Nasopharyngeal diseases are commonly seen in small animal medical practice. This lecture will review the diagnostic approach and current treatment recommendations for the most frequently seen chronic disorders of the nasal cavity and posterior pharynx including the soft palate.
Disorders of the respiratory tract should be identified anatomically (nose, larynx, trachea, etc) prior to generating a list of differential diagnoses to explain the clinical signs. When the clinical sign is cough, making an anatomic diagnosis can be difficult. In contrast, chronic diseases of the nasal cavity are readily identified because the clinical signs of sneezing and nasal discharge suggest an immediate anatomic diagnosis. In general, sneezing and nasal discharge occurs because of irritation to the nasal mucosa; any disorder causing inflammation in this area will cause these clinical signs. A first step in formulating a differential diagnosis can be taken by evaluating the nasal discharge.
Common causes of chronic sneeze, noisy breathing and nasal discharge in private practice:
2. Nasal mass
3. Lymphocytic-plasmacytic rhinitis
4. Nasal foreign body,
5. Fungal infection (aspergillosis, dogs)
6. Tooth root abscess
7. Secondary bacterial infection
8. Environmental irritants (construction debris etc)
9. Vasomotor rhinitis (non-allergic clear discharge, response is to otherwise innocuous household aerosols)
Most commonly occurs because of allergic rhinitis, viral infection (uncommon cause of chronic symptoms), environmental irritants (smoke, construction debris) and vasomotor rhinitis.
Can occur because of any of the above conditions, but more commonly is the result of lymphoplasmacytic rhinitis or nasal mass.
Can occur with fungal infection, nasal mass, foreign body, and tooth root abscess and commonly with lymphoplasmacytic rhinitis. Usually occurs because of the presence of bacteria. Importantly, bacterial rhinitis is rarely if ever a primary disorder in dogs, cats or humans. Secondary bacterial rhinitis will respond to antibiotics; however the underlying disorder will predispose to repeat bacterial infection and repeat courses of antibiotics with no cure.
Most cases of chronic nasal discharge and sneezing are treated for months to years with various and intermittent combinations of antibiotics, antihistamines and steroids. The chronicity of the signs is strong evidence that chronic antibiotic therapy should not be considered a standard of care. Ironically, infections of the urinary tract or skin (for example) that required months or years of antibiotic therapy would likely stimulate the clinician to search for an underlying cause of the infection in that organ system. This author suggests that an equally inquisitive and aggressive approach should routinely be taken by clinicians treating dogs and cats with symptoms of nasal disease that lasts more than a few weeks.
The most straightforward method of making a definitive diagnosis is by performing rhinoscopy. This procedure requires a flexible endoscope to permit evaluation of the caudal choanae as well as the cranial nasal passages. In most cases, the combination of rhinoscopy, culture and biopsy of material obtained during the procedure, and plain film radiography of the maxillae will result in a definitive diagnosis in > 90% of cases.
Multiple antihistamines are available for humans because some work better for some people and not others. The same thing is true for dogs and cats with allergic rhinitis. In my experience, Clemastine has the greatest efficacy in the canine species; Hydroxyzine has the greatest efficacy in feline patients (specific doses discussed in lecture). In most chronic cases, inhaled steroids including fluticasone have great efficacy, as they do in humans with allergic rhinitis (think "Flonase").
Surgical removal of malignant nasal masses in dogs or cats does not predictably increase quality of life or life expectancy. Chemotherapy alone may be a reasonable treatment option for nasal lymphoma, although most cases will respond best to a combination of chemotherapy and radiation. The remaining common malignant tissue types respond best only to radiation therapy.
The problem is that the vast majority of clients seen in general practice do not have the resources (time, money, energy) to pursue radiation therapy. This is an important point, because even under ideal circumstances most non-lymphoma nasal malignancies carry a prognosis of only 1-2 years with radiation therapy. And, in my experience, treatment with piroxicam and antibiotics carries a prognosis of at least 4-12 months from the time of diagnosis until euthanasia is performed. Fundamentally, the decision rests with the owner, but their decision is greatly driven by the direction we offer.
Lymphocytic Plasmacytic Rhinitis
Etiology not clear, but may be a response to allergens, exacerbations of herpes infection (in cats) and chronic intermittent colonization/infection with environmental bacteria. In cats especially, this disorder can cause significant destruction of turbinates, and this is associated with a worsening prognosis. In general, first treat with antibiotics to clear the secondary bacterial component of the disease. Next, begin inhalant therapy with fluticasone. Lastly, consider intermittent use of topical decongestants such as "little noses" nasal drops (dilute phenylephrine) on a three day on, three day off basis (avoids rebound vasodilation). If and when nasal discharge returns and is green/yellow, antibiotic therapy will be needed again. This cycle may repeat itself every few months chronically even with aggressive inhalational anti-inflammatory therapy.
