In human medicine, specialist clinicians deal exclusively with the diagnosis and treatment of diseases of the ears, nose and throat (E.N.T.). In veterinary medicine, such specialisation is rare, although individuals such as Dr Anjop Venker-van Haagen have started to develop E.N.T. medicine and surgery to such an extent that it is beginning to become a veterinary discipline in its own right. This talk is given from my perspective, a veterinarian mainly interested in cats, who has been forced to better understand diseases affecting the ear, nose, throat and oral cavity to best treat the patients under my care.
Diseases affecting these anatomical areas is commonplace in feline practice. The investigation of most cases requires equipment available in the majority of small animal clinics, although in some cases the availability of rigid and flexible endoscopes for examination of the external ear canal and nasopharynx facilitates investigations considerably. In the future, use of cross-sectional imaging modalities such as computer-assisted tomography (CT) and magnetic resonance imaging (MRI) is likely to contribute extra information concerning diseases affecting these anatomical areas.
Diseases affecting the pinna, external ear canal and middle ear
The pinna can be affected by diseases processes which affect the skin generally. Thus, lacerations are common in cats that fight, and ultraviolet-induced solar dermatitis typically results in the development of squamous cell carcinoma (SCC) in cats with non-pigmented (white or ginger) ears that spend a lot of time outdoors. Cats occasionally develop aural haematomas, usually as a result of irritation affecting the ear canal that results in scratching. Harvest mite infestations can cause severe irritation of the head and ears of cats; the diagnosis is easily made by identification of orange or yellow lesions on the ears of affected cats. Smears of these coloured lesions demonstrate the large, orange/yellow mites. We have also seen a small number of cats with sarcoptic mange affecting the skin of the pinna or the external ear canal; in these cases mites were extremely abundant, as in Norwegian scabies of human patients.
As a rule, otitis externa is less common in cats that dogs. However, young cats, outdoor cats and cats that live in colonies are commonly afflicted with Otodectes cyanotis, which results in a irritant/allergic otitis externa. A crusty black discharge is said to be characteristic, but a similar discharge can occur with other diseases of the external canal. All cats with otitis externa should be suspected of having ear mites until proven otherwise and the availability of modern, safe and effective products makes it worthwhile to treat tentatively for this disease even when mites are not detected. Direct visualisation of mites is facilitated by the use of a video otoscope, which provides both excellent illumination, magnification and a good depth of field. Material should also be obtained from the ear canal for cytological examination, as some mites or eggs can be seen in smears when adult mites have been missed using otoscopy. Mites are large, pearly white, very active and are said to 'run away' from the light source, although this is not my experience. A variety of modern treatments are now available for treating Otodectes infections e.g., friponil, ivermectin, milbemycin and selamectin. It is important to treat the whole cat, not just the ear canal, to repeat the treatment after three weeks, and to treat in-contact cats and dogs.
Occasionally, Demodex catii can cause parasitic otitis externa in cats. The diagnosis is made by microscopic examination of smears from the lining of the ear canal. Usually these cats have some underlying cause for immunosuppression, for example corticosteroid therapy or FIV infection. Treatment using topical or systemic therapy is generally successful. Bacterial otitis is rare in cats, but does occur, and should be treated using a combination of systemic and topical therapy. Systemic therapy is often easier in cats with irritated ears that otic therapy, and this is not cost-prohibitive as in larger canine patients. Occasional cats with allergic dermatitis get otitis externa as a component of their atopy or food allergy/intolerance, and treatment should be directed at the underlying allergic condition as well as the irritated ear canal.
Proliferative lesions can sometimes be observed in the ear canal of cats. Polyps, arising from the middle ear cavity or external ear canal, can occur in cats of all ages. When removed together with their stalk, these polyps may be cured using simple traction. If a pedicle is left behind, however, the problem usually recurs, necessitating more invasive surgical interventions in order to effect a permanent resolution. In older cats, ceruminous gland carcinomas can develop in the external ear canal. This malignancy can be cured by timely ablation of the entire horizontal and vertical ear canal. Invasive squamous cell carcinoma can occur in the ear canal of elderly cats. In my limited experience, this cancer already has invaded tissues outside the ear canal by the time diagnosis is made using cytology and three-dimensional imaging.
