Necrotizing Meningoencephalitis in Dogs

Though the cause of the disease is unknown, necrotizing meningoencephalitis (NME) was first recognized in the United States during the 1970’s. Initially, the disease was noticed only in pugs and was known as pug dog encephalitis. The disease has been recognized in other small breeds of dogs since 1989 and can occur in either sex.

Necrotizing meningoencephalitis has a typical anatomic distribution pattern as well as histological lesions that are different than those seen in other canine inflammatory conditions of the brain with known causes. In necrotizing meningoencephalitis, lesions are very inflammatory with meningitis. Typically, there are a minimal amount of inflammatory lesions located in the cerebellum, brainstem and spinal cord.

Necrotizing meningoencephalitis (NME) is an inflammatory disease of the central nervous system, typically with both a rapid onset and progression leading to death in dogs within a few months.

Dogs that are suffering from necrotizing meningoencephalitis will show variable symptoms that are dependent upon the part of their brain that is affected. In cases where your dog’s forebrain is impacted, symptoms may include seizures, blindness, circling, abnormal mentation and behavior changes. If the brainstem of your dog is affected, the following might be observed: changes in mentation, trouble walking and cranial nerve deficits. Other possible symptoms that may be noted in your dog include cervical pain, fever, head tilt, deafness, falling, paralysis in his face, trouble swallowing and weakness in his limbs.

• Seizures
• Blindness
• Circling
• Abnormal mentation
• Behavior changes
• Difficulty walking
• Back pain
• Fever
• Head tilt
• Falling
• Facial paralysis
• Difficulty swallowing
• Limb weakness

Types 

The forebrain is the part of the brain that is most often affected in necrotizing meningoencephalitis. Lesions in this part of the brain are what are responsible for seizures, blindness and a change in your dog’s mental status.

Involvement in the inflammation in the meninges of the brain causes cervical rigidity, pain, and fever.

Should the lesions be in the brainstem, your dog may experience head tilt, falling, deafness, facial paralysis, weakness in the muscles that are used for swallowing and paralysis of his limbs.

The cause of this disease is not known. The disease is known to develop in small dog breeds to include the following:

• Pug
• Maltese
• Chihuahua
• Pekingese
• Boston terrier
• Shih Tzu
• Coton du Tulear
• Papillon

Should you notice that something is not right with your dog, it is important to make an appointment to see your veterinarian, who will conduct a complete physical examination. Your veterinarian will also ask you for information regarding what symptoms you have noticed, when you first noticed them, and any changes in the symptoms that you have observed. In addition, if this is not your regular veterinarian, he will ask questions in order to get a complete history of your dog. The following tests may be conducted:

• A complete blood count
• Serum chemistry analysis 
• Urinalysis 

Depending on the results, your veterinarian may then recommend an MRI, which is the most reliable way to diagnose necrotizing meningoencephalitis in a living animal. Should your dog have this condition, typical findings on the imaging will include asymmetric, bilateral lesions in his forebrain. There may also be cystic areas in the parts of the brain that are necrotic. Your veterinarian may also recommend a cerebrospinal fluid (CSF) tap and/or an electroencephalogram (EEG). A bacterial and viral culture of CSF and serological testing will allow your veterinarian to rule out other causes of brain inflammation and notice if there is any increase in nucleated cells and protein which can also point to necrotizing meningoencephalitis.

Should your dog develop necrotizing meningoencephalitis, treatment goals are typically to provide supportive care and minimize his symptoms, as the prognosis is poor even with aggressive treatment. Treatment options include:

• Anticonvulsants (for example phenobarbital) to treat seizures
• Corticosteroids (for example dexamethasone or prednisone) to suppress your dog’s immune system and prevent additional destruction
• Anti-inflammatory medication
• Chemotherapy
• Rest
• Ensuring nutrition and necessary fluid intake to help your dog fight the inflammation

The prognosis for dogs with necrotizing meningoencephalitis is poor; the majority of dogs with the disease die or are euthanized within six months of their symptoms first becoming apparent.

It will be important to follow the treatment recommendations of your veterinarian to best help your dog should he be diagnosed with necrotizing meningoencephalitis. Ensuring that your dog receives proper nutrition, gets plenty of rest, remains well hydrated and has minimal stress are the best ways to help him. While the prognosis for this condition is poor, working with your veterinarian will help you to make sure your dog has the best quality of life for as long as possible despite the condition.