My doc said my lhermitte's is from anxiety and odered brain mri. wouldn't one be needed for the neck, too?

Perplexing: Lot's of etiologies for a lhermitte's phenomenon, but anxiety is not one for the textbooks yet. Since the symptoms are due to some pathology within the posterior columns of the spinal cord, a brain MRI may of course, miss any of a number of pathological processes which involve the neck and not necessarily the brain. Sounds like your doctor and you may be lacking communication interactions.

You could ask : If your doctor states the problem is from anxiety then MRI of the neck may not be indicated.