Nasal Cavity

Cats with unpigmented skin of the nasal planum may, over several years, develop squamous cell carcinoma with prolonged exposure to ultraviolet (UV-B) irradiation.¹ One paper suggests a papillomavirus may be involved in the etiology of feline squamous cell carcinoma. Older, white cats or those with lightly pigmented noses and that live in sunny climates are at risk. Lesions progress slowly through early solar damage with crusting and erythema to carcinoma in situ to invasive squamous cell carcinoma.³ Invasive squamous cell carcinoma initially is confined to the nasal planum, but it slowly becomes more extensive, affecting deep and adjacent tissues late in the course of the disease. Lymph node or lung metastases are rare.³ Cutaneous hemangiosarcoma of the nasal planum also occurs and is also thought to be associated with solar irradiation.^4,5 Basal cell tumor has been reported to occur on the nose of cats.⁶ Cancer involving the nasal planum or premaxilla is uncommon in dogs, but such tumors include squamous cell carcinoma, fibrosarcoma, melanoma, mast cell tumor, and osteosarcoma.⁷ Biopsy with histopathologic examination is necessary to diagnose cancer of the nasal planum and is important to rule out nonneoplastic causes of nasal ulceration.

Indications

Various methods have been described to treat cats with squamous cell carcinoma of the nasal planum including radiation therapy, hyperthermia, intratumoral administration of carboplatin, cryosurgery, conservative (marginal or intralesional) surgery, and photodynamic therapy.^8-13 Unfortunately, with most of these treatments, the tumor margins cannot be evaluated to ensure that an adequate volume of tissue is treated. Each of these modes of therapy has other disadvantages, including the need for special equipment and facilities for some techniques, high rates of tumor recurrence, and reported control rates for deeply infiltrating lesions of up to 55% at 1 year. Most of these techniques may work for early, small lesions or carcinoma in situ, but the most cost-effective, reliable treatment for selected patients with invasive squamous cell carcinoma is nasal planum resection. Fifteen of 20 cats with invasive squamous cell carcinoma treated with nasal planum resection were free of recurrent disease at 1 year.⁶ Nasal planum resection can also be effectively used to treat other invasive neoplasms in dogs and cats. Although the cosmetic results in cats are generally good and acceptable to most owners, dogs are more noticeably deformed by the surgery. Function is usually excellent.

Nasal Planum Resection

The animal is maintained under general anesthesia and intubated with a cuffed endotracheal tube. A maxillary nerve block is performed and the cat is anesthetized and positioned in sternal recumbency with the head slightly elevated. The surgical area is carefully palpated to try to estimate tumor extension into adjacent tissue. A small area of hair is clipped, but the tactile vibrissae are avoided, and the site is prepared for aseptic surgery. A drape with a circular hole is placed over the prepared site. The nasal planum is completely removed with a 360° skin incision made with a No. 15 scalpel blade (Figure 24-1). The incision is made so it transects the underlying turbinates. If the tumor does not extend to the lip margin, then a thin strip of skin and buccal mucous membrane is preserved at the rostral lip margins on the midline. If tumor has extended into this region, then the lip margin must be removed, resulting in a closure involving rostral advancement of the lips. This may leave the incisor teeth slightly exposed. The cartilage of the nasal planum and the turbinates are cut with an incision angled at about 45° to the hard palate (Figure 24-2). Bleeding is usually brisk. Hemorrhage is controlled by direct pressure with a sponge. Electrocautery should only be used sparingly to avoid thermal necrosis, which delays healing.
 

Once the nasal planum is removed, the skin edges retract and the nasal conchae are exposed. A pursestring suture of 3-0 monofilament nonabsorbable suture material is placed through the skin around the incision. The surgeon does not need to place any deep sutures into the cartilage or nasal mucosa. It is only necessary to tighten the pursestring suture lightly; for cats, the new nasal orifice is closed to approximately 1 cm in diameter (Figure 24-3). The entire excised nasal planum is submitted for histopathologic examination, with a request for the pathologist to examine the surgical margins carefully. India ink or other tissue marking ink may be painted on the cut edges of the specimen to delineate the surgical margins. Analgesics are used, and patients are usually sent home within 24 hours. Owners are advised not to try to clean the surgical site and are warned that the patient may sneeze blood for several days. Patients should be tempted with favored food, but they may be reluctant to eat for a few days after surgery. Older animals with compromised renal function need fluid support until water intake becomes adequate. Elizabethan collars are usually not necessary. Sutures are removed approximately 10 days after surgery, and sedation or a short course of anesthesia may be required.
 

Combined Resection of the Nasal Planum and Premaxilla

For extensive neoplasms of the nasal planum and premaxilla, nasal planum resection or premaxillectomy alone may be inadequate. Wide surgical margins can be attained using combined resection of the nasal planum and premaxilla.⁷ This technique offers a surgical treatment for large tumors in dogs that obviates the need for adjuvant or primary radiation therapy. Cosmetic results are considered acceptable by most owners.

