Meningoencephalitis is a neurological pathology that is frequently diagnosed in the small animal clinic. 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. Despite the fact that it is a disease with many unknowns to discover, more and more information is available to direct its diagnosis and treatment.
If you want to know more about meningoencephalitis in dogs, don't miss the following article on our site in which we talk about the symptoms, types and treatment of this neurological disease.
What is meningoencephalitis in dogs?
Meningoencephalitis consists of an inflammation that affects the central nervous system (CNS), with an acute/subacute and progressive course. Specifically, the inflammatory process affects the meninges (membranes that cover the CNS) and the brain. When, in addition to these structures, the spinal cord is also affected, it is referred to as meningoencephalomyelitis.
Actually, meningoencephalitides are a very extensive group of diseases that have very diverse aetiologies. In many cases, it is difficult to reach a definitive diagnosis; so much so, that in 60% of cases the specific cause of the disease is not known.
Symptoms of meningoencephalitis in dogs
The clinical picture associated with meningoencephalitis is very varied and depends fundamentally on the structures of the central nervous system that are affected by the inflammatory process. In this sense:
- When the meninges are affected, pain, stiffness and fever may be observed.
- When the brainis affected, seizures, behavioral disturbances may be observed(such as circling or pressing head against floor or wall), decreased level of consciousness (depression, stupor, or coma), and loss of vision.
- When the cerebellum is affected, intentional tremor may be observed(it is a tremor that occurs only during movement), hypermetry (exaggerated amplitude movements), loss of balance and wide base of support.
- When the brainstemis affected, a vestibular syndrome may be observed(head tilting to one side, loss of balance, circling, nystagmus, and strabismus), cranial nerve disturbance, altered level of consciousness (depression, stupor, or coma), and motor disturbance.
Also, in cases where the spinal cord is also affected, signs such asmay be seen paresis, paralysis, altered tone and reflexes , etc.
In practice, different combinations of these signs are often observed since several nerve structures are usually affected. Therefore, 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.
Types of meningoencephalitis in dogs
Meningoencephalitis in dogs can be classified into two large groups according to their aetiology: infectious and non-infectious. Next, we explain each of them in more detail.
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 (like the commonly known "mad cow disease").
In dogs, infectious meningoencephalitides have a markedly lower prevalence than non-infectious ones.
Aseptic or non-infectious meningoencephalitis
In turn, aseptic or non-infectious meningoencephalitis can be classified into two groups:
- Immune-mediated: occur when the immune system attacks or destroys the body's own components by recognizing them as foreign.
- Idiopathic: that is, of unknown origin. This group includes meningoencephalomyelitis of unknown etiology (MUE), necrotizing meningoencephalitis, granulomatous meningoencephalitis, eosinophilic meningoencephalitis, and steroid-responsive tremor syndrome.
Causes of meningoencephalitis in dogs
Although when describing the different types of meningoencephalitis we have named the main etiologies of this disease, in this section we will explain in more detail the different causes of canine meningoencephalitis:
- Pathogenic microorganisms: within this group we find viruses (such as distemper or rabies), bacteria (such as Mycoplasma, Staphylococcus, Pastereulla or Bartonella), fungi (such as Cryptococcus and Blastomyces) and parasites (such as Toxoplasma, Trypanosoma and Babesia).
- Immune system disorders: in these cases an exaggerated immune response is produced against the components of the central nervous system.
- Unknown origin: As we have explained, many of the meningoencephalitides are considered idiopathic diseases. However, it is suspected that they are pathologies of multifactorial origin, in which a genetic predisposition is combined with factors that trigger an exaggerated immune response.
Diagnosis of meningoencephalitis in dogs
The diagnostic protocol for canine meningoencephalitis is based on the following points:
- Neurological examination: A complete neurological examination will locate the lesion. Multifocal neurological signs are usually seen, indicating that multiple areas are affected.
- Cerebrospinal fluid analysis: this is the diagnostic technique of choice, although it should be borne in mind that not all lesions of the nervous system central produce an alteration of the cerebrospinal fluid. Obtaining the cerebrospinal fluid sample must be done under general anesthesia, since it is an invasive procedure. From the sample obtained, a cytological study, a culture, a biochemical analysis and a serological analysis will be carried out.
- Magnetic Resonance: Through this advanced imaging test, mass effect lesions, edema, dilatation of the cerebral ventricles and lesions can be detected. multifocal or diffuse. However, in some cases no neurological lesion is observed, so it should be borne in mind 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 inhabits.
However, 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 in life, since this will require a postmortem diagnosis of the existing lesions in the nervous system.
Treatment and prognosis of meningoencephalitis in dogs
The treatment of meningoencephalitis in dogs varies depending on its aetiology. In general terms, the treatment is based on the following points:
- Symptomatic treatment: consists of treating the symptoms associated with meningoencephalitis. For example, convulsants 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 drugs will be administered.
- Immunosupressants: they are used for the treatment of immune-mediated meningoencephalitis and meningoencephalitis of unknown origin (since they seem to have an immune component). Specifically, corticosteroids are often prescribed in combination with other immunosuppressive drugs, such as cyclosporine, azathioprine or cytosine arabinoside.
The prognosis of the disease also varies depending on the specific type of meningoencephalitis:
- In infectious meningoencephalitis the prognosis is serious. In addition, animals that survive the infection may be left with neurological sequelae.
- In the case of non-infectious meningoencephalitis, prognosis and survival times 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 depending on many factors. In any case, it must be taken into account that patients who receive early treatment have a much higher survival rate than those who do not receive it. Therefore, it is essential that as soon as any neurological sign is detected, you urgently go to a veterinary center. Only in this way will it be possible to make an early diagnosis of the disease and establish the most appropriate treatment in each case.
