Tumor of the Meninges in Dogs

Brain tumors or the meninges are common in older (over seven years old) dogs, and can form in any area of the meninges, which is the outer layer of the membrane that surrounds the brain and spinal cord. Although they are considered brain tumors, they are actually not inside the brain at all, just on the outer layer of the meninges. The most common areas that meningiomas form are around the nasal area, eyes, and base of the brain. Although this form of tumor is almost always benign, they can do just as much damage by growing and putting pressure on the brain, killing nerves and cells in the process. This can cause serious and debilitating irreversible damage, which is why it is essential to have the tumor removed before it grows large enough to cause such destruction. Luckily, these tumors grow slowly, but their presence is usually not known until they have already grown enough to cause symptoms. If your dog shows neurological symptoms, such as dizziness, confusion, seizures, vision problems, or inability to walk straight, it is important to see the veterinarian as soon as possible. Many tumors can be removed or treated without causing any lasting damage if found right away. While meningiomas can be found in all ages of any breed of dog, they are most often found in older dogs of certain breeds.

The tumor of the meninges (meningioma) is the most often reported brain tumor in dogs, and even though it is usually benign, it is a serious type of tumor that will do severe damage to your dog’s brain if not treated early. The size of the tumor and rapid rate of growth causes increased pressure on the brain and kills brain cells in the process. The symptoms depend on where the tumor is located in the brain, and can develop in any area where there is dura (outer layer of meninges). 

The symptoms of meningiomas are dependent on where they are located, but many symptoms can be mistaken for other disorders. In fact, the most common symptoms (one-sided weakness and paralysis) can be mistaken for stroke, brain swelling, and bacterial infections. Some of the most common symptoms are:

Base of skull

• Muscle twitching
• Inability to see or blurred vision
• Incoordination
• Muscle weakness (paresis)
• Eye pain
• Vision loss

Cerebral convexities (curves)

• Walking in circles
• Dragging toes
• Neck or back pain

Clivus and apical petrous bone (area around the eyes, ears, and nose)

• Weakness on one side of the body (hemiparesis)
• Inability to control movements
• Inability to balance
• Lack of muscle control (ataxia)

Olfactory groove (nasal area)

• Loss of sense of smell (anosmia)
• Dizziness

Sphenoid wing (between and around eyes)

• Facial numbness
• Blindness
• Seizures
• Shaking
• Protrusion of the eyeball
• Headaches

 Types

Meningiomas can be noncancerous (90%) or cancerous (10%) and are classified by their position:

• Base of skull
• Cerebral convexities (curves)
• Clivus and apical petrous bone (area around the eyes, ears, and nose)
• Olfactory groove (nasal area)
• Sphenoid wing (between and around eyes)

Meningiomas are most commonly found in the convex areas near the venous sinuses by the base of the skull and often there is more than one. Like other cancers, the meningiomas are most often seen in older dogs and seem to be more prevalent in Golden Retrievers and other breeds with long noses. There is no definitive cause of meningiomas, although it is more common in some breeds, such as:

• Boston Terrier
• Boxer
• Golden Retriever
• Any breed over seven years old

The only way to get a true diagnosis of a meningioma is with imaging, such as a digital radiographs (x-rays), CT scan, or a special type of MRI done with a contrast dye. However, your veterinarian will first give your dog a thorough physical examination, including height, weight, body temperature, pulse, and respiratory rate. You should provide your dog’s medical history and any recent illnesses and injuries.

The veterinarian will also take blood tests, such as a complete blood count (CBC), blood gas, and chemical panel. A urinalysis and fecal examination may also be performed. If the veterinarian finds a meningioma, he will need to do a complete body MRI or CT scan as well as an ultrasound to determine the exact location and shape of the tumors, and to see if there are tumors in any other parts of the body.

Treatment depends largely on the location and size of the tumor, but most often it includes surgery to remove the tumor. At the time, the veterinarian will also get a portion of the tumor cells for biopsy to see if it is cancerous. The veterinarian will then decide whether to use radiation and/or chemotherapy. Sometimes, medication is prescribed to control seizures and steroids to reduce swelling.

If the tumor is able to be completely removed, your dog’s survival time is approximately nine months to four years. If the tumor is inoperable, but medication and radiation are used, your dog can live up to two years. Without surgery or treatment, your dog can live for several months to a year depending on the location and size of the tumor. Many owners decide to euthanize their dog within a few months because of the pain and suffering.