Meningoencephalitis

Non- infectious meningoencephalitis (ME) is a common neurological condition in dogs which may lead to inflammation of the brain and spinal cord.

Meningoencephalitis of unknown origin (MUO) has several different subtypes depending on the type of inflammatory cell involved. It is the most common type of ME in dogs, and a diagnosis is made by eliminating infectious causes by examining the cerebrospinal fluid (CSF - the fluid that surrounds and protects the brain and spinal cord). A thorough neurological examination and CT or MRI scan also be helpful.

It is most common in young to middle aged toy breeds, but dogs of all ages and breeds can be affected. Clinical signs appear rapidly and are progressive, they include a head tilt, circling, loss of balance, seizures and blindness depending on the part of the brain that is affected.

Your vet will want to start with blood tests to rule out toxicity or metabolic disease such as diabetes or a liver problem. In MUO these tests will be normal. Further blood tests can be taken to rule out some parasitic causes (thankfully these are rare in the UK).

If your vet suspects MUO then they will recommend an MRI scan - a normal scan does not fully rule out MUO, but it is useful to exclude brain tumours. Analysis of CSF will often show increased protein levels and inflammatory cells and can be cultured to rule out a bacterial infection.

MUO is treated with immunosuppressive medications. Steroids are the most common drug used and are given at a slowly reducing dose over the course of several months. Dogs that receive treatment early in the condition and respond rapidly have much better long-term outcomes.

If the dog has not responded to treatment within a week, then prognosis is much poorer.