Meningiomas in Dogs

Meningiomas are generally slow growing and arise within the cranial cavity. Over time the meningioma will invade the brain. There are three classifications of meningiomas; Grade I or benign, Grade II or atypical and Grade III (malignant) or anaplastic.

Meningiomas are the most common primary brain tumors in dogs. Meningiomas are more prevalent in large breed dogs but have been found in small breeds. There are specific breeds that are predisposed to meningiomas such as the Golden Retriever, Boxer, Labrador Retriever, Miniature Schnauzer and German Shepherd. These tumors usually occur in dogs older than 10 years. Meningiomas are more common in long nosed dog breeds.

Depending upon the location of the meningioma within the cranial cavity or the brain, the symptoms will vary. Symptoms caused by a brain tumor can mimic those of other common brain disorders such as stroke or encephalitis. Should you notice any of these symptoms in your dog, contact your veterinarian for a full assessment.

• Seizures
• Confusion or aggression
• Other behavioral changes
• Loss of equilibrium

While the exact cause of meningiomas has not been determined, it is known that they occur in the arachnoid mater of the meninges, not within the actual brain cells. The meninges are the membranes that line the brain. Meningiomas will eventually compress the brain within the cranial cavity or they will invade the brain cells. 

In most cases, meningiomas are slow growing and respond well to treatment. There have been more aggressive or malignant forms of meningiomas that have not responded well to treatment.

A definitive diagnosis of a meningioma can only be done after a biopsy has been taken of the tumor tissue and examined under a microscope. Therefore, surgery is required to definitively diagnose meningiomas. 

A presumptive diagnosis of meningiomas can be done by performing an MRI of the brain. There are certain characteristics that meningiomas have that allow for a fairly accurate presumptive diagnosis. Meningiomas will usually appear along the outer lining of the brain and are adjacent to the skull. This can be easily seen on an MRI. The MRI cannot differentiate between the three different classifications of meningiomas. Surgery is required to biopsy the tumor and determine which grade the meningioma will be classified.

With the advancement of veterinary medicine, there are several treatment options available for dogs diagnosed with meningiomas. Many treatment plans include a combination of treatments to successfully treat the tumor. Your veterinarian will discuss each option with you and tailor a treatment plan to your dog for the best quality of life and survival. 

Palliative or Symptomatic Treatments

Palliative treatments are used to relieve some of the secondary effects of the tumor. These can include steroids or anti-convulsion medications. The primary goal of this treatment is to make your dog feel better and have a better quality of life. Your veterinarian will discuss the necessity of palliative treatments for your dog.

Surgical Removal of the Tumor

Surgical removal of a meningioma is oftentimes possible. The best surgical successes occur when the meningioma is located in front of the brain and has not infiltrated the brain cells. The size and location of the meningioma may limit the surgeon to remove the entire meningioma, thus requiring additional non-surgical treatments. 

Radiation Therapy

Radiation therapy has been used successfully as the primary treatment of meningiomas in cases where surgery is not a possibility. Most dogs are treated with radiation therapy for approximately four weeks, five days a week. The radiation therapy will be tailored to your dog’s tumor location and size to ensure maximum success in shrinking the tumor. 

Chemotherapy

While there have been no large controlled studies clearly showing the effectiveness of chemotherapy on meningiomas in dogs, some veterinarians will prescribe chemotherapy as part of a treatment plan. This is an option used for Grade III meningiomas or meningiomas that are malignant.

Recovery times vary in dogs with meningiomas depending on the grade of the meningioma and the treatment plan in place. Depending upon the location, size, and grade of the meningiomas, the survival range of your dog can be as little as a few weeks to as much as several years. 

Your veterinarian will discuss the risks involved with each treatment as well as which treatment or treatments are best suited to your dog’s case.  Meningiomas can be treatable if diagnosed early and treatments begun quickly.