1.1. Background

The cervical spine is comprised of seven vertebrae with discs between the vertebrae that are comprised mostly of water. Cervical degenerative disease (CDD) refers to a cascade of events that leads to changes of the vertebral discs resulting in disc desiccation and height loss. These changes may cause uncovertebral and facet joint hypertrophy (enlargement of vertebral joints) leading to vertebral foraminal narrowing (stenosis), which may cause radiculopathy (pain, motor and sensory deficits) as the exiting nerve roots are pinched, or more central stenosis with compression of the spinal cord and associated myelopathy (sensory and motor deficits and pain or myelopathy may be asymptomatic). While both conditions can affect the neck and upper extremities, cervical spondylotic myelopathy can also cause poor proprioception and spasticity of the lower extremities resulting in gait disturbances, as well as disturbances in bladder function caused by compression of motor and sensory neurologic pathways travelling through the cervical cord. Cervical radiculopathy and cervical spondylotic myelopathy may exist simultaneously.

Although the etiology of CDD is not fully understood, it is a common condition that becomes more prevalent with age. The estimated prevalence of any spinal degenerative disease from 2005 to 2017, in people 65 and older, based on Medicare data of approximately 1.7 million individuals, is 27.3 percent, with the highest prevalence for degenerative disc disease (12.2%).¹ In a separate Medicare database study, 3,156,215 individuals were identified with degenerative cervical disease (incidence 18.9% for females, 13.1% for males between 2006 and 2012).² However, the presence of CDD may not correlate well with symptoms.³ For example, one systematic review⁴ found the prevalence of multilevel degenerative disc pathology to be 64.5 percent in asymptomatic subjects (compared with 89.7% in a symptomatic population).

1.2. Management of Cervical Degenerative Disease

Of the over 3 million individuals with CDD in the Medicare study mentioned above, 32 percent were treated nonoperatively and 7 percent were treated with spinal fusion (permanently joining two or more vertebrae) within a year of diagnosis.² Surgical treatment for cervical radiculopathy varies and includes both anterior and posterior based procedures. When approached anteriorly, intervertebral spacers and additional plating may be used, the vertebrae may or may not be fused, and the cervical disc(s) may or may not be replaced.⁵ In addition to anterior cervical discectomy with fusion, cervical disc replacement and anterior cervical corpectomy (removal of the vertebral body) with fusion, surgical treatment for cervical spondylotic myelopathy also includes posterior procedures: laminoplasty (surgery to enlarge spinal canal by cutting the bony roof [lamina] and allowing it to open like a door), laminectomy (surgery that enlarges spinal canal by removing a portion of the lamina), and laminectomy with fusion.⁶ Nonoperative treatment of CDD includes analgesics, corticosteroids, neck immobilization, traction of the cervical spine, interventional approaches (e.g., radiofrequency ablation [a procedure that destroys nerve tissue that sends pain signals to the brain using radiowaves), physical therapy, exercises, thermal therapy, and avoidance of provocative activities.^7,8 The goals of both surgical and nonoperative treatments are to alleviate pain, improve neurologic function, and prevent progression or recurrence.

While cervical myelopathy and radiculopathy are clinical diagnoses, magnetic resonance imaging (MRI) is used to confirm levels where compression of the spinal cord or nerve roots is evident. Various degenerative features can be seen on cervical MRI such as decreased vertebral height, disc height loss, osteophyte formation, disc bulging and location, hypertrophy and ossification of the posterior longitudinal ligament, spinal cord compression and flattening, and tethering (attachment) of the spinal cord to the spinal canal.⁹ MRI findings can then help guide treatment. It is important to note that the presence of degenerative findings on MRI does not equate to symptomatic consequence. One study found that 28 percent of asymptomatic volunteers over the age of 40 years (N=23, levels=97) demonstrated cervical degenerative changes on MRI (versus 14% in those less than 40 years of age).¹⁰ Intraoperative neuromonitoring (e.g., somatosensory, motor evoked potential measurements, spontaneous and triggered electromyography) is used during cervical spine surgery to provide intraoperative assessments of neural function and detect neurological injury during surgery to potentially mitigate or prevent further injury.

1.3. Purpose and Scope of the Review

This systematic review identifies and synthesizes research on treatments for CDD in patients with cervical radiculopathy and/or myelopathy. This topic was nominated by the Congress of Neurological Surgeons (CNS), which published prior guidelines on the management of CDD in 2009.^11–14 This review is intended to be broadly useful to clinicians and policy makers, and will also inform the development of updated guidelines from CNS or others. This review also includes nonoperative management of CDD as compared with operative management, which was not part of the previous CNS guidelines.