Older dogs (over 7 years of age) are more likely to develop brain tumors than younger dogs. Of the two types of brain tumors, meningiomas and gliomas are the most common.
The type of brain tumor your dog has may be related to his/her breed. For example, long-nosed breeds like the Golden Retriever are more likely to develop meningioma. Brachycephalic dogs like Boxers and Boston terriers are more prone to glioma.
Brain tumors can be a complicated topic, but this post is going to help break it down. You’ll learn the differences in brain tumors including the signs to watch for.
Keep reading to learn what can be done to treat brain tumors in dogs to give them the longest, best quality of life.
Causes of Brain Tumors in Dogs
Risk factors for brain tumors in dogs are unknown. There are, however, a few theories that include:
- Diet
- Genetics
- Immune System Factors
- Chemical
- Environmental
The other risk factors for dogs have to do with the aging process.
Types of Brain Tumors in Dogs
Brain tumors are defined as being either primary or secondary. A primary brain tumor means that the tumor is found in the same place it originated. They originate from the brain tissue or membranes covering the brain.
Secondary brain tumors, however, are tumors that have spread to the brain from another location in the body. Examples of secondary tumors that have spread from other sites include:
- Tumors of the nasal cavity
- Nerve sheath tumors
- Pituitary adenoma
- Metastatic hemangiosarcoma
- Melanoma
Secondary tumors sometimes originate from the cranial nerves.
Meningiomas
Meningiomas are tumors that develop in the meninges. The meninges are the membranes that surround the brain and spinal cord. They tend to grow very slowly over many years without causing any symptoms.
Gliomas
Canine glioma tumors are the second most common type of brain tumor in dogs. They range from low-grade and slow-growing to high-grade malignant.
High-grade malignant brain tumors are known as glioblastoma multiformes. It’s thought that almost half of all gliomas occur in brachycephalic dogs.
Choroid Plexus Papillomas
Choroid plexus tumors can be benign (non-cancerous) or malignant (cancerous). They begin in the brain’s ventricular system and can block the drainage of cerebrospinal fluid.
Choroid plexus papillomas rarely show local invasion. Choroid plexus carcinomas, however, often spread to distant parts of the brain.
Most tumors of this type occur in middle-aged dogs with an average age of diagnosis of 6 years.
Choroid plexus tumors in dogs account for approximately 10% of all primary intracranial nervous system tumors.
D.R. Westworth, P.J. Dickinson, W. Vernau, E.G. Johnson, A.W. Bollen, P.H. Kass, B.K. Sturges, K.M. Vernau, R.A. LeCouteur, R.J. Higgins
First published: 25 August 2008https://doi.org/10.1111/j.1939-1676.2008.0170.x
“Choroid Plexus Tumors in 56 Dogs (1985-2007)”
How Long Can a Dog Live with a Brain Tumor?
There’s no set amount of time a dog can live with a brain tumor. The median survival time for a dog with a brain tumor depends on:
- How advanced the tumor is when it is found
- How successful surgical removal is
- The tumor type
- The age of the dog and his/her overall health otherwise
- Whether the dog has a primary tumor or a secondary tumor
Generally speaking, tumors that have metastasized (spread to other organs and lymph nodes) have a survival time of 2 to 4 months.
In dogs with meningiomas that are successfully removed and treated with chemotherapy, the prognosis is a little longer at 11 to 28 months.
Please remember: Every dog is different. Circumstances can vary widely. This is only a guide.
Studies show that owners are increasingly opting for treatment to extend life rather than opting to euthanize.
Making the Diagnosis of a Brain Tumor
The veterinarian will want to do a series of tests to determine the problem. There are a few ways to do this including:
Tissue Biopsy
This is the only way to make a definitive diagnosis of a brain tumor. Once a tumor is discovered, surgery is performed to remove it. At this time, a piece of tissue is taken from the tumor for examination under a microscope. This is used to define normal tissues versus diseased or cancerous tissue.
Neurological Exam
This is done through a physical examination. The veterinarian may measure your dog’s reflexes, sensitivity to light, and condition of the pupils.
