Feline brain tumors have an incidence of 3.5 per 100,000 cats, with primary brain tumors being more common than secondary tumors. The most common primary brain tumors in cats are meningiomas, which account for over 50% of cases. Clinical signs of brain tumors in cats usually develop slowly and can include behavior changes, seizures, and vestibular dysfunction. Magnetic resonance imaging is the preferred method for diagnosing brain tumors in cats. Surgery is the primary treatment for meningiomas, while radiation therapy is standard for other brain tumor types besides meningiomas. Prognosis depends on tumor type, with meningioma patients having a median survival time of 2 years after surgery.

1. Feline Brain Tumors
INCIDENCE / PATHOLOGY
Brain tumors have an incidence of 3.5 cats per 100,000 cats at risk. Primary brain tumors are more common than
secondary (metastasis) and account for 85% of feline brain tumors. Most primary brain tumors are from the brain
parenchyma (glial cells, neurons, or cells that line the interior or exterior brain surfaces such as meningeal and
ependymal cells). Meningiomas account for more than 50% to 60% of cat brain tumors (17% will have multiple
meningiomas). The most common secondary brain tumor in cats is lymphoma. Pituitary macroadenoma in cats has
been associated with secretion of growth hormone that resulted in acromegaly and insulin resistant diabetes mellitus.
CLINICAL SIGNS
Clinical signs are usually associated with a space occupying lesion and can be mild or ill-defined neurologic signs,
such as altered consciousness, seizures, and vestibular dysfunction. In most cases, clinical signs of neurologic
dysfunction occur slowly and insidiously over time, especially with meningioma. Cats with brain tumors are most
commonly presented to the veterinarian for behavior change; however, the clinical signs can be quite unspecific as
20% of cats with brain tumor presented with nonspecific clinical signs (anorexia, inappetence and lethargy) and the
brain tumor was considered an incidental finding. In one study of feline brain tumors, the overall incidence of seizures
was 23%; seizures were more commonly seen with glioma (26.7%) and lymphoma (26.3%) than with meningioma
(15%).
DIAGNOSIS / IMAGING
Computed tomography (CT) and magnetic resonance imaging (MRI) are commonly used in the diagnosis of brain
tumors, with MRI being the preferred imaging modality. Pituitary tumors have a typical location. Meningiomas tend to
have a broad-based extra-axial attachment, exhibit distinct tumor margins, and uniformly enhance with contrast.
Meningiomas tend to displace, rather than invade, the parenchymal tissue. Gliomas tend to arise from an intra-axial
location, often lack distinct tumor margins, and typically enhance poorly and nonuniformly with contrast. Choroid
plexus tumors and ependymomas tend to be intraventricular in location and often uniformly enhance with contrast.
Biopsy obtained either during surgery or using MRI or CT guidance is the only way to get a definitive diagnosis.
THERAPY
Surgery
Surgical removal is the primary mode of definitive therapy for feline meningiomas. These tumors are typically located
over the cerebral convexities and tend to peel away from normal brain tissue. Reported median survival time (MST)
for feline intracranial meningioma is 2 years. Recurrence occurs in about 20% of cases and surgery is often feasible in
these cases. For the other types of brain tumors, surgery is often not an option.
Radiation Therapy
Radiation therapy is the standard of care for the majority of primary brain tumors and pituitary adenoma with the
exception of meningiomas. Radiation can be given as conventional fractionated radiation (usually 18 to 20 fractions of
2.5 Gy) or as a stereotactic radiosurgery that consist of 1 to 3 fractions given over a 1-week period. At the moment, we
have limited information on survival of cats with brain tumors treated with radiation but it seems to be successful in the
handful of case reports and case series that have been published.
Chemotherapy
There are a limited number of reports on the use and efficacy of chemotherapy in the management of brain tumors in
cats. Lomustine and hydroxyurea have been used but there is limited data to provide validation of the utility of
chemotherapy.