Hi all,

I hope you had a restful new year. Unfortunately over the holidays my super friendly and energetic dog (Shih Tzu/Bichon mix, 3.5 years old, 14 lbs) randomly started trembling one night. It was extremely out of character. She was napping on a blanket she loves and then wouldn't move, was shaking, and walking with her tail behind her legs and wanting to go under the bed and such and not come out (out of character). The first night this happened we were able to take her on a short bathroom walk (she was fine outside...) and she slept through the night fine. The next morning after her morning walk, she got back to our apartment, was presumably fine, napped on her bed - then the same thing happened - trembling, not wanting to move (but able to...)... we ultimately put her on a blanket, pet her/comforted her, and took her to the vet. Below is a timeline and some of the weird things that I am hoping someone can help us with, because either we are over-thinking this or this is genuinely weird.

Wednesday night- first bout of trembling/not acting herself; able to go on bathroom walk, slept fine

Thursday morning- bathroom walk, quick nap, second bout of trembling *vet visit 1*

Thursday afternoon- vet said it could be a case of IVDD, which scared us a ton as a my cousin's dog had that and was eventually paralyzed in the back legs and needed emergency surgery (did end up recovering, but obviously not an ideal diagnosis). Vet said 14 days of rest and prescribed gabapentin, prednisone, and methocarbamol. By the time we got home from the vet she was exhausted and basically slept the entire night.

Friday - completely fine

Friday night - completely fine

Saturday morning (before the meds) - same thing; morning walk completely fine, got back and trembling/not acting herself; vet visit (different place) said either muscular strain or very mild IVDD and essentially told me not to worry, and continue gabapentin early. We went to a second vet because if I am being honest I was freaking out a tad and the first vet scared me by saying it was IVDD and didn't really give us any other ideas what it could be.

Sunday - completely fine

Monday morning - same as usually, morning walk is fine, fine in our bed acting normal, get back from walk and she is trembling and not acting herself (tho not entirely as bad)

Tuesday morning - same as above (but somewhat worse today than Monday, but similar to a few days ago)

Weird things/my questions the vet doesn't answer when I ask:

1. Both vets and me and my partner have felt her all over over on her back, legs, stomach, etc and she doesn't respond to any touching in terms of pain. In the past when she has hurt her paw, had a belly ache, and such she would yelp when we touched the painful area. Basically I find it a little odd I can't pinpoint the pain anywhere on her body, as in the past we were able to. The vets assured me that trembling can and is commonly from pain even without a pinpointed response - but I do find this really odd.
2. She can go back and forth from trembling to perfectly fine in a very quick change of environment. For example, during a few of the trembling episodes we took her outside and she acted completely normal (i'd say 95% normal) - wanted to play with dogs, and almost *WANTED* to keep walking, didn't seem to be in pain, and was almost like her old self - then changes when we get back home either immediately or eventually.
3. We have been trying our best to keep her rested but a few times she has run around and jumped on/off the couch and it did not trigger any trembling or pain (even on the drugs, or off the drugs). If she had IVDD or serious pain would it be so fleeting and back and forth? I know when I have hurt my back it can be randomly triggered so I'm not saying it's not possible - but it does seem odd she is almost "worse" at rest or doing nothing, than when she's being active like on a walk.
4. This never happens in our bed. I'm not sure if this is because it is more comfortable if she is indeed in pain, tired so the pain is less bothersome, or if it is something like the tremor syndrome (below) or anxiety, she is just general more comfortable so isn't triggered.
5. This also never happens when she goes to bathroom to pee or poop (arches her back).
6. She is seemingly eating/drinking fine outside of the trembling episodes.

What it could be?

1. Muscular pain/strain - she did have a very active week playing with my parents dog last week for the holidays so I am thinking this could be likely. Perhaps it doesn't always hurt but then she twists or moves just right and it triggers a pain and then she shakes from the pain and/or subsequent anxiety.
2. IVDD - perhaps very mild? Again not an expert on this but maybe it is like the above where she triggers it just right and then trembles from the pain - but again I find it super odd nothing outside triggers it when she's moving the most.
3. Being cold - she did indeed get groomed right before the holidays and does sometimes act odd after the grooming. But this was over 1 week before the initial initial incident so any grooming anxiety/itchiness I think would have subsided. BUT it did get a little colder around the time the first incident occurred so maybe she did get the chills or got cold while at rest because she didn't have time to adjust to her shorter coat in the colder weather. I do notice that when I pick her up and hold her either myself or in a blanket the trembling does get better.
4. Anxiety? Not sure if something triggered her the first night and then continued when we got back to our home - the weirder she acts, the more anxious we get (genuinely trying not to act anxious) but maybe it's a bit of a cycle that we are just going off each other making it worse - because again she seems to be fine outside and on her bathroom walk.
5. Shaker syndrome / generalized terror syndrome - something neither vets mentioned, but I saw online and saw some videos and read about - it does seem super similar to what she does. And would explain why she is maybe is just trembling but not necessarily in pain. It looks like being cold, anxious, etc. (among other things) can trigger it but not a lot is known about it.
6. Combination of some of the above!

Does anyone have any thoughts what this could maybe be? I feel terrible for her - I really do. She goes back and forth from acting like herself to whatever this is and I hope she isn't in too much pain. The more I analyze what is happening I am finding I am able to comfort her from the trembling when I hold her (it really helps) but still not sure if the tremors are from pain or something neurological. We are continuing with the gabapentin for the next 10 days or so and have a neurology appt on 1.15. I'm curious to see what your thoughts are.

Forgot to mention that all her bloodwork and general vet exam were completely fine. And it was hard to tell if the trembling at the vet was due to whatever this is, or just worse bc she hates the vet in general and knows something is up. I appreciate any responses! I am admittedly an anxious dog owner, but mostly I just feel terrible she at times seems miserable. She loves playing and being active so I am hoping this is something that will be short lived and not a long term issue, but open to your thoughts.