A nasopharyngeal polyp is a pinkish-white mass of tissue that grows from the back of the throat, Eustachian tube (the small tube that drains the middle ear into the throat) or the middle ear itself. Inflammation of the lining of one of these areas causes the tissue to become thick. Sometimes the mass will actually grow into an organized, round or oval growth that hangs down into the airway at the back of the nasal cavity. The cause of polyps is unknown; however, it is suspected that cats develop them because of reaction to infectious agents such as respiratory viruses. While polyps are most commonly seen in cats, inflammatory polyps do occur in dogs. In dogs, they typically extend into the ear canal rather than into the back of the throat (nasopharynx).
Although nasopharyngeal polyps can occur in any age cat, they are often seen in young adult cats. At first the cats will have no clinical signs, unless drainage from the middle ear is blocked. When the polyp becomes large enough, cats may develop signs, such as:
- nasal discharge,
- voice change, and
- difficulty breathing (Figure 1).
If the middle ear drainage is blocked, or if the polyp grows up into the ear instead of the throat, cats and dogs will have signs of otitis externa (ear infection) with drainage from the ear, head shaking and changes in the shape of the pupils of their eyes.
Nasopharyngeal polyps can be seen (Figures 2 and 3) or felt under the soft palate, the muscular layer of tissue that separates the back of the nose and mouth.
If the polyp is large enough, it pushes the soft palate downward, interfering with swallowing. Most cats must be anesthetized before the back of the mouth can be examined thoroughly. If the polyp originates in the middle ear, your primary care veterinarian may see it in the ear canal below the ear drum (“tympanic membrane”) with an otoscope. Occasionally nasopharyngeal polyps are diagnosed by x-ray (Figure 4) or CT examination. CT scans will also help the veterinarian determine whether the polyp has extended into the middle ear.
Presurgical biopsy of a nasopharyngeal polyp is not generally performed, especially if it is causing significant airway or swallowing obstruction. Evaluation of a removed polyp may be recommended, especially in middle aged or older pets or from the ear canal, to ensure that it just a polyp and not another malignancy.
Nasopharyngeal polyps can be removed by gentle steady traction (pulling) on the mass (Figures 5 and 6).
Unfortunately, the base of the mass cannot be removed by traction in many patients, and the mass will regrow. Therefore, removal of the base of the mass through a ventral bulla osteotomy (opening up the bony middle ear) is often performed to ensure there is no recurrence. Your veterinarian may refer you and your cat to an ACVS board-certified veterinary surgeon for this procedure. Dogs and cats with involvement of the ear canal may be treated with total ear canal ablation procedure (see Otitis Externa).
Most cats recover rapidly from the surgery and need no special care.
Postoperative complications are common with ventral bulla osteotomy, but are usually temporary:
- Horners’s syndrome (see figure 8)
- Head tilt
- Balance problems
- Recurrence of the polyp (rare after ventral bulla osteotomy)
Several critical structures are found along the outside of, or within, the bony sac (“bulla”) that forms the middle ear (Figures 7 and 8).
The temporomandibular joint (TMJ), which is the hinge of the lower jaw, and the muscles of the base of the tongue, located near the bulla, can become swollen after the surgery, so cats may be reluctant to eat or swallow. The nerve to each side of the tongue also runs along the bulla. Within the bulla, some of the nerves to the eye cross along the inner wall. These nerves are often damaged when the polyp is pulled by traction or when a ventral bulla osteotomy is performed.
About 80% of cats develop Horner’s syndrome after the procedure because of nerve damage (Figure 8). In these cats, the third eyelid is elevated, covering the bottom half of the eye, and the pupils are different sizes. Horner’s syndrome is usually temporary and does not affect the cat’s behavior or function.
Since the opening to the inner ear is also found in the bulla, about 40% of cats will show some balance problems, particularly a head tilt, and they may be wobbly and have rapid uncontrolled movements of their eyes. This condition is also usually temporary, but can affect the cat’s well-being while it lasts. The lining of the bulla, which is the source of the polyp, must be removed to prevent the polyp from re-growing. Therefore, the veterinary surgeon has to find a balance between too much cleaning, which can result in the above complications, and not enough, which can result in recurrence of the original signs.
Patients who have had a ventral bulla osteotomy will be given pain medication at home after surgery. Antibiotic therapy after surgery may be recommended if concurrent infection is suspected.
Anti-inflammatory therapy is given in some patients topically (in the ear canal) or systemically with inflammatory polyps, especially if ventral bulla osteotomy is not pursued.
An Elizabethan collar (aka “the cone” or e-collar) may be recommended to protect the incision from scratching.
Soft food or syringe feeding may be needed for those with TMJ issues. Feeding tubes are rarely needed. If your cat is not eating at home after surgery, contact your surgeon or primary care veterinarian immediately for advice.
Recurrence is common after simple extraction of the polyp. Recurrence of the polyp is uncommon after ventral bulla osteotomy. Prognosis for recovery is excellent after ventral bulla osteotomy, even in cats that develop Horner’s syndrome or balance problems after surgery, since these signs usually resolve within a month.