Chronic neck pain and cervicogenic headaches
Chronic Neck Pain and Cervicogenic Headaches
From: Current Treatment Options in Neurology 2003, 5:493-498
Potential causes of chronic neck pain and cervicogenic headache
Although this review concentrates on chronic neck pain and cervicogenic headache rather than radiculopathy or myelopathy, these patients may also have arm pain that can be radicular or referred. Radiculopathy implies there is loss of motor or sensory function because of nerve root compression or inflammation, and pain is experienced in a dermatomal distribution. Radiculopathy is usually caused by lateral disc herniation, foraminal stenosis, or a combination. Referred pain implies pain is perceived in a part of the body remote from its source and there is no compression or inflammation of nerve roots. Disorders of the neck can refer pain to the shoulders, arms, face, and interscapular area. Cervical myelopathy results from compression of the spinal cord because of narrowing of the central spinal canal caused by osteophyte formation, thickened, buckled; or calcified ligamentum flavum; or a large disc herniation. Many patients with radiculopathy or myelopathy also have axial neck pain.
Facet joint pain: Facet joints alone are the cause of neck pain in at least 23% of patients with chronic axial neck pain caused by trauma. The combination of pain that arises from facet joints and discs are the cause in an additional 41%. It is important to recognize facet joint pain because it is readily treatable. Facet joints are true synovial joints, and they allow smooth motion, but limit excess motion. Facet joints can be injured acutely, such as in whiplash, or can be damaged from chronic overuse. Facet joints are innervated by the medial branches of the dorsal rami of the spinal nerve (medial branches for short). Each joint is innervated by two medial branches.
There are no specific symptoms for facet joint pain, but their referral patterns are well described. The C6/7 joint refers to the scapula and trapezius, C5/6 refers to the trapezius and superior aspect of the scapula, C4/5 and C3/4 refer to the posterolateral neck, and C2/3 may refer to the base of the skull and greater occipital area. There are no specific findings on examination, but, anecdotally, painful facets are tender on direct pressure, whereas normal joints are not tender. The authors believe that many patients diagnosed with myofascial pain actually have facet joint pain, because it is not possible to isolate tender muscles from tender facet joints while palpating the neck. In the lumbar spine, there is no correlation between the appearance of the joints on plain radiographs, MRI, and computed tomography scan and whether they are painful the same may be true for the neck.
The only way to reliably diagnose facet joint pain is by injection, specifically medial branch block. The putative painful joint is anesthetized by placing local anesthetic around the medial branches that innervate that particular joint. Any pain that is relieved can be inferred to be from that joint.
Disc pain: It is established that intrinsic disc pathology can be a source of pain, yet many physicians cling to the belief that discs cause pain only when they compress or irritate a nerve root or the spinal cord. Using strict criteria and studying the facet joints and discs at only C4/5, C5/6, and C6/7, it was estimated that cervical discs alone are the cause of pain in at least 20% of patients with chronic neck pain caused by trauma. The facet joints plus discs are the cause in at least an additional 41% of patients.
Each disc has an inner nucleus pulposus and an outer anulus fibrosus. The anulus is crescent shaped. It is thin posterior and thick anterior. The anulus can be injured acutely or by chronic strain. Anulus tears can provoke inflammation that sensitizes its nociceptors. Tears may also decrease the structural integrity of the disc, which renders it more susceptible to deformation than normal discs under similar load. The increases in pressure during usual activities of daily living stimulate the sensitized anular nociceptors and causes pain under circumstances in which normal discs would not hurt. Midline disc herniations that do not compress neural structures may cause neck pain by the same mecervicogenic headachenisms.
The symptoms of discogenic pain are not specific, but the referral topography during discography has been elucidated. C2/3 injection provoked pain in the posterior neck and suboccipital areas (cervicogenic headache); C3/4 provoked pain in the upper and lower posterior neck and suboccipital areas (cervicogenic headache); C4/5 in the face, anterior neck, and chest; C5/6 in the posterior neck, chest, trapezius, and superior aspect of the scapula; and C6/7 in the ipsilateral scapula and trapezius. Physical examination is also not specific, but is important to rule out radiculopathy, myelopathy, systemic illnesses, and neurologic disorders. Radiographs may disclose disc space narrowing and osteophyte formation at levels of degenerated discs. MRI may disclose disc desiccation or herniation, but cannot determine whether a disc is a pain generator. MRI must be interpreted in conjunction with the history, examination, and other tests.
Many spine specialists use discography to determine whether a disc is painful. Discography is indicated only when there is severe pain that has not responded to aggressive conservative care and surgery is being considered. Discography has become much less controversial. The early studies that discredited it used techniques that are anachronistic by today’s standards and newer studies have demonstrated the value of discography. Discography must always be interpreted in the context of the whole evaluation. A needle is inserted into the nucleus and contrast is slowly injected. The pain response is the most important measure. A normal disc does not hurt. Any pain that is produced during injection is considered concordant if it reproduces the patient’s usual pain, and it is considered discordant if pain is unlike the patient’s usual pain. If it is considered positive, there must be moderate to severe concordant pain, there must be one or more control (painless) discs, and at least three discs must be studied. Radiographs are taken after injection to show any tears or leaks. Several studies have shown good surgical outcomes when discography is part of the surgical evaluation.
Myofascial pain: Although there may be a secondary component of myofascial origin, soft tissues are rarely a primary cause of moderate to severe chronic neck pain or cervicogenic headache. The authors of this paper are not aware of any peer-reviewed publications that demonstrate that there is an entity, chronic cervical sprain, or strain.
Cervicogenic headache is caused by a structural disorder of the spine, although it may precipitate or coexist with migraine. Cervicogenic headache affects up to 2.5% of the population and is the principal cause of headache in 15% to 20% of those who have five or more headaches per month. There is controversy regarding the strict definition of cervicogenic headache, some of the criteria include neck pain or neck injury, unilateral headache, ipsilateral diffuse shoulder pain, reduced range of motion, mecervicogenic headachenical precipitation of pain, and alleviation of pain with specific anesthetic blockades.
The authors consider cervicogenic headache the most cephalad extension of axial neck pain, and the most common causes as demonstrated by the best studies are the C2/3 and C3/4 discs or facet joints. In addition, the atlantoaxial and atlanto-occipital joints can cause cervicogenic headache. Descriptions of other causes of cervicogenic headache are mostly anecdotal. Although pain is often experienced in the suboccipital region and there may be temporary pain relief after local anesthetic blockade of the greater occipital nerve, there is little evidence to support the primary diagnosis of greater occipital neuralgia. Compression of the C2 nerve roots has been suggested as a cause of cervicogenic headache, but details of the regional anatomy would suggest that C2 root compression does not occur.
