Let’s review Baby’s examination again.
The neurological examination evaluates mentation, gait and posture, postural reactions (CP’s), spinal reflexes and cranial nerves.
Mentation: Baby is clearly dull and distant.
Gait and posture: He is unable to stand and walk on his own. When supported to stand, he crouches low, takes a couple of steps and lays down or falls. He seems to scuff the thoracic limbs when trying to walk. He has a tendency to fall to the left, but there is no evidence of head tilt or abnormal nystagmus or strabismus.
Postural reactions: When ‘hopped’ on one leg, he does not accurately hop on any of the limbs, however, the left thoracic limb is the worst.
Spinal reflexes were normal (not shown).
Cranial nerves: Baby does not have a menace response in either eye. Palpebral reflex is normal. Remainder of cranial nerves are normal (not shown in the video).
Q: Is this a neurological problem?
A: Yes, Baby has a neurological problem.
Q: What is your neuroanatomical localization?
A: His examination suggests a problem affecting the cerebral cortex, slightly more towards the right side. Remember that CP’s are relatively sensitive for detecting neurological disease, but by themselves don’t tell you specifically what part of the nervous system is affected. A simplistic way of approaching neuroanatomical localization is to answer “is this a problem above or below the foramen magnum?”. Dull mentation and constant pacing suggest a problem in the brain. While he does tend to fall toward the left, he does not have any other signs of vestibular disease such as nystagmus or strabismus. The pathway for ‘conscious proprioception’ for the limbs starts in the joint proprioceptor in the limb, travels up the sensory nerve, travels up the spinal cord ON THE SAME SIDE, through the medulla the CROSSES SIDES (decussates) just before the thalamus, then projects to the sensory cortex. So, a problem in the right cerebral cortex will usually cause postural reaction deficits on the left side of the body, whereas a problem in the right medulla will cause postural reaction deficits on the right side of the body.
Q: What are your differential diagnoses?
Remember the DAMNIT-V scheme:
Degenerative: This is certainly possible in a cat that has a chronic, slowly progressive, non-painful brain problem. These are uncommon.
Anomalous: While possible, it is less likely in a 16 year-old cat.
Metabolic: Possible, including hypoglycemia, electrolyte abnormalities, etc.
Neoplastic: Possible. Consider primary brain tumor or metastatic.
Nutritional: Possible, such as thiamine deficiency. Baby is fed a commercial diet, making this less likely.
Inflammatory/Infectious: While autoimmune encephalitis is common in dogs, it is uncommon in cats. Infectious causes such as Cryptococcus, Toxoplasma (click here to see the May 2012 Case of the Month about central nervous system (CNS) Toxoplasma) and feline infectious peritonitis (FIP) are more common in cats.
Trauma: Unlikely, given the chronic, progressive nature of his signs.
Vascular: Unlikely, given the chronic, progressive nature of his signs.
What tests are indicated? The referral CBC, chemistry panel, T4 and urinalysis were unremarkable. Thoracic and abdominal radiographs were unremarkable. Magnetic resonance imaging (MRI) was performed.
This first image is a sagittal, T2-weighted MRI of Baby’s head. Rostral is toward the left and dorsal is toward the top of the image. The nasal cavity is on the far left. The brain is the the light grey and white area in the middle. There is a large, ovoid mass at the dorsal aspect of the brain. Note the evidence of mass effect – the brain tissue is being pushed ventrally away from the mass. The cerebellum is normally round, but you can see how it is being compressed caudally and that there is herniation (arrows) of the cerebellum through the foramen magnum. Lastly, there is evidence of fluid within the cervical spinal cord, consistent with syringomyelia. This is the white area within the spinal cord on the right side of the image. Computed tomography (CT) scan would not show these changes.
This second image is a T1 weighted sagittal image of Baby’s head. Contrast agent has been administered. The tumor enhances with the contrast agent. Note that the tumor appears to grow from the outside and push inward on the brain. Furthermore, there is a ‘tail’ at the cranial/dorsal and caudal/dorsal aspects of the mass. This is called a ‘dural tail’ sign. While a definitive diagnosis cannot be obtained without a biopsy, the most common cause of a large, contrast-enhancing mass with broad-based dural attachment in a 16 year-old cat is a meningioma.
After discussion with the owner, brain surgery to remove the mass was elected. A craniectomy was performed. A large, tan/grey, very firm and well-adhered mass was removed. It was tightly adhered to the skull and came out en-bloc with the skull. Here is a photograph of the mass after surgery. The mass is ‘upside down’, with the skull (dorsal) at the bottom of the photo. Histopathological analysis confirmed a meningioma.
Meningioma’s tend to be very slow-growing brain tumors. They are often amenable to surgical excision. They tend to be so slow-growing that follow-up treatment is not necessary. Baby was hospitalized for three days after surgery for post-operative pain management, nutritional support and nursing care.
Here is Baby at his recheck appointment five days after surgery.
As you can see, he is more alert, is able to see and explore his surroundings. He is ambulatory with minimal ataxia and no ‘scuffing’ of his toes. We are happy to report that Baby is still doing great!
The board-certified neurologists at Southeast Veterinary Neurology are experts in medical and surgical disorders of the brain, spinal cord, nerves and muscles. Please call us at (305) 274-2777 if you have any questions about Baby's case or any other neurological condition. We are available 24/7/365 for your emergencies, consultations and phone calls.