Aggression due to brain tumour - or is it?

My 7 year old neutered male Polo has a slow growing brain tumour. He is medicated on 2 x phenolbarbitone a day which keeps things under control, mostly. This has increased steadily since he was diagnosed last August. I am told that he is now on the max doseage.
Lately, he has been showing unusual aggression towards my young dog, an entire 2 year old, who is very mild tempered and gets on fine with any dog known to him or not. This morning, just after his dose when it would not have had time to kick in, he snarled and growled at the other who was thinking of joining him on the dog settee. They normally curl up together no bother. The youngster ignored him and kept coming, the next thing I had to pull them apart from a really fast, vicious mutual attack. Polo ended up bitten in five places, though not seriously, the young one was unharmed.
The question is - this has happened three times now, does the younger one perceive that the older, sick one is going downhill and he's doing what nature tells him to do, to take over as pack leader (which I thought he had already done) or to hasten Polo's despatch? Or is Polo, having an increasingly jangly brain, giving out mixed or confusing signals? While he was "warning off" the other his tail was wagging and five minutes after the attack he was Mr soppy dog again.
I know that once Polo's back end goes, that will be it. It happened a few weeks ago but he recovered quickly so I put it down to a knock. I don't want to get to the point where he doesn't know what he's doing and causes real harm, but also don't want to make a big decision if the situation doesn't warrant it.
Any comments?

Not experienced enough to say really,only sorry that this is happening to Polo,does sound like something is going on though maybe Polo is feeling unwell and trying to say to the others leave me alone,know it can have this affect on humans so don't suppose dogs are much different.All you can do is what you are doing already and watch for the signs of when you think he has had enough.
I know when my dog Max had cancer he got touchy although we had no other dogs living with us we noticed his soppy temperament change even his barking changed to one of irritation rather than just seeing off whatever had disturbed him our Neighbours commented on the change in his bark too.

Not really qualified to comment, Gill. Just wanted to pass on a *hug* and let you know you have my heartfelt sympathy xox

Hi Gill, sorry to hear you are having a few problems. If it's any help to you the breeder of my Leon had 4 year old that became agressive at the age of two, (infact, he attacked my Tyler as a 9 week old pup and it was not due to any threat from Tyler). They continued to show him and did make him into a show champion but then they had to stop showing him as he would lung at the other dogs, snarling etc., (which is basically unheard of in the setters), one minute then all friendly and wagging tail the next. .

Anyway, at the age of 4 he badly attacked another of their dogs and then attacked the husband, they had him pts as there was no other option, they couldn't rehome him as his attacks were becoming more frequent and for no apparent reason. The PM revealed he had a slow growing brain tumour and the vet could only assume that this had been the reason for his aggression, they also owned his litter brother who was a big softy, just as they should be.

I hope this may help explain Polo's mood swings.

My friend is a trainer and had a similar thing hapen when she bred and showed rotties years back, one of her boys was unwell and when she took him to the vet he was fine one second and within the blink of an eye flew at the vet and if my friend had not been ready and had such quick reactions she thoroughly believes the vet would have been very seriously injured. She had to pin her boy down and in the end he had to be pts, they discovered he had a brain tumour and it was credited for his sudden change in behaviour as it was totally out of character. Hope Polos feeling a little more like himself soon, and big hugs to you all.x

Deccy I am so sorry to hear about Polo no doubt he doesn't feel himself and is letting other dogs know this, a form of self preservation and an instinctive thing to do when a dog is in a vulnerable situation. xx

i would get advice from your vet, personally i would think its down to the tumor interferring with his function.
maybe the youngest is picking up on his health but i wouldn't think if they have lived together without any issues before it would cause it now.
i think you are the only 1 who can judge how he is on a daily basis, he is bound to have good and bad days with it,cant the vets do a scan etc to see what state it is in to advice you more at his condition at the moment.
its hard to say what is the best thing to do but i can understand you dont want to do anything too soon, so my advice is go on the facts to base it on.

Hi Deccy,
I'm by no means an expert but just thought I'd say that we've just had this experience with the Leo's, one of my Sisters 4 was very poorly and was subsequently diagnosed with Cancer and we lost him in Feb this year but when he began to show signs of being ill one of the younger Males (entire) began challenging his dad (the poorly boy) for top dog, now he began doing this a good few weeks before we knew he was poorly and before we finally got a diagnosis so maybe it is partly nature taking its course and maybe partly due to Polo's condition

But Like Leo say's I'd be inclined to just get him checked over by the vet - just to be sure :smt001

Hi Deccy Think the others have said it all. So I shall just send you comforting cuddles and say how sorry I am to hear this is happening with Polo. Eunicex

So sorry to hear this Deccy. I'm no expert the only experience I've had with a dog with a brain tumour was when I was still with my parents and my dad actually had to shoot a dog who had 'gone mad' and flew at someones neck meaning business. The PM done by the vet showed it had a large brain tumour, but there hadn't been any noticable signs before this (bearing in mind this was a working dog..kept outside). I'm sorry reading this back you probably don't want to know that.

I think it could be either or both the reasons you've mentioned with your dogs. Polo may be giving mixed signals and/or trying to protect himself. The younger dog at two may just be reaching the age where he's wanting to assert himself. It's really difficult to know..it may be entirely unrelated.

As Eunice has already said though I'm just so sorry this is happening to Polo. *hugs*