The dog, maintained under general anesthesia and intubated with a cuffed endotracheal tube, is positioned in sternal recumbency with the mouth slightly open. The skin overlying the maxilla and upper lip is clipped and prepared for aseptic surgery. The oral mucosa of the lips and hard palate is prepared with a disinfectant such as a dilute povidone-iodine solution. The area is draped, allowing access to the oral cavity (Figure 24-4A). The upper lip is incised from the skin through the mucosa on each side of the nasal planum (Figure 24-4B). The two incisions are connected at the dorsal midline of the nose caudal to the nasal planum (Figure 24-4C). The nasal cartilages are incised to the palatal region of the maxillary bone. At the level just either rostral to or caudal to the canine teeth, depending on the extent of invasion of the tumor, the mucosa of the hard palate is incised transversely with a scalpel blade down to bone. An oscillating saw is used to cut the palatal and maxillary or incisive bone (Figure 24-5). The excised specimen is submitted for histopathologic examination, with emphasis on evaluation of margins for completeness of resection. Hemorrhage is controlled by a combination of direct pressure, electrocautery, and vessel ligation. Four or five small holes are drilled 2 to 3 mm from the cut edge of the hard palate. The submucosa of the incised lip is sutured through the holes in the hard palate with 2-0 monofilament absorbable suture material. The lip is joined on the midline of the palate with sutures that are placed approximately in the middle of each lip incision (Figure 24-6A). The mucous membrane of the lip is sutured to the mucous membrane of the hard palate, and the contralateral lip is sutured with 3-0 monofilament absorbable suture material in a continuous or interrupted pattern. This technique results in closure of the oral cavity in the form of a “T” (Figure 24-6B). The skin of the lips is closed on the midline with 2-0 or 3-0 monofilament nonabsorbable suture material. As with closure after nasal planum resection alone, the diameter of the nasal opening is reduced using a pursestring suture of monofilament nonabsorbable suture material (Figure 24-6C). The nasal opening is reduced to a size corresponding to the diameter of the nasal planum removed (Figure 24-6D).
 

Analgesia is provided using narcotics as necessary. An Elizabethan collar may be needed to prevent mutilation of the wounds. Dogs are allowed to drink water on recovery and are offered food 24 hours after surgery. Antibiotics can be given during the immediate perioperative period, but they are usually not necessary. Dogs are sent home within 2 to 3 days, and sutures are removed 10 days postoperatively.

Mild postoperative bleeding may occur and resolves within a day or so. Lip dehiscence can be avoided if the closure is tension free. Stenosis of the new nares can occur if the pursestring suture is too tight. Crusting of the nasal orifice is possible and resolves after suture removal; however, serous nasal discharge can persist.

Combined Resection of the Nasal Planum and Rostral Maxilla

For animals with malignant rostral maxillary tumors a technique has been described where the maxilla and nasal planum can be resected between PM2 and PM3.¹⁴ The postoperative appearance was acceptable to owners and there was a low risk of local recurrence which can produce long term survival for animals with certain malignancies. A preoperative biopsy is performed with appropriate tumor staging before definitive resection with this aggressive rostral maxillectomy procedure. Computed tomography (CT) is excellent for tumor staging and surgical planning.

The animal is positioned in ventral recumbency and anesthesia, analgesia and surgical preparation are similar to previously described procedures in this chapter. The mouth is held slightly open with a mouth gag or similar device and care is taken to pack the pharynx with moistened gauze swabs adjacent to a cuffed or snug fitting endotracheal tube to avoid aspiration of blood and fluid during surgery. The commissures of the lips need to remain mobile after draping to allow for labial advancement during reconstruction. The preoperative CT scan defines the extent of tissue infiltrated with tumor, and its relation to the dentition. The teeth are used as landmarks to allow the approximate edges of the tumor to be marked using a sterile marker pen. A sterile ruler is used to mark 1 or 1.5 cm beyond the borders of the tumor so that a line of “planned complete resection” can be drawn. The line of bone excision is level with or slightly caudal to the caudalmost aspect of the soft-tissue resection. This results in sufficient soft tissues to reconstruct a lip rostrally and cover the exposed maxilla. Full-thickness, labial incisions are made perpendicular to the labial margin. The incisions are continued perpendicular from the labial margin for a minimum of 1 to 2 cm and then curved to meet on the midline of the maxilla. Once the skin is scribed with a scalpel, electrocautery is used for most of the tissue division, and hemostasis is maintained by a combination of cautery and vascular clips or ligatures. The incisions are continued deeper through the subcutis and nasolabial muscles and fascia to the maxillary bone at predetermined resection levels. If this is the rostral zygomatic arch, the infraorbital neurovascular bundles will need to be divided between ligatures. If this is near the canine tooth the skin, subcutis, nasolabial muscle, and labium are reflected while preserving their vascular support from the infraorbital neurovascular bundle. These soft tissues and labium are reflected to the rostral zygomatic arch, exposing the maxilla. Once exposed, the rostral maxilla, nasal turbinates, and bony palate are amputated with a reciprocating saw. The transection is perpendicular to the maxillary axis. The rostral maxilla can then be removed following transection of the palatine mucosa parallel to and at the level of the hard palate. The palatine and sphenopalatine arteries are ligated.

Labial reconstruction is performed by transposing either a unilateral labial flap or bilateral labial flaps depending on the amount resected and the conformation of the animal. Regardless of whether a unilateral or bilateral flap is used, the lip and palate are united first. Dehiscence may be less likely when bilateral flaps are used. It may be necessary to relieve tension by incising the labiogingival reflection to mobilize the labial flap. The mucosa of the labial flap is removed except for a 0.5- to 1.0-cm width adjacent to the labial margin. This distance is determined by bringing the tissues together and identifying the contact point of the palatine mucosa and labium, and then assessing how much “new lip” there would be projecting ventrally from the palatine mucosa. Avoid making this margin overly large which may result in prehension problems after surgery. Once the mucosa is excised, the remaining mucosal margin is sutured to the palatine mucosa with interrupted 4-0 absorbable sutures, thus providing strong support and preventing mucosal inversion.

