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Dr. B.
Dr. B., Board Certified Veterinarian
Category: Vet
Satisfied Customers: 22584
Experience:  General practice veterinary surgeon with extensive experience in a wide range of species.
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My cat has been seen by 2 different vets in the past 2 weeks,

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My cat has been seen by 2 different vets in the past 2 weeks, had various tests all revel nothing, they say maybe a brain tumour. however having looked on the net it would seem that from the symptoms she has a vitamin deficiency due to the fact that for several months all she has been eating is tinned Tuna daily and I see this may cause mercury poisoning, they say is very rare.
I have shown the vets the print outs and they have said the have never heard of this and they cannot find any references in online veterinary pages.
I have now found a third vet who will give a vitamin b1 injection

Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with your wee one today.


May I ask what signs Minx is showing?
Customer: replied 3 years ago.

front legs unstable in particular left leg claws do not work as normal trouble in retracting spends most time laying down lethargic eating and using box as normal just mobility and head is down most of the time in cowering position.

Customer: replied 3 years ago.

Have you received my symptoms message?

Thank you Norman,

Can you tell me if she has any signs with her back legs?

Can she lift her head?

Does she show any pain when her neck is moved (up,down, right, left)?

Is she of any specific breed type?

Have any vets checked bloods (with electrolytes)?

Is she a purebreed of any kind?


PS- I did but have a few more questions since I am intrigued by her wee mystery.

Customer: replied 3 years ago.

Not a pure breed, makes no noise indicating pain, purrs when stroked,

moves her head when she wants, no indication of pain, as mentioned 2 vets have examined her and 2 sets of blood tests show negative to all,

I mentioned the mercury poisoning Tuna and they cannot check until Monday.

Wife has found a vet who will give her a vitamin b1 injection at 3.30 today but at our risk.

Thank you again,

As I noted before, she is an interesting wee case and I have been thinking about what you have noted with her. The reasons I asked about her breed and electrolytes, was to just check that she wasn't actually a hypokalaemia (low blood potassium kitty).

Now her signs do sound suggestive of intracranial disease. Yet without looking inside that wee head (with MRI or CT), one can only really speculate what is amiss inside. Common causes in cats would be focal infections (meningitis), brain swelling/bleeds (from trauma), cysts, parasitic infections (like toxoplasma), and as they have noted, tumors.


Now you have proposed a very interesting suggestion that is actually a consideration if we have diffuse brain signs. As I am sure you can appreciate, thiamine deficiency is quite uncommon in cats these days since the vast majority of kitties are on commercial diets with proper vitamin levels (yet any mixed animal vet can tell you that this is still a problem in lambs). And as you have noted, when we have an animal on an all fish diet (raw ones because of high levels of thiamine destroying enzymes as well as overcooked ones due to having had the vitamins degraded by high heat), we can see a decline in Vitamin B1 (thiamine). When we do, neurological disease does result and we can see wobbliness, pupil dilation, and ventroflexion (downward positioning) of the neck.


Therefore, under the circumstances, it is very reasonable to consider treating with thiamine. And I do have to admit I am a bit surprised the first 2 vets wouldn't do so (especially since B vitamins won't do any harm if her signs are due to something else). Just to note a dose for your 3rd vet in addressing thiamine deficiency, we usually give 20-100mg/cat into the muscle or under the skin every 12-24 hours before switching onto oral treatment.


Furthermore, since you noted that no one had considered this as a differential for her signs, I would site that there was a report from the UK in 2010 of a case of thiamine deficiency of the cat (LINK). So, this may be an article to get them to download and read. Otherwise, if everyone is struggling to diagnose and help Minx, consider contacting having this vet contact the authors of the paper (I can tell you that Dr. Penderis is still at the University of Glasgow and would likely be able to confirm if your vet's findings matched what they saw in their case).


Overall, there is no reason not to try thiamine with her. Mercury may be a consideration but a wee bit less likely. So, I would advise starting with this and having vet #3 perform a full neurological examination. Once they have done this, they will need to monitor treatment and perhaps contact the authors of that paper to get some guidance to whether this is the likely issue for Minx.



I hope this information is helpful.

If you need any additional information, do not hesitate to ask!

All the best,

Dr. B.


If you have any other questions, please ask me – I’ll be happy to respond. Please remember to rate my service once you have all the information you need. Thank you and hope to see you again soon! : )

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Customer: replied 3 years ago.

Thanks for your interest after 2 injections her condition has improved and our vet has read up on the subject and has recommended a further course of injections its early days but fingers crossed the solution will work, if you wish I will update you best regards, XXXXX XXXXX

Good morning Norman,

That is great news! Smile
I am very glad to hear that Minx is showing improvement.
Please do let me know how you get on with her.
To remind us both to touch base with one another, I will schedule an automatic check-in for a week's time. So, you should get a wee email from the website then.

Take care & all the best,
Dr. B.