It's not uncommon for older dogs to develop brain tumors. In this post, our Long Island veterinary specialists discuss signs of brain tumors in dogs, the serious nature of this condition, how primary and secondary tumors are diagnosed and treated and more.
Brain Cancer in Dogs
If you've noticed concerning neurological or vestibular symptoms in your dog such as increased or decreased appetite, loss of balance, vomiting and seizures, you are likely very concerned for your four-legged friend's health and searching for answers.
Symptoms may be subtle at first and mimic many other conditions, which is why many veterinarians will first treat for a soft tissue injury or arthritis. These tumors can also vary widely in their level of malignancy, and some can be effectively treated.
While brain tumors are uncommon in dogs, middle-aged or older dogs experiencing acute or progressive dysfunction in the brain should be examined.
Young dogs of certain breeds, such as the Boston Terrier and Boxer, have also seen increasing rates of brain tumors.
There is still a lot to learn about how different types of brain tumors affect dogs' health, longevity, behavior, cognition, personalities and other aspects of their lives, which can make it difficult to advise owners on the best treatment options for their pet.
What is a brain tumor?
The phrase 'brain tumor' may be one that strikes the most fear in pet owners' hearts and minds. Strictly speaking, the term is simply defined by a mass in the brain. However, it's commonly used to describe a cancerous (or neoplastic) mass in the cranial cavity.
Brain tumors can be primary, arising from the brain's cells and lining, or secondary, developing elsewhere and spreading to the brain.
Specific types of primary and secondary brain tumors seen in dogs include:
Primary
Adenocarcinoma, choroid plexus papilloma, glioma, meningioma, pituitary denoma.
Meningioma is the most common primary brain tumor in dogs, cats and humans. It originates in the arachnoid mater of the meninges (membranes lining the brain), not the brain's cells.
Therefore, meningiomas are not strictly brain tumors. However, they tend to be grouped with them since they appear within the cranial cavity and compress or invade the brain. These tumors happen more commonly in long-nosed (dolichocephalic) breeds, including the Golden Retriever. Meningiomas typically grow relatively slowly and are amenable to treatment. That said, more malignant forms do happen.
Secondary
When another tumor spreads (metastasized) to the brain from somewhere else in the body, this is a secondary tumor.
Examples of tumors that can spread to the brain include hemangiosarcoma, mammary carcinoma and melanoma.
Since these tumors have already spread through the body, they come with a very poor prognosis.
What are the signs of brain tumors in dogs?
When brain tumors compress or invade the brain, a range of concerning symptoms can appear. Resulting symptoms relate directly to the area of the brain that's affected and are not tumor-specific, meaning any disease impacting that area of the brain can lead to similar symptoms.
Brain tumors generally cause progressive symptoms in older animals. These symptoms may come on acutely, suddenly or insidiously. They may also be more or less severe depending on the day.
The Forebrain
The "thinking" area of your dog's brain is responsible for their behavior and final integration of ensory input. Tumors in the forebrain can cause:
- Continued circling or pacing
- Behavioral abnormalities, including loss of learned behavior
- Depression
- Decreased vision or awareness on one side of the body, which can cause your dog to bump one side of their body more often or misjudge even familiar spaces
- New onset of seizures (most common symptom of pets with forebrain tumors). These seizures can occur in addition to other symptoms or as the only abnormality. Whenever a dog over 5 or 6 years old experiences a new onset of seizures, a brain tumor can be ruled out by full diagnostic testing.
- Behaviors that express they are in pain
The Brainstem
Along with regulating the respiratory and cardiovascular systems, the brainstem also plays a vital role in regulating your pet's wakefulness and motor function (the ability to walk). Their sense of balance is derived from the brain stem, which also controls the nerves that are in charge of the eyes, throat, larynx, tongue and face, as well as the chewing muscles.
