What is MUE?

*The information on this page has been compiled by dog owners, not veterinary professionals. It is intended as a general overview to help families understand what MUE is and ask better questions of their vet - not as a substitute for professional veterinary advice. If you suspect your dog may have MUE, please seek urgent care from a veterinary neurologist immediately.

MUE - Meningoencephalomyelitis of Unknown Etiology (also known as MUO Meningoencephalomyelitis of Unknown Origin) - is a serious, life-threatening immune-mediated disease in dogs that causes inflammation of the brain, spinal cord, or surrounding tissues. It is an umbrella term that covers several related conditions including GME (Granulomatous Meningoencephalitis), NME (Necrotising Meningoencephalitis) and NLE (Necrotising Leucoencephalitis), all of which involve the immune system attacking the central nervous system.

How is it different from SRMA? MUE is often confused with SRMA (Steroid Responsive Meningitis Arteritis), another inflammatory condition of the nervous system in dogs. The key difference is in the name - SRMA responds reliably and often fully to steroid treatment, with many dogs achieving complete recovery. MUE is far less predictable. While some dogs respond well to treatment, others do not, and the long term outlook is much harder to determine. Distinguishing between the two typically requires CSF analysis, as the cell types present in the spinal fluid differ between conditions. For more on SRMA and why we include it in our registry, see below.

Symptoms Clinical signs can include seizures, neck and back pain, behavioural changes, balance problems (ataxia), blindness, weakness and paralysis. Every dog presents differently, which is part of what makes MUE so difficult to recognise and diagnose - even for experienced professionals. In Theo's case, the first sign was yelping in pain when touched, which initially appeared minor.

Who gets it? MUE is most commonly seen in young to middle-aged female dogs and small breeds, though as Theo's story shows, it can affect any dog at any age. Certain breeds appear to be more predisposed, including Pugs, Maltese, Chihuahuas and Yorkshire Terriers, though cases have been reported across a wide range of breeds. Why some dogs develop MUE and others don't is still not fully understood - which is one of the central questions The Theo Project hopes to help answer.

Diagnosis There is no simple definitive test for MUE. Diagnosis is typically made by ruling out other causes through MRI and cerebrospinal fluid (CSF) analysis. Because MUE cannot always be confirmed during a dog's lifetime, many cases are referred to as "presumptive" MUE. This diagnostic uncertainty is one of the reasons collecting and sharing data is so critically important.

Treatment Treatment usually involves high-dose corticosteroids such as prednisone or prednisolone, often combined with other immunosuppressive drugs such as cyclosporine or cytarabine. The goal is to reduce inflammation and suppress the immune response. Treatment protocols vary depending on the individual dog, the severity of the condition and how they respond. Long term management, including careful weaning from medication, requires close monitoring by a veterinary neurologist.

What about Chiari-like malformation? Some dogs diagnosed with MUE are also found to have Chiari-like malformation - a structural condition where the skull is too small for the brain, causing the cerebellum to push into the spinal canal. This can cause its own set of symptoms and complications, and in some cases may be present alongside MUE. Theo was diagnosed with both, along with atlanto-occipital overlap and secondary cervical syringohydromyelia. How much each condition contributes to a dog's symptoms and prognosis is not always clear - again highlighting the need for more research and data.

Prognosis Prognosis is variable and often unpredictable. Some dogs achieve remission and go on to live full, happy lives. Others do not respond to treatment. The honest answer is that we simply do not have enough data to give families the clear picture they deserve. This is precisely why the data we are collecting matters.

What about SRMA?

Steroid Responsive Meningitis Arteritis - or SRMA - is another form of immune-mediated meningitis in dogs. While it is considered a distinct condition from MUE, it shares many of the same hallmarks: sudden and often dramatic onset, elevated white blood cells in the cerebrospinal fluid, and a response to immunosuppressive treatment, primarily steroids.

SRMA tends to affect younger dogs, often under two years old, and is more commonly seen in medium to large breeds such as Beagles, Bernese Mountain Dogs, Boxers and Golden Retrievers - though like MUE it can affect any breed. The most common presenting symptoms are severe neck pain, fever, lethargy and reluctance to move. Unlike some forms of MUE, SRMA generally carries a better prognosis, with many dogs achieving full remission - though relapses are common and some dogs require long term medication.

The Theo Project welcomes SRMA submissions alongside MUE, GME and related conditions. This is because we believe that understanding all forms of canine immune-mediated meningitis together - their similarities, their differences, their triggers and their outcomes - gives us the best chance of building a picture that is meaningful to researchers. The more data we have across the full spectrum of these conditions, the more powerful that data becomes.

If your dog has been diagnosed with SRMA, their story belongs here too.

Further Reading & Research

*The resources and links on this page are provided for informational purposes only. The Theo Project does not endorse any specific treatment, product or veterinary practice.

Clinical presentation, diagnostic findings and outcome in dogs diagnosed with presumptive spinal-only meningoencephalomyelitis of unknown originpubmed.ncbi.nlm.nih.gov/28267222/

Meningomyelitis in dogs: a retrospective review of 28 cases (1999 to 2007)pubmed.ncbi.nlm.nih.gov/18631217/

The research agrees with us

In 2023 a major review of 671 dogs diagnosed with MUE concluded that there is still no single treatment proven to be superior, that previous drug dosing may not have been optimal, and that the data needed to run proper clinical trials simply does not yet exist. The researchers themselves called for better data collection, more standardised recording of cases, and improved understanding of what triggers this disease.

In other words - the scientists agree. The data gap is real. And that is exactly what The Theo Project exists to fill.

Jeffery & Granger (2023) - New insights into the treatment of meningoencephalomyelitis of unknown origin since 2009: A review of 671 casespubmed.ncbi.nlm.nih.gov/37008358/

If you suspect your dog may have MUE, please seek urgent care from a veterinary neurologist.