The cervical spine forms the upper portion of the vertebral column, providing support for the head and allowing a wide range of movements. This segment consists of seven vertebrae, labeled C1 to C7. Each vertebra, along with its associated discs and soft tissues, contributes to the neck’s flexibility and stability. The cervical spine also protects the spinal cord.
Anatomical Placement
The C5 and C6 vertebrae are located in the mid-cervical spine, just above C7. C5 is below C4, and C6 is below C5. Like other cervical vertebrae, C5 and C6 have a vertebral body in front and a vertebral arch in back, forming a protective space for the spinal cord.
The intervertebral disc between C5 and C6 is a soft, gel-like cushion that absorbs shock and provides stability and flexibility. The C5 and C6 vertebrae are also connected by paired facet joints at their back, which permit limited forward, backward, and twisting motions. These mid-cervical vertebrae are adapted to handle greater loads compared to the upper cervical vertebrae, which are smaller and more focused on mobility.
Functions and Connections
Nerve roots emerge from the spinal cord at each vertebral level. Those associated with C5 and C6 play a role in controlling movement and sensation in the upper limbs.
The C5 nerve root exits the spinal canal between the C4 and C5 vertebrae. It controls shoulder movement, including the deltoid and biceps muscles, which lift the arm and bend the elbow. It also provides sensation to the outer upper arm, extending to the elbow.
The C6 nerve root exits the spinal canal between the C5 and C6 vertebrae. This nerve controls wrist extension and helps the biceps and supinator muscles bend the elbow and rotate the forearm. It supplies sensation to the thumb side of the forearm and the thumb. Both C5 and C6 nerve roots contribute to the brachial plexus, a nerve network for the entire upper extremity.
Common Conditions Affecting C5 and C6
The C5 and C6 vertebral levels are often affected by conditions due to their load-bearing function and mobility.
One common issue is cervical disc herniation, where the intervertebral disc between C5 and C6 protrudes, potentially compressing the C6 nerve root. This can cause sharp or burning pain in the lower neck, radiating into the shoulder, arm, hand, and fingers. Weakness in the biceps and wrist extensor muscles, along with numbness and tingling in the thumb side of the hand, are also common.
Another condition is spinal stenosis, a narrowing of the spinal canal or the openings where nerve roots exit. This narrowing can compress the spinal cord or nerve roots, leading to symptoms like neck pain, arm pain, numbness, tingling, and weakness.
Degenerative changes, such as bone spurs (osteophytes) and loss of disc hydration, are also common at the C5-C6 level. These age-related changes can contribute to nerve compression, resulting in localized neck pain, stiffness, reduced flexibility, and radiating pain with numbness or weakness in the arms.