Felipedia

Nasopharyngeal polyps

Cats with nasopharyngeal polyps usually present with nasal discharge, inspiratory dyspnoea and stridor, and have a chronic non-responsive otitis, head tilt and Horner's syndrome.

Nasopharyngeal polyps are thought to occur secondary to chronic upper respiratory tract inflammation as they consist of inflammatory tissue covered by epithelium. They are thought to arise from the Eustachian tube or bulla.

They are a relatively common cause of stridor and dyspnoea, and typically occur in young cats (average age 1.5 years), and most begin to exhibit signs before they are 1 year old. Abyssinians may be predisposed.

Chronic mucopurulent nasal discharge and congestion is common, but may be absent. Inspiratory noises, usually stridor, but sometimes stertor, along with dyspnoea and open-mouth breathing have been reported.

Signs of ear disease, including chronic discharge, head tilt and possibly Horner's syndrome on the affected side, may be present.

Diagnosis

Radiographs of CT may show a soft tissue mass lesion in the nasopharynx. Rhinoscopy and otoscopy are valuable in visualising the mass and obtaining biopsy material. The polyp may be visualised directly or with a dental mirror. The rostral soft palate may bulge down into the oral cavity with pressure from the polyp.

Differential diagnosis

Tracheitis from feline rhinotracheitis virus is generally associated with other upper respiratory signs. Laryngeal paralysis or oedema, tracheal foreign body, and tracheobronchial neoplasm can be differentiated endoscopically. Nasopharyngeal stenosis may have similar signs, and caudal rhinoscopy is required to distinguish this from polyp formation.

Treatment

Surgical extirpation is the therapy of choice. Removal of the nasopharyngeal polyp usually is easily accomplished while the cat is anesthetized by grasping with forceps and applying slow steady traction. During this task, the pedicle may be seen emerging from the eustachian tube. Postoperative haemorrhage into the nasopharynx is minimal and easily controlled by packing swabs into the nasopharynx for a few minutes. The polyp occasionally cannot be removed in this way without incising the free caudal border of the soft palate to improve access. The soft palate is closed in 2 layers using an absorbable material such as Vicryl. When a polyp is removed from the nasopharynx by traction, the pedicle usually is found to be 5 to 10 mm long, sufficient to indicate that the mass probably arose in the middle ear.

Controversy surrounds the issue of bulla osteotomy in cats with nasopharyngeal polyps. Ventral bulla osteotomy is associated with a high risk of complications. It has been argued therefore that when there is no radiographic evidence of middle ear disease, bulla osteotomy is unnecessary. However, when bulla osteotomy is not performed, recurrence of nasopharyngeal polyps is quite frequent; whereas, recurrence is rare if bulla osteotomy is performed. Therefore, some surgeons recommend that bulla osteotomy be performed on the ipsilateral middle ear of every cat with a nasopharyngeal polyp. Cats with unilateral nasopharyngeal polyps may have bilateral otitis media. Bilateral polyps have been reported.

Bulla osteotomy is performed utilizing a ventral approach with the cat in dorsal recumbency. The tympanic bulla can be palpated easily on the caudoventral skull as a bony blister lateral to the larynx and medial to the mandible. The skin and subcutis are incised; and using blunt dissection, the bulla is exposed. Avoid traumatizing the hypoglossal nerve and internal carotid artery. An osteotome or fine bone forceps is used to create a window in the tympanic bulla. This will open into the larger ventromedial and caudal compartment, exposing the septum that divides the middle ear. Creating an opening in the septum provides access to the smaller dorsolateral compartment which contains the ossicles. Care should be taken to avoid traumatizing the promontory. The dorsolateral compartment lies rostrally and is believed by most observers to be the site of origin of nasopharyngeal. The middle ear is then curetted, but with discretion to avoid damage to the ossicles, the inner ear, the tympanic membrane, and the various nerves that pass through this location . The smaller cavity usually contains dense granulation tissue, whereas the larger ventromedial compartment more frequently contains thick tenacious mucus. A drain may be placed in the bulla for a few days after surgery. Removal of polyps from the nasopharynx by traction alone often causes ipsilateral postoperative Horner's syndrome This observation suggests that the middle ear has been traumatized. Horner's syndrome usually resolves within I to 3 weeks. Other complications following removal of nasopharyngeal polyps by traction alone include abscess formation and cardiorespiratory arrest associated. with induction or recovery from anaesthesia in 2 cats. 1 One author has described removing nasopharyngeal polyps from 8 cats by severing the pedicle of the polyp at the nasopharyngeal ostium of the eustachian tube. Postoperative Horner's syndrome was not observed in these cases.

When bulla osteotomy has been performed in the treatment of nasopharyngeal polyps, temporary postoperative Horner's syndrome developed in the majority of cases. Ventral bulla osteotomy in cats has been associated with temporary or permanent vestibular signs, including head tilt, nystagmus, and ataxia. Infrequently, the facial nerve may be paralysed after surgery, leading to drooping of the lip, drooling of saliva, and lack of a palpebral reflex. This neuropathy resolves in most cases.