While it may not be pleasant to think about, brain tumors are not uncommon in older dogs and cats. In fact, meningioma tumors -- slow-growing tumors that arise from the membrane surrounding the brain and spinal cord -- are the most common cause of seizures in dogs over 7 years of age.
The good news is that meningioma tumors are usually benign, meaning that they do not create cancer or spread to other areas of the body. They can, however, cause swelling and compress the brain, damaging brain nerves. This is why the symptoms of meningioma are largely neurological and behavioral.
Causes of Meningioma in Dogs and Cats
The causes of meningioma tumors in dogs and cats are not well understood. What we do know, however, is how these tumors form, which is from the skull inward. This makes meningiomas much easier to access and remove than tumors that grow deep inside the brain. Ease of removal, however, will ultimately depend on the size, location, and type of meningioma.
Meningioma tumors are classified based on the type of cells that are involved. Different cells contribute to different growth rates. All meningiomas, however, contain large numbers of progesterone receptors, which are proteins found inside of cells. In dogs, the more progesterone receptors a meningioma contains, the faster its rate of growth. There is no such correlation in cats.
The vast majority of meningiomas occur in dogs over 7 years-old and cats over 10 years-old. And for whatever reason, dogs with long snouts (such as Collies and Golden Retrievers) seem to be particularly predisposed.
Symptoms of Meningioma in Dogs and Cats
The symptoms of a meningioma tumor will largely depend on the area of the brain involved.
In dogs, seizures are the most common symptom. In addition, because most meningiomas in dogs occur in the front of the skull where olfactory lobes are located, their sense of smell may be affected. This can result in behavioral changes and loss of appetite.
In cats, symptoms can be a bit more vague. You are likely to see lethargy and other behavioral changes.
Other symptoms of a meningioma in a dog or cat may include:
- Blindness or vision impairment
- Loss of coordination
- Walking in circles
- Dragging toes
- Neck or back pain
Diagnosing Meningioma in Dogs and Cats
If you notice any of the above symptoms, contact your veterinarian. They will perform complete blood work and a urinalysis to assess your pet’s overall health. They may also take a chest radiograph to check for cancer. In many cases, brain tumors are the result of cancer that formed elsewhere in the body and then spread.
Brain imaging -- either with a CT scan or MRI -- is another central test for brain tumors. MRI tends to be the preferred method as it allows for better identification of changes within the brain.
And finally, a brain tissue biopsy may be required to definitively diagnose a meningioma.
Treating Meningioma in Dogs and Cats
Treatment for a meningioma will ultimately depend on the size, location, and type of tumor. Common treatment options include:
A complete excision of the tumor is ideal, but is not always possible. In cats, meningiomas are more rubbery and well-defined than they are in dogs, and therefore they are easier to remove. In many cats, surgery is successful and survival rates are good.
In dogs, surgery can be more complicated, as meningiomas have less-defined edges and tend to be more invasive. The median survival time for a dog who undergoes excision surgery is around 7 months, but that may be extended with radiation.
Radiation may be recommended instead of surgery (often the case with dogs) or in conjunction with surgery. Because cats tend to do so well with surgery, radiation is usually unnecessary.
Like radiation therapy, chemotherapy can either be used instead of surgery or in combination with it. It is most commonly used on dogs.
Certain medications may be prescribed to alleviate painful symptoms and reduce the frequency of seizures.
The anti-inflammatory medication Prednisone is commonly prescribed for its ability to reduce swelling and actually shrink the tumor by decreasing its blood flow.
In most cases, a meningioma will ultimately grow too large to respond to medications, but they can help in the short term.
The prognosis for pets with meningioma tumors will depend on a number of factors, including the type of cells involved in the meningioma (which can contribute to growth rate and rate of recurrence), the extent to which surgery is successful, and the pet’s overall health. To give your pet the best chance at survival, contact your veterinarian at the first sign of symptoms.
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