09/08/2026
What is inflammatory brain disease in dogs? Although dogs occasionally get infectious brain disorders, most cases are non-infectious, suspected autoimmune diseases. There are a variety of terms for these disorders, with some overlapping of these terms (which often causes confusion). The medical term for brain inflammation is encephalitis, and for meningeal (the covering of the brain and spinal cord) inflammation the term is meningitis. Usually, there is concurrent meningitis and encephalitis, and the term meningoencephalitis is used. The specific names for some of these disorders include GME (granulomatous meningoencephalitis), NE (necrotizing encephalitis), NLE (necrotizing leukoencephalitis), and MUE/MUO (meningoencephalitis of unknown etiology/origin). MUE/MUO is considered somewhat of an “umbrella” term that refers to all subtypes of non-infectious, inflammatory brain disease.
These disorders are most encountered in young to middle-aged small breed dogs with a female predominance, although they can occur in older dogs of any breed or size. Onset of clinical signs is usually rapid, and patients often worsen quickly once signs appear. Most dogs have multifocal brain lesions, rather than one area of the brain being affected. Balance problems are very common (head tilt, falling over, wobbly gait); other signs may include behavior change, loss of vision, seizure activity, and acting painful (particularly around the head/neck).
Diagnosis of these various disorders is based on clinical features combined with MRI and cerebrospinal fluid (CSF results). On MRI, bright areas in the brain tissue on certain sequences are commonly seen and they often enhance with a contrast agent. The first image is a normal brain; the second image depicts multiple bright spots in the diencephalon, consistent with inflammatory brain disease. The CSF usually reveals high white blood cell (WBC-inflammatory cells) and increased protein levels.
There are different opinions among veterinary neurologists on the “best” way to treat these dogs. What is universally accepted as standard therapy is administration of glucocorticoids (e.g., prednisone) as soon as possible. Of all the immunosuppressive drugs available to treat these patients, glucocorticoids have the fastest onset of action. They also have the most obvious side effects (drinking and urinating excessively, increased appetite and weight gain, panting). There are several other drugs that have little to no obvious side effects that can eventually allow significant reduction of the glucocorticoid dose (with resulting decrease in steroid-related side effects). These drugs include cyclosporine, azathioprine, procarbazine, mycophenolate, leflunomide, and cytosine arabinoside (injectable).
These are generally considered very serious conditions. Many affected dogs will do well for years with appropriate medication. However, the mortality in the first 1-2 weeks of diagnosis is quite high (over 20%). This may reflect more seriously affected patients, a delay in institution of therapy, or some combination of these factors. It is important for pet owners and veterinary professionals to maintain a high index of suspicion for these disorders, especially if the dog breed (small breed dogs mainly), age (young to middle-aged) and clinical features (rapid onset and progression of brain dysfunction) are consistent with inflammatory brain disease.
