Everything You Need to Know about C1 and C2 Vertebrae

While all spinal cord injuries (SCIs) can be dangerous and life-altering to the people who suffer them, there is one variety of spinal cord injury, in particular, that is considered the worst: an injury that falls within the cervical spinal cord — specifically at the C1 and C2 spinal cord injury level.

I njuries to the cervical spine at the C1 and C2 vertebrae make up just 2% of all spinal cord injuries . While they are considered the most severe of all spinal cord injuries , the effects of these injuries can vary depending on the completeness of the damage.

For identification purposes, the spinal cord is divided into multiple sections that correspond with the vertebral section of the spine in that area. Read on for more information on the fundamentals of these injuries, expected prognosis, and the latest treatments available.

What Are Vertebrae?

The spine is made up of 33 stacked bones called vertebrae. Medical professionals group these individual levels into five sections called:

The vertebrae of the spinal column are responsible for protecting the spinal cord, which is a bundle of nerves that relays messages between the brain and the rest of the body. Together, the spine and spinal cord are covered by a protective membrane, forming the spinal column. Spanning from the bottom of the skull to above the hips, the backbone supports all forms of movement — getting up, turning over in bed, standing, running, and crouching.

The first 24 vertebrae (working down from the skull) are distinct and mobile, but the remainder toward the bottom of the spine are fused and remain stable. Made of bone, and held in place with muscle and ligaments, the neck has the largest range of motion in comparison to other vertebrae.

What is a C1 Vertebra?

The seven vertebrae in the cervical region of the spine all work toward the same cause — moving the neck and holding the skull in place. On average, the human head can weigh between 10 and 13 pounds, yet the bones in the cervical spine are the smallest of all the spine’s vertebrae. However, the very first two vertebrae, C1 and C2, have the most specialized jobs; allowing a unique set of movements for the skull.

The cervical vertebrae C1 is attached directly to the skull, which allows for any nodding lateral motions. The top foremost of the vertebrae, C1, allows for a greater range of motion than normal vertebrae.

What is a C2 Vertebra?

The C2 vertebra is the axis which the C1 vertebra pivots around and lets us move our skulls from side to side in a horizontal motion. Like the C1 vertebra, a C2 vertebra has a greater degree of motion than other vertebrae that are lower on the spinal column. Since the brain stem extends through the C1 and C2, it is extremely important to the neurological system.

C1 vs C2: Anatomy and Spinal Location

The cervical vertebrae known as C1 and C2 form the top of the spine (neck) at the base of the skull. These vertebrae are uniquely shaped and have vertebral foramen (spaces within the bone) which allow the vertebral arteries to reach through to the brain and supply it with blood. This vertebral formation is only seen in the cervical region.

C1 and C2 Vertebrae Names

The C1 vertebra is referred to as atlas—so named for the Greek myth in which the titan Atlas held up the sky. The second vertebra, C2, is called the axis in reference to its purpose — enabling motion. When together, atlas C1 and axis C2 allow for rotation and swiveling of the head since the C1 vertebrae is attached directly into the skull and pivots from its C2 axis.

How Many Cervical Vertebrae Are There?

The cervical spine is located at the very top of the spinal column. Besides the atlas C1 and axis C2 cervical vertebrae , there are five additional vertebral levels within this region (for a total of seven) which are classified as C1-C7 from the top down, forming the human neck. There is an additional cervical-level injury classification site known as a C8 injury which relates to damage to the spinal cord root that exits the spinal column between the C7 and T1 vertebrae.

What Are the Functions of the Cervical Spinal Cord?

The cervical spinal cord is the uppermost section of the nerves that are inside of the neck vertebrae. This region of the spinal cord, which is referred to by vertebral levels as C1-C7, is also the most sensitive in the sense that injuries at this level are the most life-threatening. The vertebrae in this region, atlas C1 and axis C2 , support your skull, allow you to turn and move your head, and protect your spinal cord.

To put it simply, higher the injury on the spinal cord, the more damage and loss of function the individual will experience. Since the cervical spinal cord is the highest part of the spinal column, SCIs in this section of the spinal column tend to have the gravest effects.

