Thor – Brain Tumor

Thor, a 6-year-old male neutered Domestic Shorthair, presented to his primary veterinarian for signs of discomfort in his right ear and excessive scratching. Two weeks after starting treatment with Orbax and Entederm, Thor’s owner noticed that his symptoms were worsening. Thor was then referred to Southeast Veterinary Neurology for evaluation.

Upon examination, Thor was quiet, alert and responsive. His postural reactions and spinal reflexes were normal. Thor was making tight circles to the right. He was fully ambulatory with vestibular type ataxia (leaning, falling, or rolling towards one side) and a mild head tilt to the right. Thor’s cranial nerve examination showed positional vertical nystagmus; the other cranial nerves were normal. Thor had no signs of vertebral column pain.


Diagnosing the Cause

Based on Thor’s presentation during his examination at SEVN (circling, head tilt, nystagmus and ataxia), it can be determined that he was showing signs of vestibular disease.

Vestibular disease includes any disease which affects the part of the body responsible for maintaining balance (the vestibular system). Signs of vestibular disease include a head tilt, leaning or drifting to one side, and an uncoordinated gait. The signs of vestibular disease can vary in severity. Some dogs or cats may be mildly affected and are still able to walk, while more severely-affected animals may lay on their side and roll or be unable to get up. You may also see abnormal jerking eye movements (called nystagmus) or abnormal position of the eyes (called strabismus).

The components of the vestibular system reside in the inner ear and in the brainstem. Problems in either area can cause a loss of balance. If it is originating in the inner ear it is called peripheral vestibular disease, and central vestibular disease if it is originating from the brain.

The next step in diagnosing the cause was to identify if Thor was experiencing peripheral or central vestibular disease.

Signs of peripheral vestibular disease include:

  • Head tilt towards the lesion; roll towards the side of the lesion
  • Nystagmus horizontal or rotary with fast phase away from the lesion; nystagmus does not change with the head position
  • Ataxia with no loss of strength (no paresis or CP deficits)

Examples of the most common causes of peripheral vestibular disease:

  • Ear infections
  • Idiopathic “geriatric” vestibular disease

Signs of central vestibular disease include:

  • Head tilt towards the lesion (except for in Paradoxical Vestibular disease, where the head tilts away from the lesion)
  • Nystagmus vertical and/or positional (can also be horizontal or rotary)
  • Ataxia with CP deficits and/or paresis
  • Mentation Changes
  • Other cranial nerve deficits
  • Cerebellar signs (hypermetria, etc.)

Examples of the most common causes of central vestibular disease:

  • Inflammatory disease
  • Stroke or vascular event
  • Neoplasia

Thor’s symptoms indicated an origin in the brain, or central vestibular disease. Prognosis and treatment is variable depending on what the underlying cause is. Further diagnostic imaging (MRI) was recommended to determine the underlying cause.

A high-field MRI of Thor’s brain was performed. IV contrast was administered. The MRI is pictured below.

Thor - Cat Brain Tumor MRI Pre Surgery

Thor’s MRI shows a mass in his brain. (Note that there is a surface-based, strongly contrast enhancing space-occupying mass at the level of the right temporal lobe.) The mass is causing compression on the right thalamus, rostral cerebellum as well as the midline shift and ventricular asymmetry. There is evidence of dural enhancement (dural tail) as well as hyperostosis of the temporal bone overlying the lesion.

The appearance of the mass is consistent with a type of brain tumor called a meningioma. Meningiomas are tumors that grow on the outside of the brain tissue originating from the coverings of the brain. Meningiomas are common brain tumors in cats.


Treatment Options

Unfortunately, there are no cures for brain tumors in cats; however, treatment options exist that can make the symptoms easier to control and extend Thor’s quality of life.

The first treatment option was to consider surgery. Surgical treatment would involve a craniotomy to remove the tumor. Because the tumor is located within the brain, surgical ‘margins’ cannot be obtained. This meant that some tumor cells would remain and over time the tumor would grow back. The average time for tumor regrowth varies with every cat. Meningiomas tend to be slow-growing and may take several years before returning. Surgery also carries the risks inherently associated with brain surgery.

The second treatment option was to consider conservative and palliative management, which was the least risky of the two but carried a worse prognosis. Conservative management involves reducing brain swelling with prednisolone. This form of treatment does not kill tumor cells; therefore, with time the tumor would continue to grow and cause additional neurological signs.

Thor’s owner decided to proceed with surgery. A rostrotentorial approach to the right temporal lobe was performed and after durotomy, a tan, well-demarcated mass was identified. The mass was resected using blunt dissection. The bony defect was covered with SIS and closure was routine.

Thor - Cat Brain Tumor Removal Surgery

Thor recovered well from anesthesia, no post-operative complications occurred and he was neurologically normal. Although clean margins cannot be obtained for intracranial tumors, on Thor’s post-operative MRI (pictured below) the mass appears completely resected.

Thor - Cat Brain Tumor MRI Post Surgery

Following surgery, Thor was restricted to crate rest for four weeks to promote a healthy recovery and the brain mass was sent to be evaluated by a pathologist. The tumor was confirmed to be a meningioma.


Learning Points:

  1. The most common symptom of a brain tumor in a cat includes changes in behavior and walking in circles, however, other signs such as seizures and balance problems are posible.
  1. Brain tumors most often happen in older cats, however, surgical removal can provide prolonged survival of many years.
  1. MRI is the test of choice for evaluating the brain.

To learn more about brain tumors in dogs and cats, visit this link or call an expert in neurology at Southeast Veterinary Neurology. We have locations in Miami and Boynton Beach.