A recent mri showed cerebellar tonsillar ectopia up to 12 mm, does this along with having a lot of the symptoms of chiari mean that chiari is likely?

Yes. When you : follow up with the MD who ordered your MRI, you should be given a referral to a neurosurgeon to discuss any further diagnostic studies needed & treatment options.

Meets Chiari I def: Tonsilar ectopia greater than 5-6mm below the foramen magnum is considered a Chiari I malformation. Whether symptoms are associated is more individual, but usually at 12mm and greater, most are found to have associated symptoms.