Blood tests
Routine blood tests are often performed to get a complete blood count and chemistry panel. When blood tests are performed, veterinarians are able to look for:
- Cancers that come from blood cells (known as hematopoietic tumors)
- Cancers that are growing in the bone marrow
- Syndromes that are secondary to cancer (known as paraneoplastic syndromes)
- Tumors that cause changes in liver or kidney function
Chest X-rays and CT Scans
Chest x-rays are done for a number of reasons. The veterinarian may be looking for signs of any underlying condition. A chest x-ray may also show some evidence of cancer that has spread to the lungs.
MRI Scans (Magnetic Resonance Imaging)
MRI’s are able to extract a great deal of information regarding primary and secondary tumors in dogs.
They are used to detect brain tumors in dogs as well as identify strokes, bleeding in the brain, and pituitary tumors.
Abdominal Ultrasound
The veterinarian may perform an abdominal ultrasound to visualize whether the tumor has spread to other parts of the body.
Treatment Options for Dogs with Brain Tumors – Getting the Best Outcome Possible
The veterinarian is going to want to provide the best treatment options for your dog. Comprehensive diagnosis enables the veterinarian to see the whole picture. When he/she has that information and is confident in the accuracy, a customized treatment plan can be established.
Surgery
Sometimes the surgical removal of a brain tumor is the cure. Removing the entire tumor involves cutting a wide margin around the tumor to capture any cells that have started to migrate (metastasize).
Unfortunately, surgery carries inherent risks including:
- Complications of infection
- Edema (dangerous swelling of brain tissues)
- Hemorrhage (severe bleed)
The location, size, and invasiveness of the tumor will play a role in how successful surgery is.
Chemotherapy
If the surgeon doesn’t believe the tumor was entirely removed or is concerned about cancer spread, chemotherapy may be an option.
Chemotherapy helps to shrink the tumor and may help to alleviate symptoms. There are a few important things to understand about chemotherapy for dogs including the following:
Chemotherapeutic Agents
The type of blood vessels in the brain act as a blood-brain barrier. They actually prevent toxic or foreign substances from entering the brain. Unfortunately, this also applies to chemotherapy drugs.
There are, however, a few chemotherapeutic agents that will penetrate that barrier. Hydroxyurea, CCNU, and Cytosar will penetrate the blood-brain barrier. These drugs tend to improve clinical signs while (in some cases) reducing tumor size.
Does Chemotherapy Make Dogs Sick?
Surprisingly, many dogs tend to tolerate chemotherapy drugs differently than their human counterparts. Side-effects are usually milder and do not last as long.
Up to 75% of dogs have very few or no serious side-effects from chemotherapy. One reason for this may be that dogs receive less aggressive treatment than people.
Some side effects could include:
- Lack of appetite
- Vomiting
- Diarrhea
Radiation Treatment
Radiation is sometimes used alone or with other treatments like surgery. It is a traditional treatment to kill cancer cells; however, there is risk of damaging healthy tissues nearby.
Radiation therapy treatment requires repeat visits and uses a lower dose of radiation than stereotactic radiosurgery.
Stereotactic Radiosurgery
This procedure uses radiation beams to treat tumors in the brain, neck, lungs, liver, spine, and other parts of the body.
There is no incision required which may make it a safer option than putting an older dog under anesthesia. Instead, this procedure uses 3D imaging to target affected areas with little impact to nearby tissue.
Medical Management of Common Brain Tumors in Dogs
Medication is often necessary to treat clinical signs prior to a definitive diagnosis. Medications that may help include:
Steroids (Prednisone)
Steroids like Prednisone can be used to decrease inflammation of the cerebrospinal fluid. Some dogs will have dramatic improvement in clinical signs for weeks or months with steroid treatment.
Phenobarbital
Anti-seizure medications like Phenobarbital are used to control the severity of convulsions in dogs. This is another drug that can be used to manage symptoms while a definitive diagnosis is being made.
Potassium Bromide
Potassium bromide is a commonly used anti-seizure medication. It is often used in dogs with epilepsy but can also be used to lessen the severity of seizures caused by brain tumors.
