Inflammatory Brain Disorders in Dogs

Some canine conditions can lead to inflammation in the brain, frequently affecting the spinal cord and the meninges as well. Any disorders that affect the central nervous system can become very serious in a short amount of time, and inflammation of the brain is no different.

If your dog is showing signs of central nervous system disruption, it should be treated as an emergency as timely intervention is often your canine companion’s best chance at a full recovery.

Inflammation of the brain is typically a serious condition which can escalate quickly. It can be caused by infections, infestations, immune disorders, parasites, and in some cases, it appears to have a genetic component.

There are several types of disease that can cause inflammation of the brain, which may also affect the spinal cord and meninges. Symptoms of central nervous system inflammation may include:

• Behavior changes
• Blindness
• Circling
• Depression
• Facial tremors
• Fever
• Head pressing
• Head tilt
• Lethargy
• Loss of coordination
• Paralysis
• Seizures
• Sensitivity to touch
• Stiffness
• Unequal or pinpoint pupils
• Weakness

Types

The brain and spinal cord of the central nervous system are comprised of white matter, which is made up of the nerve fibers known as axons, and the grey matter which encompasses the rest of the tissues. The terms used to describe inflammation that affects the central nervous system can be differentiated by their location. 

• Encephalitis - The term encephalitis refers to the inflammation of the tissues of the brain itself
• Meningitis - Swelling of the membranes that surround both the brain and spinal cord, known as meninges, is called meningitis 
• Myelitis - An animal with myelitis will experience inflammation of the spinal column

These conditions can occur simultaneously or separately and may affect either the grey or white matter of the central nervous system or both.

There are several diseases and disorders that can cause swelling in the brain and may affect other areas of the central nervous system. A few notable disorders include:

• Bacterial Infection - Bacterial infections in the eyes, sinuses, and ears can occasionally migrate to the brain, causing inflammation 
• Fungal Infection - Some of the fungi that are known to infiltrate the brain include Coccidioidomycosis and blastomycosis
• Granulomatous Meningoencephalitis - A rapid onset disorder that can cause blindness, head pressing, and seizures; although the origins of this disorder are poorly understood, it is believed to be immune-mediated 
• Necrotizing Encephalitis - This disease, constrained to Yorkshire Terriers and French Bulldogs, causes lesions in the central nervous system that are found only on the white matter of the brain 
• Necrotizing Meningoencephalitis - Although this condition is commonly called Pug Dog encephalitis, it has been diagnosed in other small dogs such as Chihuahua, Pekingese, and Boston Terrier breeds; it is characterized by lesions that cause inflammation in both the brain and the meninges 
• Parasitic Infestation - Parasites such as Toxoplasma gondii and Neospora affect the brain directly, and external parasites like ticks may transmit inflammatory diseases that affect the brain, including Rocky Mountain spotted fever and Lyme disease
• Steroid Responsive Meningitis-Arteritis - This condition causes inflammation in both the meninges that surround the brain and spinal cord and in the arteries throughout the body that can be treated using steroid medications  
• Viral Infection - Well known viral infections that cause inflammation in the brain include distemper, rabies, and parvovirus

If your dog is showing signs of distress when you transport them into the veterinary clinic, they will be given supportive care right away, which could include intravenous fluids to prevent dehydration and to correct any imbalances in the blood, supplemental oxygen, or antiepileptic medications to control seizures. Once the patient is stabilized, the veterinarian will perform a full physical examination, including standard diagnostic tests such as a complete blood count, biochemical profile, and a urinalysis. 

A computed tomography (CT scan) or magnetic resonance imaging (MRI) may be utilized to get a clearer image of the brain along with the spinal cord and meninges that surround both. The examining doctor may also choose to get a sample of the animal’s cerebrospinal fluid using a method called a cerebrospinal tap. During this process, your dog will be anesthetized, and a needle is inserted either at the base of the skull or in the lower back and fluid will be withdrawn for evaluation. These tests can be quite helpful in diagnosing the cause of brain inflammation, but in many cases, the actual trigger may remain hidden.

The treatment of diseases and disorders that tend to cause inflammation of the brain will depend on the underlying cause of the disorder. For bacterial and fungal infections as well as infestations by protozoan parasites, antibiotic and antifungal drugs are typically prescribed in order to eradicate the disease. Corticosteroids and immunosuppressant medications may also be utilized to treat disorders like granulomatous meningoencephalitis and steroid responsive meningitis-arteritis, and anti-inflammatory medications may also be recommended. The treatment and follow-up monitoring processes for most of these conditions are fairly lengthy, extending anywhere from a few months to the rest of the animal’s life. 

Prednisone is a commonly prescribed medication for this and other disorders but can have side effects, particularly when taken over a long period of time. Early diagnosis and treatment give the patient the best chances of survival and full recovery, and dogs who have experienced these disorders will generally require more frequent monitoring in an attempt to catch any neurological issues early and prevent disorders from reoccurring.

Animals that are recovering from anesthesia, as is frequently required for the diagnosis of disorders that cause swelling in the brain, will benefit from a calm and comfortable area to return home to. They may be disoriented, and experience loss of coordination until the medication has fully left the system. The prognosis for disorders that involve the inflammation of the brain depends on the underlying cause of the disorder and the length of time between onset and treatment. Even when caught early and treated aggressively, most of these disorders require lengthy treatment times for full recovery, and many may require life-long treatments.