Necrotizing Meningoencephalitis in Dogs

Overview of Canine Necrotizing Meningoencephalitis

Necrotizing meningoencephalitis is a sporadic, fatal, inflammatory disease of the central nervous system (CNS) that has been recently described in several small breed dogs. The pugs, Maltese, Pekingnese and Yorkshire terrier have been reported to be affected in Japan, Switzerland and the United States.

This disease appears to be similar to granulomatous meningoencephalomyelitis (GME) but has a different clinical course, clinical presentation, unique microscopic appearance at necropsy, and affects different breeds. The clinical course of necrotizing meningoencephalitis is typically very rapid in onset with a fatal progression within 2 to 3 months despite aggressive treatment.

The typical signs are severe seizures, blindness, depressed consciousness, cervical pain, fever and ataxia (difficulty in walking or an uncoordinated gait). Occasionally, dogs have experience head tilt, falling, rolling, deafness, facial paralysis, difficulty swallowing, quadraparesis (weakness in all four limbs), and quadraparalysis (inability to walk in all four limbs).

The histopathologic findings at necropsy include severe, non-suppurative leptomeningitis and extensive, multifocal, often cavitating necrosis of both gray and white matter of the brain, with evidence of inflammation.

The cause of necrotizing meningoencephalitis is unknown. This may be an autoimmune disease although viral participation or drug-related causes are possible. The age distribution in the pugs, Maltese and Yorkshire terrier is middle-aged with a range of six months to ten years.

The part of the brain that is most often affected is the forebrain, which accounts for the seizures, blindness and altered mental status. The cervical rigidity/pain and fever is usually due to involvement of the inflammation in the meninges. Vestibuloauditory signs (head tilt, falling, rolling and deafness), facial paralysis, swallowing weakness, quadraparesis and quadraparalysis reflect involvement in the brainstem.

What to Watch For

Signs of necrotizing meningoencephalitis in dogs may include:

• Seizures
• Blindness
• Altered mental status
• Cervical rigidity and pain
• Fever
• Head tilt, falling, rolling
• Deafness
• Facial paralysis
• Swallowing weakness
• Quadraparesis
• Quadraparalysis

Diagnosis of Necrotizing Meningoencephalitis in Dogs

The diagnosis of necrotizing meningoencephalitis requires histopathologic examination of affected CNS tissue, which is rarely practical in living dogs. The presumptive diagnosis of necrotizing meningoencephalitis may be made by signalment data (animal’s age, sex and breed), the onset and progression of the disease, clinical signs, neuroimaging and spinal fluid analysis. Your veterinarian will perform a complete physical and neurologic examination and may order some additional tests:

• Complete blood count
• Serum chemistry analysis
• Urinalysis

Depending on the results of the individual tests above, other test may be required and could include:

• Neuroimaging (CT, MRI or ultrasound). These modalities have been shown to be quite accurate in diagnosing necrotizing meningoencephalitis.
• Cerebrospinal fluid (CSF) tap has an inflammatory component with an increased protein although these results can easily be affected by the stage of the disease, the severity of the disease and drug administration.
• Electroencephalogram (EEG)
• Bacterial and viral culture of CSF will usually rule out other causes of encephalitides.
• Serological testing of the blood will help rule out infectious causes of encephalitides.

Treatment of Necrotizing Meningoencephalitis in Dogs

• The general goals of treatment are to provide supportive care and relieve symptoms. Anticonvulsants such as phenobarbital may be given to treat seizures. Corticosteroids such as dexamethazone or prednisone are used to immunosuppress the body and prevent further destruction of brain parenchyma wrought by the disease.
• Supportive care, including rest, nutrition and fluids, allows your pet to fight the inflammation. If your pet cannot tolerate medications, food or fluids orally, some of these things can be given intravenously.

Home Care

If your dog has been diagnosed with necrotizing meningoencephalitis, follow your veterinarian’s treatment recommendation and notify him if any symptoms worsen or emergency symptoms appear. Keep your dog well-rested, warm, and well fed following the illness. Keep stress to a minimum.

Necrotizing meningitis has an overall poor prognosis for long-term recovery. Treatment is aimed at prolonging an excellent quality of life.