Basic Science

As with other segments of the spine, the etiology and specific location of the narrowing is important when treating cervical spinal stenosis. Cervical spinal stenosis can occur from a herniated cervical disc, an ossified posterior longitudinal ligament, a redundant ligamentum flavum, an ossified ligamentum flavum, a hypertrophied facet joint, or from any combination of these potentially compressive pathologies.

Stenosis in the cervical spine is of particular importance, due to the relatively small canal diameter as compared to the caliber of the spinal cord. Some surgeons now recommend surgical treatment for severe asymptomatic cervical spinal stenosis for prophylaxis against paralysis, while others recommend observation.

The clinical presentation of stenosis in the cervical spine can be that of myelopathy, radiculopathy, or both. Patients with compressive pathology secondary to a herniated disc pressing on the spinal cord may report symptoms of myelopathy, including loss of hand dexterity and gait abnormalities. Physical exam will show signs of upper motor neuron pathology, which can be manifested as hyperactive deep tendon reflexes, a positive Hoffmann sign, or as a Babinski sign. If, instead, this herniated disc places pressure on an exiting nerve root, or if the loss of intervertebral disc height causes a loss of cross-sectional area of the neuroforamen, then the patient may exhibit signs and symptoms of a particular nerve root radiculopathy. This will result in motor weakness, paresthesias, and loss of deep tendon reflexes (if applicable) for that particular cervical nerve root.

Radiographically, cervical stenosis is often diagnosed using a radiographic measurement called the Pavlov ratio. This ratio is defined as the ratio between the sagittal diameter of the spinal canal and the sagittal diameter of the vertebral body, as measured on a lateral radiograph. A ratio of greater than 1 is considered normal, while a ratio of less than 0.8 is considered to be diagnostic for spinal stenosis. A cervical MRI can help determine the etiology of the compression if the source is a herniated disc or a redundant ligamentum flavum. Additionally, an MRI can show any evidence of spinal cord compression, such as a lack of cerebrospinal fluid around the spinal cord and/or myelomalacia within the cord itself. A CT scan can be used to diagnose bony abnormalities such as osteophytes or hypertrophied facet joints.

Stenosis in the Cervical Spine

Case 1

A 63-year-old female presented to clinic with an 8-year history of worsening neck pain radiating to her bilateral shoulders and scapulae. The pain radiated primarily down her bilateral biceps and radial forearms into the thumb and index fingers of both hands. Additionally, she had noted a gradually worsening weakness in her legs, with loss of balance, worsening handwriting, and difficulty buttoning buttons and manipulating small objects with her hands. She had no bowel or bladder dysfunction. Despite nonoperative management that included activity modification, physical therapy, and nerve root and trigger point injections, her symptoms persisted and seemed to be worsening.

Physical examination revealed tenderness to palpation in the cervical paraspinal musculature as well as in the midline. She had an unsteady gait with a positive Romberg sign. Range of motion was limited by pain, and neck extension reproduced the pain, numbness, and tingling in her arms. She had weakness in her right greater than left biceps, wrist extensors, and hand intrinsics, but intact sensation throughout all dermatomes. Reflex testing was significant for global hyperreflexia and a positive Hoffmann sign bilaterally.

Radiographs, seen in Figure 50-1A and B, demonstrate loss of normal cervical lordosis, severe spondylosis, and a spondylolisthesis of C4 on C5. Sagittal and coronal MRI cuts, seen in Figure 50-2A and B, demonstrate significant spinal stenosis, loss of normal disc height, and severe spinal cord compression with myelomalacia.

FIGURE 50-1 A and B. AP and lateral radiographs demonstrating severe spondylotic changes and a 4 mm anterolisthesis of C4 on C5.

FIGURE 50-2 A and B. MRI showing severe stenosis from C3 to C7 with cord compression at multiple levels and signal change within the spinal cord.

The patient was taken to the operating room for a combined anterior and posterior cervical decompression and fusion. Discectomies and interbody fusion were performed with allograft spacers and an anterior plate at C4-5, C5-6, and C6-7. This portion of the procedure restored normal lordosis and addressed the anterior pathology, including reduction of the spondylolisthesis at C4-5. The posterior procedure included laminectomy from C3 to C7 with screw and rod fixation from C3 to C7 as well (Figure 50-3A and B).

FIGURE 50-3 A and B. AP and lateral postoperative radiographs. Note the restoration of natural cervical lordosis accomplished through multiple anterior discectomies. Posterior decompression and fusion creates additional space for the spinal cord and provides increased stability for fusion.

Postoperatively, the patient did well, with complete resolution of her arm pain. At last visit, her gait and balance were steadily improving, with overall improved function compared to preoperatively.

Clinical Practice Guidlines

Cervical radiculopathy can be successfully treated nonoperatively with activity modification, oral medications, and selective nerve root block injections. Operative indications include symptoms that are recalcitrant to nonoperative treatment as well as development of myelopathy. The natural history of cervical myelopathy is that of a stepwise progression of symptoms alternating with periods of nonprogressive neurological symptoms.

The location of the compressive pathology in cervical stenosis is important, as it dictates the operative approach. Cervical stenosis due to a central or moderate-sized posterolateral cervical herniated nucleus pulposus is best treated with an anterior approach, in order to adequately remove the compressive pathology. This anterior cervical discectomy is typically combined with a fusion. Fusion is achieved with or without instrumentation, consisting of an anterior plate and screws. Anterior cervical discectomy and fusion (ACDF) has been described with good results without the use of instrumentation. An anterior cervical discectomy (ACD) without fusion is rarely performed today, and is almost never performed for multilevel disease. Discectomy without fusion has been reported in a prospective, randomized trial to be equivalent to ACDF for the treatment of cervical radiculopathy.¹ For the treatment of myelopathy, ACD without fusion has been reported to result in good relief of neck and arm pain as well as a 76% rate of return to work.² However, ACD without fusion has been shown in other case series to be associated with worsening of preexisting cervical myelopathy in 3.3% of cases.³ Worsening of symptoms after ACD without fusion was also reported by Nandoe Tewarie et al in a retrospective review of 102 patients evaluated up to 18 years after surgery.⁴ While ACD alone has been shown to be successful in the treatment of cervical myeloradiculopathy, the possibility of worsening of symptoms, combined with the difficulty of revision of anterior cervical surgery, makes this a possible yet unattractive surgical option.

If the compressive pathology is secondary to redundant ligamentum flavum, hypertrophied facet joints, or other posterior pathology, then a posterior approach allows the surgeon to directly decompress the offending agent. A posterior-only approach is only indicated if neutral or lordotic alignment of the cervical spine is maintained. A kyphotic deformity in the cervical spine often mandates an anterior approach to restore the normal cervical sagittal alignment. Decompression from a posterior approach consists of laminotomy, laminectomy, or laminoplasty. Removal of significant portions of the facet joints should be avoided in order to avoid causing iatrogenic postlaminectomy cervical kyphosis. Raynor et al reported a cadaveric study comparing the potential degrees of instability on biomechanical testing of intact specimens, and following 50% facetectomy, and 70% facetectomy. The conclusion of this study was the recommendation that a facetectomy should involve less than 50% of the facet joint in the absence of fusion, in order to avoid spinal instability.⁵ Postlaminectomy kyphosis after posterior cervical decompression alone is common when there is evidence of hypermobility on preoperative flexion-extension radiographs. A cervical fusion should be considered after posterior decompression if:

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