C1 and C2 Spinal Cord Injury Symptoms

Because the cervical spine is closer to the brain, and therefore affects a larger amount of the human body, spinal cord injuries that affect the atlas C1 and axis C2 sections of the spinal cord frequently result in death. For those who survive, these injuries often involve the loss of function to the neck and everything below it — which may result in full paralysis.

Other related effects include the loss of ability to:

• Clear saliva from the mouth;
• Speak clearly; and
• Control bladder and bowel functions.

When someone experiences complete or partial paralysis from the neck down — their trunk and all four limbs — it is commonly referred to as tetraplegia or quadriplegia. An injury to the cervical vertebrae C1 and a C2 spinal cord injury are both considered highly rare injuries to sustain. More common cervical spinal cord injuries affect the C4 and C5 levels of the spinal column.

Types of C1 and C2 Cervical Spinal Cord Injuries

Although injuries can occur at this level, they are not very common. Medical professionals see more injuries to the C4 and C5 area. The most frequent cause of a C1 fracture is diving, followed by vehicular accidents, and then falls that impact the head.

C1 and C2 Vertebrae Breaks, Fractures, and Misalignments

Atlas C1 and axis C2 injuries are the most severe because damage to the spinal cord at any level has potential to remove communication to the rest of the body below that point. Due to the high level and placing of these vertebrae at the top of the neck, having a C2 or C1 vertebrae out of place or suffering sustained damage is most often fatal (or leaves the individual fully paralyzed).

In addition to the initial vertebral injury, the interference at the C1 and/or C2 level can cause the vertebral arteries to inflict neurological damage; leaving the brain without a vital source of blood.

Symptoms following an injury to the cervical vertebrae C1 and C2 may include:

• Complete paralysis of arms and legs
• Muscle atrophy
• Limited head and neck movement
• Compromised continence control
• Trouble breathing without apparatus and assistance
• Ability to speak reduced or impaired

Treatment for C1 and C2

Immediate treatment is crucial in the case of a cervical vertebrae C1 or C2 injury, and the head must be securely stabilized to prevent any further damage. It is likely that the person may have suffered a concussion, and so may be unable to accurately report pain.

Keeping the head and neck in a constant position is one method of encouraging healing; one that is still in use today through various immobilization apparatuses, such as hard-collars or halo vests. Depending on the injury, an individual may have to wear these medical devices for a number of months. The halo vest has been used for many years. However, more recently, it has been shown to be effective at preventing any further neurological injury in people with cervical spine injuries.

Direct lateral mass screws are used to ensure no further movement of the vertebrae while preserving the upper cervical motion segments for the future. This surgical method has been extensively used, and studies have proven to be safe, with minimal complications and low rate of morbidity for cervical myelopathy treatment.

C1 and C2 Spinal Cord Injury Recovery

A person’s ability to heal and recover some function after a cervical spinal cord injury will vary from person to person depending on a variety of factors, including:

• Their health at the time of their injury (body type, existing medical conditions, etc.);
• How soon they received treatment and their injury was stabilized;
• The completeness of the injury;
• Whether anti-inflammatory and steroid medications were used after the injury to relieve swelling and pressure on the spinal cord;
• Whether the SCI survivor went through therapies and treatments at a rehabilitation facility that specializes in spinal cord injuries; and
• Whether the patient, their friends, family, or caregivers stick with a consistent care plan to aid their recovery.

People with these injuries also can get around with the help of power wheelchairs that are equipped with special assistive technologies that allow them to control the chair’s movement through unconventional means. However, they will require 24-hour care and assistance from family, friends, and/or a professional caregiver.

Incomplete vs Complete Injuries

Spinal cord injuries are considered either incomplete or complete, meaning that the communication between the spinal cord and the brain is either partially impeded or fully impeded. This could be due to tissue inflammation that is pressing against the spinal cord nerves, foreign objects, or partial or complete severance of the cord itself. This can result in the partial or full loss of motor and sensory functions below the injury site.

When someone experiences complete or partial paralysis from the neck down — their trunk and all four limbs — it is commonly referred to as tetraplegia or quadriplegia. An injury to the cervical vertebrae C1 and C2 spinal cord injury are both considered highly rare injuries to sustain. More common cervical spinal cord injuries affect the C4 and C5 levels.

