How Common Are Brain Tumours in Dogs?
Brain tumours are not rare in dogs. Post-mortem studies suggest that primary brain tumours occur in roughly 14 per 100,000 dogs per year, and the true incidence is likely higher when secondary (metastatic) tumours are included. The risk increases significantly with age: the majority of dogs diagnosed with brain tumours are over five years old, with peak incidence in dogs aged seven to twelve years. Certain breeds are predisposed to specific tumour types, and understanding these associations can help owners and vets interpret symptoms in context.
There are two broad categories of brain tumour in dogs: primary tumours, which originate within the brain or its coverings, and secondary tumours, which represent metastases from cancer elsewhere in the body (such as carcinomas, haemangiosarcoma, or lymphoma spreading to the brain). This article focuses primarily on the two most common primary brain tumour types: meningioma and glioma.
Meningioma: The Most Common Primary Brain Tumour
Meningioma arises from the meninges — the protective membranes that surround the brain and spinal cord. It is the most commonly diagnosed primary intracranial tumour in dogs and, importantly, one of the more treatable. Meningiomas tend to be slow-growing, well-demarcated masses that compress rather than invade surrounding brain tissue. This characteristic makes them surgically accessible in many cases.
Meningiomas in dogs most commonly affect older, larger breeds. Dolichocephalic (long-nosed) breeds such as Golden Retrievers, German Shepherds, and Labrador Retrievers appear over-represented. The most frequent site is the convexity of the cerebral hemispheres or the skull base, and the clinical signs reflect the location — focal seizures, behavioural changes, or progressive neurological deficits depending on which brain region is being compressed.
Treatment and Outcomes for Meningioma
Dogs with meningioma have several treatment options, and outcomes are considerably better than many owners expect when first confronted with the diagnosis.
- Surgical resection: For accessible meningiomas, surgical removal via craniotomy performed by a specialist veterinary neurosurgeon offers the best outcomes. Median survival times of 7–12 months are reported with surgery alone, and some dogs survive two years or more. Surgical risk depends heavily on tumour location and the individual dog's health status.
- Radiotherapy (RT): Definitive-intent radiotherapy — typically stereotactic radiosurgery (SRS) or fractionated RT — achieves excellent local tumour control for meningiomas and is the preferred treatment when surgery is not feasible or when residual tumour remains post-operatively. Median survival times of 12–20 months are achievable with RT, and some long-term survivors are reported.
- Palliative management: For dogs where surgery and RT are not pursued, corticosteroids (prednisolone) can reduce peritumoral oedema and provide meaningful symptomatic relief. Anti-epileptic drugs manage seizures. Median survival with palliative care alone is typically 1–3 months, though this varies widely.
Glioma: Brain Tumours in Brachycephalic Breeds
Gliomas originate from the glial cells — the supportive cells of the brain — and include astrocytomas, oligodendrogliomas, and glioblastomas. Unlike meningiomas, gliomas are infiltrative: they grow into the surrounding brain tissue rather than compressing it from outside, making complete surgical resection extremely difficult.
One of the most striking epidemiological findings in canine brain tumour research is the strong predisposition of brachycephalic breeds to gliomas. Breeds significantly over-represented include:
- French Bulldogs
- English Bulldogs
- Boxers
- Boston Terriers
- Pugs
The reason for this breed predisposition is not fully understood but is thought to relate to the compressed skull architecture of brachycephalic breeds and the resulting altered brain morphology. Gliomas in these breeds often affect the cerebral hemispheres, and focal seizures — particularly tonic-clonic seizures with a focal onset — are a very common presenting sign.
Gliomas tend to carry a worse prognosis than meningiomas due to their infiltrative nature. Surgical debulking may be considered in some cases but rarely achieves long-term disease control alone. RT is the cornerstone of treatment, and palliative corticosteroid therapy provides short-term symptomatic benefit.
New Onset Focal Seizures in a Middle-Aged Dog: Take It Seriously
A crucial clinical rule in veterinary neurology is this: a new onset of focal seizures in a middle-aged or older dog should be treated as a brain tumour until proven otherwise. This is not alarmism — it is pragmatic clinical reasoning based on the age-related incidence of brain tumours and the fact that focal seizures (rather than generalised tonic-clonic events) are particularly associated with structural brain disease.
Focal seizures involve abnormal motor, sensory, or behavioural activity limited to one part of the body — facial twitching, repetitive chewing movements, one limb jerking — or manifest as sudden behavioural changes, fly-catching behaviour, or episodic vocalisations. They may or may not progress to a generalised seizure. In a young dog (under five) with no other neurological signs and a normal examination, idiopathic epilepsy is a more likely explanation. But in a seven-year-old Boxer with a two-month history of progressive focal motor seizures, a brain tumour must be the primary differential diagnosis until imaging says otherwise.
MRI: The Gold Standard for Diagnosis
Magnetic resonance imaging (MRI) is the definitive diagnostic tool for brain tumours in dogs. It provides far superior soft tissue detail compared to CT scanning, allows characterisation of tumour type, location, and extent with high accuracy, and guides surgical and radiotherapy planning. MRI requires general anaesthesia in dogs and is performed at specialist referral centres and veterinary teaching hospitals.
On MRI, meningiomas typically appear as well-defined, contrast-enhancing extra-axial masses with a characteristic "dural tail" sign. Gliomas tend to appear as poorly defined intra-axial lesions with irregular or ring enhancement. While MRI findings can suggest a tumour type with reasonable confidence, definitive diagnosis requires histopathology — either from a biopsy sample or from tissue obtained during surgery.
Additional diagnostic steps often include chest radiographs and abdominal ultrasound to check for primary tumours elsewhere (in case the brain lesion is metastatic), and full blood work to assess the dog's fitness for anaesthesia and any planned treatment.
Referral to a Veterinary Neurologist
Any dog suspected of having a brain tumour should be referred to a specialist veterinary neurologist without delay. Your general practice vet plays an important role in initial assessment, stabilisation, and initiating anti-epileptic therapy where needed, but the full range of diagnostic and treatment options is only available through specialist neurology and oncology services.
At the referral appointment, the neurologist will perform a detailed neurological examination to localise the lesion, discuss the options for imaging, and outline the treatment pathway most appropriate for your dog. This consultation is also an opportunity to discuss the realistic outcomes honestly, including what quality of life can be expected during treatment.
Survival Times with Radiotherapy: 12 to 20 Months
One of the most important pieces of information for owners of dogs with brain tumours is that modern radiotherapy can deliver genuinely meaningful survival times. Published data for dogs with meningioma treated with RT consistently report median survival times of 12–20 months, with many individual dogs surviving considerably longer. For gliomas, outcomes are less favourable but still meaningful — median survival times of 6–12 months with RT are reported in some series.
Stereotactic radiosurgery (SRS), which delivers high-dose radiation with sub-millimetre precision in one to three sessions, is now available at several UK veterinary referral centres and offers an attractive treatment option for suitable tumours. Quality of life during and after RT is generally well preserved, particularly in the post-treatment period once any acute radiation effects have settled.
Every dog is different, and outcomes depend on tumour type, location, grade, and the individual patient's health. But a brain tumour diagnosis is no longer the immediate death sentence it once appeared. With the right specialist team, many dogs live comfortably for a year or more after diagnosis.
Written by Sarah Bennett