Chihuahua strange leg spasm

Question
A few days ago my 4lb female chihuahua had a strange leg spasm/cramp in her back leg. Which prevented walking, she seemed as though she couldn't put pressure on it at all, and she was trembling like crazy. Shortly after calming her down she was back to running and playing. Then today it happened again, in the front leg. This time it was awkwardly curled up and looked as if it had a mind of it's own trying to reach for her head. Very strange... And again accompanied by a lot of trembling, then POOF, like it never happened. She is walking around just fine. My concern is that over a week ago my 14month old son dropped a 1lb jar of dressing on her back from a couple feet above, which seemed to cause her severe pain so we immediately rushed her to the emergency vet. They gave her a quick exam and said she was absolutely fine. She was back to walking and playing like normal shortly after. But maybe it caused some kind of nerve damage? I have no idea and I can't afford thousands of dollars for an MRI. Help me?

Answer
Marissa,
I would take her back in to the vets and have an xray done on her back. It sounds like she has a pinched nerve or something going on from this jar being dropped on her back. Now, granted, Chihuahuas are prone to seizures, and these can come on from stress, and this injury would be very stressful.

She may have some minor damage but she seems to need some anti-inflammation drugs for this. A quick exam is not enough-she needs a better exam and something to determine whether or not this is her back or a seizure (petite mal).

Please let me know what you find out and how she does.