If tumors in the brainstem affect your dog's breathing, they can rapidly turn fatal. That said, the first typical symptoms of brainstem disease are vestibular symptoms (loss of balance) and weakness on one side of the body. A range of additional symptoms such as change in voice, inability to move the eyes, challenges swallowing and others.
Vestibular symptoms can include:
- Involuntary eye flicking (nystagmus)
- Abnormal eye position
- Vomiting and loss of appetite
- Head tilt
- Leaning and falling to the side of the head tilt
- Circling to the side of the head tilt
- Drunken gait with loss of balance (ataxia)
The Cerebellum
This part of the train interacts closely with a dog's vestibular system to control coordination of movements, posture and balance. Symptoms of cerebellar disease include:
- Normal strength
- Uncoordinated gait marked by dramatic goosestepping
- Swaying of the trunk
- Head tremors that are significantly worse when your dog is focused on food or other objects, but disappear when he's relaxed
- Wide-based stance
- Vestibular signs such as head tilt (sometimes)
How is a dog's brain tumor diagnosed?
If you've noticed a new onset of neurological symptoms in your dog and your pooch is 5 years or older, a brain tumor should be suspected. Brain tumors usually appear in the brain's oft tissues and with rare exceptions, cannot be detected with radiographs of the skull.
Your veterinary specialist will take the following diagnostic measures using magnetic resource imaging (MRI) or computed tomographic (CT) scans:
- Complete a full physical and neurological exam to check for other health conditions and learn which area of the brain is affected by neurological symptoms.
- Conduct routine blood work to rule out systemic issues and assess risk for anesthesia.
- Take thoracic radiographs to learn whether the cancer has spread (metastasized) to the lungs (a common area for this to occur).
- Perform a CT or MRI of the brain while your dog is under general anesthesia. Generally, MRIs will reveal more details than a CT and is the test of choice when checking for brain tumors.
That said, an MRI is more extensive and less widely available than a CT. Though CT images will reveal most choroid plexus paillomas and meningiomas, they may fail to detect gliomas. A lot of artifact can also appear in CT images when your vet specialist assess the brainstem and cerebellum. If your pet has symptoms of brainstem or cerebellar disease, or if the specific dog breed is predisposed to gliomas (e.g. a Boston Terrier), we recommend an MRI. - While your vet specialist may suspect a type of mass or tumor based on its appearance on a CT or MRI, a sample of the tumor must be tested through biopsy or surgery. It's vital to identify the cell types involved, which will reveal the type of the tumor and grade of its malignancy.
What is the prognosis?
Prognosis for brain tumors in dogs is poor, but there is also limited knowledge on this. The most consistent and reliable determinants of prognosis are the type of tumor and histologic grade. With treatment, some dogs can be helped significantly. The average (median) survival time is around 2 months with supportive care alone.
Meningiomas and pituitary tumors tend to respond better to treatment and have longer survival rates than gliomas or other intra-axial brain tumors.
Dogs with Grade I meningiomas have a more favorable prognosis than Grade II or Grade II meningiomas. While there is a lack of data in veterinary literature on this, higher grades tend to have worse prognoses.
What are treatment options for brain tumors in dogs?
Depending on your pet's circumstances and other factors, your veterinary specialist may recommend one or a combination of treatment options, such as:
- Surgery, followed by conventional finely fractionated radiation therapy (tends to offer best survival outcomes, when surgery is possible)
- Surgery and chemotherapy (when radiation therapy is not available, chemotherapy may be considered following surgery)
- Radiation therapy (the backbone of most cancer treatment for dogs tends to be effective at improving neurological symptoms, reducing tumor size and increasing longevity/length of life)
- Chemotherapy alone (this treatment of choice for metastatic brain tumors tends to improve neurological symptoms and quality of life for many dogs, with a median survival time of 5 to 6 months)
- Supportive medications such as prednisolone, omeprazole and anticonvulsants
Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding pets. For an accurate diagnosis of your pet's condition, please make an appointment with your vet.