Neck Pain in Adults _________________________________________________________________________
Cervical Spondylosis Cervical spondylosis is osteoarthritis, a chronic degenerative disorder that affects cervical vertebral bodies, intervertebral disks (as disk herniation and spur formation), and contents of the spinal canal (i.e., nerve roots and/or spinal cord). It may also affect the facet joints and longitudinal ligaments, but this is debated [65]. Cervical Facet Joint (Z-Joint) Arthropathy Facet joint arthropathy describes osteoarthritis and degenerative changes in facet joints and usually follows the development of cervical degenerative disk disease. The degenerative changes resemble those of other joints, including osteophyte formation, osteosclerosis, thinning of articular cartilage, and hypertrophy (thickening) of the facet joint capsule, ligamentum flavum, and articular process. Facet joint hypertrophy distorts articular surfaces, leading to axial or referred pain [49]. Cervical Spondylotic Myelopathy Cervical spinal cord compression causes cervical spondylotic myelopathy, the most serious degenerative disorder consequence. Reversible neurologic deficits occur with cord compression of 40% or greater [61]. Abnormal movement and cervical spondylotic myelopathy symptoms can develop from cervical spinal cord damage with traumatic compression or ischemia from arterial compression or cervical spondylosis [60; 65]. In patients with cervical spondylotic myelopathy, co-occurring cervical radiculopathy is frequent and co-occurring stenosis is occasional [65]. NECK PAIN PATHOPHYSIOLOGY In most patients with chronic neck pain, identifying and treating the pain mechanism(s), rather than spinal tissue pathology, is more effective. Pain from tissue injury or disease that resolves with tissue healing is a symptom of the tissue damage, and resolution typically occurs within three months of onset. Pain becomes a disease entity (rather than a symptom) when it persists after healing or resolution of the original tissue insult [3]. Chronic (more than three months) neck pain can develop from acute pain of any cervical spine origin, but it is substantially more difficult to control and can be severely consequential to patients [2; 67]. Normal Pain Processes The somatosensory system enables the perception of pain, touch, pressure, temperature, position, movement, and vibration. This system begins with receptors of peripheral sensory neurons (nociceptors) in skin, muscles, joints, and fascia (peripheral tissue). In response to potentially harmful pressure, temperature, or biomechanical stress (noxious stimuli), nociceptor fibers send signals to the dorsal root ganglia (containing the cell bodies of sensory neurons),
In acquired cervical spinal stenosis, degenerative disk or facet disease pathologically narrows the canal in middle-aged and older patients. Cervical spondylosis (arthritis) may progress to stenosis, and stenosis to cervical spondylotic myelopathy, but this sequence is variable and difficult to predict. However, adults with asymptomatic stenosis show age-related increases in cervical spondylosis. Congenital cervical spinal stenosis occurs in younger, athletic patients when bony anomalies narrow the spinal canal diameter <13 mm [59; 61]. Cervical Whiplash Injury In cervical whiplash, diverse symptoms develop following a rapid sequence of injuries [16; 19; 62]. The first is cervical hyperextension injury. A driver/passenger is struck from behind, which throws the body forward, but the head lags to hyperextend the neck. When the head and neck reach maximum extension, the neck snaps into flexion. The head is then thrown forward, flexing the cervical spine and resulting in rapid deceleration injury. The chin truncates forward flexion, but it can remain sufficient to cause longitudinal distraction and neurologic damage. Hyperextension may occur in the subsequent recoil. Within 100 ms, the cervical spine is compressed from below; as lower segments extend with upper segments flexed, the cervical spine assumes an S-shaped curve. In a split-second, all cervical segments are forced backward into extension. Whiplash-like loads of combined shear, bending, and compression forces can injure facet joints/capsules, and facet injury is the most common source of chronic post- whiplash pain. Spinal bones, ligaments, muscles, tendons, and disks may also become injured [41; 63; 64]. The diverse constellation of post-whiplash symptoms, termed WAD, reflects the range of potentially injured tissue. Symptoms can include neck pain and stiffness, occipital headache, thoracic or lumbar pain, and referred pain or numbness to shoulders, arm, or scapula. Paraspinal muscle tightness and spasm, neck tenderness, and reduced range of movements are common. Patients may also experience headache, jaw pain, fatigue, dizziness, vertigo, blurred vision, or nausea. Insomnia, depression, and general anxiety or travel anxiety when in a car can follow acute whiplash. Symptoms can be severe, often without imaging abnormalities [16; 19]. Degenerative Disorders of the Cervical Spine As noted, x-rays show degenerative cervical spine abnormalities in many asymptomatic adults, making the boundary between normal aging and disease difficult to define. Even severe degenerative changes can be asymptomatic but can eventually lead to neck pain or neurologic complications [14]. Vertebral body, disk, and facet joint degeneration decreases foraminal and canal width, initiates inflammatory processes, and promotes nerve compression/irritation, chronic neck pain, and progressive radiculopathy symptoms [14; 23; 24; 51; 58; 61; 65; 66].
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