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.