What are the causes of inflammatory CNS disease?
Causes of inflammatory CNS disease can be either infectious or non-infectious. Infectious causes are probably the least common and can be due to viral (Distemper in dogs, feline-infectious peritonitis, FIV), bacterial, protozoal (Toxoplasma, Neospora) or fungal agents. Non-infectious causes are more common and include breed-specific disorders of Yorkshire terriers, Maltese, Pug as well as presumed immune-mediated disorder (granulomatous meningo-encephalitis also known as GME).

The later is probably the most common cause of inflammatory CNS disease in dogs. Why the immune system suddenly becomes 'over-excited' and decides to inflame the CNS remains a mater of speculation. Other rare non-infectious causes include pre- (inflammation that will turn into cancer with time) and para- (cancer outside of the nervous system having distant effect - in that case inflammation of the brain) neoplastic disorder.

What are the signs of inflammatory CNS disease?
The signs of inflammatory CNS disease vary according to which part of the CNS is inflamed (brain, spinal cord and/or meninges).

When meningitis occurs on its own, pain, stiffness of the gait, reluctance to move the neck and hunched-up back are the most common signs. Fever is only seen in less than half of the cases and its absence can therefore not be used to discard the possibility of meningitis. Encephalitis and myelitis are associated with neurological signs reflecting which part of the nervous system is inflamed.

How do you diagnose inflammatory CNS disease?
Unfortunately, the diagnosis of inflammatory CNS disease cannot be based solely on the clinical and/or neurological signs as other neurological condition (tumour, bleed) can potentially cause similar signs. Contrary to the common belief, even the most severe meningitis or encephalitis may not show up on any blood test.

Further tests such as CT-scanner or MRI can re-enforce the suspicion of inflammatory disease. Cerebrospinal fluid analysis (see fact sheet) collection is probably one of the most useful tests. Not only this can help to confirm the presence and type of inflammation but important test can be carried out to look for an infection. In rare occasion, cerebrospinal fluid can be normal despite the presence of an inflammatory CNS disease.

How can inflammatory CNS disease be treated?
Treatment of inflammatory CNS disease depends on the primary cause. In case of infectious cause, treatment consists mainly of antibiotic with the exception of fungal and viral causes. In case of non-infectious cause, treatment is based on trying to counteract the 'over-excitation' of the immune system by giving immuno-suppressing drugs. High dose of corticosteroids (prednisolone) is the mainstay treatment.

Other drugs such as azathioprine, cytarabine, mycophenolate, cyclosporin, cyclophosphamide can also be used in combination with corticosteroids. The short-term aim of the treatment is to return the animal to normal using high dose of medication. When this aim is achieved, the medium term aim is to slowly reduce the quantity of drug without the animal relapsing. The long-term aim is ideally to take the animal off any drug but more commonly to find the lowest dose of medication that will keep him/her free of signs. The main risk of using these drugs is to shutdown the bone marrow making the dog or the cat more prone to infection.

Can inflammatory CNS disease be cured?
In the majority of animal, inflammatory CNS disease can be controlled. This means that the animal can have a normal life but will need to remain on medication for many month even years. Unfortunately, a small number of animals with too severe inflammation may not improve despite aggressive treatment. Another small number of animals that returned to normal and were taken off medication can experience relapses months after.

If you are concerned about the health of your pet you should contact your veterinary surgeon.