Head tilt, Wobbly: Ear infection or something worse?

[Scruttabun]

Hi! First of all, I'm so happy this forum exists and I've used it quite a few times to learn over the years.
Unfortunately my guinea pig Rollie has been sick, I feel like I have nowhere else to turn and need some advice from some experienced owners.

Age: 5.5
Sex: Male
Breed: Abyssinian
History: Rescued at 2.5, sanctuary said he was an "accident" baby, they surrendered the whole litter
No cage mates: they tried pairing him but he fought, so I adopted him (I work from home and hang out with him a lot)
Diet: unlimited timothy/oat/orchard hay, leafy greens of varying types, occasional fruits and treats but gets soft poops so I limit them
One month ago (August 15) I noticed Rollie was slightly tripping/falling on his right arm.
I took to an exotic veterinarian, they did an x-ray and saw arthritis in the knees and noticed the shoulder was hypermobile, so they gave me childrens liquid vitamin C believing it could be deficiency-related, as well as meloxicam for pain.
Two weeks ago (Sep 1), I noticed his eyes had a very subtle nystagmus to the right, so I rushed him back but they did not notice it. They used isoflurane to sedate him and drew blood for a basic metabolic panel, and the only thing abnormal was a higher level of amylase. Vet said it could be cancer so I have an ultrasound scheduled for Sep 28 (the small mammal ultrasound person comes in then with a much better machine than the one they have). They gave me meclazine to help with any dizziness he was experiencing and sent me home.
Last Friday (Sep 11), he had a head tilt to the right on and off, accompanied by a difficult time walking, but still eating. I took him back to the vets and they sedated him to get a skull X-ray and more blood for a CBC. CBC came back fine, X-ray showed a "disorganized/cloudy" appearance in his left ear, described as "inner ear has some thickening and inflammatory changes." I was given two oral antibiotics: Enfrofloxacin (baytril) and Metronidazole. He has been on it for now four days but lost his appetite 2 days in. I'm feeding him the recommended critical care and he perks up usually.

Today (Tuesday sep 15), he is quite lethargic but still runs around after his syringe feeding and still eats his favorite greens voluntarily and picks at hay, but he has become quite wobbly which is concerning. I will include some videos to show his weakness. Should the antibiotics be helping a potential ear infection by now? Or does it take longer than 5 days to work? Furthermore, should I be concerned about E. cuniculi? My veterinarian said it is rare in guinea pigs. My previous guinea pig lived to be 5.5 and had VERY SIMILAR symptoms that started with weakness in one limb, then turning into a head tilt resulting in his death on September 13... Its strange that it's the same time of year and age. Any advice is welcome and I GREATLY appreciate anyone who takes the time to read and watch the videos.
I understand it may also just be his time, but I'm a desperate pet owner and he is my little buddy

Videos from Sep 15:

https://imgur.com/a/cant-lift-head-to-get-lettuce-tzROcu7
https://imgur.com/a/hobbling-falling-TsmF2x1

 

[Claire W]

Hello. I am very sorry you have a poorly piggy. I once had a guinea pig who had an ear infection who was very wobbly and had a head tilt and it took two weeks for her to get better so it could just be that the antibiotics haven’t had the full effect yet.

To be honest, I’d give him a bit more time before jumping to the worst case scenario but I wouldn’t rule it out x

 

[Piggies&buns]

I’m sorry to hear this.
Antibiotics build up in the system over time, taking up to 5 days to reach full efficacy, so you are only just at that point of them working at full force.
I hope he is ok

 

[Wiebke]

Hi

Unfortunately, it is impossible for us to tell. A sudden head tilt can be the result of a stroke or a neurological event, a blocked ear or an ear infection or - if you also have rabbits - potential e.cuniculi.
Long term blindness doesn't usually have that quick an onset, but sometimes a head tilt may develop later unless the blindness has a neurological cause.

Unfortunately, there is no treatment for strokes or other one-off neurological events when it comes to guinea pigs and precious little research.

So your vet has done the best they can: treat for an infection after checking that the ear canal is clear. If you have rabbits, then it may be worth checking for potential transmission (including through you via infected rabbit food or cage debris accidentally contaminating guinea pig dishes or bottles).

Here is what little information there is on neurological issues in guinea pigs: Neurological Issues (Seizures, Strokes, E.cuniculi etc.) - Symptoms and Care

Anyway, I am keeping my fingers firmly crossed that it is an infection.