Arachnoiditis occurs in the lumbar spine for the most part. This will cause leg symptoms and possibly bowel and bladder dysfunction. Neck pain and facial muscle stiffness are not part of the syndrome.
Cramping and muscle stiffness can be caused by Parkinson’s disorder among other pathologies.
I do look at MRI scans for free (at this point) and you are welcome to call the office and send them in. The forum does not allow uploading of MRI images for security reasons (viruses).
Dr. Corenman