Otitis media is not-uncommon in cats, and typically results from an ascending infection up the auditory tube from the nasopharynx. Less frequently it occurs secondary to parasitic or bacterial otitis externa. Cats with middle ear infections develop signs of peripheral vestibular disease, either unilateral or bilateral. Sometimes Horner's syndrome is present also. The diagnosis is often tentative, based on characteristic clinical signs and response to therapy. In some cases, radiographs of the tympanic bullae or CT of the head is used to confirm the anatomical diagnosis. Material for culture is sometimes obtained via myringotomy or via operative bulla osteotomy. Typically, otitis media is the result of bacterial infection with organisms that normally reside in the nasopharynx, such as Pasteurella species and obligate anaerobes. Acute cases often respond to a two to four week course of clindamycin, doxycycline or amoxicillin/clavulanate. Some cases, however, require surgical drainage, through a bulla osteotomy or the external ear canal (via a myringotomy), to effect a cure. We have seen a very small number of cats where otitis media, and sometimes concurrent otitis externa, is referable to cryptococcosis.
Disease of the nasal cavity, choane and nasopharynx
In young cats, viral upper respiratory tract infections are the most common cause of nasal cavity disease. Although these infections are generally self-limiting, the author recommends prophylactic therapy using doxycycline or clindamycin to prevent adverse sequelae such as pyothorax, ascending infections of the auditory tube and chronic rhinosinusitis. Recent work suggests that interferon-omega may be useful in these cases, however it is virtually cost-prohibitive at present to recommend routine use for this purpose.
By far and away the most common disease of the nasal cavity of adult cats is post-viral rhinosinusitis (synonyms: snuffler cat, snuffles, etc). This a chronic disease condition thought to occur as a sequelae of Herpesvirus or Calicivirus infection of the nasal passages, which result in extensive destruction of turbinates, leading to residual foci of infection with secondary bacterial pathogens. These cats are presented for chronic nasal discharge, sneezing and epiphora. Severe cases may also show lassitude and inappetence. Such cases are diagnosed on the basis of a history of presumptive viral respiratory tract disease and results of endoscopic, cytologic and three dimensional imaging studies. There are no definitive diagnostic features, and usually the diagnosis is reached by excluding other differentials such as cryptococcosis, foreign bodies (e.g., grass awns, projectiles) and neoplasia. Some cases can be cured by long courses of antimicrobial therapy. Because anaerobic bacteria are likely secondary invaders in many cases, clindamycin, at an anti-anaerobic dose given for at least eight-weeks, can be curative. Such long courses are only indicated if there is an initial and sustained response to therapy. The rationale of continuing therapy for such a long time is based on the notion that the infection is a deep-seated osteomyelitis/chondritis. Many cases respond to antibiotics, but relapse during or after a long course of therapy. Some of these cases may respond to major surgical interventions e.g., radical turbinectomy via a ventral rhinotomy, or implantation of antibiotic-impregnated bone cement into the frontal sinuses. Large series of surgically managed cases have not been published, however, suggesting that surgery may help in some cases, but not others. Many cats are not severely affected, and owners often elect to ignore the problem or dose affected cats with antimicrobials intermittently, as required.
