Axial Neck Pain, Radiculopathy, and Myelopathy: Recognition and Treatment
Neck pain, radiculopathy, and myelopathy are common presentations of cervical pathology across populations and age groups. Many people experience neck pain at some point in their lives, and nearly everyone has cervical spondylosis associated with aging, although for most it does not produce a limitation in activity. A typical 12-month prevalence rate of neck pain for working adults is 30% to 50%; for children and adolescents, the rate is 20% to 40%.1 Limitation of activity related to this pain has a 12-month prevalence of 2% to 11%.1 To simplify the broad presentation of cervical pathology and best assign its treatment, it is helpful to divide patient findings into axial neck pain, radiculopathy, and myelopathy.
Axial Neck Pain
Axial neck pain can arise from a variety of conditions but occurs primarily from muscular or ligamentous factors and joint pain. The etiology of neck pain arising from a muscular origin is not entirely clear, but it has been shown that in patients with primary muscular pain, there is a lower level of high-energy phosphates in the affected muscle than in normal muscle tissue.2 Whether this is the cause or effect of the pain has yet to be determined. Neck pain also can arise from other joint pain and be referred from primary pain in the temperomandibular joint or craniovertebral junction or from the facet joints in the spine itself.3 Because of the widespread prevalence of facet joint degeneration and lack of consistent presentation with axial neck pain, it is not recommended to assign the presence of pain solely to degenerative changes in the facet joints.3
Diagnosis of Axial Neck Pain
Patients with axial neck pain typically present with pain or soreness in the posterior neck muscles, with frequent radiation to the occiput or shoulder regions that does not usually follow a dermatomal distribution.3 There often is stiffness of the neck, and headaches are common as well. As a general rule, pain in the posterior neck that is exacerbated by neck extension, especially with rotation to the affected side, stems from a discogenic source. Pain that is aggravated by flexion is typically myofascial in origin.3 Because of the frequency of referred pain causing axial neck pain, it is important to rule out other etiologies that are not directly related to the neck, such as temporomandibular joint pain, infection, or neoplasm, to best direct treatment (Table 1).
Treatment of Axial Neck Pain
The simplest treatments for axial neck pain stem from lifestyle and activity modifications (Figure 1). Smoking cessation and avoidance of activities that place strain on the neck (excessive extension or flexion) are early treatment options. There is some evidence for the effectiveness of active physical therapy combined with patient education emphasizing a quick return to normal function in helping to ease axial neck pain.1 Scientific data on the benefits of other nonoperative treatment options, including acupuncture, educational pamphlets, “neck school,” and use of collars, are lacking, but these modalities are often prescribed.1,4 The use of interlaminar epidural steroid injections has been shown to be extremely effective, with short-term relief in as many as 96% of patients and 1-year improvement between 68% and 79%.5 Transforaminal epidural steroid injections are slightly less efficacious, though they still produce positive short-term and long-term relief in more than 60% of patients.5 A medial branch block, which functions by anesthetizing the innervation of facet joints, is often administered if the pain is suspected to originate from these joints.6 Improvement of symptoms after medial branch block is also indicative that radiofrequency ablation will likely be effective.7 This technique is performed by percutaneously placing an electrode against the nerves supplying the painful joint. These electrodes are then heated to 80°C to produce lesions in the nerves and prevent pain transmission. Radiofrequency ablation was shown to be very effective by Lord et al, with a median return of pain at 263 days for patients receiving treatment and 8 days for patients in the control group.8
Because most cases of axial neck pain are self-limited or effectively alleviated with nonsurgical treatment, operative interventions are a last resort and are indicated only after an extended period of time without improvement from nonoperative treatment. There are also contraindications for surgery to treat axial neck pain, including psychosocial problems such as anxiety and depression6 and pain stemming from multiple spinal levels. This has led to the recommendation that computed tomography (CT) examination, physical evaluation, psychological testing, and other diagnostic testing be performed before operative interventions are considered.9
Surgical options for the treatment of axial neck pain include cervical fusion and cervical arthroplasty. In anterior cervical discectomy and fusion, the cervical disc is removed from an anterior approach, replaced with a bone graft, and the adjacent vertebrae are fused. If osteophytes are present, they may be removed as well. Anterior cervical plates may be used to augment fusion, provide stability, and prevent bone graft kick-out. Arthroplasty is similar to anterior discectomy except that there is no fusion of the spine, but rather implantation of a disc replacement. The advantages to this technique are maintenance of flexibility and range of motion after surgery and a theoretical benefit of less adjacent-level degeneration. Several different cervical disc arthroplasty devices are available in the United States, and specific use is driven by both patient and surgeon preference. Both of these techniques show excellent short-term and long-term improvement in severe neck pain12,13 and headaches,14 with arthroplasty producing similar or better results in multiple studies and no evidence of long-term spinal cord trauma because of the additional mobility conferred by arthroplasty.12-15
Radiculopathy is the result of compression of a spinal nerve root, which causes pain and numbness in a dermatomal distribution (Figure 2), muscle weakness, and impaired deep tendon reflexes.16-18 Cervical radiculopathy has an estimated prevalence of 3.5 cases per 1,000,19 with the highest rate of incidence in the sixth decade of life.20 Symptoms typically manifest as pain traveling down the neck and shoulder into the arm of the patient. The pain can vary substantially, ranging from sharp localized pain to dull general pain in the neck and upper extremity. In general, the presence of muscle weakness and loss of sensation correspond with increased severity. This is due to the relative number of neurons that must be damaged to produce each set of symptoms, with pain requiring the least neuronal damage and total loss of sensation requiring the most.21