Information produced by Clare Rusbridge, Stone Lion Veterinary Group

Recently a feline facial pain / mutilation syndrome has been recognised which is especially prevalent in Burmese cats although occasional cases have been seen in the domestic shorthair, Burmilla and Siamese. Orofacial pain disorders such as trigeminal neuralgia are well described in humans and FOPS shows some similarities to these. The trigeminal nerve conveys sensory information, e.g. pain and touch, about the face and mouth to the brain. Trigeminal neuralgia is characterised by severe pain in the distribution of the trigeminal nerve, usually the jaw. 1 The pain is precipitated by trigger factors of which the most common is facial movement e.g. chewing. For trigeminal neuralgia to occur it is proposed that there is a combination of  two factors 1) damage/sensitisation of the ending of the trigeminal nerves, e.g. by dental disease and 2) dysfunction of processing of sensory trigeminal information within the brain.
A more unusual human facial pain syndrome, part of the spectrum of trigeminal neuralgia, is glossodynia (burning mouth syndrome). 2 This is described as a burning or prickling sensation of the oral mucosa, most commonly at the front of the tongue. 3 In many of the affected cats, tongue discomfort seems to be the primary problem and it is not unusual for the initial presentation to be to an emergency clinic with acute onset severe tongue mutilation.
Many of the affected Burmese cats are closely related and this raises the question of a hereditary susceptibility. It is possible that these cats have an inherited disorder of central trigeminal apparatus processing. They subsequently acquire a peripheral lesion such as dental disease and FOPS develops. A familial trigeminal neuralgia is also recognised (rarely) in humans 4,5,6.

Clinical signs and course
The clinical signs are characterised by exaggerated licking and chewing movements, with pawing at the mouth. Typically the discomfort is unilateral or worse on one side and can be episodic or continuous. In the episodic version the distress often occurs after eating or grooming and lasts between 5 minutes and 2 hours. There is often a short period of anxiety preceding the episode. The activity is not suggestive of a seizure; the cat remains alert and can be distracted, although with considerable difficulty in some cases. Some cats have continuous discomfort that increases in intensity when excited or stressed. These cats are often anorexic and in considerable distress, requiring paw bandaging and /or an Elizabethan collar to prevent severe mutilation. Some cases appear to be associated with oral disease, which can be divided into 4 groups

1. Mouth ulceration, especially as a consequence of Calici virus infection or primary vaccination
2. Cutting permanent teeth
3. Dental disease, most commonly periodontal disease and dental resorptive lesions.
4. Recent routine dental treatment including extraction.

Treatment of, or natural resolution of the mouth lesions can result in improvement, however many cases have recurrences which can be more difficult to successfully treat. In the kittens the problem resolves when the mouth ulceration/teething does, however these cats may have a recurrence when adult.  Other possible influences include stress, either from systemic disease, pregnancy, or environmental factors e.g. a multi-cat household. Spontaneous remission and recurrence is common.

Diagnosis
Diagnostic work up of affected cats includes ruling out predisposing medical problems, especially dental disease. Specialist opinion and good quality dental radiographs are recommended. Dental resorptive lesions are one of the more common associated diseases and poor dental treatment resulting in retained roots can aggravate the problem. It is also important to explore the history for possible psychological factors, e.g. stress from multi-cat household, and implement appropriate management. Neurological examination, MRI and CSF analysis are normal in cases of FOPS however these tests are useful to rule out other causes of trigeminal disease.

Treatment
Any dental disease should be treated however bearing in mind that as dental work can aggravate this condition it is worth considering referral to a veterinary dentist. Medical treatment is dependant on the underlying disease, if there is one. Some cases with gingivitis have appeared to respond to antibiotics, although spontaneous remission could not be ruled out. Non-steroidal anti-inflammatory drugs (NSAIDs) such as Metacam (not licensed in the cat) are effective analgesia for some mildly affected cases. Opioids e.g. Buprenorphine (Vetergesic) can be useful for hospitalised cases; however anti-epileptic drugs (diazepam, phenobarbitone or carbamazepine) give the most sustained and consistent relief. Phenobarbitone (dose rate 2-3mg/kg every 12 hours) is the preferred drug because of the greater risk of idiosyncratic liver failure with diazepam. Occasionally life-long therapy is required. A serum phenobarbitone concentration should be assessed two weeks after initiating the drug. Most cats require a serum concentration of 20-25mg/l (100-120μmol/l) to control episodes. The dose of phenobarbitone should be adjusted as appropriate. All cats receiving phenobarbitone should have liver function assessed at least every 12 months. The human anti-epileptic drug carbamazepine has also been used clinically and experimentally, however no long term studies on the pharmacokinetics or safety have been done. It is available as a 100mg/5ml solution and is used at a dose rate of 25mg every 12 hours. Regular monitoring of haematology is advised as this drug’s main adverse effect in humans is haematological. None of the anti-epileptic drugs are licensed for use in the cat and owners should be made aware of the risks and sign an appropriate disclaimer.
For those with a behavioural component or contributing stressful environment then alternations to the environment (e.g. own litter tray, feeding area and private space) are essential in addition to behavioural modification. Use of pheromone diffusers (e.g. Feliway) may be useful. Finally, drugs such as selegiline may be effective however this should always be used in combination with alterations to the environment and application of behavioural modification.

Breeding advice and DNA collection program
Studies on hereditability have not been performed however an autosomal recessive inheritance would fit with the limited data that is currently available. An autosomal recessive inheritance would mean that that both Tom and Queen of an affected cat either have or carry the condition. Because environmental factors, such as dental disease and stress, influence the disease not every animal with an affected genotype will necessary have clinical signs. In addition the signs of the disease might occur after the animal has been breed.  This makes it particularly difficult for a breeder to select disease free stock and consequently a DNA collection programme has been established in collaboration with the DNA archive for Companion Animals, Manchester (see links below). It is hoped that ultimately the disease gene can be identified enabling easy screening for potential breeding stock. In the meantime breeders are advised not to use any cat which has had signs of the disease even if the signs are not persistent. It would also be wise not to use the Tom and Queen of affected cats, especially the Tom as his genetic influence can be so far reaching.

References