Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine
Utrecht, The Netherlands
Clinical Signs of Diseases of the Nasal Plane and Nasal Cavities
The same is true for all respiratory patients in that the history provides very important information. For instance abnormalities of the nasal plane; depigmentation, inflammation, crust formation, dehydration and hyperkeratosis are usually noted by the owner. Especially unilateral discharge, purulent material coming from one side of the nose, is the most clear indicator of intranasal disease. Sneezing and reverse sneezing are other indicators of nasal and nasopharyngeal disease. Nature and type of the discharge (serous, mucopurulent, haemorrhagic) are important in determining the diagnostic approach.
Clinical Examination of the Nose
After the history has been taken, a thorough clinical examination of the respiratory tract has to follow. The following items give the most diagnostic information however on nasal diseases and should always be checked. Nasal plane depigmentation can be associated with inflammation of the nasal plane or can be the result of a severe or very chronic rhinitis and is often seen for instance in patients with fungal disease. Because of the destruction of conchae with fungal disease, the air passage usually is normal. Air passage is usually abnormal, diminished, in patients with tumors or large foreign bodies. Pain on palpation of the nose is highly indicative of fungal disease as well and is almost never encountered in patients with nasal tumours. Checking the oral mucosa and teeth by simply lifting the upper lip, can show dental problems as a likely cause of nasal discharge. Especially in bilateral nasal discharge, a check up for systemic abnormalities should be performed. Additional examination of the nose and nasal cavities primarily consists of diagnostic imaging (radiography, CT-scan, MRI) and endoscopy. Culture, cytology and histology are only used in conjunction with nasal endoscopy.
Finally, when a diagnosis cannot be made with the diagnostic procedures discussed above, or in case of foreign bodies that cannot be removed via endoscopy, a surgical exploration of the nasal sinuses or nasopharynx can be necessary.
Diagnostic Imaging of the Nose
Radiography is the number one additional diagnostic procedure to perform for patients with nasal disease. The standard lateral view is especially helpful for detecting abnormalities of the frontal sinuses, the nasopharynx and in combination with oblique views in detecting dental problems. The standard dorsoventral view does not provide any information on the rostral aspect of the nose, since upper and lower jaw over-project each other here. The intra-oral dorsoventral view is the most informative and helpful view for assessment of the nasal cavity. CT-scan imaging is a more expensive technique, and requires general anesthesia as well, but produces images that represent thin, cross-sectional slices of the skull without problems of superimposition inherent to survey radiography.
Endoscopy of the Nasal Cavities
The simplest method of rhinoscopy is the one using an otoscope. Depending on the size of the animal and the cones used, a fair part of the rostral nasal cavity can be visualized. For a complete rhinoscopy, a variety of rigid and flexible instruments can be used, but a rigid scope is preferable and provides adequate visualisation of the nasal sinuses. Wolf and Storz endoscopes are the most used types, a 2.7 mm rigid scope can be used for cats, a 3.5 mm scope for big cats and small dogs and the 4.5 mm scope can be used in very large dogs. Different types of grasping and biopsy forceps can be brought into the nose, next to the scope itself (rigid forceps), or through the working canal of the scope (flexible forceps).
Diseases of the Nasal Plane
Congenital malformation of the nasal plane in the form of stenotic nares is part of the brachycephalic obstructive syndrome (BOS) and is a common finding in brachycephalic dogs, but also occurs in Persian cats. Other congenital malformations are clefts of the primary or secondary palate. Most abnormalities can be corrected surgically.
Primary inflammation of the nasal plane is associated with loss of the parasympathetic nerve supply and can occur for instance with chronic otitis media. Secondary inflammation can be due to any chronic rhinitis or epistaxis or is associated with general skin disorders like thallium intoxication, leishmaniasis, pemphigus, DLE, SLE, mycosis, contact dermatitis and vasculitis.
