Brain Tumors

About Brain Tumors

Dogs and, less commonly, cats are susceptible to developing brain tumors. The incidence of brain tumors is thought to be higher in dogs than people. Brain tumors can arise from different cells in the brain. This includes the coverings of the brain called the meninges (meningioma), the brain tissue itself (glioma) or the cells that line the fluid filled ventricular spaces (chorid plexus papilloma/sarcoma and epedymoma). It is also possible for tumors that arise in other parts of the body to metastasize (spread) to the brain.

Is it a Brain Tumor?

Clinical signs of a brain tumor depend on its location in the brain. Tumors of the cerebrum are one of the most common causes of new-onset seizures in dogs over 7 years of age. Dogs are often neurologically normal early on and display only seizures and/or behavior changes. Brain stem tumors most often present as vestibular (the balance system) dysfunction. Diagnosis of a brain tumor requires some form of advanced imaging- CT or MRI. MRI is usually preferred to allow better detail of the brain and tumor tissues. Based on the imaging features a general conclusion as to potential tumor types are possible, but does not replace a pathologist’s evaluation of the tumor tissue.

Meningiomas appear to be the most common tumors in dogs and cats, but any type of tumor is possible. Meningiomas are usually benign, but more malignant variants occur. They arise from the surfaces that are covered with meninges. They are usually the most amenable tumors to remove surgically and can have very positive outcomes with this treatment. Gliomas are almost always malignant and are often in locations that do not respond well to surgery. Ventricular tumors are often benign, but may be more difficult to remove based on their location. Metastatic tumors are not usually treated surgically as they often represent wide-spread cancer in the patient. Medical therapy to control swelling, seizures, and inflammation may help for a period of time in patients with metastatic tumor in the brain.

Treatment

There are 4 general categories of treatment that may be offered for your pet if he/she is diagnosed with a brain tumor: surgery, radiation, chemotherapy and palliative therapy.
 

Surgery
The treatments offered depend on tumor type, tumor location and accessibility, age of the patient, other underlying diseases, and how the patient is doing clinically. Surgery is most often used as treatment for meningiomas and other surgically accessible tumors.

Radiation Therapy
Radiation therapy is most commonly used for non-accessible tumors, pituitary tumors, gliomas and as an adjunct therapy with surgery. Most chemotherapy drugs are not useful for brain tumors as many of these drugs do not readily enter the brain tissue.

Chemotherapy
There are select chemotherapeutic agents that can be used to treat brain tumors. Chemotherapy is not typically the preferred primary therapy but is used in those cases where surgery and/or radiation are not being considered because of the prognosis, costs of other therapies, or age of the animal. It may also be used as an adjunct therapy to other treatments.

Palliative Therapy
Palliative therapy is based on maintaining quality of life by treating the secondary effects of the tumor such as edema (swelling) and inflammation. Palliative therapy also consists of treating symptoms, for example using anticonvulsant medication to control seizures. Palliative type therapies are also used in animals that are undergoing surgical therapy, radiation or chemotherapy.

Minimally Invasive Surgery

One of the most difficult aspects of treating a brain tumor surgically is physical access to the tumor and the small size of the cranial vault of dogs and cats. Lack of complete removal of meningiomas often results in recurrence of the tumor within 6-18 months. Visualization of the most common locations for tumors makes complete removal difficult without causing injury to the normal brain tissue. Dr. Klopp has been using endoscopic assistance now for many years and has seen an improvement of outcomes and disease-free intervals in her patients when compared to cases treated before the use of the endoscope. Some of her cases are living several years. Endoscopic-assistance in brain surgery has also lead to better access to previously inaccessible regions and in some cases allows minimally-invasive approaches.

Case Study: Snocat's Story

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