Cervical spondylotic myelopathy (CSM) is a neck condition that arises when the spinal cord becomes compressed—or squeezed—due to the wear-and-tear changes that occur in the spine as we age. The condition commonly occurs in patients over the age of 50.
Because the spinal cord carries nerve impulses to many regions in the body, patients with CSM can experience a wide variety of symptoms. Weakness and numbness in the hands and arms, loss of balance and coordination, and neck pain can all result when the normal flow of nerve impulses through the spinal cord is interrupted.
What is the anatomy of the spine?
Your spine is made up of 24 bones, called vertebrae that are stacked on top of one another.
The seven small vertebrae that begin at the base of the skull and form the neck comprise the cervical spine.
Other parts of your spine include:
Spinal cord and nerves. The spinal cord extends from the skull to your lower back and travels through the middle part of each stacked vertebra, called the central canal. Nerves branch out from the spinal cord through openings in the vertebrae (foramen) and carry messages between the brain and muscles.
Intervertebral disks. In between your vertebrae are flexible intervertebral disks. They act as shock absorbers when you walk or run.
Intervertebral disks are flat and round and about a half inch thick. They are made up of two components:
- Annulus fibrosus. This is the tough, flexible outer ring of the disk.
- Nucleus pulposus. This is the soft, jelly-like center of the disk.
What causes CSM?
Cervical spondylotic myelopathy (CSM) is caused by changes that occur in the spine as we age. These changes in the discs are often called arthritis or spondylosis.
Cervical Disk Degeneration
Bone spurs. As the disks in the spine age, they lose height and begin to bulge. They also lose water content, begin to dry out, and become stiffer. This problem causes settling, or collapse, of the disk spaces and loss of disk space height.
As the disks lose height, the vertebrae move closer together. The body responds to the collapsed disk by forming more bone—called bone spurs—around the disk to strengthen it. These bone spurs contribute to the stiffening of the spine. They may also make the spinal canal narrow—compressing or squeezing the spinal cord.
Herniated disk. A disk herniates when its jelly-like center (nucleus pulposus) pushes against its outer ring (annulus fibrosus). If the disk is very worn or injured, the nucleus may squeeze all the way through. When a herniated disk bulges out toward the spinal canal, it can put pressure on the spinal cord or nerve roots.
As disks deteriorate with age, they become more prone to herniation. A herniated disk often occurs with lifting, pulling, bending, or twisting movements.
Other Causes of Myelopathy
Myelopathy can arise from other conditions that cause spinal cord compression, as well. Although these conditions are not related to disk degeneration, they may result in the same symptoms as CSM.
Rheumatoid arthritis. Rheumatoid arthritis is an autoimmune disease. This means that the immune system attacks its own tissues. In rheumatoid arthritis, immune cells attack the synovium, the thin membrane that lines the joints.
As the synovium swells, it may lead to pain and stiffness and, in severe cases, destruction of the facet joints in the cervical spine. When this occurs, the upper vertebra may slide forward on top of the lower vertebra, reducing the amount of space available for the spinal cord.
Injury. An injury to the neck—such as from a car accident, sports, or a fall—may also lead to myelopathy. For example, a "rear end" car collision may result in hyperextension, a backward motion of the neck beyond its normal limits, or hyperflexion, a forward motion of the neck beyond its normal limits. Because these types of injuries often affect the muscles and ligaments that support the vertebrae, they may lead to spinal cord compression.
What are symptoms of CSM?
Typically, the symptoms of CSM develop slowly and progress steadily over several years. In some patients, however, the condition may worsen more rapidly.
Patients with CSM may experience a combination of the following symptoms:
- Tingling or numbness in the arms, fingers, or hands
- Weakness in the muscles of the arms, shoulders, or hands. You may have trouble grasping and holding on to items.
- Imbalance and other coordination problems. You may have trouble walking or you may fall down. With myelopathy, there is no sensation of spinning, or "vertigo." Rather, your head and eyes feel steady, but your body feels unable to follow through with what you are trying to do.
- Loss of fine motor skills. You may have difficulty with handwriting, buttoning your clothes, picking up coins, or feeding yourself.
- Pain or stiffness in the neck