Depigmentation of the nasal plane can be diffuse, idiopathic and acquired in the Labrador retrievers and Siberian Husky or focal (vitiligo) as seen in Rottweiler dogs and Collie dogs. Depigmentation can also be the result of auto-immune disease processes like DLE and SLE or develop in the course of for instance fungal disease of the nasal cavities, but is then accompanied by inflammation of the nasal plane and/or chronic rhinitis.
In dogs, squamous cell carcinoma is the most common tumour type of the nasal plane. Other tumours in this site are lymphoma, fibrosarcoma, hemangioma, melanoma, mast cell tumour and fibroma. SCC's are usually seen in adult or aged animals and are locally invasive but late to metastasize. They are however erosive and deeply infiltrative. Diseases of the nasal plane in cats are uncommon with the exception of tumours. The most common tumor of the nasal plane in cats is squamous cell carcinoma (SCC). This tumor manifests itself as a progressive ulcerative and erosive inflammation of the nasal plane. Excessive sunlight exposure and lack of skin pigmentation are two major risk factors associated with development of SCC. Various methods have been described to successfully treat cats with squamous cell carcinoma of the nasal planum including radiation therapy, hyperthermia, intratumoural administration of carboplatin, cryosurgery, conservative surgery and photodynamic therapy. The most cost-effective, reliable treatment for selected patients with invasive SCC is nasal plane resection however. This is also the recommended treatment for other tumors of the nasal plane in dogs and cats.
Diseases of the Nasal Cavities
Bilateral rhinitis is very common in both dogs and cats and is usually the result of a primary viral infection with secondary bacterial infection. Although definite criteria are lacking, loud and frequent sneezing with large amounts of bilateral watery discharge fit with allergic rhinitis. An exact etiology is unknown, but these signs are commonly seen in dachshunds in the Netherlands, but other breeds, for instance terrier breeds, are affected as well. In most cases, histopathologic examination of inflamed mucosa shows an eosinophilic inflammation. Chronic lymphoplasmacytic rhinitis in dogs and chronic non-specific rhinitis in cats are diagnosed when all other causes of chronic rhinitis have been excluded. This chronic form of rhinitis in cats is most probably the result of a chronic viral upper respiratory tract infection. In case of bilateral nasal discharge and systemic illness, bronchopneumonia should be suspected.
Nasal Foreign Body
Frequent sneezing is the primary clinical sign of nasal foreign body, with rubbing of the front paws at the nose. In subacute to chronic cases, unilateral mucopurulent discharge will be the most obvious clinical sign. During rhinoscopy under general anesthesia the foreign body usually can be seen and be removed with special forceps. Flushing and suction of nasal discharge are necessary when foreign bodies are covered in discharge and cannot be visualised immediately. Foreign bodies that cannot be removed under endoscopic guidance will have to be removed surgically.
Mycotic rhinitis is a common disease in dogs and usually caused by Aspergillus species. This disease is rare in very young and brachycephalic dogs, but is often seen in Golden Retriever and Rottweiler dogs in the Netherlands, male and female dogs are equally affected. Erosion of the nasal planum with depigmentation and an abundant unilateral or bilateral sanguinopurulent, mucopurulent or hemorrhagic nasal discharge are usually noted.
The diagnosis can be made on clinical signs and radiographs of the nasal cavity and frontal sinus with evidence of turbinate destruction and irregular areas of increased and decreased radiolucency. On rhinoscopy cavernous areas caused by marked destruction of turbinates and conchal atrophy can be seen, as well as obvious mats of fungal hyphae. When there is no macroscopical evidence of fungal hyphae in the nasal sinus, trepanation of the frontal sinus should be done. Samples for culture and cytologic and histopathologic examination should always be collected.
Oral administration of azole antifungal agents is effective in only 43% to 70% of cases, requires months of therapy and is costly. Topical therapy is therefore indicated and advised by most specialists. Natamycin, amphotericine B, itraconazole and clotrimazole can be infused into the nasal passages and frontal sinuses of dogs either as a single or with repeated infusion. A success rate of 70% has been reported with single infusions of clotrimazole. Success rates up to 90% have been described after surgical tube placement and treatment with enilconazole; after trepanation of both the nasal and frontal sinus on the affected sides, tubes are sutured in place for topical instillation of an enilconazole solution (2dd 10 mg/kg, dilute 1:10) for 14 days.
