Meningoencephalitis in Dogs - Causes, Treatment and Life Expectancy

Meningoencephalitis in Dogs - Causes, Treatment and Life Expectancy

Meningoencephalitis is a neurological pathology that is diagnosed in small animal clinics with relative frequency. It consists of an inflammation of the central nervous system that can manifest with a wide variety of neurological signs depending on the affected area. Although we know its cause in some circumstances, it is often idiopathic. For this reason, it may be known as canine meningoencephalitis with unknown origin. Despite our lack of understanding of its pathogenesis, we do have options in terms of diagnosis and treatment.

At AnimalWised, we look more closely at meningoencephalitis in dogs. We will look at what we know if its possible causes, but we focus on its symptoms, treatment and life expectancy of affected animals.

What is meningoencephalitis in dogs?

Meningoencephalitis is an inflammation that affects the central nervous system (CNS), with an acute/subacute and progressive course. This means it can begin fairly rapidly and will worsen over time. Specifically, the inflammatory affects the meninges (membranes that cover the CNS) and the brain. When the spinal cord is also affected, it is referred to as meningoencephalomyelitis.

Meningoencephalitides refers to a very extensive group of diseases that have very diverse etiologies. In many cases, it is difficult to reach a definitive diagnosis. In fact, in 60% of cases the specific cause of the disease is not known, making it idiopathic, i.e. of unknown origin.

Symptoms of meningoencephalitis in dogs

The clinical picture associated with meningoencephalitis is varied and depends fundamentally on the structures of the central nervous system that are affected by the inflammation. Specifically, this includes the brain tissue, as well as surrounding tissues and fluids. In this sense, we can see:

  • When the meninges are affected, pain, stiffness, and fever may develop.
  • When brain is affected, seizures, behavioral changes (such as the dog walking in circles or pressing their head against the floor or wall), decreased level of consciousness (depression, stupor, or coma), and vision loss may be seen.
  • When the cerebellum is affected, intention tremor (a tremor that occurs only during movement), hypermetria (exaggerated movements), loss of balance and wide support base can be seen.
  • When the brainstem is affected, vestibular syndrome (tilting of the head to one side, loss of balance, circling, nystagmus, and strabismus), cranial nerve disturbance, altered level of consciousness (depression, stupor, or coma) and motor disturbance are usually observed.

In cases where the spinal cord is also affected, signs such as paresis, paralysis, altered vocal tone and reflexes may be observed, among others.

Different combinations of these signs are usually observed since several nervous structures are usually affected. Meningoencephalitis in dogs should be included in the differential diagnosis of most patients with nervous symptoms, since almost any acute or subacute neurological condition can be compatible with this pathology.

Meningoencephalitis is only one type of encephalitis in dogs. Take a look at some of the others with our article on the symptoms and treatment of canine encephalitis.

Types of meningoencephalitis in dogs

Meningoencephalitis in dogs can be classified into two general groups based on their etiology: infectious and non-infectious. We explain each of them in more detail in the following sections:

Infectious meningoencephalitis

They are those produced by pathogenic microorganisms such as viruses, bacteria, fungi or parasites. Some authors point out that they can also be caused by prions (structurally abnormal proteins), the same underlying cause of diseases such as mad cow disease. In dogs, infectious meningoencephalitides are much less prevalent than noninfectious ones.

Aseptic or non-infectious meningoencephalitis

Aseptic or non-infectious meningoencephalitis can be classified into two groups:

  • Immune-mediated: occurs when the immune system attacks or destroys the body's own components by recognizing them as foreign.
  • Idiopathic: i.e. of unknown origin. This group includes meningoencephalomyelitis of unknown etiology (MUE), necrotizing meningoencephalitis, granulomatous meningoencephalitis, eosinophilic meningoencephalitis and steroid-responsive tremor syndrome.

If you want to know more about different canine neurological diseases, take a look at our article on brain tumors in dogs.

Causes of meningoencephalitis in dogs

When describing the different types of meningoencephalitis we have discussed the main etiologies of this disease. In this section, we are going to explain in more detail the different causes of both infectious and non-infectious canine meningoencephalitis:

  • Pathogenic microorganisms: within this group we find viruses (such as distemper or rabies virus), bacteria (such as Mycoplasma, Staphylococcus, Pastereulla or Bartonella), fungi (such as Cryptococcus and Blastomyces) and parasites (such as Toxoplasma, Trypanosoma and Babesia).

