Feline nasopharyngeal polyps (Proceedings)

Feline nasopharyngeal polyps (inflammatory polyps, middle ear polyps, aural polyps) are benign growths that originate from the middle ear or the Eustachian tubes of young cats. True nasopharyngeal polyps extend into the pharyngeal cavity causing signs of upper airway obstruction including stertor, nasal discharge, gagging, dysphagia, and dyspnea. Aural polyps extend from the middle ear through the tympanic membrane and into the external ear canal resulting in symptoms of otitis externa. More severe signs include evidence of middle ear disease such as Horner's syndrome or facial nerve paresis, or inner ear disease such as head tilting, ataxia, and nystagmus. The exact cause of nasopharyngeal polyps is unknown. Although an association with chronic upper respiratory tract infection has been proposed, a recent study could not detect calicivirus or herpesvirus in polypoid tissue. Other suggested etiologies include chronic otitis media, ascending nasopharyngeal infection, and a congenital origin. Nasopharyngeal polyps predominantly affect young cats; the reported mean age ranges from 14 months to 3 years. However, polyps have also been reported in older cats as well. No breed or sex predisposition has been identified.

Diagnosis

A nasopharyngeal polyp should be suspected in young to middle-aged cats who present with signs of upper airway obstruction, otitis media, or otitis externa. Otoscopic and oropharyngeal examination using heavy sedation or general anesthesia is required to diagnosis a nasopharyngeal polyp. Care should be taken when anesthetizing cats with possible upper airway obstruction due to the potential for respiratory decompensation. The nasopharynx can be evaluated by a variety of methods:

• Digital palpation of the soft palate

• Soft palate retraction using a spay hook

• Visual inspection of the dorsal nasopharynx using a dental mirror

• Flexible fiberoptic endoscope that will retroflex over the soft palate

Polyps are typically smooth, shiny, pedunculated, and light pink in color. Differentials for nasopharyngeal polyps include neoplasia, foreign body, and granuloma. A complete diagnostic work-up for an animal with a nasopharyngeal mass includes bloodwork, thoracic radiographs, and imaging of the tympanic bullae. Thoracic radiographs are indicated to look for signs of lower airway disease and to rule out metastatic neoplasia. Echocardiography could be considered in cases of long-standing severe upper airway obstruction that could result in pulmonary hypertension. The tympanic bullae can be imaged with standard radiography, however the sensitivity for detecting otitis media is poor, with a false-negative rate of 25%. However, radiographs can be used to rule out evidence of overt neoplasia, such as bony proliferation and lysis. Advanced imaging, such as computed tomography (CT) and magnetic resonance imaging (MRI), is extremely useful in diagnosing otitis media and locating polyps. Nasopharyngeal polyps are definitively diagnosed from histopathologic examination following surgical removal.

Treatment

There are multiple options for removal of nasopharyngeal polyps. The two most common approaches are polyp removal by traction (± prednisolone therapy) and ventral bulla osteotomy. Traction may be considered initially, however the owner must be made aware of the likelihood of recurrence. The polyp is visualized by retraction of the soft palate using a spay hook or stay suture. The polyp is grasped with Allis tissue, alligator, or right-angled forceps, and gently avulsed from its origin. Recurrence following removal by traction ranges from 36 to 41%. A recent study described the addition of prednisolone therapy following traction and had a 0% recurrence rate in 8 cats receiving traction and prednisolone versus a 64% recurrence rate in 14 cats receiving traction alone.

Ventral bulla osteotomy (VBO) is the treatment of choice, even in cats without evidence of otitis media. VBO provides the best and easiest access to the middle ear from which polyps are thought to arise. The cat is placed in dorsal recumbency with the head and neck extended over a sandbag or rolled towel. Following blunt surgical dissection between the digastricus muscle laterally and the styloglossus and hyoglossus muscles medially, the bulla can be palpated. The hypoglossal nerve and ligual artery run medial to the hyoglossus muscle and should be retracted gently to avoid damage. The feline tympanic bulla is unique in that it is divided into two compartments by a bony septum. The bulla is entered through the larger ventromedial compartment using a Steinmann pin. The osteotomy is enlarged using rongeurs. The dorsomedial compartment is carefully entered to avoid damaging the promontory over which the postganglionic sympathetic fibers run. Any fluid or exudates within the bulla should be collected and submitted for aerobic bacterial culture. Small curettes can be used to remove the polyp and epithelial lining of the tympanic bulla. Don't forget to submit the excised tissue for histopathology. The tympanic cavity is thoroughly lavaged prior to closure. I do not utilize passive drains in this surgery. Drain placement is controversial and been proven unnecessary in dogs following total ear canal ablation and lateral bulla osteotomy.

Complications

Multiple complications can occur following VBO, including Horner's syndrome, vestibular disease, facial nerve paralysis, hemorrhage, and recurrence. Horner's syndrome is very common following both VBO (57 to 96% incidence) and removal by traction (43% incidence) although most cases resolve within two to four weeks. Aggressive debridement of the tympanic bulla may also result in vestibular disturbance (4 to 42% incidence) manifested by head tilting, ataxia, and nystagmus.

Postoperative Care

Broad-spectrum antimicrobials should be administered while awaiting culture and susceptibility results. Postoperative pain is managed using systemic narcotics (morphine, hydromorphone) for 24 to 48 hours. Steroids OR non-steroidal anti-inflammatory drugs can be utilized for at-home pain management. For anorexia or nausea associated with vestibular disease, we administer meclizine (12.5mg PO daily) until the cat begins eating again, usually within 1 to 2 days.

Suggested reading

Donnelly KE, Tillson DM. Feline inflammatory polyps and ventral bulla osteotomy. Compend Contin Educ Pract Vet 2004;26:446-454

Kapatkin AS, Matthiesen DT. Results of surgery and long-term follow-up in 31 cats with nasopharyngeal polyps. J Amer Anim Hosp Assoc 1990;26:387-392

Kudnig ST. Nasopharyngeal polyps in cats. Clin Tech Small Anim Pract 2002;17:174-177

MacPhail CM Innocenti C, Kudnig ST, et al. Atypical manifestations of feline inflammatory polyps in three cats. J Fel Med Surg 2007;9(3)219-225

Muilenburg RK, Fry TR. Feline nasopharyngeal polyps. Vet Clin North Am Small Anim Pract 2002;32:839-849.