The mucus produced by the feline species is rich in sialic acid. This bit of trivia is clinically important because the sialic acid residues give the feline mucus a distinctive thick, ropey texture. Imaging having a cold and then having your hands tied behind your back so that you cannot blow your nose. This is the problem cats have with trying to clear the copious thick discharge that develops within their nasopharynx. Most cats cannot sneeze forcefully enough though their narrowed nasal passages to clear the material. In these cases, suction and flush procedures performed during rhinoscopy serves an additional important function to clear the discharge in way that the patient likely will never be able to do on their own.
Nasal Foreign Body
Can be removed during rhinoscopy. The nasal cavity should be flushed with sterile saline solution so that any remnants of the foreign material are likely to be removed.
Nasal Fungal Infections
Most commonly aspergillosis and most commonly in dogs. Ironically, I have diagnosed aspergillosis in two cats in the last three months prior to this lecture. The most effective treatment (65-90% cure rate with one or two treatments) requires infusion of antifungal medication (enconazole or clotrimazole) into the nasal cavity and sinuses. This infusion is under pressure, and is left in place for about 1 hr, during which the patient is turned every 15 minutes or so to maximize contact of the infusate with the nasal mucosa.
Prior to beginning this approach, I treat patients with Itraconazole for 3 months, assuming the patient shows dramatic improvement. This approach only cures about 30% of patients, and the drug is expensive. However, it cures 30% of patients! Importantly, it acts as a chemical debriding agent to maximize the effect of clotrimazole or enconazole infusion if that is required. Importantly, if the patient is to undergo infusion therapy, a CT or MRI is performed immediately prior to the infusion to confirm that the cribriform plate is intact. Infusion of enconazole or clotrimazole with a perforated cribriform plate can be fatal.
Tooth Root Abscess
Treatment is obvious.
Secondary Bacterial Infection
As stated, this is never a primary problem, and is frequently present because the underlying disease compromises the integrity of the nasal cavity to protect against normal inhaled flora. Chronic lymphocytic plasmacytic disease may predispose to anaerobic infection in some 10-20 % of cases, in addition to the common Staphs, Streps, E coli, Pasteurella, and Pseudomonas. Antibiotic selection should be based on culture and sensitivity results, but also based on the potential for mixed infections including anaerobic bacteria.
This is a common cause of clear nasal discharge and nasal cavity obstruction. It is distinct from "allergic rhinitis" in that there are no primary "allergens" involved in the nasal response. Instead, the signs are the result of a reaction to otherwise benign household substances. This can include almost anything such as hairspray, detergents, perfumes, although in most cases the cause remains unproven. The good news is that this disorder is very responsive to intermittent use of decongestant drops.
Evaluation of the Nasopharynx
For purposes of this lecture we will confine ourselves to elongated soft palate.
Elongated Soft Palate
Elongated soft palate is a well recognized problem in most brachycephalic breeds. It is present in virtually all English Bulldogs, although the clinical signs that result are variable from patient to patient.
Elongated soft palate can be assumed in most dogs that snore. By itself, this is not considered a "disease" so much as an annoyance for some owners. It is worth noting however that the English Bulldog is a naturally occurring animal model for sleep apnea in humans. If your bulldog patient appears drowsy on the exam table, it is very possible that the patient is actually sleep deprived, similar to humans with this disorder
There are two significant problems associated with elongated soft palate. The first issue often goes unrecognized as directly resulting from elongated palate and that is vomiting and gagging. The best way to think of the relationship between elongated soft palate and vomiting is to consider the effect of putting your finger down your throat to initiate a gag reflex. This same gag reflex occurs in these animals when the soft palate is drawn caudally into the recesses of the pharynx. The gag/vomit reflex can be controlled to some extent with drugs such as metoclopramide or Cerenia. Ideally however, the best approach to the problem is to shorten the soft palate.
The second, better recognized and usually more significant clinical problem is obstructed breathing. This anatomic defect can cause significant negative inspiratory pressures and the inversion and collapse of the arytenoids cartilage.
Surgical Correction of Elongated Soft Palate Using Coblation
Surgical approaches to elongated soft palate include traditional cutting with a scalpel, cautery-assisted cutting and laser-assisted cutting of the distal end of the soft palate. All these procedures induce various degrees of bleeding, significant pain and some degree of swelling. A new technology, bipolar radiofrequency ablation (coblation), has been used in human medicine for the past 7 years to shrink and stiffen the soft palate without actually cutting tissue. Approximately 20% of the tonsillectomies performed in the United States in human patients are currently done using coblation technology.
The actual technique involves a 10-15 second insertion of a 1-2 mm wide probe into three places within the submucosa of the distal aspect of the soft palate. The technology produces an ionized saline layer that disrupts molecular bonds within tissue without using heat as the primary mechanism. At the voltage gradient produced by the coblation probe, the sodium and chloride particles gain enough energy to dissociate the tissues molecular bonds, and this causes volumetric reduction in the tissues within the submucosa of the palate. Over a period of 4-6 weeks, further reduction in the size of the elongated portion of the soft palate occurs, with a resulting reduction in airway obstruction.
We have performed coblation on 8 dogs with elongated soft palate at the time of this writing. Results of this procedure will be presented during lecture.