The spinal cord is a central pathway transmitting signals between the brain and the rest of the body. This structure, an extension of the brainstem, extends from the base of the skull to the lower back. Along its length, the spinal cord gives rise to nerves that form a vast communication network. These nerves carry motor commands for movement and sensory information like touch, temperature, and pain.
The Intervertebral Foramina
The 31 pairs of spinal nerves exit the vertebral column through specific openings called intervertebral foramina. The term “intervertebral” means “between vertebrae,” referring to the individual bones of the spine. “Foramen” is Latin for an opening or hole. These openings are located between adjacent vertebrae, serving as dedicated passageways for spinal nerves to leave the central nervous system and extend to various body regions.
There are 31 pairs of these openings, corresponding to the 31 pairs of spinal nerves: eight cervical, twelve thoracic, five lumbar, five sacral, and one coccygeal. Each intervertebral foramen is formed by the notches of two adjacent pedicles, parts of the vertebrae. The posterior aspects of the vertebral bodies and intervertebral discs also contribute to their boundaries. These foramina are smallest in the cervical region and increase in size as they descend through the thoracic and upper lumbar regions.
Protecting Spinal Nerves
The primary significance of the intervertebral foramina is providing a protected pathway for emerging spinal nerves. The bony structure of the vertebrae surrounding these openings safeguards delicate nerve roots from compression and injury. This protective enclosure helps maintain the integrity of nerves as they transition from the spinal cord to the peripheral nervous system.
Beyond nerves, these foramina also accommodate blood vessels, such as radicular arteries and veins, which supply the spinal cord and nerves. This arrangement ensures motor and sensory signals transmit without interruption between the brain and body. The posterior (dorsal) root ganglion, containing sensory neuron cell bodies, is also situated within the intervertebral foramen.
When Space Becomes an Issue
If the intervertebral foramina narrow, a condition called foraminal stenosis can occur. This narrowing can be caused by age-related changes, such as bone spurs (osteophytes), herniated discs, or thickened ligaments within the spinal canal. When the space is reduced, it can directly compress spinal nerves or the blood vessels passing through it.
Compression of spinal nerves, often called radiculopathy, can lead to symptoms like localized pain, numbness, tingling, or weakness in affected regions. This compression highlights the importance of intervertebral foramina in maintaining proper nerve function.