Foraminal stenosis is narrowing of the small bony tunnel—the intervertebral foramen—where a spinal nerve root exits the spine. When that opening tightens, the exiting nerve can be pinched, producing pain, numbness, tingling, or weakness that travels into an arm or leg. It can occur in the neck (cervical) or lower back (lumbar and lumbosacral), and it is one of the most common reasons a nerve root becomes compressed.