What do you do with a confused cat?
Sigalment: 12 year old FS Domestic short-haired cat
History: 2-3 week history of seeming "confused", and a recent onset of circling right more than left. These very astute owners observed the cat seemed to walk into a room, forget why it entered, stand there, and then leave again. Additionally, she wasn't as bright as is typical for this indoor-outdoor Wisconsin cat. Birds would land on the feeder outside of the window and she appeared uninterested.
Physical examination: Normal TPR, normal exam. This was a remarkably fit cat for her age!
Neurologic examination:
Mentation: Obtunded
Cranial nerves: absent left menace response, normal PLR and normal menace response on the right. The cat was less responsive to facial stimulation on the left lip but did respond to hemostat pinch. All other cranial nerve exam findings were within normal limits.
Gait: Ambulatory with mild proprioceptive ataxia and occasional circling right
Postural reactions: absent tactile placing left pelvic limb, intermittent on left thoracic limb, normal on right thoracic and pelvic limbs.
Spinal reflexes: normal all limbs, and c. trunci
Okay..take a moment and put all of that together in your mind. I'll take this moment to remind you that my next Webinar is on Wednesday July 15th (TOMORROW) and we'll be talking about lesion localization. If you're interested in joining me to practice on cases just like this please go to https://barnesveterinaryservices.com/ce-opportunities and sign up!
Back to this case. How did you do? Here is how I would talk myself through this one...
1. The cat has a change in mentation..the problem MUST be intracranial.
2. There is a menace deficit - the affected parts could be cranial nerve 2, forebrain or cranial nerve 7.
2a. PLR is normal (this is cranial nerve 2, midbrain and cranial nerve 3) so we can eliminate cranial nerve 2 as a possible cause of the menace deficit.
2b. The cat did not have any noted change to motor of the face (run by cranial nerve 7), so we can eliminate cranial nerve 7 as a cause for the menace deficit.
2c. Finally, one must remember that the menace response crosses and enters the opposite side forebrain so, since we have narrowed the problem down to the forebrain we then must comment that it is the RIGHT forebrain we are concerned about
3. Circling is either a vestibular or forebrain sign. This cat did not have evidence of vestibular disease so we could consider this another forebrain sign. Animals circle towards their lesion, thus supporting a RIGHT forebrain lesion.
So far, so good?
4. Tactile placing goes from the toes, up the ipsilateral spinal cord, brain stem (crossing at the midbrain) and enters the opposite side forebrain. Voila! We don't have any evidence of spinal cord disease, or brain stem disease in this cat (no cranial nerve deficits) so this also suggests a RIGHT forebrain lesion.
What about that sensory deficit on the cranial nerve exam? This actually suggests a proprioceptive change to the face! This finding might be the only finding we didn't routinely teach in veterinary school because it's an oddity. But, it is a crossing tract and reflects forebrain disease.
So, what lesion localization did you come up with? Scroll to the bottom to see if you are correct.
Diagnosis
We diagnosed a brain tumor on MRI (see image above) and took this kitty to surgery. The mass was removed entirely, and was eventually diagnosed as a meningioma. Meningiomas are locally invasive, rarely spreading, intracranial tumors in cats. With complete surgical resection no additional treatment is needed! The cat went back to her normal personality, stopped circling, and regained vision in the left eye post operative (by the 1 month recheck...not immediately). Pretty cool stuff, huh!?
I hope you have a safe and fun week. Keep those consults coming and I hope to see you at the Webinar tomorrow!
Answer: RIGHT forebrain.