Some causes of the neck and spine narrowing are aging, arthritis and inherited conditions, according to the National Institute of Arthritis and Musculoskeletal and Skin Diseases. This is in part because the bones and joints that make up the vertebrae potentially get bigger as a person ages.
The vertebrae might also develop bone spurs, and the ligaments that keep them stable may thicken and harden, claims NIAMS and Mayo Clinic.
Arthritis can also cause narrowing of the spine, says NIAMS. This narrowing, or stenosis can come about because of osteoarthritis or rheumatoid arthritis. Osteoarthritis is often the result of aging and wears down the cartilage that cushions the space between the vertebrae. The body sometimes reacts to this by developing bone spurs. Rheumatoid arthritis is an autoimmune disease in which the body attacks the joints. It is not a common cause of spinal stenosis.
Herniated disks are also causes of narrowing of the spine, according to Mayo Clinic. As time goes on, the disks can dry out and crack. Material then leaks out of the disk and presses against the spinal nerve. Tumors and injuries also narrow the spine.
Other patients are born with medical conditions that put them at risk for narrowing of the spine, says NIAMS. Some people have a curvature of the spine called scoliosis, while others are born with an abnormally narrow spinal canal.