Dog Breeds That May be Prone to Brain Tumors
Long-nosed dog breeds (known as dolichocephaly) are more prone to meningiomas (tumors that originate in brain cells). These breeds include the following:
- Golden Retriever
- Doberman Pinscher
- Border Collie
- Scottish Terrier
- Old English Sheepdog
- Boxers
When to Euthanize a Dog With a Brain Tumor
Determining the best time to euthanize a dog with a brain tumor is extremely difficult. The most useful, objective tool to use is quality of life assessments. Questions you may ask yourself include:
- Are my dog’s symptoms being adequately treated?
- Is my dog in pain?
- Is my dog able to experience the pleasures of being a dog?
- Can my dog eat?
- Can my dog exercise?
- Is my dog interested in what’s going on or is he/she sleeping all day?
- What does the veterinarian suggest?
This is a very difficult decision to make that will require some soul-searching and objective third-party advice.
Brain Tumors in Dogs – 9 Signs to Watch For
Brain tumors in dogs are not always evident right away. Symptoms could be vague or non-existent in the early stages. Unfortunately, common neurologic signs may not be observed until the cancer has advanced.
Feline brain tumors are often vague or nonspecific. Signs may include anorexia and/or lethargy.
Below is a comprehensive list of symptoms, and the type of brain tumor that could be causing them.
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Signs to watch for include:
#1. Seizures
Seizures can be partial (simple) or complex (grand mal). It’s common for dogs to have at least one seizure within their lifetime.
One seizure does not signify a brain tumor in dogs. However, if seizures worsen over time, become more frequent, or are accompanied with some of the other signs noted below, it’s important to bring your dog to a veterinarian.
#2. Head Tilt
Head tilts sometimes accompany seizures in dogs. They may happen randomly as well and they are not the same as when a dog is listening or waiting for something.
Dogs with a head tilt may shake their heads or attempt to push their heads into the wall or other surfaces. They might also exhibit other unusual behaviour like lack of coordination, stumbling, rolling around on the ground, etc.
#3 . Changes in Behavior
Dogs experience a wide variety of emotions. However, if there are marked behavior changes (sudden aggression, fearfulness, confusion, etc.) it’s time to take him/her to the veterinarian.
#4. Unsteady Gait or Wobbly Movements
This is usually easy to spot because it’s so different from the way your dog normally moves. He/she may suddenly sway to the side, stumble, or walk in an awkward way that isn’t attributed to some other reason.
#5. Vision Changes
A dog’s vision will change as they age. Cataracts, uveitis, and glaucoma are all possible reasons for vision loss.
If your dog is experiencing signs of vision loss (confusion at night, unable to find common things in the house, etc.) see a veterinarian to rule out other causes.
#6. Head Pressing
Head pressing is exactly what it sounds like. Sometimes, dogs with brain tumors will press their heads into a hard surface, like the wall.
Dogs with tumors do this because of intracranial pressure caused by a growing tumor
#7. Rapid Eye Movements (Nystagmus)
Rapid eye movements in dogs are defined when a dog is obviously unable to control eye movement. You may notice your dog’s eyes moving back and forth very quickly.
#8. Circling
Dogs will often circle around or in their beds before settling down. That is normal. However, if your dog begins to spin in circles for no obvious reason, take note of how long this is happening, when, and how often.
#9. Excessive Panting and Lethargy
Panting and fatigue are common in dogs, particularly after being out on a hot day. Excessive panting can signify any number of things from anxiety to pain.
If you notice that your dog is more tired than usual and also exhibits some of the signs noted above, it’s a good idea to make an appointment with the veterinarian.
SHORT GLOSSARY OF MEDICAL TERMS
Canine Glioma
This type of tumor starts within the glial cells of the brain or spinal cord .
Canine Meningiomas
Brain tumors that start in the membranes covering the brain.
Metastatic
This means that cancer has spread to other parts of the body.
Primary Brain Tumors
A primary tumor refers to the original tumor and its location.
Secondary Brain Tumors
Secondary tumors refer to cancer cells that have moved away from the initial site.
Summary
The only way a veterinarian can make a definitive diagnosis of a brain tumor is through surgical excision or biopsy of tissue. The signs noted in this post are a good indicator that there may be a tumor growing; however, any one of the signs noted could also be something else.
The diagnosis of a brain tumor is scary and heartbreaking; however, it’s important to have the information so that you can best treat your dog.
Treatment options often involve chemotherapy and radiation.
SOURCES:
Veterinary Health Center University of Missouri