Mycotic rhinitis occurs in the cat, but unlike the equivalent group of infections in dogs, aspergillosis is rare while cryptococcosis is reasonably common. Cats with cryptococcosis present for signs of rhinitis such as sneezing, nasal discharge and epistaxis. Sometimes the mucosa within the naris is swollen, or there is a polypoid mass protruding from the nostril(s). Some strains of Cryptococcus are invasive, and give rise to deforming disease of nearby structures, such as the nasal planum, bridge of the nose, hard palate, tooth roots, while in other cases there is involvement of the regional lymph node(s). Diagnosis is readily made by cytology of nasal discharges or aspirates from swellings, and confirmed by culture on bird seed agar or using the cryptococcal antigen agglutination test. Most cases of localised nasal cryptococcosis can be cured using monotherapy with itraconazole or fluconazole. Severe or refractory cases benefit from combination therapy using amphotericin B and flucytosine, with follow-up azole therapy. In contrast to canine aspergillosis, nasal aspergillosis in the cat is invariably an invasive disease, with the propensity to penetrate the overlying bones and give rise to disease of nearby structures e.g., the retrobulbar space, nasal bridge. Topical therapy (such as used in the dog) is inappropriate for such infections, which instead require treatment with itraconazole and sometimes amphotericin B.
Nasal neoplasia gives rise to progressive signs of nasal cavity disease, often with extension of the malignancy to adjacent structures, such as the bridge of the nose, the retrobulbar tissues or the olfactory lobes of the brain. In our practice, lymphosarcoma is the most common nasal malignancy, followed by squamous cell carcinoma, adenocarcinoma and tumours arising from bone or cartilage. Of these diseases, lymphoma has the best prognosis as perhaps 50% of cases (or more) attain durable remissions with multi-agent chemotherapy, and indeed some can be cured. Squamous cell carcinoma is amenable to radiotherapy and some cases partially respond to carboplatinum. Bone and cartilage tumours may be treated using sumarium.
In some cats with nasal cavity disease, there is preferential involvement of the caudal portion of the nasal cavity, the choane or the nasopharynx. These animals usually do not have nasal discharge, epistaxis or sneezing. Instead, they have signs of stertor, snoring or halitosis and in extreme circumstances they learn to breathe through their mouth. A variety of disease processes can cause these signs. Lymphosarcoma and cryptococcosis sometimes present in this fashion. On physical examination, a mass in the nasopharyngeal region can sometimes be palpated through the soft palate (typically under sedation or anaesthesia), and a needle aspirate through the palate can be diagnostic. Such masses are readily visualised using a flexible endoscope retroflexed behind the soft palate. Alternately, a vigorous nasal flushing technique often dislodges a large portion of the offending mass, which can then be submitted for laboratory investigations and histopathology. Other disease processes which can involve the nasopharynx include blades of grass (which get caught behind the soft palate after being vomited), grass awns, polyps arising from the opening of the auditory tube, webs of scar tissue resulting from previous viral infection (giving rise to nasopharyngeal stenosis). Foreign material can often be dislodged by flushing using a 10 mL syringe tightly wedged in one nostril or removed using a retroflexed endoscope. Counter intuitively, flushing through the least obstructed nostril is often most effective in dislodging mass lesion(s) or foreign material. It is our experience that nasopharyngeal polyps do not recur if they are removed with a substantial amount of 'stalk', and if antibiotics are given for two-weeks following the procedure. Recurrent nasopharyngeal polyps generally requires bulla osteotomy as well as polyp removal to effect a cure. Be warned, some cats have bilateral polyps, and other have bifid polyps with a components in both the nasopharynx and the ipsilateral external ear canal.
Disease of the oral cavity and pharynx
Disease of the oral cavity is common, however many lesions are missed merely because clinicians sometimes do not take the time to properly inspect every cat's mouth during routine physical examination. This is a sin I have been guilt of. Feline dentistry is beyond the scope of the present talk, however it is important to emphasise that periodontal disease is one of the most important preventable causes of disease in domestic cats and that feeding fresh raw chicken wings, lamb shanks and other 'raw meaty bones' on a regular basis is critical to the overall health of cats.
Chronic Calicivirus infection gives rise to refractory disease of the gums and fauces. In these patients, there is sufficient antibody-mediated response to virus to produce all the classic signs of inflammation, however there is insufficient cell-mediated immunity to throw off the virus and thereby eliminate the chronic carrier state. Up until recently, treatment had involved radical extraction of molar and premolars, antibiotics such as doxycycline, metronidazole or clindamycin and (when necessary) the minimal anti-inflammatory dose of corticosteroids required to dampen down the inflammation. Recent work, however, suggests that some of these cats can be cured using feline interferon-omega, or thalidomide, and these treatments can be supplemented by local administration of topical agents such as Bonjela. The natural product slippery elm has also been used with benefit in some of these cases.
