Brain tumors occur in dogs of any age, any sex and any breed, but are most frequent in older dogs, with the greatest incidence in dogs of over 5 years of age. The cause of brain tumors in dogs is not known. Genetic, environmental, dietary, viral, traumatic and immunologic factors have been considered. A broad spectrum of tumors occurs in dogs. Gliomas, (for example, astrocytomas and oligodendrogliomas) and meningiomas are the most commonly seen canine brain tumors. Gliomas can range in malignancy from low grade and slow growing, to high grade, poorly differentiated malignant tumors known as glioblastoma multiforme. Oligodendroglioma is a form of glioma that arises from glial (supportive) cells of the brain and often contain solid mineral deposits, which are mostly calcium, but also small pockets of blood and cysts. Glial cell tumors and pituitary tumors most frequently occur in brachycephalic breeds (breeds with short noses such as French Bulldog and English Bulldog), but also in the Boxer, Golden Retriever, Doberman Pinscher, Scottish Terrier and Old English Sheepdog (Bobtail).
Seizures are the most common presenting symptom of oligodendrogliomas. Radiation is currently the treatment of choice for gliomas. Chemotherapy is a reasonable alternative when treating a glioma if radiation is not an option. It is important to understand that most brain tumors can be treated but not cured. Thus the major aim of treatment is to extend a good quality of life for as long as possible. Radiation therapy of brain tumors in dogs typically involves administration of multiple fractions over several weeks. Fractionation is used to minimize damage to normal tissue. The aim of surgical removal of a brain tumor is either to cure the disease by complete removal (which only occurs rarely), or to alleviate the clinical signs by decompressing the brain. This can be life saving if the mass is very large. Brain tumors can be removed surgically if they are located in a site that can be reached safely. Gliomas are more difficult to remove because they lie deep within the substance of the brain.
- Small Animal Clinical Oncology. Stephen J. Withrow, E. Gregory MacEwen
- Oligodendroglioma and Oligoastrocytoma (American Brain Tumor Association)