Nasopharyngeal Polyps in Cats: Key words - stertor, traction, and bulla osteotomy

Nasopharyngeal (NP) polyps in cats are characterized by well-circumscribed solid masses that are found in the nasopharynx, tympanic bulla, and Eustachian tube.  They are benign and thought to be secondary to inflammation from bacterial or viral infections.  Similar polyps can also be present in the external ear canal.  Affected cats are usually young (less than 1 year) but all ages can be affected.

Clinical Signs

Presenting signs of nasopharyngeal polyps may vary depending on location. Inspiratory stertor is commonly found due to the fleshy mass just dorsal to the soft palate causing obstruction of the nasal passages. Stertorous breathing in cats should alert the clinician to a mass lesion in the nasopharynx since other causes, such as elongated soft palate, are uncommon in cats.

Signs of otitis media, such as Horner’s syndrome, head tilt, and pain may also be seen. (Fig. 1) 

Fig. 1: Right sided Horner's syndrome seen in a kitten with a
NP polyp. 

Polyps in the external ear canal can result in or be secondary to otitis externa causing head shaking, ear scratching, and malodorous otic discharge.

Diagnosis

A thorough oral examination should be performed. Sedation will probably be necessary since the polyp will likely be obscured by the soft palate. If the mass is large enough simple palpation of the soft palate with a finger may indicate a mass effect. Retraction of the soft palate with stay sutures or a spay hook, with the cat in dorsal recumbency, should expose the mass. (Fig. 2)

Fig. 2: NP polyp in a cat (arrow) adjacent to the soft palate (SP) The cat is in
dorsal recumbency.

Otoscopic examination should also be performed to look for extensions of polyps into the external ear canal. Cleaning of otic discharge and debris may be necessary to adequately expose the mass.

Differential diagnoses for nasopharyngeal polyps are lymphosarcoma, other types of  neoplasia, foreign body, or congenital anomaly of the pharynx or upper airway. In one study of nasopharyngeal disorders in 53 cats 49% of them were diagnosed with lymphosarcoma and  28% were diagnosed as polyps.(1)

Imaging

Skull radiographs with emphasis on the tympanic bulla may provide useful information. Affected cats may show radiographic signs of chronic otitis media such as bony proliferation of the bulla and increased soft tissue density within the bulla.(Fig. 3)

Fig. 3: Bony proliferation of the bulla (arrow) secondary to
a nasopharyngeal polyp in a cat.

However, radiographs of the bullae are not a very sensitive imaging test and significant changes may be present with normal appearing bullae on films.

CT scans are a more sensitive and diagnostic imaging modality for bulla disorders and are useful in cats with nasopharyngeal polyps or other bulla diseases. Increased soft tissue density is commonly seen in one or both bullae. (Fig. 4)

Fig. 4: CT scan of a cat with a NP polyp showing increased soft tissue density
within the bulla. (arrow)

In cases of severe infection or invasive neoplasia, lysis of the bulla may be seen. These findings are useful for preoperative evaluation of cats undergoing ventral bulla osteotomy, a recommended surgery for cats with nasopharyngeal polyps or other chronic middle or external ear disease.

Treatment

Traction

Surgical removal of the polyps is the most effective means of relieving clinical signs. Under general anesthesia the cat is placed in dorsal recumbency and a mouth speculum placed to allow exposure of the oral cavity and pharynx. The soft palate is retracted rostrally with either stay sutures or a spay hook. Gentle manipulation of this tissue is important since it is sensitive and prone to edema with manipulation.  Even under anesthesia many cats will exhibit discomfort while the soft palate is being manipulated. Once the polyp is exposed, grasp it with either stay sutures or Allis tissue forceps.(Fig. 5) Gentle but firm rostral and ventral traction is placed on the polyp and continued until the mass is removed. 

Fig. 5: NP polyp (arrow) being removed by traction.

The tissue frequently has a large round component that is connected to a tail that is the Eustachian tube portion of the polyp. Control hemorrhage with direct pressure on the affected pharyngeal tissues.

Bulla Osteotomy

To completely remove the polyp tissues, ventral bulla osteotomy is then performed. Which side to operate depends on the preoperative imaging or lateralizing clinical signs. If lateralization was not possible or if changes are seen bilaterally on imaging, both bullae are ostetomized to be sure of removing all remaining polyp tissues. Although most polyps are unilateral, the author recently treated a cat with bilateral polyps requiring osteotomy of both bullae.

Small fragments of polyp tissue are usually found in the tympanic bullae exposed by the ventral bulla osteotomy. (Fig. 6-7)

Fig. 6: Diagram of a ventral bulla osteotomy in a cat. Rongeurs are used to
remove the ventral aspect of the bulla and expose both compartments.
from: Boothe H. Surgery for otitis media and otitis internal.
From: Saunders Manual of Small Animal Practice3rd ed., Birchard and Sherding, editors. Elsevier, 2006, pg. 601.

Fig. 7: Bulla osteotomy in a cat with NP polyps. The ventral floor of the
bulla has been removed. Note the polypoid tissue filling the bulla cavity. (arrow)

It is important to expose both compartments of the bulla when performing the osteotomy (ventral-medial and dorso-lateral chambers). Care is taken not to injure components of the inner ear, located dorsally in the bulla, when doing polyp excision and curretage.  Save all tissues removed for histopathology and obtain samples from the bulla for culture and sensitivity.

Postoperative Care and Complications

Routine supportive care including analgesics and antibiotics are administered postoperatively. Antibiotic choice is guided by results of culture and sensitivity of samples obtained from the bullae.

Common complications after polyp removal are pharyngeal swelling and Horner’s syndrome due to injury to sympathetic nerves in the middle ear. Both of these problems are usually mild, short term in duration, and not requiring treatment. Recurrence of polyps is more likely if only the nasopharyngeal portion is removed. In a clinical study of 31 cats with nasopharyngeal polyps, 5 recurred postoperatively, 4 of which did not have a bulla osteotomy. (2)

References

1. HS Allen, J Broussard, and K Noone (1999) Nasopharyngeal diseases in cats: a retrospective study of 53 cases (1991-1998). Journal of the American Animal Hospital Association: November/December 1999, Vol. 35, No. 6, pp. 457-461. 
2. Kapatkin, AS, Matthiesen, DT, Noone KE. et.al. Results of surgery and long-term follow-up in 31 cats with nasopharyngeal polyps. J Am An Hosp Assoc 1990 Vol 26 No 4 pp. 387-392.