The first neck vertebra, also known as the atlas or C-1, is a small donut-like ring located at the top of the spine. It is in close proximity to the brain stem, which is the part of the central nervous system responsible for controlling a number of vital body functions. One of these very important functions is the muscle balance of the spinal column.
When the atlas is subjected to a stress or injury, it can become partly misaligned in relation to the skull and the other vertebrae in the neck.
We call this the Atlas Subluxation Complex Syndrome or the ASC Syndrome. Even a slight structural misalignment of the upper neck will result in a muscular response that shifts the body balance from normal and adds stress to the spinal column.