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Featuring Demian Dressler, DVM and Sue Ettinger, DVM, Dip. ACVIM (Oncology), authors of The Dog Cancer Survival Guide

Signs of Brain Cancer In Dogs

Updated: May 15th, 2024

Tumors in the brain are very tough for us in veterinary medicine today. There are two reasons for this.  One is that they are hard to diagnose without advanced imaging like CT or MRI.  These are not available to everyone, since many do not live within a reasonable distance, and they are not cheap.

The second reason is they are hard to treat.

Let’s look at both of these topics.  First, how would a vet suspect a brain tumor in a dog without the use of one of these imaging tools?

I would like to introduce some words to you.  One is “unilateral.”  When a medical problem is unilateral, it means it is occurring on only one side.  There is a phrase that you should know as well: “space occupying lesion”.  A space occupying lesion means that the problem takes up space and most commonly displaces or puts pressure on the surrounding tissue.

One of the very first things a vet will do is try to decide where in the body the problem is going on.  This is called the “anatomical diagnosis”.  We try to pinpoint the organ, tissue or system that we believe is the location of the issue in the body.

Next,  vets will usually come up with a list of possible disorders that could affect that area.  These are the “differential diagnoses,” which means a list of different possibilities that are ranked in order of what is most likely to what is least likely.

When we create these possibility lists, we will use information about the dog to help narrow them down and rank them.  Age is a big one.  Certain diseases are more common in young dogs and certain are more common in older dogs.  Breed is another since certain breeds are more prone to certain problems.

Sex is another, and whether a dog has been spayed or neutered.  All of these things impact probabilities.

The history you give a vet will also help. Did the problem start suddenly or slowly?  What about appetite, thirst, and other signs of illness? Is it worsening?

Is there weight loss?

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The physical exam helps a lot.  Here is where the rubber meets the road with brain cancer, and the words you learned above come into play.

When we think about brain cancer, most of the time the dogs will have some sort of brain sign.  These include seizures, blindness, and other obvious signs like that.  (Note that other body parts can be diseased and produce these signs.)

Now, one key point your vet may pick up is that the brain signs in a dog are unilateral- they issue seems to be affecting one side more than the other.  When this occurs, there is some assymetry going on.  One side is different from the other.

Perhaps we have a loss of coordination, but it affects the left side more than the right side.  Or maybe a pupil is dilated or constricted in the right eye but not the left.  Possibly the retina (seen by looking in the eyeball) looks different on one side.  Could be there is a droop or weakness in the muscles of the face.

These all point to things that are assymetrical.

If it looks like the problem is in the brain (which is concluded after laboratory testing), there are not many common brain problems in dogs that affect one area of the brain but not other areas.  One of the most common is a space occupying lesion, or a tumor.

But wait!  Other things can do it too.  For example, a stroke (vascular accident) can sometimes happen in dogs.  A common one is a problem with the vestibular system, which is responsible for keeping balance. This is called geriatric vestibular syndrome. Rarely, inflammation or infections can do it.  These all can have signs that affect either the left or right side of the body.

Now, more information can be gathered to help sort these things out.  A critical piece of information for us is what is happening with the problem over time.  Strokes most commonly stay the same severity or get better.  Geriatric vestibular syndrome almost always gets better.

Tumors however do not.  They progress.  Inflammation and infections in the brain get worse too.

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Most of the time one can rule out the majority of the brain inflammation and infections with blood work and a spinal tap.

So if the problem is pointing to brain (the organ), in an older dog, and it seems like it looks assymetrical (affecting a single area but not the adjacent area), it is progressing over time, and lab testing rules out the other things that can look like it, we are left with brain tumor as number one.

This is how vets will sometimes talk about brain tumors without the benefit of a CT or MRI. They are talking about the highest probability.

As far as treatment is concerned, doing brain surgery on dogs is not routinely done simply because most of the time the technique has not been well worked out.  There are some rare neurosurgeons out there that have done it successfully but they are few and far between.