• Complete injuries refer to instances in which a person retains no sensation or movement below the level of injury
• Incomplete injuries are not this finite. They may allow for some feeling, movement on one side of the body, or even movement in some limbs.

The American Spinal Injury Association (ASIA) devised a scale, the ASIA Impairment Scale, to classify injuries based upon a combination of criteria to assess whether an injury is complete or incomplete. Further information about completeness can be found by reviewing that scale.

The C1 Vertebra

The C1 vertebra, known as the atlas, is the superior-most vertebra in the spinal column. It plays vital roles in the support of the skull, spinal cord, and vertebral arteries and provides attachment points for several muscles of the neck.

C1 Anatomy

The C1, or first cervical vertebra, is commonly called the atlas due to its unique position in the spine. In Greek mythology, Atlas was the titan who held the Earth on his shoulders, just like the atlas holds the skull on top of the neck.mycontentbreak The atlas is located at the top of the neck, just inferior to the condyles of the occipital bone of the skull and superior to the C2 vertebra.

The atlas is the thinnest and most delicate of the cervical vertebrae, consisting of a thin ring of bone with a few small projections. Unlike most vertebrae, there is no body or centrum on the anterior end of the atlas. Instead, there is a thin band of bone known as the anterior arch and a small mass on its anterior surface known as the anterior tubercle. The anterior arch curves posteriorly and laterally from the anterior tubercle and has a smooth joint-forming process on its posterior side. The posterior of the anterior arch meets the odontoid process of the C2 vertebra (axis) to form the median atlantoaxial joint.

On either side of the anterior arch are the lateral masses, which are the widest regions of the atlas. Each lateral mass has a smooth, oval, cup-like depression known as the superior articular facet on its superior surface. The superior articular facets form the atlanto-occipital joint with the condyles of the occipital bone of the skull, allowing the head to flex and extend at the neck. On the inferior side of each lateral mass is a short, flat, cylindrical projection of bone known as the inferior articular facet. The inferior articular facets are extremely smooth on their inferior surfaces and form the lateral atlanto-axial joint between the atlas and the axis.

Extending laterally from each lateral mass is an irregular ring of bone known as the transverse process. Each transverse process surrounds a tiny transverse foramen, a hole that provides room for the vertebral artery and vein to travel through the neck. The transverse process protects the blood vessels in the transverse foramen and serves as an attachment point for muscles that move the neck.

The posterior arch extends posteriorly from the lateral masses and completes the ring of the atlas around the hollow vertebral foramen. While it is thin throughout its length, the posterior arch widens slightly at its posterior-most point to form the posterior tubercle. The posterior tubercle is similar in structure and function to the much larger spinous process found in most vertebrae. Slight depressions on each side of the posterior arch provide room for the C1 spinal nerve to exit the vertebral foramen and allow the vertebral artery to pass into the vertebral foramen before entering the skull at the foramen magnum of the occipital bone.

C1 Physiology

The atlas plays a vital role in the support and movement of the head and neck. Several muscles in the neck pivot the skull at the atlanto-occipital joint to make the head flex and extend in a nodding motion. Of these muscles, the longus colli muscle inserts at the anterior tubercle of the atlas and the rectus capitis posterior muscle arises from the posterior tubercle. Lateral flexion, or rotating the head from side to side, requires pivoting of the skull and atlas at the atlanto-axial joint. Many neck muscles work together to rotate the head, but several of these muscles — including the rectus capitis lateralis and obliquus capitis superior — arise from the transverse processes of the atlas. In addition, several intertransversarii muscles connect the transverse processes of the atlas to those of the axis, allowing lateral flexion of the entire neck to pull the head laterally toward one of the shoulders.

The atlas also plays a vital role in the protection of the delicate structures of the neck. The spinal cord and spinal nerves that pass through the vertebral foramen of the neck are shielded from physical injury by the bony ring of the atlas. Compared to the other vertebrae of the spine, the vertebral foramen is much larger in the atlas, providing significant space for movement of the soft nervous tissue during flexion and rotation of the head and neck. The transverse foramina also play an important protective role for the vertebral arteries and veins that provide vital blood flow to and from the brain. The bony tissue of the transverse processes of the atlas prevents these blood vessels from being compressed or damaged on their way through the neck.

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