Cervical spinal stenosis

“Stenosis” means narrowing. Cervical stenosis usually refers to a narrowing of the spinal canal, which is a heart-shaped hollow space in the center of the vertebral ring shown in the drawing from the 19th century Gray’s Anatomy textbook (see: Gray, Henry; Carter, Henry Vandyke (1858), Anatomy Descriptive and Surgical, London: John W. Parker and Son).

The spinal cord of the neck runs through the cervical spinal canal formed by the seven cervical vertebrae and is protected by the skin layer, muscles, ligaments, and the vertebrae. In addition, the spinal cord is suspended in spinal fluid, which is contained in the water-tight sleeve that surrounds the spinal cord. The spinal nerve roots arise from the sides of the spinal cord and travel through the neural foramina between the vertebrae and connect the spinal cord with the nerves of the arms.

Types of spinal stenosis

The term “stenosis” or narrowing of the spinal canal is used in reference to the three major hollow spaces of the spinal column, which contain and protect the spinal cord and the nerve roots.

• Narrowing involving the center of the spinal canal is termed central spinal stenosis.
• Narrowing of the “side areas” of the spinal canal below the small vertebral (“facet”) joints is called lateral recess stenosis or “subarticular” stenosis.
• Narrowing of the bony passages (“foraminae”) through which the nerve roots exit the spine is called foraminal stenosis.

While any one of these three spaces of the spine can be narrowed (stenotic) in isolation, there is often a combination of two or more of these compartments which are narrowed. Your neurosurgeon will use the information obtained from your diagnostic imaging studies (usually MRI and x-ray studies) to match up your complaints with specific sections of spinal cord and/or your spinal nerve roots, which are affected due to compression.

The history and examination, which your neurosurgeon obtains when you are in the office are compared with the findings on the diagnostic imaging studies. In many cases, a mild compression of nerve roots and the spinal cord does not need to be treated surgically.

Determining whether a surgery is needed or whether a non-surgical option, including watchful waiting is preferable is sometimes not straight-forward. Degenerative conditions of the spine are extremely common, particularly in the 50+ age group and an aggressive surgical approach is sometimes not in the best long-term interest. Spine surgery requires time away from the family and the job, causes pain because of the tissue disruption of surgery, requires a sometimes lengthy recovery, and does not guarantee that preoperative levels if pain or function improve. A fusion surgery will cause permanent loss of flexibility of the spine and, despite best surgical technique, equipment, care, and implants, may result in complications and inability to resume preoperative levels of activity.

Because diagnostic imaging findings often do not simply translate into treatment decisions, it requires both the science and the art of medicine, the training and experience of a neurosurgeon, and the time spent together in the exam room with the patient to find the best treatment plan.

Central cervical spinal stenosis and myelopathy

Significant cervical spinal stenosis may result in compression of the spinal cord in the neck. Occasionally, severe, permanent impairment of spinal cord function (myelopathy) may result. Compression of cervical spinal nerve roots may result in pain, numbness or weakness in the neck, shoulders, arms, forearms and hands.

The onset of painful or unpleasant symptoms may be slow or fast, depending on the exact circumstances. If the spinal cord is compressed by bone spurs, there may be no pain at all and the patient may be entirely unaware of the cord compression and of any impairment that it causes. The most common causes of cervical spinal stenosis are a combination of one or all of the following:

• congenitally small central spinal canal diameter (the baseline spinal canal size varies from person to person)
• chronic disk degeneration with disk bulging (“hard” discs) and bone spurs (osteophytes)
• acute disk herniations (“soft” disc)
• enlargement (hypertrophy) of facet joints, ligaments or laminar bone
• vertebral slip and altered mobility (subluxation, spondylolisthesis)
• postural abnormalities, including loss of lordosis or hyperlordosis

The majority (95%) of symptomatic spinal cord compression (myelopathy) in people of age 55 or greater is due to cervical spinal stenosis. Cervical myelopathy is frequently not painful and occasionally can result in rapid, irreversible and devastating loss of spinal cord function. Myelopathy eventually develops in most individuals whose spinal canal cross-sectional area is reduced to under 30% of normal baseline. Motor weakness, hyperactive reflexes, sensory changes, problems with steadiness when walking, and bowel and bladder malfunction are usually the result. People with cervical myelopathy from stenosis often find it difficult to maintain balance of their gait and stance and have a tendency to stumble and fall. The patients themselves may be in denial about their unsteadiness and tend to down-play the significance of prior falls and ongoing balance issues. Affected individuals tend to move slowly, hold on to furniture and other items, and become more sedentary as time goes by. Eventually, even short walks inside the house, including trips to the bathroom at night, become very difficult and quite dangerous because of the associated fall risk.

Surgery for central cervical spinal stenosis and myelopathy

Several factors, most importantly the main direction of the compressive force on the spinal cord, help determine which surgical approach to the cervical spine is the best.

If the main compression comes from in front of the spinal cord surgery is done from a frontal (anterior) approach. An incision is made in the skin of the front of the neck for anterior cervical discectomy (removal of the affected disc) at one or more spinal motion segments, which is usually combined with a fusion and instrumentation procedure. In cases where the compression force exerted on the spinal cord involves structures behind the vertebral body and not just behind one or several disc spaces, the complete vertebral body (cervical corpectomy) may need to be removed in addition to the disc spaces above and below and the resulting gap will need to be filled by a larger spacer than is necessary for a discectomy. In addition, a larger instrumentation construct will need to be placed from the front or sometimes additionally for more stability from behind the spinal cord. In cases where the main compressive force against the cervical cord comes from the back, the spinal cord can be decompressed from behind through laminectomies. In some instances, in order to prevent instability after cervical laminectomies, surgeons add a posterior fusion and instrumentation construct.

In cases of significant cord compression in patients who present with myelopathy, there are often no good non-surgical treatment alternatives. Cervical myelopathy tends to worsen without surgery but the speed with which that progression occurs is often difficult to predict, which makes it advisable for patients to be informed and well-aware of the signs of worsening of function and to agree to regular follow-up visits with their neurosurgeon in case they opt for watchful waiting.

Surgical decompression is intended to halt the progression of impairment but people with myelopathy often do not recover fully and remain significantly disabled, even after their spinal cords have been decompressed. This is perhaps the best argument to proceed with surgery sooner rather than later and when early signs of myelopathy are first present.