Meningiomas in Dogs

Overview of Canine Meningiomas

Meningiomas are a common, well-defined brain tumor arising from the meninges, which is the covering surrounding the brain. Meningiomas usually occur in older dogs greater than 8 years old. There does not seem to be a sex predisposition for brain tumors.

Meningiomas are very slow growing tumors that compress the brain rather than invade brain tissue. Because they are slow growing, the brain may be able to compensate or adjust to their presence.

Symptoms most often associated with brain tumors are personality changes such as not wanting to play, altered appetite, sleeping and hiding; seizures; weakness in the limbs; uncoordinated walking; or abnormal eye/facial symmetry. Meningiomas may be quite large before they cause symptoms. Symptoms may be caused by swelling and edema, which is a build-up of fluid around the tumor.

If a meningioma grows very slowly, its symptoms may appear so gradually that they are overlooked for a long time.

Diagnosis of Meningiomas in Dogs

• Your veterinarian may ask the general history of your pets’ medical past as well as the first appearance of symptoms and will perform a complete physical to check for general signs of health.
• A neurologic examination may be included to characterize and localize the area of the brain being affected.
• Laboratory tests may be done to check the general health of the other systems in the body such as the bone marrow, liver and kidney.
• Laboratory tests are part of a pre-anesthetic screening needed prior to further brain imaging.
• Depending on your veterinarian’s access to some of the advanced diagnostic tools necessary to diagnose meningiomas, your pet may be referred to a specialist such as a neurologist, internist, or oncologist.
• Brain imaging consisting of either a CT (computed tomography) scan or an MRI (magnetic resonance imaging) to look at the brain. Both techniques require anesthesia because the pet must lie very still for 30 to 60 minutes. Although MRI is a better imaging method than CT, availability and cost may limit its use in many cases.

Treatment of Meningiomas in Dogs

• Treatment for a canine meningioma depends on a number of factors. Among these are the type, location, and size of the tumor as well as your pet’s age and general health.
• Your veterinarian develops a treatment plan to fit each patient’s needs and other factors. Some important questions to ask your veterinarian include what treatments are available and how effective are the treatments.
• Meningiomas are treated with surgery, radiation therapy and chemotherapy. Several methods may be used in combination or individually. Before treatment begins, most dogs are given steroids to relieve edema. They may also be given anticonvulsant medicine to prevent or control seizures.
• Surgery is the usual treatment for most meningiomas. To remove a brain tumor, a neurosurgeon performs a craniotomy, or makes an opening in the skull.
• Radiation therapy or radiotherapy uses high-powered rays to damage cancer cells to stop them from growing. It is best used to destroy microscopic tumors following surgery. Radiotherapy can be used when surgery is not possible. Your pet may be heavily sedated or anesthetized for each radiotherapy session.
• Chemotherapy, or administration of drugs that are used to kill cancer cells, may be recommended.
• Side effects occur with any treatment recommended for brain tumors in your pet. The best person to ask regarding side effects for suggested or considered treatment is your veterinarian that is directing treatment.
• The treatment of cancers in general are often related in terms of prognosis. It is important to remember that statistics are based on averages from a large number of patients. They cannot be used to predict what will happen to a certain patient because no two cancer patients are alike. The doctor who takes care of the patient and knows the pet’s medical history is in the best position to discuss your pet’s prognosis. It is important to know that not even your veterinarian can tell exactly what will happen with your pet.

Follow-up Care for Dogs with Meningiomas

Meningiomas are a kind of brain tumor that affects dogs and arise from the meninges (the covering surrounding the brain). The incidence of brain tumors in dogs is 14.5 per 100,000. Between 40 to 60 percent of all brain tumors in dogs are meningiomas.

There does not seem to be a sex predisposition for brain tumors. Meningiomas occur in older dogs greater than 8 years old. Golden Retrievers, mixed breeds, Labrador Retrievers and boxers have the highest incidence of brain tumors although a causal effect has not been established.

Meningiomas are usually microscopically benign but due to their location adjacent to vital structure of the brain, they may be biologically devastating. Meningiomas are very slow growing tumors that compress the brain rather than invade brain tissue.

Because they are slow growing, the brain may be able to compensate (adjust to their presence). Symptoms most often associated with brain tumors are personality changes such as not playing, altered appetite, sleeping and hiding; seizures; weakness in the limbs; uncoordinated walking; or abnormal eye/facial symmetry.

Meningiomas may be quite large before they cause symptoms. Symptoms of meningiomas depend mainly on their size and their location in the brain. Symptoms are due to damage to vital brain areas and by pressure on the brain as the meningioma grows within the limited space in the skull. Symptoms may be caused by swelling and edema, which is a build-up of fluid around the tumor.

Symptoms may also be due to hydrocephalus (water on the brain), which occurs when the tumor blocks the flow of cerebrospinal fluid and causes it to build up in the ventricles. If a meningioma grows very slowly, its symptoms may appear so gradually that they are overlooked for a long time.

In-depth Information Diagnosis

• In investigating your pets’ symptoms, your veterinarian may ask the general history of your pets’ medical past as well as the first appearance of symptoms. Your veterinarian may perform a complete physical to check for general signs of health.
• A neurologic examination may be performed to characterize and localize the area of the brain being affected.
• An examination of the eyes may be done to check for swelling caused by a tumor pressing on the nerve that connects the brain and the eye.
• Laboratory tests may be done to check the general health of the other systems in the body such as the bone marrow, liver, and kidney.
• Laboratory tests are also part of a pre-anesthetic screening needed prior to further brain imaging.

