Hi and welcome to the Chiari forum if you are a new poster....sorry I couldn't check your bio, I get an error page?? Anyway , to answer your question I have to ask you a couple....first when you had your recent MRI what was it of? A brain MRI, cervical spine, thoracic , lumbar? Have you had a CINE MRI?
I ask because you said the cerebral tonsils remain the same as a prior MRI, but again it depends on where they are looking to know what else may be going on.
Most times issues like shaking or referred pain is a miscommunication to the brain.....same with drop attacks and so on......but what is causing it is more important .
I am wondering if you developed a syrinx.....due to your description of the symptoms.