Senior Cat dealing with mystery illness(es)?

Hello all! New hear, but hoping y’all can help us figure out what’s wrong with our sweet boy. Details are below. Long story short, we've taken him to multiple vets, gotten tons of tests done, but still don't have any solid idea as to what's wrong with him. The latest vet says the only option left is to do a biopsy and potentially subject him to chemo. Before we put him through any of that, I thought we’d give this sub a shot to see if anyone has any idea what our boy is dealing with. On a related note, if there are any other places y’all recommend we post this info, we’re all ears. Thank you in advance for all of your help! Cat Details:

• Breed: Domestic short hair, orange and white tabby (ginger cat)
• Age: 14 years 10 months
• Sex: Male
• Neutered?: Yes
• Weight: 11 Lbs
• Location: Los Angeles, urban/suburban neighborhood

Symptoms:

1. Imbalanced, unsteady movement. Specifically, head tilt, falling over whilst playing, difficultly jumping up to and down from previously easily accessible spots, and walking in circles. Most pronounced when he gets up after being asleep or chilling for a while.
2. Change in energy levels. Still affectionate and engaging, but overall less energetic and more lethargic than before.
3. Change in appetite. No longer eats kibble and now only eats prescription wet food.
4. Weight change. Cat was at 14 Lbs and is now down to 11 Lbs
5. Bizarre eye dilation. Specifically, pupils will dilate and remain dilated for hours. And while eyes were dilated, cat is very disoriented, anxious, and seems to have trouble seeing. These episodes would trigger many of the above symptoms, with cat going around in circles and sometimes sniffing things. Very strange and nerve-wracking to observe.

Symptoms timeline:

• Symptoms started since November 26th 2023
• Symptoms have improved somewhat since getting put on his new diet then and he appears to have stabilized. Better appetite and normal pees/poos. But still no official diagnoses or any idea as to why things have improved

Test notes and overall results:

• We have been to several vets, including a neurologist
• List of tests:
  • Senior blood panel
  • Urinalysis
  • Physical exams
  • X-rays
  • MRI
  • Spinal fluid extraction
  • Ultrasound
• Results summary:
  • Not a tumor
  • Heart, spine, and middle ear are fine
  • Does not appear to be metabolic disorder like say, thyroid issue
  • Blood pressure is fine
  • Ultrasound shows some nodules on his liver and pancreas. Vet says they could be benign or cancerous, but we can't be sure unless we biopsied him.
  • Neurologist also ruled out seizures, and said that pupil dilation would not last for hours with a seizure

That’s pretty much the gist of it. Any ideas? Thank you! -Deer

Hello and thank you for this fascinating history.  It sounds as though your vet and then your neurologist have been to quite a lot of trouble to find the cause of this - and that you've been through the mill as these investigations have taken place. Even though finding something on an MRI is generally bad news, it's always frustrating when nothing is found.  However, MRI scans can only see so fine detail, even in the human world. I personally have had quite serious neurological symptoms from a brain lesion than isn't big / dramatic enough to visible on an MRI scan.  Your neurologist will hopefully have carried out neuro exams to classify the symptoms, and should be able to  explain how big a lesion (lump or abscess or whatever) would have to be to cause these signs, ie whether the absence of a large lump on the scan rules a lump or lumps out as a cause in this case.

It sounds as though you and your neurologist actually have a better understanding of your cats' case than I can hope to glean from here.  I usually advise people of some good questions to put to specialists to straighten things out in your head:  1) What could still be causing these symptoms?  (We call this the differentials list)   2) How could we tell the difference between these possibilities?   3) What would the advantages be of taking this step (eg knowing the answer and getting mental peace, ruling out a thing that could possibly be treated, either permanently or for a few weeks, and so on - will be specific to your cats' case)  4) What would the disadvantage be of taking this step? (Examples might be cost, or surgical / anaesthetic risk / possible side effects and so on).   5) What would they do in your position?

While 'mystery illnesses' sound stressful and vague, it can be useful to regard the process as a series of sequential decisions;  your vet might not know what it is, but they can help you to understand what is best to do next.  It sounds as though you are at a crossroads; to risk the next stage of investigation or not?   This is always a stressful decision and once you have a handle on the arguments in favpur of taking a biopsy, and the arguments against it, it is likely to be your feelings and finances that will guide you.  You have already authorised more investigation for your cat than most people would do; perhaps obviously, given my background as a vet, I would love to know the answer.   However, your cat is a person and you are people and when dealing with people, logical investigation to get the answer has to be balanced against what is right by the 'people' in this case.  The answer is subjective; what is right and wrong for you and your cat is often a gut feeling.  Hence medicine is an art and not a science.

'What would the advantages / disadvantages be' is always vital to understand.   I hope that you feel that you can make a decision that feels right for you all at the crossroads.