Brain tumours in dogs and cats can either arise within the brain (a primary brain tumour) or arise outside the brain and spread (metastasis) to the brain (a secondary brain tumour).
Approximately 50% of brain tumours in dogs are primary and 50% are secondary, whereas in cats the majority (70%) are primary.
The most common type of primary brain tumour in both cats and dogs is a meningioma. Other common primary tumours include gliomas and choroid plexus tumours. Lymphoma, haemangiosarcoma and pituitary gland tumours are common secondary brain tumours but a wide variety of tumour types can be involved.
Treating a tumour in a pet is often complicated, so it is a good idea to be well informed so you can make the best choice for them.
Signs of brain tumours
The clinical signs depend on the location of the tumour within the brain and in the case of secondary brain tumours, where else in the body the tumour is located.
The types of clinical signs which may indicate a brain tumour include:
- Seizures – these are the most common symptom
- Persistent circling in one direction
- Loss of coordination (ataxia)
- Permanent tilting of the head in one direction
- Depression
- Changes in the sounds they make, eg a dog’s bark may sound different
- Paralysis
- Difficulty swallowing
- Vomiting
- Loss of appetite
- An inability to move their eyes or abnormal positioning of the eyes
- Head tremors
Important note: these signs do not always indicate the presence of a tumour and may be caused by something different. It is impossible to diagnose or exclude the presence of a brain tumour via clinical signs alone.
What causes brain tumours?
It is not yet clear why pets develop brain tumours. Like humans, it may be a mix of genetic and environmental factors. Lifestyle isn’t known to be a cause of brain tumours.
Tumours are often age related and are generally more common in dogs over five years old. Cats with tumours have an average age of approximately 12 years.
Certain dog breeds are also more likely to develop brain tumours, such as those with squashed faces like Boxers and Boston terriers. Male cats are more commonly affected.
Diagnosis
To begin with, a thorough physical examination is needed and this includes a neurological examination to look at the pet’s reflexes, response to light and so on.
An MRI scan is typically used to examine the brain tissue but in some cases a CT scan may be done. These are done under general anesthetic. A chest x-ray may also be done to check if the tumour has spread. Imaging will generally be sufficient to confirm the presence of a tumour and in the case of MRI, there are certain characteristic features that help indicate tumour type. Biopsies are generally not used for brain tumours because they are a risky procedure and their findings generally do not affect the treatment options.
Blood tests may also be done to check that organs like the kidney and liver are working well and to look at their white and red blood cells.
Treatment
The treatment that is chosen depends on a number of factors including the tumour’s location within the brain, what type it is and whether it is primary or secondary. The extent to which the individual cat or dog is affected by the tumour is also considered.
Some tumours are more susceptible to treatment. In many cases, it is not possible to cure the tumour but treatments can help manage the symptoms as part of their palliative care.
Definitive treatment of the tumour can involve surgery and or radiation therapy. Chemotherapy is rarely an option as most brain tumours are not very responsive to it.
Surgical removal of primary brain tumours is a possibility if the tumour is sufficiently small, accessible and confined to one area. Some meningiomas in dogs and cats can be managed surgically. It is important to remember that there is a considerable risk associated with brain surgery and in many instances it is not possible to remove all of the tumour and cure the pet.
For certain types of tumours, radiotherapy may be used. Sometimes it can be used after surgery to remove any remaining bits of tumour and reduce the chances of regrowth. Again, radiation rarely provides a cure but can give cats and dogs a good quality of life for some time following diagnosis. Radiation therapy is only available at a few centres in the UK.
Speaking to specialists like an oncologist or neurologist will help you understand the treatment options better. You can then weigh up the ethical and financial implications of the various treatment options. Sometimes euthanasia is considered to be the kindest option.
If you’re concerned your pet is showing symptoms of a brain tumour, then book an appointment with your GP vet. They will assess your pet, and if they are diagnosed with a tumour, you can ask your pet to be referred to us for treatment. Find out more about the referrals process here.
Alternatively, for more information about common illnesses, surgery and treatments for dogs and cats, head on over to our blog.