However, there is a new technology out there in New York that can help.  Dr. Sue Ettinger, an oncologist who is working with me on the second edition of The Dog Cancer Survival Guide, works at The Animal Specialty Center. The facility houses the most sophisticated tool for treating brain tumors in dogs in the country.

It is called the Cyberknife.  The apparatus is capable of directing many small doses of radiation at brain tumors in dogs from multiple directions during the treatment, in an effort to destroy the tumor without harming the patient.

Other approaches I discuss with my clients in the Guide include diet, supplements like Apocaps, life quality enhancement, touch therapies, and considering homeopathy.  A closer look at homeopathy in brain tumors, in particular gliomas, can be found here.

Please keep your vet involved in all steps in your dog’s treatment plan.


Dr D


Leave a Comment

  1. Marci Spadafore on February 19, 2018 at 3:12 pm

    Wow, great article. The way it was organized made the subject so easy to understand. Thank you!

  2. hayley on April 16, 2016 at 1:36 am

    hi my brother has a staffy .. about a week ago he had a stroke and lost balance his eyes was going really fast .. he is still weak on his right side , and since he has had a stroke he has startd dribbling .. still weak on his right side and his ride sided face has dropped .. what could this be please he isnt drinking as much as he used to and he also hasnt eating much at all

  3. Pam Pollock on March 25, 2015 at 12:29 pm

    i have a 8 year old giant Schnauzer that monday was not able to chew food or swallow water. the vet said she think he has a mass on this brain stem, has anyone heard of this befor

  4. Lois on March 14, 2015 at 1:51 pm

    I had a puppy that had issues. His left eye would bulge out off and on. And when I told him to the vet his eye was normal looking. He also had Pano of which made him not let us touch his leg. He was growling for no apparent reason. And when he put his head between my legs, I would rub his neck up and down and all around. I didn’t know if he just liked it or if he had a serious pain in his head. He would only go half way up the stairs and just sit there. And when he played ball he would change his mind and just stop. This was not normal as to when he was under a year old. He would be 2 years old now. A vet had said that he could have had a brain tumor and that is why he is biting us. He was highly intelligent German Shepherd with superior lineage. Could he have had a tumor as someone had suggested? I just put him down last Friday because between his Pano and his fear aggression and his biting caused me concern for him and us.
    Apollo’s sad mommy

  5. Susan Kazara Harper on February 22, 2015 at 4:10 pm

    Andrea, we’ve been so backed up, and I’m sorry you didn’t get a reply before this. How is your girl now? Has she been to a vet? Any news?

    • Susan Kazara Harper on February 22, 2015 at 4:11 pm

      Hi Toni, We’ve been so backed up and I apologize you didn’t get any response before this. Is there any more news? How is your dog doing?

    • Mandy on February 15, 2019 at 12:05 pm

      I have a 12yr old dog that is half English bulldog but we don’t know the father. Well for 2-3 days she wouldn’t stand , barely ate, shook and coughed a few times for 1 night. She’s been herself for 2-3 days now but when we woke up her right eye was turned upward. Could she have possibly had a stroke?

      • Dog Cancer Vet Team on February 18, 2019 at 8:46 am

        Hello Mandy,

        Thanks for writing. As we’re not veterinarians here in customer support, we can’t offer you medical advice, however we can provide you with information based off Dr. Dressler’s writings 🙂

        We couldn’t find anything with regards to the signs and symptoms of a stroke in dogs, however there is an article on the Signs of Dog Cancer Decompensation that you may find helpful as does list some of the signs of cancer as coughing, limping, and loss of appetite, to name a few.

        You should consult with your veterinarian to find out what might be causing these problems, and to find out if your girl did have a stroke.

  6. Andrea on January 24, 2015 at 1:22 pm

    My 7 year old pitbull has suddenly started walking in circles, staring into corners and recently became snappy, aggressive and barking when you try to move her. Her balance is off and she no longer cares about anything. She doesnt respond, come or acknowledge tricks she knows. Im so worried about her and am in a cash jam. Does any of this point in a particular direction so I can at least have a small idea of the news I’ll hear from the vet?