Bilateral advancement flaps are also prepared by incision of the labiogingival borders as necessary to permit tension-free advancement of the flaps on the approximate midline. The labial mucosa is once again débrided leaving only a 0.75- to 1.0-cm margin of labial mucosa to be sutured to the palatal incision as a palatobuccal recess. This length of recess is chosen to ensure the margin will not be trapped between the teeth during chewing or interfere with food transfer into the mouth. Prior to suturing, the left and right lips are aligned toward the midline using temporary sutures. As the palatolabial suturing progresses from lateral to medial, the labial margins are drawn into apposition. As with the unilateral flap the labial submucosa can be first sutured to the edge of the incised palatine bone using small holes drilled in the palatine bone with a 0.0625-inch Kirschner wire. The remaining lip union is reconstructed beginning along the ventral aspect, aligning the labial margin with a nonrolling figure-ofeight suture. Suturing progresses using the same suture pattern in the submucosa, muscle, subcutaneous, and dermal layers.

The dorsal and rostral portions of the incision are left open forming the nasal orifice. And it is advisable to create an orifice approximately twice the desired final size to compensate for the expected contraction during healing. The nasal orifice size can be controlled using a purse-string type pattern of suture as with simple nasal planectomy.

Analgesic protocols are aggressive and include premedication with an opioid (i.e., oxymorphone at 0.2 to 0.5 mg/kg intramuscularly [IM] or morphine at 0.2 to 0.6 mg/kg IM) and infraorbital nerve blocks performed bilaterally prior to surgery using bupivacaine (0.5 to 1.0 mL of a 0.75% solution used per site). During general anesthesia, constant-rate infusions of fentanyl (0.01 mg/kg per hour) may be administered. At the time of extubation, the opioid administered preoperatively is repeated, and a postoperative analgesic opioid protocol is instituted. This can be buprenorphine (0.07 mg IM q 6 hours) which can be continued for up to 60 hours. Following a loading dose of the appropriate opioid (i.e., morphine 0.5 mg/kg intravenously [IV]; oxymorphone 0.2 mg/kg IV; or fentanyl 0.002 mg/kg IV), dogs can receive constant-rate infusions of morphine (0.05 mg/kg per hour), oxymorphone (0.13 mg/kg per hour), or fentanyl (0.002 to 0.006 mg/kg per hour) for 24 hours to provide a constant level of analgesic drug. Carprofen (2.0 mg/kg per os [PO] q 12 hours) may be initiated 12 hours after surgery and continued postoperatively as necessary.

An Elizabethan collar is often used until healing is complete and it may be necessary for oronasal suction to be instituted as needed to keep the nasal passages clear, using a pediatric suction device. Some animals do not eat readily, and feeding can be supplemented with a food gruel administered through a pharyngostomy tube for a short term up to 7 days. Topical petrolatum-based antibiotic ointment can be placed around the nasal orifice wounds to reduce wound crusting and debris. Additionally, topical misting of physiological saline can be delivered via a conventional spray bottle to humidify and cleanse the nasal turbinates. Some animals are able to eat soft food offered on a plate between 12 and 30 hours after surgery and may be discharged to their owners once eating on their own. Owners may be advised to keep the new rostral orifice patent and clean using saline-soaked cotton balls for 1 month postoperatively. Antibiotics such as cefazolin 20 mg/kg IV are given immediately preoperatively and every 90 minutes during surgery and postoperative antibiotics are generally not necessary.

Although this technique is very similar to the combined resection of the nasal planum and premaxilla it is more extensive allowing wide resection of larger tumors. The advantage of such a technique is that it has the potential to increase the number of animals in which “complete” resections can be performed. However, the disadvantage of such a surgery is the possibility of interfering with the animal’s ability to eat and drink making oral spillage of both food and water possible. The technique does offer the opportunity for prolonged tumor-free remission times for animals with certain neoplasms that involve the rostral maxilla, if tumor-free margins can be obtained.

