I have heard of a few cases of neuromuscular therapists reversing chiari one when the pelvis is in flexion and the neck in extension. Your pressure headaches are consistent with the neck in extension since it is the suboccipital muscles at the base of the skull that would be extremely tight. With the neck in extension the spinal cord is tethering the tonsil down into the foramen magnum of the skull competing for space with the brain stem. There just ain't room for both! The corrections are all soft tissue work (massage). The trouble is going to be to find someone familiar with the work. It's an advanced training that most massage and physical therapists are not taking. Good luck! It's gentle work that won't hurt and worth trying since you have to wait anyway. Don't let a chiro touch it! They'll make you worse. Most know, some don't. Best wishes to you, ~p