Oligodendroglioma
A broad spectrum of tumors occurs in dogs. Gliomas, (for example, astrocytomas and oligodendrogliomas) and meningiomas are the most commonly seen brain tumors in dogs. Brain tumors occur in dogs of any age, any sex and any breeds. They are most frequent in older dogs, with the greatest incidence in dogs of over 5 years of age. Certain breeds have a higher incidence of some tumor types. Glial cell tumors and pituitary tumors occur commonly in brachycephalic breeds (breeds with short noses such as French and English bulldog). Breeds most often affected include Boxer, Golden Retriever, Doberman Pinscher, Scottish Terrier and Old English Sheepdog (Bobtail). The cause of brain tumors in dogs is not known. Genetic, environmental, dietary, viral, traumatic and immunologic factors have been considered.
Oligodendroglioma belongs to the group of rain tumors called gliomas that arise from glial, or supportive cells of the brain. Oligodendrogliomas arise from oligodendrocytes
cells within the brain. The role of normal oligodendrocytes is to form a covering layer for the nerve fibers in the brain. Oligodendrogliomas are soft, greyish-pink tumors. They often contain solid mineral deposits – which are mostly calcium - called calcifications. Oligodendrogliomas may also contain small pockets of blood and/or cysts. Gliomas can range in malignancy from low grade and slow growing, to high grade, poorly differentiated malignant tumors (known as glioblastoma multiforme).
CAUSES
The exact cause of these tumors, as well as other
types of brain tumors, is unknown. We do know that tumors develop when a normal cell, for some unknown reason, becomes abnormal. That abnormal cell may produce the wrong number of proteins or enzymes, or it may be missing genetic material containing the cell’s basic instructions. When that abnormal cell reproduces itself, it creates two abnormal cells. Those two cells reproduce to create four cells, four cells create
eight, and so on. This reproduction continues, resulting in a "lump" of abnormal cells. That lump is called a tumor. Scientists now know that the cells of some oligodendrogliomas contain abnormal genetic material.
In humans, oligodendrogliomas have an indolent course, and patients may survive for many years after symptom onset. Their good prognosis relative to other parenchymal tumors probably stems from inherently less aggressive biological behavior and a favorable response to chemotherapy, a recently discovered finding based on genetic characteristics.
SIGNS
Seizures are the most common presenting symptom of oligodendrogliomas Other symptoms vary by location and size of the tumor, and can include
weakness, or visual symptoms. Whenever a dog or cat that is greater than five or six years of age has a new onset of seizures, a brain tumor is a possible differential and ruled out by a full diagnostic workup.
TREATMENT
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. Dogs with an oligodendroglioma may survive 66 weeks. 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.
The cost of radiation varies geographically, but is usually in the region of $3000-4000. 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.
Go Pets America recommends seeking the advice of your local veterinarian for the most appropriate vaccination program and for the diagnosis and treatment of your pet's health problems. For vaccination requirements please contact your state and local licensing authorities.
Adapted from:
1. Small Animal Clinical Oncology By Stephen J. Withrow, E. Gregory MacEwen
2. NC State College of Veterinary Medicine Department of Clinical Sciences
3. Oligodendroglioma and Oligoastrocytoma. American Brain Tumor Association
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