References

1. Hargis AM. A review of solar-induced lesions in domestic animals. Compend Contin Educ Pract Vet 1981: 3: 287-293.
2. Munday JS, Dunowska M, DeGrey S: Detection of two different papillomaviruses within a feline squamous cell carcinoma: case report and review of the literature, NZ Vet J 57: 248-251, 2009.
3. Withrow SJ. Tumors of the respiratory system. In: Withrow SJ, MacEwen EG, eds. Veterinary oncology 2nd ed. Philadelphia: WB Saunders, 1996: 268-286.
4. Hargis AM, Ihrke PJ, Spangler WL, et al. A retrospective clinic-pathological study of 212 dogs with cutaneous hemangiomas and hemangiosarcomas. Vet Pathol 1992: 29: 316-328.
5. Miller MA, Ramos JA, Kreeger JM. Cutaneous vascular neoplasia in 15 cats: clinical, morphologic, and immunohistochemical studies. Vet Pathol 1992: 29: 329-336.
6. Withrow SJ, Straw RC. Resection of the nasal planum in nine cats and five dogs. J Amer Anim Hospt Assoc 1990; 26: 219-222.
7. Kirpensteijn J, Withrow SJ, Straw RC. Combined resection of the nasal planum and premaxilla in three dogs. Vet Surg 1994; 23: 341-346.
8. Carlisle CH, Gould S. Response of squamous cell carcinoma of the nose of the cat to treatment with X rays. Vet Radio 1982; 5: 186-192.
9. VanVechten MK, Theon AP. Strontium-90 plesiothcrapy for treatment of early squamous cell carcinomas of the nasal planum in 30 cats. In: Proceedings of the 13th Annual Conference of the Veterinary Cancer Society. Columbus, OH 1993: 107-108.
10. Theon AP, Madewell BR, Shearn VI, et al. Prognostic factors associated with radiotherapy of squamous cell carcinomas of the nasal plane in cats. Am J Vet Assoc 1995; 206: 991 – 996.
11. Theon AP, VanVechten MK, Madewell BR. Intratumoral administration of carboplatin for treatment of squamous cell carcinomas of the nasal plane in cats. Am J Vet Res 1996; 57: 205-210.
12. Peaston AE, Leach MW, Higgins RJ. Photodynamic therapy for nasal and aural squamous cell carcinoma in cats. J Am Vet Med Assoc 1993; 202: 1261-1265.
13. Fidel JL, Egger E, Blattmann H, et al: Proton irradiation for feline nasal planum squamous cell carcinoma using an accelerated protocol. Vet Radiol and Ultrasound, 42: 569-575, 2001.
14. Lascelles BDX, Henderson RA, Sequin B, Liptak JM, Withrow SJ. Bilateral rostral maxillectomy and nasal planectomy for large rostral maxillofacial neoplasms in six dogs and one cat. J Amer Anim Hospt Assoc 2004; 40: 137-146.

Introduction

Dogs and cats with chronic nasal and paranasal sinus disease are usually diagnosed and treated without the need for rhinotomy (surgical exploration of the nasal cavity). Rhinotomy is only indicated if other diagnostic techniques fail to provide a definitive diagnosis or if required as part of a therapeutic protocol. Potential candidates for rhinotomy have symptoms that may include: nasal discharge, epistaxis, sneezing, gagging, stertorous breathing, dyspnea, fetid breath, nasal discomfort, or nasal deformity. Causes of diseases of the nasal cavity and paranasal sinus can be difficult to identify, but are commonly of infectious (fungal, bacterial, or viral) or neoplastic origin. Other inciting causes include foreign bodies, trauma, parasites (Pneumonyssus caninum, Linguatula serrata), dental disease, congenital anomalies, and lymphocytic plasmacytic inflammation.¹

Diagnostic Procedures

A standard protocol for evaluation should be used for all dogs and cats presenting with chronic nasal disease. The protocol should include a thorough history and physical examination. In addition, a complete blood count, serum chemistry profile, coagulation profile, radiographs, computed tomography (CT scan), magnetic resonance imaging (MRI), serology, cytology, culture, rhinoscopy, and nasal biopsy may be required for accurate diagnosis and prognosis.^2-6 The clinical history provides important diagnostic clues. A destructive process is suspected if the discharge changes from unilateral to bilateral. Sneezing suggests involvement of the rostral or middle nasal chambers and gagging suggests nasopharyngeal involvement. A history of trauma or dental disease might suggest an oronasal fistula.

Physical examination findings are as follows: Epistaxis may indicate a systemic disease, an acute nasal disease, or an ulcerative, destructive disease. A mucopurulent discharge with or without epistaxis suggests chronic rhinitis. Obstruction of nasal airflow through one or both nostrils suggests a unilateral or bilateral condition. Facial or palatal deformity suggests neoplasia. Mouth breathing may indicate nasopharyngeal obstruction. Labored breathing suggests possible pulmonary involvement with a fungal or neoplastic condition. An ocular discharge may indicate nasolacrimal duct erosion. General debility suggests systemic disease.

A complete blood count, serum chemistry panel, and urinalysis should be obtained to assess overall patient status. A coagulation profile is indicated if exploratory rhinotomy is planned or if epistaxis is a major clinical sign. In addition, serologic evaluation for Ehrlichia canis may be beneficial when epistaxis is the predominant clinical sign. Serologic evaluation for Aspergillus and Penicillium species can be beneficial when fungal disease is suspected. Serologic tests for Crytptococcus, FeLV, FIV and heartworms may also be indicated. Nasal swabs for culture or cytologic evaluation are of limited value but may be helpful in identifying parasites, cryptococcoses organisms and single bacterial infections. Positive fungal cultures can be obtained in 40% of normal dogs.

