Brain Tumors in Dogs

Few words can strike as much fear into the heart of a pet owner as hearing the vet say, "Your dog has a brain tumor." Unfortunately, these growths are not that uncommon in dogs, particularly seniors.

There are several different types of brain tumors, or cancers, that can strike dogs, but all are basically a mass of cells that are dividing in an uncontrolled fashion, creating a growth that displaces normal tissue inside the dog's brain. Depending on the type of tumor and its location, symptoms of these lesions can include a staggering gait, holding the head in a tilted position, abnormal eye movements, behavior changes, weakness in the limbs, and seizures.

While any dog can develop a brain tumor, they mostly strike dogs over the age of five. In addition, certain breeds are more prone to these lesions. Boxers, Old English Sheepdogs, Scottish terriers, doberman pinschers, and golden retrievers are more likely to develop brain cancer than other breeds.

Although brain cancer is a very serious diagnosis that often does not have a good outcome, you may still have some quality time left with your pet as long as you seek out treatment as soon as you notice symptoms of this devastating condition.

What Are Brain Tumors?

Brain tumors are lesions that consist of cells dividing in an uncontrolled, abnormal fashion. There are several types, generally divided into two categories: primary and secondary.

Primary brain tumors, or cancers, originate from the brain itself or from its lining. There are several types of primary brain tumors. Some of the most common in dogs include:

• Meningioma, which grows from the outer lining of the brain. This is the most common type of primary brain tumor in dogs, as well as in cats and humans. Meningiomas are especially predominant in long-nosed breeds of dog, including collies, than other breeds of dog.
• Glioma, which is a tumor that originates in the glial cells of the brain. Glial cells help support brain structure. This type of tumor is somewhat more common in short-nosed breeds such as the pug.
• Choroid plexus tumors develop in the tissues that produce cerebrospinal fluid. This type of cancer isn't specific to any particular breed.
• Pituitary adenomas develop within the pituitary gland, which is located near the base of the brain. Poodles, Boston terriers, and dachshunds are more prone to this type of tumor than other breeds.

Secondary brain tumors are those which spread (metastasized) from cancer in another area of the body. These types of tumors typically have a very poor outcome.

Symptoms of Brain Tumors in Dogs

Because there are various types of brain tumors that grow in different parts of the brain, symptoms can vary quite a bit. Some common signs to watch for include:

The location of the tumor within the brain can influence the symptoms your dog develops. Tumors in the front of the brain are likely to cause seizures, which overall is the most common symptom of brain tumors in dogs. Other common symptoms with tumors in the front of the brain are walking in circles and vision loss, which can be sudden and strike one or both eyes. Your dog likely will develop behavioral changes, as well, such as irritability, acting lost or uncertain of where it is, loss of formerly known behaviors, and shyness or withdrawal.

Tumors located toward the back of the brain often cause changes in the dog's gait, such as stumbling or appearing unsteady. Your dog might become weak on one side of its body or develop weakness in its legs. Abnormal eye movements, called nystagmus, are common with these tumors, as is a head tilt to either side. You may also notice that your dog doesn't seem as alert as usual or seems excessively sleepy.

Causes of Brain Tumors

Currently, the exact causes of brain tumors in dogs are not clear. Certain factors could have an influence including diet, environment, exposure to certain viruses, and even trauma. As certain breeds are more prone to developing brain tumors than others, there may be genetic factors as well.

Diagnosing Brain Tumors in Dogs

Your vet will discuss the symptoms you are seeing at home, observe your dog, and perform a thorough physical examination to check for abnormalities. Your vet will especially look for signs of neurological problems, such as abnormal eye movements, difficulty walking normally, or other unusual behaviors or movements.

Blood and urine tests to rule out other potential causes of the symptoms generally come next. Your vet might also want to draw a sample of cerebrospinal fluid from your pet's spine to look for signs of infection or other abnormalities that can cause neurological symptoms.

Typically, your vet will also take x-rays of the dog's chest to look for signs of cancer in the lungs or other organs that might have spread to the brain.

An MRI or CT scan of the brain, which will be done under anesthesia to keep the dog perfectly still, is one of the best diagnostic tools for brain cancer. However, these are expensive tests, and some pet owners may decide against them for that reason.

A biopsy of the brain lesion may also be ordered. This is the only way to definitively diagnose a specific type of brain tumor.

Treatment & Prevention

Once a brain tumor is diagnosed, some owners decide against aggressive treatment in favor of palliative treatment that keeps the dog as comfortable as possible for as long as it has good quality of life. Palliative treatment can include pain medications, anti-nausea drugs, anti-seizure medications, and steroids to help slow the growth of the tumor.

There are three basic medical treatments for brain tumors: radiation, chemotherapy, and surgery. Your veterinarian will probably refer you to a veterinary oncologist to discuss these options and whether they are appropriate for you and your dog. The choice of treatment, or a combination of treatments, will depend on your dog's type of cancer, its overall health, its age, and whether the cancer has spread from another area of the body. You will also need to consider whether or not you can afford a potentially very expensive course of treatment.

Because the causes of brain tumors are mostly unknown, and the development of these cancers are unpredictable, there is little that can be done to prevent them beyond the normal good care of your dog, which should include a high quality diet, regular exercise, annual well-dog visits to your veterinarian, and prompt treatment for any diseases or conditions that your dog develops.

Prognosis for Dogs with Brain Tumors

Although certain treatment options can at least help to improve a dog's quality of life and may slow the progression of the disease, it is important to be aware that following the diagnosis of a brain tumor, the long-term prognosis is guarded to poor. This is especially true if the tumor is a secondary cancer from elsewhere in the body.

Survival times vary depending on the type of tumor, but if your dog has the most common type, meningioma, you can expect it to live around three months with palliative care only. Chemotherapy can extend that to an average of six months, and radiation therapy often gives dogs up to a year of good quality of life. These are averages, though, and your dog may live longer, or not as long, depending on its unique situation.

Regardless of what treatment option you choose, take steps to monitor your dog's quality of life after a brain tumor diagnosis. You'll want to make sure your dog is still comfortable and happy for as long as possible.

Meals, walks, socialization, playing with favorite toys, and other favorite activities for your dog should be kept as close to normal as your dog's condition allows. When these things start becoming too difficult for your dog to manage, or your pet is clearly in pain and no longer enjoying life, it may, unfortunately, be time to discuss euthanasia with your veterinarian.