If you’ve been diagnosed with an upper cervical (neck) disorder, it’s important to learn as much as you can about it. An anatomy lesson is a good place to start. This article will help you understand key anatomical structures in the skull and spine, with the goal of helping you better understand your condition.
The Craniovertebral Junction: Where Your Head and Neck Meet
Head and upper neck disorders may be called craniovertebral (or craniocervical) junction abnormalities (CVJ). The CVJ is one of the unique and complex areas of your body, as this is where your brain transitions to your spine.
The CVJ is composed of the occipital bone, atlas (C1), and axis (C2), along with a network of complex nerve and vascular structures. The occipital bone, atlas, and axis are responsible for most of the spine’s rotation, extension, and flexion—simply put, no other place in your spine moves more than the CVJ.
Let’s take a closer look at the primary structures in the CVJ: The occipital bone, atlas, and axis.
The occipital bone is a bone that covers the back of your head; an area called the occiput. The occipital bone is the only bone in your head that connects with your cervical spine (neck).
The occipital bone surrounds a large opening known as the foramen magnum.
The foramen magnum allows key nerves and vascular structures passage between the brain and spine. Namely, it is what the spinal cord passes through to enter the skull. The brainstem also passes through this opening.
The foramen magnum also allows 2 key blood vessels traversing through the cervical spine, called the vertebral arteries, to enter the inner skull and supply blood to the brain.
The Atlas: The Top Bone in Your Cervical Spine
The occipital bone rests upon the atlas, the first bone in your neck. The atlas is named after the Greek God Atlas, who held up the world on his shoulders.
A pair of synovial joints, known as the atlanto-occipital joint connect the atlas and your skull.
The atlas is also known as C1, and while other bones in your spine are numbered in such a way (eg, the first bone is your lumbar spine is known as L1), this vertebra is much different in shape and function compared to the rest of your vertebrae.
The atlas is ring-shaped and has the important task of supporting the head. It’s also responsible for facilitating movement in head and neck. When you nod your head “yes,” that’s the atlas at work. It serves as a pivot, and it allows your head to move forward and backward.
The axis is positioned directly below the atlas and is also known as C2. Like the atlas, the axis is distinct in appearance and function from the rest of your vertebrae.
Between C1 and C2, there two synovial joints called the atlanto-axial joint. These joints facilitate rotation at this level.
The axis has a superior extension (upward), which is a peg-like bone called the dens. The dens fits within the ring of the atlas and with the axis, allows your head to rotate. So, when you shake your head “no,” that’s the axis at work.
If you’d like to view a short video that highlights the atlas and axis, watch Cervical Spine Anatomy Animation.
The Craniovertebral Junction: The Most Important Place You Never Heard About
The CVJ is arguably the most critical part of your body, and you may have never considered all the structures that work together and connect here. The intersection of the base of your skull and top of your spine is chock-full of essential neurological and vascular activity. If you have been diagnosed with an upper cervical disorder, it’s important to have a general understanding of the structures in your head and neck. This will help you have informed and productive conversations with your doctor, and enable you to be an engaged participant in your treatment decisions.