Radiographs of the thorax and skull are taken to demonstrate the extent of disease involvement. Radiographs of the thorax are taken in the awake patient to evaluate for evidence of cardiac or pulmonary disease (metastasis or infection). Skull radiographs require general anesthesia to allow accurate evaluation of the nasal cavity and paranasal sinuses. Skull images are performed prior to rhinoscopic, flush, or biopsy procedures to avoid iatrogenic fluid densities within the cavities. Skull radiographs should include lateral, ventrodorsal, rostrocaudal, and rostroventral caudodorsal open mouth or occlusal views. The two most useful radiographic views are the ventrodorsal view of the maxilla made using intraoral radiographic film and the rostrocaudal projection highlighting the frontal sinuses. Skull radiographs are examined for evidence of increased or decreased tissue densities, distortion or loss of turbinates and bone, and symmetry between right and left sides of the nasal cavity and sinuses. The same changes are evident on CT and MRI images but they localize lesions better than radiographs. CT images provide good anatomic detail of bony tissues while MRI images are superior for evaluating soft-tissue structures.³

Rhinoscopy is useful because it allows visual assesment of lesions and acquisition of specimens for further evaluation.^4-6 The diagnostic success of rhinoscopy-assisted biopsy is 83% (78 of 94 dogs) when performed by an experienced clinician.⁶ Rhinoscopy is performed on an anesthetized patient in sternal or lateral recumbency following skull imaging and sample collection for cultures. Violent sneezing with possible damage to instruments and mucosa resulting in hemorrhage may occur if anesthetic depth is inadequate. The nasal mucosa is sensitive to manipulation; it bleeds easily, and this may obscure visualization. Therefore, patience, gentleness, suction, and lavage are advantageous during this procedure. The least affected side of the nasal cavity is examined first. The rostral aspect of the nasal cavity may be visualized with an otoscope and appropriate speculum. The caudal choanae and nasopharynx can be viewed with a dental mirror or rigid scope with a 120° lens when the soft palate is retractated rostrally. Visualization of the entire cavity is achieved with a flexible pediatric bronchoscope (< 1 cm diameter) or a rigid scope (bronchoscope or arthroscope, 2 to 5 mm diameter) with a working piece (outer sheath) to allow suction, lavage, and biopsy. Both normograde and retrograde rhinoscopy is performed to completely visualize the nasal cavity and nasopharynx. After complete rhinoscopic examination, suitable biopsy forceps are used to collect tissue for culture and histologic evaluation.

Lesions that are not accessible to biopsy during rhinoscopy may be sampled by nasal flushing or coring procedures. These procedures are performed in the anesthetized patient. Gentle flushing of the nasal cavity with saline does not usually dislodge tissue for evaluation. Nasal coring, pinch, punch, or needle biopsy are more effective biopsy techniques.⁶ To prevent aspiration, the endotracheal tube cuff is inflated, gauze sponges are placed in the nasopharynx and the nose is tilted ventrally during sampling. To prevent penetration of the cribriform plate, biopsy instruments should be marked and not advanced further than the distance from the external nares to the medial canthus of the eyes. One technique for nasal coring uses a stiff plastic tube inserted through the nares and vigorously moved in and out of the nasal passages while flushing saline and aspirating tissue. The collected lavage fluid, debris and tubing are examined for tissue fragments. Repeating biopsies when samples are nondiagnostic is preferred to rhinotomy in most cases.

Patients whose disease has not been diagnosed by the foregoing procedures are candidates for exploratory surgery. Rhinotomy may also be included in treatment protocols for fungal diseases, tumors, and foreign bodies. Rhinotomy can be performed using dorsal, ventral, or lateral approaches. The approach chosen depends on the location and extent of the lesion. The objectives of rhinotomy include the following: 1) To obtain sufficient samples from the nasal cavity or sinuses to achieve a definitive diagnosis. 2) To completely remove or debulk a lesion. 3) To facilitate administration or effectiveness of adjuvant therapy. 4) To minimize patient morbidity. 5) To maintain a cosmetically acceptable appearance.

In addition to a standard surgical pack, equipment which may be needed for rhinotomy includes a periosteal elevator, Gelpi retractor, oscillating saw, air drill, pins and pin chuck, osteotome and mallet, bone curette, rasp, bur, rongeur, trephine, fenestrated tubes, and synthetic mesh. If temporary carotid artery occlusion is performed in conjunction with rhinotomy, vascular occlusion is accomplished with umbilical tape, vascular tape (Vas-Tie@, Sil-Med Corp., Taunton, MA) or bulldog vascular clamps.

Surgical Anatomy

The nasal cavity is bound by the nasal bones dorsally, the maxilla laterally, and the hard palate ventrally. The orbit contributes to the lateral boundary of the nasal cavity and frontal sinuses. The nasal cavity is separated into two fossae by the nasal septum. The maxilloturbinates fill the rostral portion of each fossa and the ethmoturbinates extend caudally to the cribriform plate and frontal sinus (Figure 24-7). When dividing the dorsoventral nasal height at the medial canthi of the eyes, the nasofrontal opening occupies the dorsal third, the cribriform plate the middle third and the sphenoidal sinus recess and caudal nasal meatus (internal nares or choanae) the ventral third. The paranasal sinuses are hollow, membrane lined, air-filled diverticuli from the nasal cavity that invaginate into adjacent bones. They are not fully developed at birth and continue to grow as the animal matures. The limits of the frontal sinus vary with the age, breed and head shape of the patient. Dogs have a frontal sinus divided into three compartments and a maxillary sinus (recess). Cats have an undivided frontal sinus, and in addition to the maxillary sinus, they have a sphenoid sinus.
 

Communication between the frontal sinus and the nasal cavity occurs through small ostia in the ethmoid region. Mucous membrane swelling reduces the size of these openings and can obstruct drainage, leading to sinus mucocele formation. The blood supply to the nasal cavity is extensive and originates from the branches of the maxillary artery, a terminal vessel of the external carotid artery.

