The most common sign of a brain tumor in dogs is a seizure, especially if your dog has never had one before and is over seven years old. About 50% of dogs with brain tumors in the front part of the brain experience seizures as their first noticeable symptom. But seizures aren’t the only warning sign, and many dogs show subtler changes weeks or even months before anything dramatic happens. Knowing what to watch for can help you catch the problem earlier.
The Most Common Warning Signs
Brain tumor symptoms in dogs depend on where the tumor is growing. Tumors in the front of the brain, which is the most common location, tend to cause seizures and personality changes. Tumors in the back of the brain near the brainstem are more likely to cause balance problems, including a head tilt, stumbling, or walking in circles.
Here are the signs most frequently linked to brain tumors in dogs:
- New-onset seizures: A seizure in a previously healthy older dog is one of the strongest red flags. It may look like full-body convulsions, or it may be subtler, like brief episodes of staring, facial twitching, or jaw chomping.
- Circling or disorientation: Walking in tight circles, often in one direction, or appearing confused about where they are.
- Head tilt: A persistent tilt to one side, sometimes paired with abnormal eye movements.
- Loss of balance: Stumbling, falling to one side, or difficulty navigating stairs or doorways they used to handle easily.
- Vision changes: Bumping into furniture or walls, especially on one side, or failing to track objects with their eyes.
Dogs may also show more general signs like lethargy, loss of appetite, and weight loss. These overlap with many other conditions, which is part of what makes brain tumors tricky to recognize early.
Subtle Behavioral Changes That Come First
One of the most important things to understand is that brain tumors often change a dog’s behavior before they cause obvious neurological problems. Your dog might seem “off” in ways that are hard to pin down. They may become unusually clingy or withdrawn, lose interest in play, forget commands they’ve known for years, or show new aggression or anxiety. Some dogs develop changes in their sleep patterns, sleeping far more than usual or becoming restless at night.
These behavioral shifts can precede a clearly abnormal neurological exam by an average of about 78 days, with a range anywhere from 2 days to over a year. That gap is long enough that many owners initially chalk the changes up to aging or stress. If your older dog’s personality has shifted and the change persists or worsens over weeks, it’s worth bringing up with your vet rather than assuming it’s just “getting old.”
Which Dogs Are Most at Risk
Brain tumors can occur in any dog, but they are far more common in older dogs. The median age at cancer diagnosis across all types in dogs is about 8.8 years, and brain tumors follow a similar pattern. Purebred dogs tend to be diagnosed at younger ages than mixed breeds.
Certain breeds face higher overall cancer risk. Roughly 50% of Irish Water Spaniels and Flat-Coated Retrievers die of cancer. Brachycephalic breeds (those with short, flat skulls) like Boxers, Boston Terriers, and Bulldogs have a well-documented predisposition to a type of brain tumor called a glioma. Larger breeds and Golden Retrievers are also frequently affected. If your dog belongs to a higher-risk breed, some veterinary oncologists recommend beginning general cancer screening as early as age 4, while age 7 is a reasonable starting point for most dogs.
How Brain Tumors Are Diagnosed
If your vet suspects a brain tumor based on your dog’s symptoms and neurological exam, the next step is almost always an MRI. This is the single most important diagnostic tool for brain tumors in dogs. An MRI can reveal a tumor’s size, location, and shape, and experienced veterinary radiologists can often distinguish a tumor from other causes of neurological symptoms like infections or strokes based on how the mass appears on the scan.
Your dog will need to go under general anesthesia for the MRI, since they have to stay completely still. The scan typically takes 45 minutes to an hour. In some cases, your vet may also recommend collecting a sample of cerebrospinal fluid (the liquid surrounding the brain and spinal cord) to rule out infections or inflammation that can mimic tumor symptoms.
A definitive diagnosis technically requires a biopsy, but brain biopsies are uncommon in veterinary medicine. Few clinics have the specialized equipment to perform them safely, the procedure carries real risks, and the cost is significant. In practice, most dogs are diagnosed presumptively based on MRI findings combined with their clinical signs, age, and breed. This approach is accurate enough that many treatment decisions are made without a tissue sample.
What a Diagnosis Means for Your Dog
Brain tumors in dogs are serious, but a diagnosis is not an immediate death sentence. How long your dog can live and how well they can feel depends heavily on the type of tumor, its location, and which treatment path you choose.
The two most common primary brain tumors in dogs are meningiomas (which grow from the membranes surrounding the brain) and gliomas (which grow from the brain’s supporting tissue). Meningiomas tend to be more treatable because they often sit on the brain’s surface rather than deep within it.
Treatment Options and Survival Times
For dogs with suspected meningiomas, radiation therapy and surgery are the two main treatment options. A large study comparing the two found that dogs treated with radiation had a median survival of about 696 days (roughly 23 months), while dogs treated with surgery had a median survival of about 297 days (roughly 10 months). Modeling that accounted for differences between the groups estimated the gap was smaller but still meaningful: around 22 months for radiation versus 16 months for surgery.
Stereotactic radiosurgery, a newer approach that delivers a single, precisely targeted radiation dose, shows similar results. In one study, 64% of treated dogs were alive at one year and 24% at two years, with a median survival of about 519 days (17 months). Over half of the dogs in that study showed noticeable clinical improvement after treatment.
Not every family can pursue advanced treatment, whether due to cost, the dog’s age, or other health problems. Palliative care, which focuses on comfort rather than curing the tumor, typically involves medications to control seizures and reduce brain swelling. This approach keeps many dogs comfortable for a meaningful period, though long-term survival with palliative care alone is generally shorter than with radiation or surgery.
What to Watch for Starting Now
If you’re reading this because something about your dog’s behavior or movement doesn’t seem right, the most useful thing you can do is start keeping a simple log. Write down what you’re seeing, when it happens, and how often. Note whether symptoms come and go or are getting worse. This kind of record is genuinely helpful for your vet because neurological symptoms can be intermittent, and your dog may look perfectly normal during a clinic visit.
Pay particular attention to any combination of signs: a new seizure plus a personality change, or a head tilt that comes with loss of appetite. Single symptoms have many possible explanations, but clusters of neurological and behavioral changes in an older dog raise the suspicion significantly. A thorough neurological exam by your vet is a reasonable first step and can help determine whether advanced imaging like an MRI is warranted.