Upper Back Issues

Cervical Spinal Stenosis

Causes
The bony spinal canal normally has more than enough room for the spinal cord. Typically, the canal is 17 to 18 millimeters around, slightly less than the size of a penny. Spinal stenosis occurs when the canal narrows to 13 millimeters or less. When the size drops to 10 millimeters, severe symptoms of myelopathy occur. Myelopathy is a term for any condition that affects the spinal cord. The symptoms of myelopathy result from pressure against the spinal cord and reduced blood supply in the spinal cord as a result of the pressure.

Spinal stenosis may develop for any number of reasons. Some of the more common causes of spinal stenosis include:

  • congenital stenosis
  • degeneration
  • spinal instability
  • disc herniation
  • constriction of the blood supply to the spinal cord

Congenital Stenosis
Some people are born with a spinal canal that is narrower than normal. This is called congenital stenosis. They may not feel problems early in life, but having a narrow canal to begin with places them at risk for stenosis. Even a minor neck injury can set them up to have pressure against the spinal cord. People born with a narrow spinal canal often have problems later in life, because the canal tends to become narrower due to the affects of aging. These degenerative changes often involve the formation of bone spurs (small bony projections) that point into the spinal canal and put pressure on the spinal cord.

Degeneration
Degeneration is the most common cause of spinal stenosis. Wear and tear on the spine from aging and from repeated stress and strain can cause many problems in the cervical spine. The intervertebral disc can begin to collapse, shrinking the space between vertebrae. Bone spurs may form that protrude into the spinal canal and reduce the space available to the spinal cord. The ligaments that hold the vertebrae together may become thicker and can also push into the spinal canal. All of these conditions narrow the spinal canal.

Spinal instability
Spinal instability can cause spinal stenosis. Spinal instability means there is extra movement among thebones of the spine. Instability in the cervical spine can happen if the supporting ligaments have been stretched or torn from a severe injury to the head or neck. People with diseases that loosen their connective tissues may also have spinal instability. For example, rheumatoid arthritis can cause the ligaments in the upper bones of the neck to loosen, allowing the topmost neck bones to shift and close off the spinal canal. Whatever the cause, extra movement in the bones of the spine can lead to spinal stenosis and myelopathy.

Disc herniation
Spinal stenosis can occur when a disc in the neck herniates. Normally, the shock-absorbing disc is able to handle the downward pressure of gravity and the strain from daily activities. However, if the pressure on the disc is too strong, such as from a blow to the head or neck, the nucleus inside the disc may rupture through the outer annulus and squeeze out of the disc. This is called a disc herniation. If an intervertebral disc herniates straight backward, it can press against the spinal cord and cause symptoms of spinal stenosis.

Constriction of the blood supply to the spinal cord
The changes that happen with degeneration and disc herniation can choke off the blood supply that goes to the spinal cord. The sections of the spinal cord that don’t get blood have less oxygen and don’t function normally, leading to symptoms of myelopathy.

Symptoms
Cervical stenosis usually develops slowly over a long period of time. This is partly because degeneration in later life is the main cause of spinal stenosis. Symptoms rarely appear all at once when degeneration is causing the problems. A severe injury or a herniated disc may cause symptoms to come on immediately.

The first sign to appear in some patients is a change in the way they walk. They don’t realize this problem is coming from their neck. But pressure on the spinal cord in the neck can affect the nerves and muscles in the legs, leading to changes in the way they walk. Eventually their walking pattern gets jerky and they lose muscle power in the legs. This is called spasticity.

Most patients also have problems in their hands. The main complaint is that their hands start to feel numb. Others feel clumsy when doing fine motor activities like writing or typing. The ability to grip and let go of items becomes difficult because the muscles along the inside edge of the palm and fingers weaken.

Shoulder weakness also develops in many patients. This happens most often when the spinal cord is compressed in the upper part of the neck. Most affected are the shoulder blade muscles and the deltoid muscle, which covers the top and outside of the shoulder. These muscles weaken and begin to show signs of wasting (atrophy) from not getting nerve input.

The area where the spinal cord is compressed in patients with stenosis is very close to the nerves that go to the arm and hand. The problem that compresses the spinal cord in the neck may also affect the nerves where they leave the spinal column. Nerve pressure can cause pain to radiate from the neck to the shoulder, upper back, or even down one or both arms. It can also cause numbness on the skin of the arm or hand and weakness in the muscles supplied by the nerve.

Pressure against the spinal cord also creates problems with the bowels and bladder. Mild spinal cord pressure makes you feel like you have to urinate more often. But it also makes it difficult to get urine to flow (urinary hesitancy). Moderate disturbances cause people to have a weak flow of urine, making them dribble urine. They also have to strain during bowel movements. In severe cases, people aren’t able to voluntarily control their bladder or bowels. This is called incontinence.