Preoperative Preparation

Analgesics are administered in the preoperative period. After the anesthetized animal is intubated, the endotracheal tube cuff is inflated, and the pharynx is packed with gauze sponges to prevent drainage of fluids into the distal trachea. Hair is clipped and the surgical site is aseptically prepared for the selected approach.

Surgical Techniques

Temporary Carotid Artery Occlusion for Rhinotomy^7-8

Occluding the common carotid arteries reduces blood loss during exploration of the nasal cavity, improves visualization during surgery, facilitates exploration and obviates blood transfusions in most patients. Although hemorrhage (50 to 100 ml/25 kg body weight) still occurs during removal of the turbinates and nasal mucosa, it usually diminishes within a few minutes. Suction is advantageous but not necessary for visualization. Release of the carotid arteries at the conclusion of surgery does not result in clinically significant hemorrhage and nasal packing is not necessary. The common carotid arteries can be occluded for two to three hours with no evidence of neurologic or ischemic damage in dogs. Carotid artery occlusion in cats is not recommended because collateral blood supply is inadequate to maintain cerebral perfusion.⁹

Temporary carotid artery ligation is performed after positioning the patient in dorsal recumbency with the front legs secured caudally along the chest and the neck dorsiflexed by positioning it over a pad. Incise skin along the ventral cervical midline from the larynx to midtrachea. The paired sternohyoideus muscles are separated and retracted to expose the trachea. To locate the carotid sheath, the surgeon palpates the carotid pulse dorsolateral to the trachea, then bluntly dissects the adjacent loose connective tissue and exteriorizes the carotid sheath. The surgeon carefully incises the carotid sheath and separates the external carotid artery from the vagosympathetic trunk and internal jugular vein. The carotid artety is occluded with a vascular tie (Vascular Ties^®, Sil-Med Corporation, 700 Warner Blvd., Taunton, MA 02780), umbilical tape or a vascular clamp (Figure 24-8). The procedure is repeated on the opposite carotid artery and the skin incision is closed with a continuous suture pattern or staples. The surgical site is covered with an adherent, sterile dressing. Immediately after rhinotomy, the surgeon exchanges contaminated instruments and gloves and positions the patient to allow reexposure of the carotid arteries. The ventral midline incision, is opened, the carotid arteries are exposed, and the vascular clamps or ties removed. The surgeon lavages the area thoroughly and apposes sternohyoid muscles, subcutaneous tissue and skin in separate layers.
 

Dorsal Rhinotomy

Dorsal rhinotomy allows access to the entire nasal cavity and the frontal sinuses.⁸ After the anesthetized animal is intubated, the endotracheal tube cuff is inflated, and the pharynx is packed with gauze sponges to prevent drainage of fluids into the trachea. The patient is positioned in ventral recumbency, then the dorsum of the head is clipped and prepared for surgery. The surgeon begins the rhinotomy by making a midline skin incision over the nasal cavity and frontal sinus which extends caudal to the orbits (Figure 24-9). The dense fascia and periosteum overlying the bone are incised, elevated and retracted laterally. The bone is scored with a scalpel blade to outline a unilateral or bilateral bone flap depending on the extent of the disease and the exposure necessary (Figure 24-10). The flap is made using an oscillating saw, drill, osteotome and mallet, or trephine and rongeurs. The margins of the bone are beveled inward if bone flap replacement is anticipated. In addition, pre-drilling holes in the flap and adjacent bone margin for suture placement aids in easier bone flap reattachment. The bone flap is elevated from the underlying turbinates with an osteotome or periosteal elevator. The bone flap is reflected rostrally leaving it attached to the dorsal parietal cartilage of the rhinarium by the nasal ligaments if flap replacement is planned (Figure 24-11). After exposing the nasal cavity and frontal sinus, the surgeon suctions secretions or exudate and explores the area. The lesion and involved turbinates are removed or sampled for biopsy with forceps, a bone curette and Metzenbaum scissors. (Figure 24-12). Total turbinectomy is often necessary to eliminate extensive areas of nasal mucosa with chronic irreversible hyperplasia. One should avoid traumatizing or perforating the cribriform plate during turbinectomy. Identifiable bleeding vessels are ligated. When external carotids are not occluded it may be necessary to control hemorrhage with cautery, iced saline, or pressure. Tissues are submitted for histologic and culture evaluation . During a unilateral rhinotomy, if the nasal septum has been perforated or eroded by the disease process, the other fossa is explored and curetted through the septal defect or by creating a second bone flap. When mucoid secretions fill the frontal sinuses, the surgeon enlarges the ostia and breaks down the septae to facilitate drainage. The caudal nasal meatus (internal nares/choanae) should be probed with a hemostat to verify patency. The nasal cavity and sinuses are lavaged with saline or lactated Ringer’s solution before closure to remove debris and blood clots. Fenestrated indwelling tubes are placed if necessary for adjuvant therapy. These drains are placed through a trephine hole into the frontal sinus and extend into the nasal fossa.
 

