Cervical spinal stenosis is caused by a narrowing of the spinal canal in the neck, and the most common reason is age-related wear and tear on the spine’s discs, bones, and ligaments. A normal cervical spinal canal measures roughly 12 to 21 mm across. When that space shrinks below about 13 mm, it’s considered relatively narrowed; below 10 mm is classified as absolute stenosis. An estimated 5% of adults have cervical stenosis at one or more levels, and that number climbs to nearly 9% in people over 70.
Several different processes can cause this narrowing, sometimes working together over years. Here’s what drives each one.
Age-Related Disc and Bone Changes
The most common cause by far is cervical spondylosis, a catch-all term for the gradual breakdown of structures in the neck. It starts with the discs. These rubbery cushions between each vertebra begin drying out and flattening as early as your 40s. As they lose height, two things happen: the vertebrae sit closer together, and the spine becomes less stable.
Your body responds by growing extra bone along the edges of the vertebrae. These bony projections, called bone spurs, are essentially the spine’s misguided attempt to reinforce itself. Bone spurs can jut inward toward the spinal canal or into the openings where nerve roots exit, directly compressing the spinal cord or nearby nerves. At the same time, the tough ligaments that run along the spine stiffen and thicken with age, making the neck less flexible and further reducing the available space inside the canal.
Because all of these changes accumulate slowly, many people develop significant narrowing before they ever notice symptoms. Cadaver studies show that roughly 29% of people in their 60s and 33% of those 70 and older have at least one level of cervical stenosis, though only a fraction of them would have experienced problems during life.
Bulging and Herniated Discs
Disc degeneration doesn’t just shrink the cushion between vertebrae. Over time, small cracks develop in a disc’s tough outer shell. The gel-like center can push through those cracks, creating a bulge or a full herniation that protrudes into the spinal canal. A bulging disc can press directly on the spinal cord or on the nerve roots branching off from it.
This can happen gradually as part of the same degenerative process described above, or it can occur more suddenly after a twisting motion or injury. A disc herniation on its own may not cause stenosis, but when it’s layered on top of bone spurs and thickened ligaments in an already-narrowing canal, it can be the change that tips someone from no symptoms into noticeable pain, numbness, or weakness.
Being Born With a Narrow Canal
Some people start life with a spinal canal that’s naturally smaller than average. This is called congenital cervical stenosis, and it’s defined as a canal diameter under 10 mm at two or more levels in the neck. People with congenital stenosis may never know it until a relatively minor degenerative change or injury compresses the cord in a space that had very little room to spare.
Canal size varies by race and ethnicity. A 2025 study found that average canal diameters at the pedicle level were 11.4 mm in White patients, 10.5 mm in Asian patients, 10.4 mm in Black patients, and 11 mm in Hispanic patients. These differences are small in absolute terms but meaningful when you consider that every millimeter counts inside a tight canal. People with naturally smaller canals face a higher baseline risk of developing symptomatic stenosis later in life.
Ligament Calcification (OPLL)
A less common but important cause is a condition in which the ligament running along the back of the vertebral bodies gradually turns to bone. Known as ossification of the posterior longitudinal ligament, or OPLL, it creates a rigid bar of calcified tissue that pushes into the spinal canal from the front. Because the ligament sits directly behind the vertebrae and in front of the spinal cord, even moderate thickening can compress the cord.
OPLL is most common in East Asian populations, where it affects about 2.4% of people. In non-Asian populations, the rate drops to roughly 0.16%. It’s twice as common in men as in women and typically becomes symptomatic in the 50s or 60s. Symptoms can include numbness and weakness in the arms or legs, difficulty with fine hand movements, and in severe cases, bladder or bowel problems.
Rheumatoid Arthritis and Inflammatory Disease
Rheumatoid arthritis (RA) doesn’t just affect the hands and knees. It can target the joints and ligaments of the cervical spine, particularly at the top two vertebrae. In RA, the lining of the joints produces inflammatory tissue called pannus, which releases enzymes that destroy cartilage, ligaments, and bone. As these structures erode, the vertebrae become unstable and can slip out of alignment.
The most common problem is at the junction between the first and second vertebrae, where up to 49% of RA patients develop some degree of instability. The second most common issue is upward migration of the peg-shaped bone on the second vertebra into the base of the skull, seen in up to 38% of RA patients. Lower in the neck, destruction of the facet joints and discs can cause a characteristic staircase pattern of misalignment at multiple levels, affecting up to 20% of patients. Each of these shifts reduces canal space and can compress the spinal cord from different angles.
Trauma and Pre-Existing Narrowing
A sudden injury to the neck, such as a car accident, a fall, or a sports collision, can cause cervical stenosis directly through fractures or dislocations that push bone fragments into the canal. But trauma also plays a subtler role: people who already have a mildly narrowed canal are far more vulnerable to spinal cord injury from even minor impacts.
This vulnerability comes down to two factors. First, a smaller canal means less room for error, so even a modest disc bulge or bone shift from an impact can compress the cord. Second, there’s less cerebrospinal fluid surrounding the cord in a tight canal, and that fluid normally acts as a shock absorber. Without enough of it, the cord takes the brunt of any sudden force. This is why some athletes with undiagnosed congenital stenosis experience temporary paralysis after a tackle or collision that wouldn’t injure someone with a wider canal.
How Multiple Causes Overlap
In practice, cervical spinal stenosis rarely comes from a single cause. A person might be born with a canal on the narrower end of normal, develop disc degeneration in their 40s, grow bone spurs in their 50s, and then herniate a disc after a minor fall in their 60s. Each change chips away at the available space until the spinal cord or nerve roots run out of room. This layering effect explains why stenosis becomes dramatically more common with age and why two people with the same degree of disc degeneration on an MRI can have completely different symptoms: the one with a naturally wider canal still has space to spare.