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Brain Tumors in Dogs

What Is a Brain Tumor in a Dog?

A tumor represents an abnormal growth of tissue within a dog’s body, potentially manifesting in various areas, including the brain. Tumors can be categorized broadly into benign, indicating non-cancerous growths, and malignant, indicating cancerous growths. Brain tumors are further classified into primary or secondary types.

A primary brain tumor originates within the brain or its surrounding layers known as the meninges. Conversely, a secondary brain tumor emerges as a result of the spread or invasion of cancer cells from another primary location. Metastasis refers to the process wherein tumor cells detach from the primary tumor, traverse through the body, and settle in another location, such as the brain. Invasion occurs when a tumor extends into nearby bodily tissues, leading to secondary brain tumor formation.


  • Seizures (the most prevalent symptom)
  • Sensitivity to touch in the head or neck region
  • Vision problems
  • Lack of coordination or instability in movement
  • Abnormal behaviors like repetitive circling
  • Heightened reactivity
  • Lethargy or excessive fatigue
  • Decreased appetite
  • Head tilting
  • Inability to regulate urination or bowel movements


The direct causes of brain tumors in dogs remain unknown. Studies suggest that various factors, including diet, environmental conditions, genetics, and the health of the immune system, may contribute to their development. While brain tumors can occur at any age, they are more commonly observed in dogs older than 5 years.

Certain breeds with specific head and nose shapes seem to have a higher susceptibility to brain tumors compared to others. These include:

  • Dolichocephalic dog breeds: These breeds possess an elongated head and nose. Examples include the Collie, Greyhound, Dachshund, Italian Greyhound, and Great Dane. They are more prone to developing meningioma, a type of brain tumor originating in the brain’s surrounding membranes.
  • Brachycephalic dog breeds: These breeds feature a shorter nose and flatter face. Examples include the Pug, Shih Tzu, Bulldog, Boxer, Boston Terrier, Pekingese, and Mastiff, among others. They are more predisposed to developing glioma, a type of tumor that originates in the brain or spinal cord.


In older dogs, a suspicion of a brain tumor arises from abnormal neurological signs. The initial step for veterinarians involves conducting a comprehensive physical examination to assess any indications of neurological impairment affecting the dog’s brain, spinal cord, and nerves.

Blood tests, including a complete blood count and serum blood chemistry, are typically conducted to rule out alternative causes of seizures or unusual behavior. While routine bloodwork cannot conclusively diagnose a brain tumor, it helps in eliminating other potential causes of the dog’s symptoms.

To evaluate whether the cancer has metastasized, chest X-rays and abdominal ultrasound examinations are often recommended. About 55% of brain tumors do not originate in the brain but metastasize from other sites. Even primary brain tumors may have spread to other areas.

Imaging of the brain is imperative to confirm the presence of a brain tumor. X-rays cannot penetrate the skull sufficiently to visualize the brain. Therefore, computed tomography (CT) or magnetic resonance imaging (MRI) scans are essential for brain imaging and tumor localization. Dogs are typically administered general anesthesia during CT or MRI procedures to prevent movement. Veterinary neurologists commonly conduct CTs and MRIs.

Based on the appearance of a mass on the CT or MRI, the veterinarian may suspect the type of tumor present. However, a biopsy is necessary to accurately identify the tumor type. Other conditions that may resemble tumors or cancer on CT or MRI scans include abscesses, parasites (such as toxoplasmosis), cysts, blood clots, and inflammatory lesions.


Upon diagnosing a brain tumor in your dog, your veterinarian or veterinary neurologist will collaborate with you to determine the most suitable treatment plan based on the tumor type and whether it has metastasized.

There are three primary treatment modalities available:

Surgery: The objective of surgery is to excise the brain tumor. However, this is often feasible only if the tumor is situated on the brain’s surface. Dogs diagnosed with meningioma are more likely to benefit from surgery, although tumor recurrence is probable. This specialized procedure is exclusively performed by veterinary neurosurgeons. Tumors located deeper in the brain pose surgical challenges due to the risks associated with cutting through healthy brain tissue.

Radiation therapy: Radiation therapy is commonly employed to target and reduce the size of brain tumors. While radiation may induce adverse effects such as nausea, mouth ulcers, and ear infections, these can be managed with medication. Although radiation can swiftly improve the dog’s condition, it seldom eradicates the entire tumor. Typically, brain tumors treated with radiation recur within eight to 14 months.

Chemotherapy: Chemotherapy is not frequently utilized for treating brain tumors in dogs. The brain is shielded by a network of blood vessels that serve as a barrier to prevent harmful substances, including chemotherapy drugs, from accessing the brain and tumor in substantial quantities.

Medication: Medications may be administered independently to enhance your dog’s comfort and quality of life, or in conjunction with surgery, radiation therapy, or chemotherapy. Common medications may include steroids to decelerate tumor growth and reduce brain swelling, as well as anti-seizure medications to manage seizures associated with the brain tumor.

Living and Management

Dogs diagnosed with a brain tumor require ongoing care under the supervision of their veterinary neurologist. Since brain tumors are seldom curable and often recur despite complete surgical removal or radiation treatment, consistent monitoring is essential to enhance the dog’s lifespan while preserving their quality of life.

Regular examinations play a pivotal role in prolonging your dog’s life and managing their symptoms effectively. These examinations typically involve imaging studies and an assessment of common symptoms associated with brain tumors, such as seizures.

Dog owners must remain vigilant for potential complications. For instance, brain tumors can elevate pressure within the dog’s skull, making swallowing more challenging. This may result in accidental inhalation of food or water, leading to a lung infection known as aspiration pneumonia.

Medications will likely be prescribed for the duration of your dog’s life. These medications serve to alleviate symptoms and address the underlying brain tumor. For instance, anti-inflammatory drugs aid in reducing swelling and pressure, while anti-seizure medication helps regulate and prevent seizures.

Brain Tumors in Dogs FAQs

What is the life expectancy of a dog with a brain tumor?

The life expectancy of a dog with a brain tumor depends on the tumor’s location and the treatment received. Dogs with tumors in the lower brain region generally have a shorter life expectancy compared to those with tumors in the upper region. Below are the estimated life expectancies based on treatment:

  • Supportive care only: two to four months
  • Surgery: six to 12 months
  • Chemotherapy: seven to 11 months
  • Radiation: seven to 24 months
  • Surgery with radiation: six to 30 months

How common are brain tumors in dogs?

Research indicates that brain tumors affect approximately 15 out of every 100,000 dogs and constitute 2–5% of all canine cancer diagnoses. Certain breeds may have a higher predisposition to developing brain tumors than others.

Do brain tumors come on suddenly in dogs?

Some brain tumors progress slowly over months or years, while others emerge rapidly and aggressively.

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