Feline resorptive lesions are an important cause of tooth and gum disease in cats, and the associated pain can cause teeth chattering, reduced appetite and weight loss in some patients. The cause of these lesions is controversial, however the requirement for extraction of affected teeth is not in doubt. It should be emphasised that recent information suggests that there is no need to remove the tips of tooth roots that snap-off during attempted removal of affected teeth, as these are resorbed spontaneously.
Intraoral collagenolytic granulomas are a bizarre feline manifestation of allergic disease. They may be either proliferative, or ulcerative, and are typically situated on the tongue or palate, although they can appear in any lesion within the oral cavity. I have seen one cat with a large lesion arising from the pharynx, which also had involvement of the larynx. A very characteristic feature is the presence of yellow or white foci within the larger lesion, these areas corresponding to microscopic areas of lytic collagen, and the presence of such foci is virtually diagnostic of this aetiology. Often 'rodent ulcers' or miliary dermatitis are present concurrently. Ideally, these cases should be treated by finding and eliminating the underlying cause of the hypersensitivity reaction, e.g., fleas in cases where flea antigens are the underlying immunologic trigger. When this is not possible, monotherapy using a six to eight week course of cyclosporine is successful in many cases, and has less side effects than older treatments regimens such as prednisolone/chlorambucil. In patients with proliferative lesions, preliminary debulking using a scalpel can be very helpful also.
'Menrath's ulcer' (synonym: bleeding palatine ulcer) refers to a unusual syndrome in which, for some reason, cats with allergic skin disease develop life-threatening bleeding from an ulcer on the palate immediately adjacent to the upper canine tooth. It is thought that over grooming associated with pruritic skin disease somehow results in the papillae on the tongue abrading the hard palate until a branch of the palatine artery is eroded. When this occurs, significant haemorrhage results, however because the cat continues to lick the ulcer and therefore potentiate the haemorrhage. Because the blood emanating from the bleeding ulcer is swallowed, the owner (and veterinarian!) may not appreciate the cause of the bleeding until the cat is almost dead. By this stage, a typed blood transfusion may be required to save the patient. On-going haemorrhage is best controlled by placing a horizontal mattress or cruciate stitch (using deep bites) across the ulcer so that ensuing pressure stops the haemorrhage. The ulcer can be hard to appreciate when the gums are very pale as a result of hypovolaemic shock and anaemia; for this reason, a thorough oral cavity examination is mandatory in all cats presented for severe (and typically acute) anaemia. To prevent this problem recurring in the future, efforts of the clinician should be directed towards treatment of the underlying skin disease e.g., using flea control, hypoallergenic diets, antihistamines, corticosteroids or cyclosporine, as appropriate.
The tongue can be affected by a variety of disease processes, and experienced feline clinicians routinely elevate the tongue using digital pressure in the intermandibular space to facilitate examination of the frenulum. Doing this routinely will ensure that linear foreign bodies caught around the lingual frenulum will never be missed! Squamous cell carcinoma (SCC) is the worse disease process which can affect the tongue, and typically affects its base. However, inflammatory diseases resembling lingual SCC have been encountered by the author. These lesions, which may result from secondary infection following penetration by foreign bodies, have responded promptly to debulking (biopsy) and antimicrobial therapy. We have been surprised recently to have diagnosed lingual lymphoma (rather than SCC) in a cat with a grossly abnormal tongue; this patient responded favourably to multi-agent chemotherapy.
Finally, tonsils should be examined during routine oral cavity examination. Tonsillar SCC occurs in the cat, although most cases the author has diagnosed have been presented for unilateral mandibular lymphadenomegaly. The cause of metastatic disease was not apparent until the oral cavity was examined.