Nasopharyngeal Polyps

Nasopharyngeal polyps are relatively uncommon lesions in cats which, when large enough, can be an important cause of chronic upper respiratory signs. Several reports have described the clinical presentation and the management of this disease in cats, which may reflect the increased incidence or may simply be the result of increased awareness of this lesion. Only one case report on nasopharyngeal polyps in dogs was found. The age at presentation, presenting signs, histological appearance of the polyp, treatment and postoperative course in this dog were similar to those reported in cats.

Origin and Etiopathogenesis: The etiology and the pathogenesis of nasopharyngeal polyps are incompletely understood. Speculations concentrate on congenital or inflammatory origin.

The Eustachian tube and the tympanic cavity (middle ear) originate from the first pharyngeal pouch (tubotympanic recess), and it has been proposed that nasopharyngeal polyps develop as a result of a congenital defect in this tubotympanic recess. No other congenital defects associated with polyps have been described, so this hypothesis is weak. Nevertheless, the lesion does occur in young cats.

An inflammatory basis for nasopharyngeal polyps has also been proposed. This hypothesis is based, at least in part, on the usual histologic characteristic of polyps, in particular, the presence of inflammatory cells within well-vascularized connective tissue. This stromal core is typically covered by respiratory epithelium. The inflammatory component is a consistent finding, but whether it is a cause of the polyps is not known.

It is also uncertain whether the auditory tube or the middle ear is a site of origin for the polyps. One report of four cases provided evidence for the auditory tube as the site of origin. All cats in this series were under two years of age and had a short clinical history of respiratory disease with no clinical signs, or clinical or radiographic evidence of middle ear involvement. It was concluded that middle ear disease is not a primary factor in the development of the polyps.

In another report of four cases, affected cats ranged from two to five years of age. Three of these cats had clinical signs of otitis media either preceding or following the onset of the respiratory signs. In one cat, polyps were found in both the external ear canal and nasopharynx. Histologically, these lesions were similar to one another. This case provided evidence that these polyps had developed in association with chronic otitis media, probably involving the tympanic membrane.

Signalment and Presenting Clinical Signs: Nasopharyngeal polyps are diagnosed more frequently in young cats (with a mean age at the time of diagnosis of 1-1/2 years) than in older cats. Nevertheless, the lesions has been recognized in cats less than 6 months and up to 15 years. No sex or breed predisposition has been identified.

A wide variety of presenting signs has been reported in cats with nasopharyngeal polyps. The most common signs are partial upper respiratory obstruction including respiratory stridor, dyspnea, nasal discharge, sneezing, coughing and dysphagia. Less frequent signs include otitis, typically otorrhea, aural irritation, and vestibular signs such as head tilt.

Diagnosis: Diagnosis is based on finding a soft tissue mass above the soft palate, in the nasopharynx, or in the external ear canal. Examination of the oro- and nasopharynx of anesthetized cats is usually required to visualize the lesion. The caudal edge of the soft palate can be drawn forward with a non- traumatic hook to allow inspection of the mass, and a dental mirror placed within the caudal aspect of the pharynx to evaluate the area above the soft palate. Polyps appear as glistening, pedunculated, red, pink or grayish masses in the nasopharynx. Otoscopic examination to evaluate the ear canals and the tympanic membranes for signs of otitis media while the cat is under anesthesia is also recommended since most cats with nasopharyngeal polyps have otitis media. Radiographs of the tympanic bulla are also recommended to assess for bony destruction. Computed tomography could be utilized in some cases when radiographs are inconclusive. Hematology and serum biochemistry values in cats with nasopharyngeal polyps are typically unremarkable. Calicivirus was isolated from two of three cats in one study.

Treatment: Surgical resection is the only reported successful treatment of nasopharyngeal polyps. Surgical removal of the polyp by traction is simple and usually uncomplicated. Retraction of the caudal edge of the soft palate may be sufficient in some cases to allow the removal of the polyp with Allis forceps, using traction at the base of the attached pedicle. However, in some cases, the free (caudal) border of the soft palate requires incising to improve access.

Performing bulla osteotomy in cats with nasopharyngeal polyps may be necessary when the middle ear is involved. Although the risk of complications is significant, some veterinary surgeons recommend an ipsilateral bulla osteotomy for every cat with a nasopharyngeal polyp. This recommendation is based on a reported recurrence rate of up to 35% without, but only 2% with, bulla osteotomy.

Temporary postoperative Horner's syndrome (ptosis, miosis, prolapsed third eyelid, enophthalmos) is the most common complication of bulla osteotomy. Other complications include temporary or permanent signs of vestibular nerve paralysis (head tilt, nystagmus, and ataxia) or, rarely, facial nerve paralysis (drooping of the lip, drooling of saliva, lack of palpebral reflex. Otherwise, the prognosis for complete recovery after polypectomy is good.

-by Suliman AlGhazlat, Class of 2002

-edited by Evan Janovitz, ADDL Pathologist

References:

1. Pope ER, Constintinescue GM, 2000: Feline respiratory tract polyps. Kirk's Current Veterinary Therapy 13: 794-796.

2. Parker and Binnington AG: 1984, Nasopharyngeal polyps in cats: three case reports and a review of the literature. JAVMA 21: 473.

3. Cameron JG, Dill-Macky E, Hodson DR: 1994, Nasopharyngeal polyp in a cat. Australian Veterinary Practitioner March, 1994.

4. Seitz SE, Losonsky JM, Maretta SM; 1996, Computed tomographic appearance of inflammatory polyps in three cats. Veterinary Radiology and Ultrasound. 37: 99-104.

5. Fingland RB, Gratzek A, Vorhies MW, Kirpensteijn J, 1993: Nasopharyngeal polyp in a dog. J Am Anim Hosp Assoc. 29: 311-314.

6. Kapatin A, Matthiesen OT, Noon K, Church ET, Scavelli TD, Patnaik AK: 1989, Results of surgical treatment of nasopharyngeal inflammatory polyps in 31 cats. Veterinary Surgery, 18: 59.