The bone flap is replaced or discarded depending on the extent of disease and the surgeon’s preference. The flap is discarded if it is involved in the disease process or if fragmentation occurs during removal. If the flap is being replaced, drill three or four holes in the flap and the adjacent margins of the defect. The surgeon then preplaces nonabsorbable sutures (nylon, polypropylene) through the holes, positions the flap, and ties the sutures to secure the flap. (Figure 24-13). One should not use wire to secure the bone flap if radiation therapy is being planned. Occasionally, when the defect is large, if the flap is discarded and cosmetics are critical, a bone graft or synthetic mesh is stretched across the bony defect and secured. Potential risks with the use of such implants include sequestration and infection. Soft tissues are apposed in three layers (fascial/ periosteal layer, subcutaneous tissues, and the skin) using continuous suture patterns. Air leakage from the rhinotomy site and subcutaneous emphysema may be controlled by suturing a stent over the surgical site, placing a drain in the frontal sinus and nasal cavity or leaving a small gap between tissue edges during closure.
 

Technique variations may be necessary depending on the disease type and extent. Postoperative nasal flushing, prevention of emphysema, and brachytherapy for tumors is facilitated by placing a drain in the frontal sinus and nasal cavity through a trephine hole (Figure 24-14). An incision is made through the soft tissues and a hole in the bone is drilled or trephined just lateral to the midline on a line connecting the rostral margins of the supraorbital processes. Biopsy and culture specimens may be collected through this hole if not previously obtained. A fenestrated tube is inserted into the sinus, advanced into the nasal cavity and secured to the skin. The hole is allowed to heal by second intention after tube removal. Protocols for treatment of nasal fungal diseases may include packing the nasal cavity with medicated gauze or creating a stoma. Stomas are created by securing the skin edges directly to the margins of the bony defect.^10-11 Creation of a stoma facilitates topical therapy postoperatively. If the stoma is small it may heal by second intention, otherwise following conclusion of medical therapy the skin edges are debrided, undermined, and apposed. Removal of lesions in the rostral nasal cavity may be facilitated by extending the incision through the rhinarium lateral to the nasal septum.
 

Ventral Rhinotomy

Ventral rhinotomy allows exploration of the nasal cavity and nasopharynx.⁸ Evaluation and evacuation of the frontal sinuses is limited to the rostral half with ventral rhinotomy. Concurrent mandibulotomy may be performed to improve access to the caudal nasal cavity and nasopharynx. Although most surgeons prefer dorsal rhinotomy, advantages of ventral rhinotomy include improved cosmesis and less risk of subcutaneous emphysema. Disadvantages include incomplete access to the frontal sinuses and the potential for oronasal fistula formation.⁹

The patient is positioned in dorsal recumbency with the oral cavity maximally exposed by hanging and securing the mandible in a wide, open-mouth position. One should use mild antiseptic solutions (0.05% chlorhexidine or 0.1% or 1% povidone-iodine) to cleanse the oral cavity prior to incising tissue.

Cranial Ventral Rhinotomy

The mucoperiosteum of the hard palate is incised on the midline from the level of the canine teeth to the fourth premolar to expose lesions restricted to the rostral nasal cavity. Alternatively, the nasal cavity may also be exposed using a “U” shaped mucoperiosteal incision parallel to the dental arcade (Figure 24-15A). After incision, the surgeon elevates and retracts the mucoperiosteum to expose the hard palate while preserving the major palatine arteries during incision and dissection. The major palatine arteries emerge from the major palatine foramen at the caudal edge of the fourth upper premolar and course rostrally, midway between the midline and dental arcade. Remove a rectangular palatine bone flap with an oscillating saw, air drill or osteotome (Figure 24-15B). Alternatively, rongeurs are used to create an access window in the hard palate. The lesion and involved turbinates are removed with forceps and curettage. The surgeon lavages and suctions the area prior to replacing or discarding the bone flap as with dorsal rhinotomy (Figure 24-16). The mucoperiosteum is apposed using a one or two layer closure with simple interrupted sutures (3-0 or 4-0 polydioxanone, polypropylene).
 

Caudal Ventral Rhinotomy

Caudal ventral rhinotomy is selected for exposure of lesions in the caudal nasal passages and nasopharynx. A midline cranial ventral rhinotomy incision can be extended to expose the nasopharynx when necessary. A midline soft palate incision is made beginning 5 to 10 mm rostral to the tip of the soft palate and extending through the mucoperiosteum of the hard palate as far as necessary to expose the lesion adequately (Figure 24-17) Stay sutures are placed in the incised edges of the soft palate to facilitate retraction and to minimize trauma. The mucoperiosteum is elevated and the hard palate is rongeured as far rostrally as necessary for exposure. The surgeon explores, removes the lesion, and lavages the area. The soft palate is apposed in two (nasal and pharyngeal mucosa) or three layers (nasal mucosa, muscle and connective tissue, and pharyngeal mucosa) with simple interrupted or continuous monofilament sutures (4-0 polydioxanone, polypropylene) (Figure 24-18) The mucoperiosteum is apposed with one or two layers of simple interrupted sutures.
 

Lateral Rhinotomy

Lateral rhinotomy is occasionally used to approach lesions in the rostral one fourth to one third of the nasal passages. Approaches using incisions through either the skin or the alveolar mucosa have been described. These approaches are performed with the animal in lateral or sternal recumbency. The surgeon directs the incision dorsocaudally from the angle of the rhinarium toward the nasomaxillary notch between the dorsal and ventral parietal cartilage. (Figures 24-19 and 24-20) The accessory cartilage is invariably transected. The edges of the incision are retracted with stay sutures to expose the rostral nasal passages. The incision is closed in three layers (nasal mucosa, cartilage or subcutaneous tissue and skin).

