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
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
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