The C6-C7 spinal motion segment bears the primary load from the weight of the head and provides support to the lower part of the neck. The lower end of this motion segment articulates with the first vertebra of the thoracic spine (T1).
Due to its load-bearing function, the C6-C7 motion segment is susceptible to degeneration, trauma, and intervertebral disc dysfunction.
Anatomy of the C6-C7 Spinal Motion Segment
The C6-C7 spinal motion segment includes the following structures:
- C6 and C7 vertebrae. The C6 vertebra is structurally similar to most other cervical vertebrae, except C1 and C2. Key components of the C6 vertebra include a vertebral body, a vertebral arch, 2 transverse processes, a spinous process, and a pair of facet joints. While the C7 vertebra is similar to C6, it has a few unique features:
- A more prominent spinous process is present in C7, which is also known as vertebra prominens. This process (a bony protrusion or hump) can be felt at the base of the neck and provides attachment to more neck muscles compared to the other cervical vertebrae.
- The transverse foramen (bony hole) of C7 does not contain the vertebral artery (the artery that supplies blood to the brain), unlike the other cervical vertebrae.1
- An extra cervical rib may form from C7 in rare cases. This rib either terminates freely in the soft tissues or fuses with the first rib.2
- C6-C7 intervertebral disc. A disc made of a gel-like material (nucleus pulposus) surrounded by a thick fibrous ring (annulus fibrosus) is situated in between the C6 and C7 vertebrae. This disc protects the vertebrae by providing shock-absorption during neck motion.
See Cervical Discs
- C7 spinal nerve. The C7 spinal nerve exits through the intervertebral foramen between the C6 and C7 vertebrae. This nerve has a sensory root and a motor root.
- The C7 dermatome is an area of skin that receives sensations through the C7 nerve. This dermatome includes areas of skin covering the shoulders, back of the arms, and the middle finger.
- The C7 myotome is a group of muscles controlled by the C7 nerve. These muscles include those involved in straightening the elbow, lifting the wrist, elongating the fingers to an outstretched hand, and the triceps muscle in the upper arm.
The C6 and C7 vertebrae help protect the spinal cord within the spinal canal.
Common Problems at C6-C7
Due to its load-bearing function, the C6-C7 motion segment may be affected by a number of problems:
- Disc herniation .The C6-C7 intervertebral disc is one of the most common to herniate in the cervical spine.3 Herniation may result from injury or age-related wear and tear.
- Spondylosis. Spondylosis or chronic degeneration of the vertebrae, disc, and other structures in the spine is common at the C6-C7 level.4 Spondylosis may result in stenosis or the narrowing of the intervertebral foramina or spinal canal due to the formation of bone spurs (osteophytes).
- Fracture. Research suggests about 20% of traumatic neck fractures occur at the C6 vertebral level and 19% occur at C7.5 Fractures at this level typically result from high-energy trauma, such as automobile crashes, falls, or sports injuries
Injury to the vertebrae and/or intervertebral disc at the C6-C7 level is a common source of C7 radicular nerve pain.3,4,6 Severe trauma to this level may also injure the spinal cord. In rare cases when the C7 vertebra forms a cervical rib, compression of surrounding blood vessels and/or nerves may occur, resulting in thoracic outlet syndrome.2,7
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Common Symptoms and Signs Stemming from C6-C7
A vertebral and/or disc injury at the C6-C7 motion segment may cause immediate or delayed symptoms. A dull ache or burning pain may occur in the lower cervical area, often accompanied by neck stiffness.
When the C7 nerve is compressed or irritated, additional complaints may follow, such as:
- Pain from the neck radiating to the shoulder down to the middle finger.3
- Numbness in the palm, index finger, and middle finger.3
- Weakness in the upper arm, forearm, elbow, and wrist; affecting the motion of these regions.3
When the spinal cord gets injured at C6-C7, pain, weakness, or paralysis may occur in one or more parts of the body below the injured level. Reduction of bowel, bladder, and/or breathing functions may occur in some cases.
Typically, nonsurgical treatments are tried first to control the symptoms of C6-C7 injuries. If nonsurgical treatments do not provide relief, surgery may be considered.