Alternatively, the alveolar mucosal technique provides acceptable exposure to the rostral nasal cavity and avoids transection of nasal cartilage or bone.¹² The surgeon retracts the lip dorsally and palpates the rostrolateral aspects of the right nasal and incisive bones. An incision is made through the alveolar mucosa along this ridge from the nasal bone to the rostral end of the interincisive suture. Using a periosteal elevator, the mucosa is reflected in a dorsal and medial direction along with the dorsal lateral nasal cartilage. After exploring and collecting tissue samples the alveolar mucosa is apposed with simple interrupted sutures.
 

Postoperative Management

After surgical procedures involving the nasal cavity and sinuses, pharyngeal sponges (if placed) are removed, and the animal is recovered in a slightly head down position. The endotracheal tube is removed with the cuff slightly inflated to prevent tracheal aspiration of fluid and other debris. Analgesics are given for three to five days as needed. Good analgesia is obtained with parenteral hydromorphone (or a constant rate infusion of morphine/ lidocaine (See Chapter 9). The patient’s vital signs are monitored carefully and supportive care is administered as needed.

Blood transfusions are sometimes (16% of cases) necessary even following carotid occlusion.⁹ Sneezing and mild epistaxis are expected for several days. A serous to serosanguineous discharge occurs for several days to weeks depending on the primary disease condition and the effectiveness of adjuvant therapy. Breathing sounds are harsh and resonant. Inward and outward movement of the skin flap is expected if the bone flap is discarded. Appetite may be depressed for several days. Cats tolerate rhinotomy poorly and may not readily resume eating. Diazepam or oxazepam may be given to stimulate their appetite. Chewing on hard objects is forbidden if the hard palate bone flap is discarded. Patients are discharged from the hospital within 2 to 3 days following surgery unless complications or adjuvant therapy dictates longer hospitalization.

Complications

Complications of rhinotomy include hemorrhage, entrance into the cranium, pain, subcutaneous emphysema, airway obstruction, nasal discharge, fistula and disease recurrence. Intraoperative hemorrhage is minimized by temporary occlusion of the external carotid arteries and good hemostasis during surgery. Packing the nasal cavity is discouraged as it may lead to hyperventilation and subcutaneous emphysema; in addition removal of the packing material 2 to 3 days after surgery is painful. Postoperative hemorrhage is rare however blood transfusions are sometimes necessary to replace lost volume.

Disease erosion of the cribriform plate or curettage may result in exposure of the brain and subsequent cerebral edema. Tumor extension into the cranium should be suspected when the animal exhibits neurologic signs or when defects in the cribriform plate are identified with computed tomography. Animals with brain edema should be treated with rapid-acting water soluble intravenous corticosteroids, osmotic agents (mannitol), hyperventilation, hyperbaric oxygen, calcium channel blockers and antioxidants.

Subcutaneous emphysema occurs when air leaks from the nasal cavity into the subcutaneous tissues at the surgical site and is usually associated with violent sneezing or obstruction to nasal airflow. Airflow may be obstructed by nasal packing, occlusion of the nares with crusted blood and secretions, or severe mucosal edema. Subcutaneous emphysema is usually self-limiting and resolves within one to two weeks. It may be prevented by suturing a stent over the surgical site, inserting a drain, or creating a stoma and avoiding obstruction of the nasal passages. Subcutaneous emphysema is primarily a cosmetic concern although it could facilitate spread of infection. The animal’s comfort may improve if the subcutaneous air is aspirated and a drain is placed into the nasal cavity to reduce recurrence.

Rhinotomy is a painful procedure. Analgesics should be given at the conclusion of surgery and as needed for 3 to 5 days. Anorexia is expected following surgery and may be due to pain or a diminished sense of smell. Anorexia is more severe in cats than dogs because they depend on their ethmoturbinates for olfaction and appetite stimulation. Cats are given diazepam or oxazepam to stimulate their appetite if necessary. Dogs usually require no treatment and have a normal appetite within a few days. After ventral rhinotomy, animals should not be allowed to chew on hard objects. Oronasal fistulas develop if dehiscence occurs or when soft tissues are perforated by hard, sharp objects.

Although airway obstruction is uncommon it may occur following rhinotomy. Animals should be monitored closely during recovery. Obstruction may be due to failure to mouth breath, mucosal edema and anxiety. These animals should be sedated and provided with supplemental oxygen in a quiet, cool environment. Corticosteroids should be given to reduce mucosal edema. An endotracheal or tracheostomy tube is indicated if dyspnea is severe.

A serosanguineous nasal discharge is expected following rhinotomy. The discharge diminishes and becomes more serous as denuded bone is covered with epithelium. If the primary disease has been eliminated the discharge remains minimal and serous. If the disease progresses or the area becomes infected, the nasal discharge increases and becomes mucopurulent or hemorrhagic. Chronic infections are treated with antibiotics selected on the basis of culture and sensitivity tests.

Recurrence of most diseases is expected after rhinotomy unless appropriate adjuvant therapy is instituted. Rhinotomy for foreign body removal might be an exception if irreversible chronic rhinitis and osteomyelitis have been avoided. Rhinotomy for fungal disease should be followed with administration of topical antifungal agents, and rhinotomy for neoplasia should be followed by radiation therapy, to extend the animal’s disease free period.

References

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