Intranasal tumours are more common in dogs than in cats. Most tumours are malignant and occur in middle-aged and old animals (median age between 8 and 10 years). No sex or breed disposition has been found. Eighty percent of canine intranasal tumours are malignant and approximately two thirds of them are of epithelial origin (adenocarcinoma, SCC and undifferentiated carcinoma). Their malignant nature is reflected more by their progressive local invasiveness than by distant metastasis to lymph nodes and lungs. Micrometastases have been reported however and remained subclinically for 12-36 months.
Clinical signs include nasal discharge, sneezing, epistaxis, facial and/or oral deformity, epiphora due to obstruction of the nasolacrimal duct, stridor, exophthalmos due to a retrobulbar mass effect and central neurologic signs usually due to expansion of the tumour through the cribriform plate. Air passage through the nose is usually obstructed.
The diagnosis is made on clinical signs, radiographic signs showing destruction of normal turbinate pattern and diffuse increased soft tissue density, CT-scan or MRI and histopathologic examination of rhinoscopy assisted biopsy.
Radiotherapy appears to be the most effective treatment for nasal tumours. Most studies have investigated orthovoltage irradiation (125-400 keV) but megavoltage irradiation has been reported as well. The optimum dosage and method of delivery have not been determined. Median survival times of 13 months for dogs and 11.5 months for cats with non-lymphoid nasal tumours treated with megavoltage have been reported. Whether radiation therapy should be combined with surgical debulking is controversial. Surgery as the sole treatment of dogs with nasal tumours has not prolonged survival time. However, surgery may palliate clinical signs in some dogs by alleviating obstruction and epistaxis. Chemotherapy, immunotherapy and cryosurgery do not improve survival. Malignant lymphoma can be treated rather successfully however with combination chemotherapy.
Oronasal Fistulae and Palatal Defects
Acquired oronasal fistulae are abnormal communications between the nasal and oral cavities caused by trauma or disease. They are most often caused by dental disease. An oronasal fistula results when a deep maxillary periodontal pocket progresses to the apex of the tooth, lysing bone between the apex of the alveolus and the nasal cavity or maxillary sinus. They are usually seen in middle-aged and older small breed dogs with a history of dental disease. Common clinical signs are sneezing and chronic unilateral serous or mucopurulent nasal discharge. Periodontal pockets and oronasal fistulae are treated with dental extraction and closure of the defect with mucoperiosteal or mucosal flaps and antibiotics.
Congenital oronasal fistulas are abnormal communications between the oral and nasal cavities involving the soft palate, hard palate, premaxilla and/or lip. Congenital palatal defects result when the two palatine shelves fail to fuse during fetal development as a result of inherited, nutritional, hormonal, mechanical and toxic factors. Particularly brachycephalic breeds are affected purebred dogs have a higher incidence than mixed breeds. Females are more commonly affected than males. The cleft is present at birth, although it is not always recognized immediately.
Clinical signs are difficulty nursing, nasal regurgitation (drainage of milk from the nares), nasal discharge, coughing (aspiration pneumonia), gagging and failure to thrive are common problems.
The diagnosis is based on clinical signs and visual examination of the lip, hard and soft palate. Radiographic examination of the skull is not necessary, but thoracic radiographs are useful in evaluating for aspiration pneumonia.
Most animals with defects of the palate are euthanised or die. Surgical treatment generally is delayed until the patient is at least 8 weeks of age. At that time they are better anesthetic candidates and tissues are less friable and hold sutures better. The primary goal of repairing cleft palate is to reconstruct the nasal floor. Several procedures may be necessary before the entire cleft is permanently reconstructed. The prognosis for hard palate defects is good, but dogs with large defects of the soft palate and muscular hypoplasia have a poor prognosis.