Definition

Cervical spinal stenosis refers to pathologic narrowing of the spinal canal that can be either congenital or acquired. The congenital type is commonly due to short pedicles that produce an abnormally shallow central spinal canal [1]. Less frequently, congenital stenosis may be associated with developmental disorders, such as achondroplasia, Klippel-Feil syndrome, Morquio syndrome, and trisomy 21 (i.e., Down syndrome) [2,3]. The main contributing factors in development of the acquired type are the degenerative, hypertrophic, age-related changes that affect the intervertebral discs, facet joints, and uncovertebral joints as well as the ligamentum flavum (Fig. 7.1). On radiologic imaging, these degenerative changes are present in 25% to 50% of the population by the age of 50 years and in 75% to 85% by 65 years [4–6]. Some of the other factors that may contribute to pathologic narrowing of the spinal canal are degenerative spondylolisthesis, ossification of the posterior longitudinal ligament, and atlantoaxial subluxation as seen in rheumatoid arthritis; rarely, it may be secondary to such extradural pathologic processes as metastatic disease, abscess formation, and trauma [7]. Aside from age, other demographic factors do not contribute significantly to the development of cervical stenosis [8]. Whereas ossification of the posterior longitudinal ligament was once considered specific to the Japanese, it has since been well documented in Western and other Asian populations [9].

Symptomatic spinal cord compression, or cervical myelopathy, commonly occurs at the cervical levels C5-C7, given the relatively increased mobility of these segments and the subsequent development of degenerative “wear and tear.” Concomitant compression of the exiting cervical nerve roots is also typically observed in cervical spondylotic disease. Symptom production can occur by constant, mechanical compression of the neural elements or be of an intermittent, dynamic nature as seen with extremes of cervical flexion and extension. Chronic compression can lead to local cord ischemia with subsequent development of cervical myelopathy [10].

Symptoms

Symptomatic presentation of cervical spinal stenosis can differ from patient to patient, depending on the pathologic process, the anatomic structures, and the cervical levels involved. Intervertebral disc degeneration and zygapophyseal joint arthritis commonly are manifested with axial neck pain. Patients with cervical foraminal stenosis may complain of radicular arm pain as well as of paresthesias, dysesthesias, numbness, and weakness of the upper extremity. On the other hand, patients with cervical central canal stenosis can present with myelopathic symptoms of the upper and lower extremities, neurogenic bladder or bowel, sexual dysfunction, and unsteady and stiff-legged gait as well as weakness, paresthesias, or numbness of the lower extremities. Lower extremity pain is not known to be a clinical symptom unless concomitant lumbar spinal disease is present.

Physical Examination

Physical examination findings of the patient with cervical stenosis should be consistent with upper or lower motor neuron signs, depending on the spinal level involved. Lower motor neuron findings are more commonly seen in the upper extremities; these include muscle atrophy, diminished sensation, decreased reflexes, diminished muscle tone, and weakness. Upper extremity myelopathic findings, such as hyperactive reflexes, increased tone, and present Hoffmann sign, can also be observed in cases of upper and mid cervical spinal cord involvement. A Spurling sign (radicular pain on axial loading of an extended head rotated toward the involved extremity) can also be present. A well-documented feature of cervical spondylotic myelopathy is so-called myelopathy hand, characterized by wasting of intrinsic and extrinsic hand muscles, loss of power of adduction and extension of the ulnar two or three digits, and inability to rapidly grip and release. Myelopathy hand is demonstrated by the hand grip-and-release test, which measures alternating closed-fist and full finger extension movements (normal result is 20 times in 10 seconds); the finger escape sign is tested with fingers fully extended and adducted, noting a tendency for ulnar digit spread [11].

Lower extremity examination is more consistent with upper motor neuron findings in the presence of cervical stenosis with myelopathy. Increased reflexes, Babinski sign, sustained or unsustained clonus, spasticity, weakness, decreased tactile and vibratory sensation, impaired proprioception, and neurogenic bowel or bladder can be seen. Lhermitte sign, an electric-like sensation that the patient reports going down the back when the neck is flexed (Fig. 7.2), can sometimes be elicited [12]. Refer to Chapter 1 for more detail.

Functional Limitations

The functional limitations depend on the extent of neurologic involvement. A person with mild symptoms can still be completely independent with activities of daily living, mobility, household chores, and work duties. In some cases, pain and weakness can produce various degrees of disability in self-care, such as grooming, bathing, and dressing, as well as in more physically demanding functions, especially in the community setting, such as lifting, carrying, and ambulation. Bowel and bladder incontinence as well as abnormalities of mood and sleep can further lead to social isolation and an increased level of actual and self-perceived disability. In extreme cases, paraplegia and quadriplegia can limit nearly all functional activities.

Diagnostic Studies

Facet and uncovertebral joint arthropathy, loss of intervertebral disc space, neuroforaminal narrowing, and presence of spondylolisthesis can be evaluated with cervical spine radiographs; if dynamic instability is suspected, flexion-extension views are advised. Presence of osseous and soft tissue disease as well as the extent of nerve root and spinal cord compression can be assessed by magnetic resonance imaging (MRI) (Fig. 7.3). Cervical myelography can provide additional information on the behavior of neural elements during flexion and extension. An upright dynamic MRI study may be able to provide the same information on the behavior of neural elements with less procedural invasiveness [13] (Fig. 7.4). Somatosensory evoked potentials can confirm the presence of myelopathy, and electromyography can confirm peripheral nerve root involvement [14].

Several radiologic criteria exist to define what constitutes significant stenosis of the cervical spine. The normal anterior-posterior dimension of the spinal canal at C3 through C7 is 16 to 18 mm [15