  7. amy new on August 21, 2014 at 10:50 am

    My dog is a Golden Retriever. He has never really played fetch but he always ran after what I threw and sniff it then come back with out it. He was jumpy and loved running round the garden. Recently I noticed he looks in the direction we throw something as if he saw me throw it but cant see it in the air or land. He no longer jumps. He has never barked. he isn’t eating or drinking as much s he used to. And just walks round the garden slowly then just goes to sleep then he just strolls around. I know there is something wrong but my parents and sisters other relatives and friends think he is fine but I have always spent more time with him and I know he’s not ok. I also often think he is limping but then I look at him again and he’s not. Is he just getting old or is there something wrong.

    • Susan Kazara Harper on August 22, 2014 at 11:52 am

      Amy, It sounds like you know your dog better than anyone, and it also sounds like you’re best bet it to take your dog to a vet. It might be “getting old”, but getting old doesn’t have to mean we stop playing. Please make an appt with a good vet, and before you go I suggest you take short videos on your phone of your dog walking, getting up, all the things that you think have changed. What are his poos like? Solid and well shaped, or runny? Take the short videos to your bet and explain your concerns. It may be that your dog just needs a little help with something, but you won’t really know until you go. Waiting will not make anything better. Go to the appt with a list of what you are concerned about, and your videos to show. Good luck!

  8. Vlatko on August 4, 2014 at 8:58 pm

    Hi guys, mby i m on wrong session but i realy need help !!
    My dog started to bide the root of the tail near anus and made small wound. He s ok but on a moments he start to run like in house without control and than sit and breath like he s afraid of something. Sometimes when he walk he got problem with moving going on side without stabilisation (his right leg doesent work well and falling on that side). Idont know is this problem with anal sacs or a neuro problem. Please give some advise soon as u can and i m sorry about language. Thx in advance

    • Susan Kazara Harper on August 6, 2014 at 1:47 pm

      Hello Vlatko,
      I understand your concern. There’s no way to diagnosis anything online. Something is definitely bothering him, and the best thing you can do is to make an appointment with your vet and get him checked out. It may be a very easy fix, so please don’t waste time worrying about the worst possible diagnosis. Please don’t wait. This will not get better, and might get worse. A vet visit is needed here, and you will both be much happier when you know what it is, and get some help. Good luck!

  9. Margo C on May 9, 2014 at 7:24 am

    Our 10 year old lab has been diagnosed with dementia or a brain tumor. We ruled out everything else with blood work, and because of his age, CT/MRI is too risky for him to go under anesthesia. The dog just constantly walks around and paces. He won’t lie down unless you force him to. He just walks around in circles for hours at a time. He is starting to go to to the bathroom in the house, as well as lose his ‘perception’ of things by putting his paws in his water bowls. He doesn’t bark nor wag his tail and stares into corners, we aren’t sure he even recognizes us. We were going to try Anipryl, but have decided to try some homopathic remedies, since we only know it’s one of the two. This all started happening within the last 5 to 6 weeks. Any one else’s thoughts/opinions would be greatly appreciated.

  10. Lester Kwok on May 9, 2013 at 1:51 am

    Dr D;

    Most vet in Singapore has given up hope on Jill (please see her scans at

    All vets treating her only want to put her to sleep except for Dr Ly. He has taken a personal interest in her (see

    He is puzzled with why Jill has not been showing any sort of pain, signs and symptoms of brain cancer. Jill is on most supplements recommended for cancer treatment and also BARF diet. One additional thing Jill is on is O2 therapy. I am a diving instructor and I have access to medical grade O2 used for decompression treatments. I have placed Jill in O2 cages and “helmets”. Using a the calculation of 100% exposure of O2, I have derived a short formula for her without risking her to Oxygen toxicity.

    Dr Ly is now wondering about it. Is it O2, or the Nanodiamond treatment for cancer that I am putting Jill on, or is it the supplements. He has advised not to go for any more MRI or CT scans but I am rather skeptical about not sending her for scans. Without the scans, I will not be able to judge or gauge her condition anymore.

    What do you suggest?

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