Anatomy of Craniocervical Junction
Overview of the Upper Cervical / Craniocervical Junction (CCJ)
To help you understand how the craniocervical junction, meaning the cranio (head) and cervical (neck) can be affected by congenital conditions, injury and disease, it’s helpful to understand the key parts of the craniocervical junction and how it functions. Because of the complexity of this area, we have split it out into several sections:
- Craniocervical Junction
- Atlanto-occipital
- Atlantoaxial joint, the Brainstem
- Spinal Cord and Cerebrospinal Fluid
- Nerves
- Blood Vessels
- Lymph Vessels.
Again, the CCJ is where the brain connects with the body, and it involves a lot of vital body parts and systems, so we have tried to keep it as simple as possible while conveying the basics so that you and your healthcare provider can fully investigate to rule out the many possible reasons for your symptoms, un-wellness and disability. If you prefer to watch a basic video on this subject, please scroll down to the end of this page and watch the video(s).
1.) The Craniocervical Junction (CCJ)
The craniocervical junction (CCJ) (also referred to as the Craniovertebral Junction (CVJ in some literature) is a major joint that is located in the region from the base of the skull to the upper cervical spine, specifically down to the top second vertebrae called the Axis or C2 vertebrae. Again and a bit more specifically, it comprises of the lower surface of the skull, the top spinal vertebrae i.e. C1 (atlas) and C2 (axis), as well as muscles and connective tissues that attach the skull to the cervical spine.
The CCJ contains the medulla (i.e. the spinal cord, that forms (or attaches per se) to the lowest part of the brainstem and contains control centers for the heart and lungs. It also contains the cervical spinal cord, the central nervous system (CNS), multiple cranial nerves, essential blood vessels (arteries & veins) and lymph vessels relating to the brain and the cerebrospinal fluid (CSF) system. Reference
2.) Atlanto-occipital
To split the craniocervical junction (joint) in two parts, there is the upper portion, called the Atlanto-occipital, which is where the skull, (also known as C0 or the Occiput) rests on top of the 1st cervical spine vertebrae, C1 (which is called the Atlas). This part of the CCJ is dynamic (i.e. it moves) and is responsible for flexion and extension.
Strong ligaments, muscles, small facet joints and occipital condyles (OC) hold the head on and allow the head (with an average weight of 15 lbs.) to move around (i.e. flex, extend, rotate, tilt etc.).
- Learn more about key ligaments: Alar, Apical and Transverse, Capsular Ligaments Tectorial Membrane – Watch a video by Education Spine called Craniocervical Junction Model – Helping to explain the craniocervical syndrome
3.) Atlantoaxial Joint
The second and lower portion of the craniocervical junction is the Atlantoaxial joint, which is where the Atlas (C1) joins with the 2nd cervical spine vertebrae, C2 which is called the Axis. This part of the CCJ is dynamic (i.e. it moves) and is responsible for flexion, extension and rotation. The Atlas rests on top of the Axis. The Axis’ (C2) dens (also referred as the odontoid process), the part that is like a peg pointing upwards, fits into the Atlas and is held on by ligaments, muscles and facet joints. The dens allows the rotation of the head.
- Watch video here
4.) The Brainstem, Spinal Cord and Cerebrospinal Fluid
The lowest part of the brain, the brainstem, which connects to the spine, as well as some nerves and blood vessels is housed in the craniocervical junction. Here will briefly cover some of the major functions of each of the 3 components of the brainstem: the medulla oblongata, pons, and midbrain.
Inside the craniocervical junction is the brainstem which is the stalk-like part of your brain, that connects your brain to your spinal cord. Shepherd Center explains the anatomy of the spinal cord and how it works. The spinal cord is a very important part of our central nervous system. It’s the overall system that controls and coordinates the activities of our body. The main job of the spinal cord is the communication system between the brain and the body by carrying messages via nerves that allow us to move and feel sensation.
5.) The Nerves of the Cranium and Cervical Spine
Cranial Nerves
Medical News Today explains that the functions of the cranial nerves are sensory, motor, or both. Sensory cranial nerves help a person see, smell, and hear. Conversely, motor cranial nerves help control muscle movements in the head and neck.
Each nerve has a name that reflects its function and a number according to its location in the brain.
The 12 cranial nerves include the:
- olfactory nerve
- optic nerve
- oculomotor nerve
- trochlear nerve
- trigeminal nerve
- abducens nerve
- facial nerve
- vestibulocochlear nerve
- glossopharyngeal nerve
- vagus nerve
- accessory nerve
- hypoglossal nerve
To explore the functions of each of the cranial nerves and look at a diagram you can continue to learn more by referring to Medical News Today’s article on What are the cranial nerves?
Nerves of the Cervical Spine (Neck)
6.) The Blood Vessels
The major blood vessels of the neck contain the carotid system of arteries and the jugular system of veins. Listen to Sam Webster who will explain these parts and systems with visuals.
7.) The Lymph Vessels
The lymph nodes of the head and neck can be divided into two groups; a superficial ring of lymph nodes, and a vertical group of deep lymph nodes. Learn more by watching: Knowing Anatomy who will explain the lymph nodes of the head and neck.
Anatomy – Why learn human anatomy?
Additional Materials on the Anatomy of the Craniocervical Junction and Cervical Spine:
In this episode of eOrthopodTV, Orthopaedic Surgeon Randale C. Sechrest, MD narrates this animated video describing the basics of the anatomy of the cervical spine.
The Craniocervical Syndrome and MRI by Francis W. Smith and Jay S. Dworkin.