Foraminal stenosis, or foraminal narrowing, is a condition of the spine that can cause pain and other symptoms resulting from spinal nerve root compression. At every level of the spine, a pair of nerve roots runs through the spinal column via small openings called foramina (singular: foramen). When stenosis, occurs in the foramina, the space available for the nerve roots to pass is reduced. While narrowing of the foraminal canals does not necessarily elicit symptoms, if a nerve root is irritated or compressed, it can cause pain that radiates along the length of the nerve, as well as tingling, numbness or weakness within the muscle group innervated by the affected nerve.
Most cases of foraminal stenosis are related to gradual anatomical deterioration that is associated with the aging process. The vertebrae, intervertebral discs and other spinal components break down after years of wear and tear, especially within the cervical (neck) and lumbar (lower back) regions of the spine. Usually, this anatomical degeneration affects one side of a vertebral segment, producing unilateral foraminal stenosis. Sometimes, degeneration affects both sides of a vertebral segment, and this is known as bilateral foraminal stenosis.