Depending on your veterinarian’s access to some of the advanced diagnostic tools necessary to diagnose meningiomas, your pet may be referred to a specialist such as a neurologist, internist or oncologist.

• Brain imaging consisting of either a CT (computed tomography) scan or an MRI (magnetic resonance imaging) to look at the brain. Both techniques require anesthesia because the pet must lie very still for 30 to 60 minutes.
• Special contrast agents are used to enhance the likelihood of detecting a brain tumor.
• Depending on the results of the brain imaging studies, your dog may need a skull X-ray that can show changes in the bones of the skull caused by a tumor. X-rays may also show calcium deposits, which are present in some types of brain tumors.
• Although MRI is a better imaging method than CT, availability and cost may limit its use in many cases.

In-depth information on Therapy

• Treatment for a canine meningioma depends on a number of factors. Among these are the type, location, and size of the tumor as well as your dog’s age and general health.
• Your veterinarian develops a treatment plan to fit each patient’s needs and other factors.
• Your veterinarian may consult with other doctors who treat brain tumors. If your pet has been diagnosed with a brain tumor, you may want to learn all you can about the disease and treatment choices.

Here are some important questions to ask your veterinarian:

• What treatments are available?
• How effective are the treatments?
• What types of treatment are available?
• What are the expected benefits of the treatment?
• What are the risks and side effects of treatment?
• What can be done about side effects?
• What are the costs involved for treatment?
• What effects will the treatments have on my pet’s normal activity?
• What kind of follow-up care will my pet need?
• Make a list of these questions before you see your veterinarian. Take notes when the questions are answered. After consulting with your veterinarian, write down any further questions you may have. Your veterinarian is the best person to answer your questions.
• Meningiomas are treated with surgery, radiation therapy, and chemotherapy. Several methods may be used in combination or individually.
• Before treatment begins, most dogs are given steroids, which are drugs that relieve edema. They may also be given anticonvulsant medicine to prevent or control seizures.\
• Surgery is the usual treatment for most meningiomas tumors. To remove a brain tumor, a neurosurgeon performs a craniotomy (making an opening in the skull). Depending on the location and type of meningioma, the neurosurgeon will attempt to remove the entire tumor. If vital structures could be damaged by removing the entire tumor, a subtotal (partial) resection may be done. This debulking procedure helps to relieve symptoms by reducing pressure on the brain and reduces the volume of tumor to be treated by radiation therapy or chemotherapy.
• Some tumors cannot be removed. In such cases, the doctor may do a biopsy. A small piece of the tumor is removed so that a pathologist can examine it microscopically to determine what kind of tumor it is. This helps the doctor decide which treatment to use.
• Radiation therapy or radiotherapy uses high-powered rays to damage cancer cells to stop them from growing. It is best used to destroy microscopic tumors following surgery. Radiotherapy can be used when surgery is not possible. Radiation therapy is typically given externally by a large machine.
• Treatment can be given in a number of schedules from a weekly to daily basis for several weeks. The treatment schedule depends on location and type of tumor as well as patient factors such as health and age. Radiation therapy schedules also depend on availability of the radiotherapy machine. Radiation therapy is usually directed just to the tumor and the tissue close to it. Radiation therapy is typically given over an extended period to protect healthy tissue in the area of the tumor.
• Your pet may be heavily sedated or anesthetized for each radiotherapy session.
• Some radiation therapy units may offer outpatient therapy sessions in which your pet is admitted for the day for treatment and is discharged later in the day.
• Stereotactic radiosurgery is a newer way to treat partially resected for non-resectable meningiomas. Treatment is given in just one session in which high-energy rays are directed at the tumor from many angles. In this way, a large dose of radiation reaches the tumor without damaging adjacent brain tissue. Radiosurgery, also called the gamma knife, requires anesthesia and may not be widely available.
• Chemotherapy employs drugs that are used to kill cancer cells and may be recommended for your pet to treat a meningioma. Chemotherapy may consist of one drug or a combination of drugs that may be given by mouth, intravenously, or by injecting the drug directly into the cerebrospinal fluid.
• Chemotherapy is usually given in cycles; a treatment period followed by a recovery period. Most drugs can be given on an outpatient basis. You will need to monitor your pet’s general health, appetite, and temperature depending on the pet’s chemotherapy regimen.
• Side effects occur with any treatment recommended for brain tumors in your pet. The best person to ask regarding side effects for suggested or considered treatment is your veterinarian that is directing treatment.
• You may want a second doctor to review the diagnosis and treatment plan. A second opinion can be requested from your original veterinarian or an organization such as the American College of Veterinary Internal Medicine (www.acvim.org) or the Veterinary Cancer Society (www.vetcancersociety.org).
• The diagnosis of meningioma in your pet will probably change his life and the people who are about them. The changes can be difficult to handle. Emotions such as fright, anger, and depression are normal reactions when faced with a serious health problem. Share and discuss these feelings with other caregivers. Sharing can help everyone feel more at ease and can open the way for others to show their concern and offer their support.
• Worries regarding tests, treatments, hospitalization, and costs are common. Your health care team may be able to provide support, calm fears, and ease confusion.
• The treatment of cancers in general are often related in terms of prognosis. It is important to remember that statistics are based on averages from a large number of patients. They cannot be used to predict what will happen to a certain patient because no two cancer patients are alike. The doctor who takes care of the patient and knows the pet’s medical history is in the best position to discuss your pet’s prognosis.
• It is important to know that not even your veterinarian can tell exactly what will happen with your dog.