Spinal Stenosis ∓ Myleopathy

Overview

Stenosis means narrowing, and when referenced to the spine means narrowing or constriction of the spinal canal, which contains the spinal cord and nerves. The neck region (cervical spine) is much less accommodating and forgiving (than the lumbar region) of neurologic compression, and when the spinal cord compression is moderate or severe, it generally manifests as myelopathy.

Myelopathy is the clinical scenario of spinal cord compression causing (upper motor neuron - UMN) neurologic dysfunction such as gait disturbance (trouble walking), pathologic reflexes (increased reflexes and spasticity), muscle weakness, and/or numbness (sensory deficits). The natural progression of this condtion is usually a slow, gradual deterioration in a step-wise fashion, although some patients present with a rapid decline of physical function and/or paralysis.

Causes

The most common cause of cervical spinal stenosis is degenerative osteoarthritis of the spine, specifically disc degeneration, formation of disc-osteophyte complex (DOC, bone spurs), hypertrophy (overgrowth) of the ligamentum flavum and the formation of large osteophytes adjacent to the facet joints. There is usually significant stiffness, and occasionally is associated with compensatory subluxation and instability. This is a gradual process that causes progressive compression of the spinal cord and neural elements. Mechanical irritation may cause a local inflammatory response, and decreased vascularity may cause decreased conduction of the nerve signals. Although aging and degeneration is the most common cause of stenosis, patients may have other medical conditions or trauma that predisposes them to develop spinal stenosis. Rarely, the posterior longitudinal ligament may become extremely calcified, and is called ossification of the posterior longitudinal ligament (OPLL).

Symptoms

The degenerative process is typically slow and relentlessly progressive. Patients often have neck pain and stiffness. Subtle changes in gait (walking) and balance may be the only symptoms present initially. Also, patients tend to have difficulty with fine motor function and coordination such as writing or buttoning a button. When the stenosis and myelopathy is severe, most patients will develop long tract signs (UMN) consisting of a wide-based gait, balance difficulties, and weakness. Patients tend to develop proximal weakness (hip flexors, quadriceps) in the legs prior to the distal groups (gastrocnemius, anterior tibialis), and may have difficulty rising from a chair. The symptoms can be gradual, and in patients with minimal neck pain, these patients may seek medical attention very late in the course of this condition. Patients may be so disabled and weak that they require the use of a wheelchair for mobility. In some instances of severe cervical spinal stenosis, a minor trauma can cause paraplegia. This condition is called central cord syndrome (a type of spinal cord injury), and requires emergent medical attention.

Physical Findings

The physical findings for most patients with cervical spinal stenosis are limited. Patients may or may not demonstrate tenderness and spasm, but usually have decreased cervical spine range-of motion. If the spinal cord is severely compressed, there may be significant numbness (loss of sensation) in the arms or legs and some of the arm and leg muscles may be focally weak. Deep tendon reflexes may be increased. There may be clonus and spasticity in the legs. Pulses and vascularity of the legs should be normal. If not, the patient may also have concomitant vascular disease and vascular claudication.

Imaging Studies

Plain x-rays of the spine will not show spinal stenosis because an x-ray only shows bone structures, not the cartilage disc, ligaments, or spinal nerves. However, the spine x-rays may reveal that the patient has severe osteoarthritis, and this would suggest a high probability of spinal stenosis if correlative symptoms were present. A magnetic resonance imaging test (MRI) is necessary to clearly define the severity and extent of spinal stenosis and neurologic compression, and is noninvasive (no needles or dye injection). Before MRI was invented, patients were required to have a CT, myelogram, or CT-myelogram in order to confirm the diagnosis of herniated nucleus pulposus. MRI is now much easier to perform and generally provides better visualization of the stenotic lesions. However, some patients are not able to have an MRI, such as those patients with a cardiac pacemaker, and must have one of the other described imaging tests.

Laboratory Tests

There are no laboratory tests used to diagnose spinal stenosis. Occasionally, specific tests are ordered to rule out infection or other causes or neck pain, radiculopathy, and myelopathy.

Diagnosis

The condition of cervical spinal stenosis and myelopathy is not uncommon, and clinicians must be aware of its possibility when evaluating patients with neck problems. It can be complicated when the symptoms or physical findings are atypical. Some patients may only complain of neck pain without overt neurologic abnormalities. All patients with significant arthritis seen on plain x-rays should be considered for additional studies such as MRI to evaluate the extent of spinal canal compromise. It is important for the clinician to conduct a thorough history and clinical examination prior to formulating a diagnosis so as not to misdiagnosis this condition. Imaging studies (and occasionally laboratory tests) must be used to clarify the diagnosis.

Treatment Options

The treatment of cervical spinal stenosis often depends on the severity of a patient's symptoms and the severity of neurologic compression. Patients with mild or moderate stenosis may respond initially to conservative treatments. Conservative treatments may consist of oral anti-inflammatory medications and pain medications. Muscle relaxant medications should be used for severe pain and muscle spasms, and only for short duration in elderly patients. Complications secondary to medications are more common in the elderly, and all medications should be closely monitored by the prescribing physician. Physical therapy and modalities may also be utilized (with caution), primarily to improve a patient's strength, endurance, and level of function. Manipulation should not be utilized. Epidural steroid injections may provide short-term improvement of pain symptoms.

When a patient has severe spinal stenosis and myelopathy, or a patient with mild or moderate stenosis has failed conservative modalities, surgical intervention is considered. Patients with severe spinal cord compression and/or severe myelopathy with weakness are indicated for surgery. The goal of surgery is to remove the compression from the spinal cord, to improve a patient's pain and level of function, as well as prevent further deterioration of function and worsening pain. If the majority of pressure is coming from osteophytes in the front (anterior) or the spine, then an anterior corpectomy with strut graft and fusion may be considered. If the majority of the compression is occurring in the back part of the spinal cord, then a laminectomy or laminaplasty may be performed. Occasionally, patients with severe, multiple level stenosis will require both front (anterior) and back (posterior) of the neck surgery to adequately decompress and stabilize the spine. Generally, a cervical spinal fusion will always be required and recommended in addition to the decompression component. Spinal instrumentation may also be utilized to impart immediate stability and increase the fusion (bone healing and mending together) rate. There is a high rate of success for patients treated surgically, however, careful preoperative evaluation and delicate perioperative and postoperative management is particularly important to ensure success and avoid complications.

Selected Bibliography

Lees F, Turner JWA: Natural history and prognosis of cervical spondylosis. BMJ 1963;2:1607.

Emery SE, Bohlman HH, et al: Anterior cervical decompression and arthrodesis for the treatment of cervical spondylotic myelopathy: two to seventeen-year follow-up. J Bone Joint Surg Am 1988;80:941.

Fujiwara K, et al: Morphometry of the cervical spinal canal and it srelation to pathology in cases with compression myelopathy. Spine 1988;13:1212.

Fujiwara K, et al: The prognosis of surgery for cervical compression myelopathy: an analysis of the factors involved. J Bone Joint Surg Br 1989;71:393.

Koyanagi T, et al: Predictability of operative results of cervical compression myelopathy based on preoperative computed tomographic myelography. Spine 1993;18:1958.

Yonenobu K, Hosono N, et al: Laminoplasty versus subtotal corpectomy: a comparative study of results in multisegmental cervical spondylotic myelopathy. Spine 1992;17:1281.