Meningioma in Dogs and Cats
Meningioma is the most common brain tumor in dogs and cats. About 50% of all brain tumor cases in dogs are attributed to meningioma, while the incidence in cats is about 56%. Continue reading to learn more about this type of brain cancer in pets, including causes, symptoms, and care.
What is a meningioma?
There are distinct differences between intracranial meningiomas in dogs and cats in terms of their histopathologic (microscopic) appearance, treatment, and prognosis. Spinal meningiomas, paranasal, and orbital meningiomas have also been reported in dogs but are not very common.
The brain is lined with membranes called meninges. Meningioma is a tumor of the meninges rather than the cells of the brain. Thus, many experts don’t recognize meningiomas as brain tumors.
However, meningiomas are usually grouped under brain tumors because they occur within the cranial cavity and grow inward from the skull to compress or invade the tissues of the brain.
The causes of meningiomas in dogs and cats are not well understood or identified. Meningiomas in dogs are likely to be malignant. These tumors are usually benign; however, their biological behavior may be malignant.
Although they’re relatively slow-growing tumors, meningiomas still create a potential problem because of the limited space within the dog or cat’s skull. As the tumor grows, it will encroach on the space within the skull, crowding out the brain and cerebrospinal fluid. As the meningioma compresses the brain tissues, it can lead to inflammation and further swelling. This can eventually damage the nerves of the brain.
What pets are at risk for meningioma?
Meningiomas are more common among dolichocephalic (long-nosed) dogs. In a 2020 retrospective survey of canine intracranial tumor cases, a significant breed predisposition was observed for meningioma in the Rough Collie, Golden Retriever, Miniature Schnauzer, and Scottish Terrier.
Meningioma is generally a disease of older pets. Most dogs diagnosed with the tumor are older than 5 years of age, with an average age of 9 years. It’s the most common underlying cause of seizures in dogs over six years old. In cats, the average age at diagnosis is 12 years old.
In dogs with intracranial meningiomas, a female sex predisposition has been reported, with a male: female ratio of 0.6, which is similar to that among humans with these tumors.
There is no breed predisposition for meningiomas in cats. But in cases of affected cats, domestic short-haired and long-haired cats are over-represented. Meningiomas tend to be slightly more predominant among male cats.
Signs of Meningioma in Dogs and Cats
The symptoms largely depend on the part of the brain area that’s involved.
In dogs, meningiomas mostly cause chronic progressive clinical signs due to the tumor’s slow growth. The most common symptom observed in dogs is seizures. Other signs include incoordination, blindness, and changes in behavior.
On the other hand, symptoms exhibited by affected cats are vague and usually involve changes in behavior, vision loss, circling, partial or mild paralysis (paresis), and gait abnormalities. Compared to dogs, seizures are less common in cats.
How are meningiomas diagnosed?
A brain tumor is a primary consideration in middle-aged or older dogs or cats that are exhibiting neurological symptoms with a progressive course.
The dog or cat may be subjected to several laboratory tests and diagnostic procedures including the following:
- Complete blood cell count (CBC)
- Biochemistry panel
- Chest x-rays
- Abdominal ultrasound
- Computed tomography (CT)
- Magnetic resonance imaging (MRI)
To get a presumptive diagnosis of meningioma in dogs and cats, magnetic resonance imaging (MRI) and computed tomography (CT) are the techniques of choice.
Treatment Options for Pets with Meningioma
The treatment regimen of meningioma in dogs and cats involves the following:
Surgery not only removes the tumor but also allows obtaining tissue samples for biopsy to help with a better treatment plan. The postoperative survival times depend to a large extent on the type of meningioma.
Surgery to completely remove the tumor is the primary option for most cases of meningioma in cats. Meningiomas in cats often consist of fibrotic tissue and don’t usually infiltrate the tissues of the brain, making them easier to remove with surgery compared with meningiomas in dogs.
Meningiomas in dogs are less well-defined but tend to be more invasive, thus making it hard for the veterinary surgeon to determine where to cut.
Radiation can increase the survival time of affected animals when the meningioma can’t be removed. Radiation treatments may be performed daily, weekly, monthly, etc. depending on the preferred method.
Radiation can be used as the only procedure for meningioma treatment or in combination with surgery. In dogs, surgery with radiation therapy tends to yield the best results.
Radiation therapy may not be necessary for cats after the tumor has been completely removed. Cats also have a better long-term prognosis than dogs.
3. Radiosurgery (Stereotactic Radiosurgery)
This procedure involves targeting a well-defined area (the tumor) in the brain with a specific dose of radiation. This is indicated for deep tumors.
Compared to radiation that uses only one beam, radiosurgery focuses several beams on the target. The procedure is preferred by many veterinary surgeons because it’s a one-time treatment rather than a series of radiation treatments. For the treatment to work, the meningioma must be less than one inch in diameter.
Chemotherapy, together with surgery and radiation, target the primary tumor.
For chemotherapy to be effective against meningiomas, the drugs that are administered must be able to cross the blood-brain barrier. There are only a few medications that are currently available, and the results are not as favorable in cats as in dogs.
Medications, such as steroids and anticonvulsants, are given to treat the secondary tumor effects.
Stroke (Vascular Accidents) in Pets
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