PET Q&A: Seizures in dogs
Q. My 13-year-old golden retriever, Cassie, recently began having seizures. My veterinarian is concerned he may have a brain tumor and recommends an MRI. Is there anything we can do if a brain tumor is found?
I am sorry to hear about Cassie. Seizures are the most common neurological problem in dogs, but that does not make them any less upsetting to witness. Canine seizures have many causes, with epilepsy being the most common. However, dogs that experience their first seizure at an older age have a greater likelihood of having a brain tumor as the cause.
Most dogs diagnosed with brain tumors are older than 9 years of age. Brain tumors can occur in any breed, and while they are rare in the overall dog population, some breeds are overrepresented. Boxers and golden retrievers, for example, are predisposed to developing brain tumors.
There are several types of brain tumors, and they can arise from the brain tissue itself (gliomas), the surrounding tissues (meningiomas, or skull tumors) or a distant site and then spread or metastasize to the brain (lymphoma, melanoma, hemangiosarcoma). Golden retrievers are prone to developing meningiomas, whereas boxers are more likely to be diagnosed with gliomas.
The first step in determining if a dog has a brain tumor is to visit your veterinarian for an examination. Based on the description of the seizure episodes, the patient history (any changes in behavior, personality, vision, etc.) and the results of the examination, your veterinarian may refer you to a specialty hospital for evaluation by a neurologist. Blood work, abdominal ultrasound and radiographs of the chest may be recommended prior to advanced imaging of the brain, usually an MRI. A patient needs to lie perfectly still during the MRI, so general anesthesia is used. General anesthesia carries risks, which need to be discussed with your veterinarian. If a brain tumor is identified on the MRI, the neurologist and radiologist will attempt to determine which tumor type it may be. A definitive diagnosis is ideal; however, biopsy of the mass is not always possible due to the invasiveness of the procedure.
Meningiomas originate from the surface of the brain, from the meninges which are the tissues overlying the brain. They are slow-growing tumors and push the brain aside as they grow. In dogs, they also send out small finger-like projections that invade the brain tissue. If they are in the front and top portion of the brain, surgical removal is possible. The decision to pursue brain surgery is a difficult one. There are risks. However, most patients undergoing brain surgery are successfully discharged from the hospital.
Unfortunately, in dogs, surgery alone is not curative. Other treatment options, such as radiation therapy or chemotherapy, can be combined with surgery to improve outcome. These therapies also can be used alone when surgery is not an option. Dogs tolerate radiation therapy to the brain well, and treatment times have become shorter, thanks to increased availability of the more advanced stereotactic radiation therapy. Oral chemotherapy is another option for treating meningiomas, and is usually well tolerated.
Lastly, palliative care with steroids is a treatment option. Steroids reduce swelling around the mass and help treat many of the clinical signs and changes associated with the tumor. Steroids alone do not reduce the size the mass; however, they greatly improve the quality of the life of the patient.
In addition to any of these therapies, seizure medication must be used. Knowing about the tumor will help your vet know which medicine to use.
Gliomas are more aggressive tumors that originate from within the brain tissue itself. Surgery is usually not feasible or recommended, which leaves radiation therapy, oral chemotherapy and palliative steroid therapy as the treatment options.
A diagnosis of a brain tumor is devastating; however, there are several options regarding diagnosis and treatment. Your veterinarian is the best person to begin the discussion with.
— Kerry Bailey, DVM, DACVIM (neurology), Oradell Animal Hospital