  • Alterations of the immune system: in these cases an exaggerated immune response is produced against the components of the central nervous system.

  • Unknown origin: as we have previously explained, many of the meningoencephalitides are considered idiopathic diseases. However, it is suspected they are pathologies of multifactorial origin, in which a genetic predisposition is combined with factors that trigger an exaggerated immune response.

If you want to know more about parasitical diseases which can result in brain tissue inflammation, take a look at our article on babesiosis in dogs.

Diagnosis of meningoencephalitis in dogs

The diagnostic protocol for canine meningoencephalitis is based on the following factors:

  • Neurological examination: a complete neurological examination will allow the lesion to be located. Multifocal neurological signs are usually seen, indicating that multiple areas are affected.

  • Cerebrospinal fluid analysis: this is a very effective diagnostic tool, but it must be taken into account that not all central nervous system injuries produce an alteration of the cerebrospinal fluid. Obtaining the cerebrospinal fluid sample is an invasive procedure and so must be performed under general anesthesia. From the sample obtained, a cytological study, a culture, a biochemical analysis and a serological analysis will be carried out.

  • Magnetic resonance: this advanced imaging test can detect mass effect lesions (usually tumors), edema, dilation of the cerebral ventricles and multifocal or diffuse lesions. In some cases no neurological lesion is observed, so it must be taken into account that normal resonance images should not rule out this disease.

  • Other diagnostic tests: including blood tests, urinalysis and serology of the main infectious diseases present in the territory in which the animal lives.

We must know that some meningoencephalitis (such as necrotizing meningoencephalitis or granulomatous meningoencephalitis) require a histopathological diagnosis for confirmation. This means that it will not be possible to reach a definitive diagnosis while the dog is still alive. For a confirmational diagnosis, a postmortem of the existing central nervous system lesions will be required. This can be cost prohibitive, so many dogs remain undiagnosed.

Learn more about canine diagnostic tools with our article on how to understand a dog's blood test.

Treatment and prognosis of meningoencephalitis in dogs

The treatment of meningoencephalitis in dogs varies depending on its underlying cause. In general terms, the treatment is based on the following points:

  • Symptomatic treatment: consists of treating the symptoms associated with meningoencephalitis. For example, anti-convulsant drugs will be administered in patients with convulsive crises, analgesics in patients with severe pain due to meningitis, or diuretics in patients with cerebral edema.

  • Antibiotics: should be administered in the case of infectious meningoencephalitis. Depending on the causal agent, antibacterial, antifungal or antiparasitic agents will be administered.

  • Immunosuppressants: these are used to treat immune-mediated meningoencephalitis and meningoencephalitis of unknown origin (since the later also appears to have an immunity-related component). Specifically, corticosteroids are usually prescribed in combination with other immunosuppressive drugs, such as cyclosporine, azathioprine or cytosine arabinoside.

Learn more about one of these medications with our article on azathioprine for dogs.

Life expectancy of dogs with meningoencephalitis

The prognosis of the disease also varies depending on the specific type of meningoencephalitis:

  • Infectious meningoencephalitis: the prognosis is serious. In addition, animals that overcome the infection may be left with neurological sequelae.
  • Non-infectious meningoencephalitis: the prognosis and survival rates are highly variable. The prognosis is generally grave, especially when the signs are multifocal and when there is no initial favorable response to treatment.

As we can see, the life expectancy of a dog with meningoencephalitis varies according to different factors. In any case, dogs which receive early treatment have a much higher life expectancy than those who go untreated. As soon as any neurological signs appear, it is essential the dog is taken to a veterinarian for diagnosis and treatment. The life expectancy can then be best determined.

This article is purely informative. AnimalWised does not have the authority to prescribe any veterinary treatment or create a diagnosis. We invite you to take your pet to the veterinarian if they are suffering from any condition or pain.

If you want to read similar articles to Meningoencephalitis in Dogs - Causes, Treatment and Life Expectancy, we recommend you visit our Neurological diseases category.

Bibliography
  • Gutierrez, E., Blanco, B., Novales, M., Lucena, R., Hernandez, E., & Ginel, P. J. (2009). Update on the diagnosis and treatment of meningoencephalitis. Royal Academy of Veterinary Sciences of Eastern Andalusia, 22(1), 243-253.
  • Puccio, E. (2020). What do we know about meningoencephalomyelitis of unknown origin (MOD)?. Argus, 222, 62-66.