Brain Tumors in Dogs

A brain tumor is a serious condition caused by improper cell division in tissues associated with the brain. These cells are unable to receive the “stop growing” signal and continue to divide, forming masses that can replace or damage healthy brain tissue. Brain damage can cause abnormal behavior, weakness or lethargy, and difficulty moving. Only a veterinarian can properly identify and diagnose a brain tumor, so make an appointment as soon as possible if your pet exhibits unusual behavior or tremors.

• Tremors
• Abnormal Behavior
• Lethargy
• Weakness
• Loss of appetite
• Vision loss or impairment
• Bleeding in the brain
• Tissue necrosis
• Abnormal hair loss/growth

• Exposure to carcinogens, either acutely or over one’s lifetime
• Genetic predisposition

Brain tumors vary widely in the type of malignant growth, their location, size and rate of growth. The symptoms of a brain tumor will be determined by two factors: the part of the brain the tumor is damaging, and any other structures nearby. For example, it is not uncommon for bone tumors deep inside the nasal cavity to spread to the brain, causing persistent sneezing and bloody noses, or for brain tumors beneath the eye socket to press on the optic nerve and cause blindness or double vision. Thus, any abnormal behavior or unusual symptom such as bleeding from the nose should be reported promptly to a veterinarian, as this may be an early clue to a hidden illness.

There are many steps a veterinarian can take to successfully diagnose a brain tumor, beginning with a simple head x-ray. This procedure can easily be done in most clinics and thanks to digital imaging, can provide results immediately. However, plain-film x-rays do not always provide enough detail to properly identify or even visualize the tumor, especially if it is of a similar density to brain tissue. Therefore, if the x-ray turns up an inconclusive or negative result, a CT scan with contrast is usually the next choice. A CT scan is essentially a series of pictures taken via a rotating x-ray camera that are re-assembled into a 3D image. To better distinguish the potential tumor from the surrounding tissue, a special dye will be injected using an IV. This dye often causes a sensation of tingling warmth, but is not painful and will not harm your pet.

Another diagnostic tool that may be used is the MRI. MRI technology using magnetic pulses to image the interior of the body, and is better for diagnosing tumors composed exclusively of soft tissue. These machines can be somewhat loud or intimidating, but owners may be allowed to accompany and comfort their pet.

Finally, when the tumor is confirmed and located, one or both of the following may be necessary. First, if the tumor is accessible to surgeons, a biopsy (small sample of tissue) will be taken for testing to identify the tumor. If the tumor is not accessible, or additional information is required, blood or cerebrospinal fluid may be taken for testing, as immunological markers may be present that will identify the tumor.

The treatment for a brain tumor will vary widely based on the nature and location of the tumor, the size and how early it was diagnosed. In general, an accessible tumor will be removed surgically, along with radiation or chemotherapy. Radiation therapy with Cobalt-60 has shown significant increases in survival rates compared to surgery alone.

An inaccessible tumor cannot be treated surgically, and so chemotherapy/radiation may be employed. Steroids to reduce swelling and anticonvulsants to stop seizures may also be used to minimize symptoms and provide the dog with some comfort, but this is usually to ease the passing of the animal, and is not a cure.

In general, outlook for dogs with brain tumors is guarded or poor. Well-defined, single brain tumors that have not grown to excessive size and may be accessed surgically have the best chance of a successful outcome. Tumors in groups or inaccessible to surgeons have the poorest prognosis. Radiation therapy can be used to extend a dog’s life over a few additional months, but is not usually a cure. Palliative treatment to make a dog more comfortable is often given, including steroids, anticonvulsants, and painkillers.