul odor from the mouth, and hyporexia that started approximately 3 years earlier. The dog was treated at various first opinion practices by means of sedated explorations of the extra- and intraoral lesions, where foreign plant material was retrieved on multiple occasions. A combination of primary closure and placement of Penrose drains was attempted, samples were collected for microbial culture tests, and analgesia and antimicrobial therapy based on culture results were prescribed. Over the course of 3 years, the following antimicrobials were prescribed: amoxicillin/clavulanate, ampicillin, amikacin, cefovecin, cephalexin, minocycline, and orbifloxacin. Due to the progressively worsening nature of the lesions, size, and invasion into deeper tissues after attempted repairs, the dog was referred.

On presentation, the dog appeared clinically stable. A large (20 × 20 mm) draining tract overlying the bridge of the nose between the eyes was observed (i.e., affecting the frontal, nasal, and maxillary bones). There were four additional cutaneous draining tracts noted approximately 4 × 4 mm ventral to the left eye, to the lateral side of the right eye, between the eyes, and on the medial aspect of the right eye (Figure 1). An intraoral examination revealed an oronasal fistula extending from the right maxillary canine tooth to the right maxillary fourth premolar tooth (Figure 2A). The right maxillary buccal frenulum remained intact. There was mucopurulent discharge and crusting surrounding the multiple draining tracts. There was bilateral mandibular lymphadenopathy. Incidental physical examination findings included cataracts with nuclear sclerosis, iris atrophy, heterochromia iridum, and anisocoria. The hematologic assessment revealed leukocytosis (14,900/μL; reference interval 6,000–13,000/μL) characterized by mild neutrophilia (11,507/μL; reference interval 3,000–10,500/μL). The serum biochemical values were within reference ranges. The dog underwent general anesthesia for conventional computed tomography (CT) (HiSpeed FX/i or LightSpeed16, GE Healthcare, Waukesha, WI) of the skull with and without contrast (880 mg/kg, IV, iopamidol). Computed tomographic findings included multifocal to coalescing lucent osseous lesions predominantly affecting the cortical bone of the right rostral maxilla (Figures 3A,B). There was a resultant large draining tract affecting the nasal, frontal, and maxillary bones that communicated with the cutaneous surface (Figure 3C). Differential diagnosis included a neoplastic process (i.e., squamous cell carcinoma, osteosarcoma, and round cell tumor) or an infectious etiology (i.e., coccidiomycosis, aspergillosis, and bacterial infection); a component of osteomyelitis associated with the nasal fistulae was anticipated. There was a mildly contrast-enhancing soft tissue structure in the right frontal sinus (which could reflect a neoplastic mass or granuloma). The right mandibular and medial retropharyngeal lymph nodes were enlarged (it was unknown whether they were reactive or metastatic). Finally, severe right temporomandibular joint osteoarthritis was observed, which may be secondary to prior trauma or infection of the joint. The CT was followed by rhinoscopy and was performed using a combination of intra- and extraoral (trans-fistulous) approaches. The findings confirmed most of the previously described osseous and soft tissue lesions noted on CT. No gross lesions consistent with fungal plaques were found. Following rhinoscopy, samples of the lesions were surgically harvested utilizing rongeurs and iris scissors for histopathological evaluation, as well as microbial and fungal testing. A Stent bandage was placed and kept in place for 3 days. The dog was discharged with analgesia (carprofen 2.2 mg/kg, PO, q12h and gabapentin 10 mg/kg, PO, q12h) and a broad-spectrum antimicrobial amoxicillin/clavulanate (13.75 mg/kg, PO, q12h).

