Brain Tumor in Cats and Dogs

Brain tumors are relatively common in older dogs and cats. Some tumors are "primary" brain tumors, meaning that they originate from the tissue in the brain cavity, and some are "secondary" brain tumors, or those that originate from outside the brain cavity but then invade the brain by extension (for example, from the nose) or via the blood (metastasis). Most brain tumors are diagnosed in dogs and cats older than 5 years and mainly in pets 9 years of age and older. Younger animals, though, can also be affected. Any pet can develop a brain tumor, but some breeds seem to be more predisposed, such as Golden Retrievers, Boxers, and male domestic short-hair cats.

Signs and Symptoms

Clinical signs of brain tumor depend on both the location of the tumor within the brain and its size. The most common symptoms of a brain tumor are circling (aimlessly walking in circles), confusion, change in behavior, head tilt, loss of balance, and seizures. Seizures are present in almost 50% of cases. Of course, not all pets with those clinical signs have a brain tumor! Any other disease affecting the brain can also cause those clinical signs. For example, a pet that starts having seizures between 6 months and 5 years of age is more likely to have epilepsy, whereas an older) animal with a sudden onset of seizures probably does not have epilepsy and is more likely to have a brain tumor.

Besides having a rapid growth rate, tumors can cause other associated problems such as bleeding, swelling, and compression of the brain adjacent to the tumor. Because of these factors, symptoms can develop quickly in some animals even though the mass has been growing for some time. Most cats with a brain tumor will be brought to the veterinarian because of a change in behavior. Sometimes, the only observation is that they are "not doing right." As you can see, no specific symptom can confirm a brain tumor.

Whenever your pet is showing signs of a health issue your first step is to contact your primary care veterinarian. If it is indicated that your pet may suffer from a brain tumor or another serious condition, a veterinary specialist is available at an ExpertVet certified hospital.


Because the brain is well protected within the skull and most brain tumors will not cause changes in blood tests, advanced imaging of the brain by CT-scan or magnetic resonance imaging (MRI) is necessary to diagnose a brain tumor. A CT-scan is a technique using x-rays that makes images of “slices" of the brain. MRI is a technique using an extremely strong magnet (magnetic field) to produce good quality, detailed images of the entire brain. Both techniques are pain-free and noninvasive. However, because the pet must lie completely still for these procedures, anesthesia is required in most cases.

Before advanced imaging is performed, blood tests, radiographs, and other diagnostic procedures might be recommended to rule out other diseases and to make sure that your pet can tolerate anesthesia. After the CT-scan or the MRI, a spinal tap and fluid analysis might be recommended to rule out other diseases that can mimic a brain tumor. Sometimes the type of tumor can be determined by imaging alone; however, it might be necessary to obtain a biopsy to know exactly what type of tumor it is.