Meet Maxwell

Maxwell, a 12 year old Domestic Shorthair, presented to the emergency service after his owners found him flailing around at home.  He had been more lethargic over the past week.

Maxwell was blind, vocalizing inappropriately, and ataxic with diffuse muscle tremors. The episode the owners described was most likely a seizure. Maxwell was given valium which resolved the tremors.

Bloodwork was normal and radiographs revealed arthritis of his spine and stifles.  He was stabilized with Phenobarbital and steroid therapy. He remained blind and somewhat ataxic but became brighter and was eating well by the next day.  

Maxwell was then sent for an MRI of his brain. The MRI revealed a large (2.5 cm X 1.8 cm) mass over the right parietal and temporal lobes with edema, obstructive hydrocephalus and herniation of the occipital lobe. This imaging was suggestive of a meningioma.

Tumors of the nervous system are rare, but brain tumors are more common than spinal cord or peripheral nerve tumors.  Brain tumors in cats are less common than dogs occurring at 3.5 per 100,000. Tumors of the nervous system, in general, rarely metastasize. The effects of brain tumors usually result from expansion and displacement caused by the tumor itself or edema from the presence of the tumor or the destruction of surrounding brain tissue. Therefore, clinical signs are typically subtle and overlooked by owners until the advent of more serious disturbances, such as seizures or paresis.  Brain tumors are usually slow growing, but again, signs may appear acutely.  

Seizures are typically rare but are the most frequently recognized symptom by owners. Owners also report more nonspecific signs such as lethargy, dullness, depression, inactivity, or inappetence. More specific signs including aggression, disorientation, hiding, staring at the wall, increased vocalization, crouched posture, inappropriate elimination, increased sleeping, decreased grooming, and decreased jumping have also been reported. The most common signs tend to be associated with changes in vision. Seizures have been reported to occur in 20-25% of cats with meningioma.  Previous literature in 141 cats with diagnosed meningioma at necropsy report only 68 of these cats had neurologic clinical symptoms before their death.  

Maxwell was taken to surgery for a craniotomy, and the tumor was completely removed. Histopathology of the mass confirmed a meningioma, fibromatous subtype, with complete margins.

In general, meningiomas may arise from the meninges anywhere in the brain. The underlying cause that facilitates these cells to multiply out of control is unknown, and whether it occurs because of genetics, hormones, trauma, diet, immunological factors, or environment or a combination is yet to be determined. Most commonly these tumors are noncancerous or benign, though rarely they can be cancerous or malignant. These tumors occur most commonly as solitary masses (can be multiple masses in cats) that tend to grow slowly and expand toward the brain parenchyma or spinal cord, causing compression and atrophy and can at times cause erosion of the adjacent skull bone. Meningiomas are the most common brain tumor in cats, with males and Domestic Shorthairs being predisposed. In cats, they comprise around 10% of tumors not of blood origin and 56% of central nervous system tumors found at necropsy.  

Advanced imaging, such as CT and/or MRI, is required for diagnosis and follow-up management of the meningioma.  Although metastasis appears to be rare, a complete staging procedure should be preformed to ensure no evidence of tumor exists elsewhere, especially in an older patient.

Until recently, the treatment of primary brain tumors in dogs and cats was usually palliative and noninvasive.  Corticosteroids and anticonvulsants are typically warranted to decrease associated edema and control seizures, if present. More aggressive treatment options are now becoming more available. If the location of the tumor allows surgical access, surgery is the treatment of choice for cats. Radiation therapy may be considered in dogs and those cats when tumor resection is not complete, but chemotherapy is not effective with this type of tumor.  

In cats and humans, meningiomas can usually be surgically resected with a permanent cure if the tumor is superficial on the dural surface and is easily accessible. Severe complications associated with this surgery are reported to be around 20% with death immediately after surgery due to herniation and bleeding. Clinical signs typically improve within a week to two weeks after surgery with a median survival time for cats of 22 months with 50% still alive 2 years after surgery.  Dogs are typically best treated with radiation therapy as meningiomas in dogs is more invasive and adhered to the local brain tissue and difficult to remove surgically. Median survival time in dogs is 322-413 days as opposed to 6 days without therapy. In people, median survival rates for benign meningioma with surgical resection and/or radiation therapy is around 12 years.  

Maxwell returned for his two week recheck and suture removal.  He had no additional neurologic episodes or seizures, and his sight had returned.  The owners reported he is doing very well at home and is quickly getting back to his normal playful self despite his bad haircut and a new tough looking scar.

Written by Laurie Nelms, DVM

References:
Cancer in Dogs and Cats:  Medical and Surgical Management, Second Edition.  Morrison, WB.  2002.
Canine intracranial primary neoplasia:  173 cases (1986-2003). Journal of Veterinary Internal Medicine.  2006 (20).
Feline Oncology:  A Comprehensive Guide to Compassionate Care.  Ogilvie, GK and Moore, AS.  2001.
Intracranial neoplasia in 61 cats:  localization, tumor types and seizure patterns.  Journal of Feline Medicine and Surgery.  2006 (8).
MayoClinic.com
Small Animal Clinical Oncology.  Withrow, SJ and Vail, DM.  2007.