The biopsy sample submitted for histopathological evaluation consisted of exudate with crust and an osseous fragment associated with soft tissue (Figure 4). The bone tissue was a fragment of lamellar bone (mature bone) rimmed multifocally by woven bone (immature bone) (Figure 4A). Multifocally resorption lacunae occupied by multinucleated osteoclasts were noted in the absence of osteoblasts, indicative of bone remodeling (Figure 4B). Infection of the bone medullary cavities was not noted. The crust and exudate suspended large numbers of intact and degenerate neutrophils admixed with bacterial cocci colonies and birefringent foreign material resembling plant and pollen (Figures 4C–E).

Soft tissue associated with the bone fragment included loose fibrous connective tissue infiltrated by scattered lymphocytes and plasma cells and round clusters of lymphocytes (lymphofollicular hyperplasia). This fibrous connective tissue was lined by primarily pseudostratified columnar ciliated epithelium that was multifocally substituted by squamous epithelial lining, indicative of squamous metaplasia (Figure 4).

The microbial culture and susceptibility results revealed the presence of multi-drug resistant coagulase-negative Staphylococcus spp., and therefore, the antimicrobial treatment was changed to enrofloxacin (10 mg/kg, PO, q12h) for 4 weeks, as it was identified as the susceptible antimicrobial of choice.

The diagnostic results were consistent with severe soft tissue infection and extensive osteolysis of the frontal, maxillary, and nasal regions, resulting in multiple intra- and extraoral draining tracts. The presence of foreign plant material likely complicated the healing process or was a part of the initiating process. It was elected to first minimize the infection before reconstructive surgery was attempted, by means of an extended antimicrobial therapy. The reconstructive phase was staged in two procedures. First, an extraoral repair was performed using advancement flaps for the smaller defects (Figure 5A) and a superficial temporal axial pattern flap (Figures 5B–D) to restore the large mid-facial draining tract. Superficial temporal axial pattern flap was performed as previously described (9–11). Briefly, the base of the flap was located at the level of the zygomatic arch. The width of the flap approximated the length of the zygomatic arch: The caudal orbital rim was the rostral border of the flap, and the caudal aspect of the zygomatic arch represents the caudal flap margin. The flap length was the mid-dorsal orbital rim of the opposite eye. The flap was elevated deep to the frontalis muscle to help preserve its blood supply. The flap was elevated from the distal aspect and advanced towards its base (11). Advancement flaps recruited adjacent lax tissue and moved linearly to fill in the defect. A combination of poliglecaprone 25 4-0 in a simple interrupted pattern for the deeper layers and Nylon 3-0 in a simple interrupted pattern for the skin was used to close the surgical sites. The dog was hospitalized for supportive care and close observation for 2 days to observe for initial flap vitality (Figure 5E). An Elizabethan collar was placed until the recheck evaluation. The owner reported that the dog was doing well at home, and a 10 days postoperative photograph was obtained through electronic communication (Figure 5F). At the 2 weeks postoperative recheck, in person, the flaps exhibited appropriate healing and the sutures were removed.

Eight weeks after the extraoral reconstruction, the dog underwent a second-stage procedure to address the intraoral draining tracts that communicated with the nasal passages and were considered extensive oronasal fistulas. A comprehensive oral health assessment and treatment, including a full mouth radiograph, was performed. No tooth extractions were required, and periodontal cleaning was performed before the closure of the defects. Large mucoperiosteal flaps were raised and undermined to allow for tension-free closure (Figures 2B,C).

Six months later, the dog was presented for a clinical recheck and a follow-up CT evaluation. The dog was reportedly doing well at home, and no dehiscence of the previously repaired oronasal and extraoral fistulas was noted (Figures 2D, 5G,H). Pre-anesthetic laboratory work revealed that all results were in reference ranges, and the previously noted lymphocytosis had resolved. The dog underwent general anesthesia for a repeat skull CT to assess the healing status. Clinical and CT imaging demonstrated advanced repair and remodeling processes, resolved small bone defects, and a substantial reduction in the size of the large central bone defect in the maxillary, nasal, and frontal bones consistent with clinically resolved infection, repair, and remodeling processes (Figures 3D–F).