Abstract
Cervicogenic headache is a syndrome characterized by chronic hemicranial pain that is referred to the head from either bony structures or soft tissues of the neck. The trigeminocervical nucleus is a region of the upper cervical spinal cord where sensory nerve fibers in the descending tract of the trigeminal nerve (trigeminal nucleus caudalis) are believed to interact with sensory fibers from the upper cervical roots. This functional convergence of upper cervical and trigeminal sensory pathways allows the bidirectional referral of painful sensations between the neck and trigeminal sensory receptive fields of the face and head. A functional convergence of sensorimotor fibers in the spinal accessory nerve (CN XI) and upper cervical nerve roots ultimately converge with the descending tract of the trigeminal nerve and might also be responsible for the referral of cervical pain to the head.
Diagnostic criteria have been established for cervicogenic headache, but its presenting characteristics occasionally may be difficult to distinguish from primary headache disorders such as migraine, tension-type headache, or hemicrania continua.
This article reviews the clinical presentation of cervicogenic headache, proposed diagnostic criteria, pathophysiologic mechanisms, and methods of diagnostic evaluation. Guidelines for developing a successful multidisciplinary pain management program using medication, physical therapy, osteopathic manipulative treatment, other nonpharmacologic modes of treatment, and anesthetic interventions are presented.
Neck pain and cervical muscle tenderness are common and prominent symptoms of primary headache disorders.
1 Less commonly, head pain may actually arise from bony structures or soft tissues of the neck, a condition known as
cervicogenic headache.
2 Cervicogenic headache can be a perplexing pain disorder that is refractory to treatment if it is not recognized. The condition's pathophysiology and source of pain have been debated,
3-5 but the pain is likely referred from one or more muscular, neurogenic, osseous, articular, or vascular structures in the neck.
6
The trigeminocervical nucleus is a region of the upper cervical spinal cord where sensory nerve fibers in the descending tract of the trigeminal nerve (trigeminal nucleus caudalis) are believed to interact with sensory fibers from the upper cervical roots. This functional convergence of upper cervical and trigeminal sensory pathways allows the bidirectional referral of painful sensations between the neck and trigeminal sensory receptive fields of the face and head.
6
Patients with cervicogenic headache will often have altered neck posture or restricted cervical range of motion.
16 The head pain can be triggered or reproduced by active neck movement, passive neck positioning especially in extension or extension with rotation toward the side of pain, or on applying digital pressure to the involved facet regions or over the ipsilateral greater occipital nerve. Muscular trigger points are usually found in the suboccipital, cervical, and shoulder musculature, and these trigger points can also refer pain to the head when manually or physically stimulated. There are no neurologic findings of cervical radiculopathy, though the patient might report scalp paresthesia or dysesthesia.
Diagnostic imaging such as radiography, magnetic resonance imaging (MRI), and computed tomography (CT) myelography cannot confirm the diagnosis of cervicogenic headache but can lend support to its diagnosis.
17 One study reported no demonstrable differences in the appearance of cervical spine structures on MRI scans when 24 patients with clinical features of cervicogenic headache were compared with 20 control subjects.
18 Cervical disc bulging was reported equally in both groups (45.5% vs 45.0%, respectively).
A comprehensive history, review of systems, and physical examination including a complete neurologic assessment will often identify the potential for an underlying structural disorder or systemic disease.
19 Imaging is then primarily used to search for suspected secondary causes of pain that may require surgery or other more aggressive forms of treatment.
20 The differential diagnosis in cases of suspected cervicogenic headache could include posterior fossa tumor, Arnold-Chiari malformation, cervical spondylosis or arthropathy, herniated intervertebral disc, spinal nerve compression or tumor, arteriovenous malformation, vertebral artery dissection, and intramedullary or extramedullary spinal tumors.
A laboratory evaluation may be necessary to search for systemic diseases that may adversely affect muscles, bones, or joints (ie, rheumatoid arthritis, systemic lupus erythematosus, thyroid or parathyroid disorders, primary muscle disease, etc).
Zygapophyseal joint, cervical nerve, or medial branch blockade is used to confirm the diagnosis of cervicogenic headache and predict the treatment modalities that will most likely provide the greatest efficacy. The first three cervical spinal nerves and their rami are the primary peripheral nerve structures that can refer pain to the head.
The suboccipital nerve (dorsal ramus of C1) innervates the atlanto-occipital joint; therefore, a pathologic condition or injury affecting this joint is a potential source for head pain that is referred to the occipital region.
The C2 spinal nerve and its dorsal root ganglion have a close proximity to the lateral capsule of the atlantoaxial (C1–2) zygapophyseal joint and innervate the atlantoaxial and C2–3 zygapophyseal joints; therefore, trauma to or pathologic changes around these joints can be a source of referred head pain. Neuralgia of C2 is typically described as a deep or dull pain that usually radiates from the occipital to parietal, temporal, frontal, and periorbital regions. A paroxysmal sharp or shocklike pain is often superimposed over the constant pain. Ipsilateral eye lacrimation and conjunctival injection are common associated signs. Arterial or venous compression of the C2 spinal nerve or its dorsal root ganglion has been suggested as a cause for C2 neuralgia in some cases.
11,20-23 The third occipital nerve (dorsal ramus C3) has a close anatomic proximity to and innervates the C2–3 zygapophyseal joint. This joint and the third occipital nerve appear most vulnerable to trauma from acceleration-deceleration (“whiplash”) injuries of the neck.
24 Pain from the C2–3 zygapophyseal joint is referred to the occipital region but is also referred to the frontotemporal and periorbital regions. Injury to this region is a common cause of cervicogenic headache. The majority of cervicogenic headaches occurring after whiplash resolve within a year of the trauma.
25
Of interest are reports that patients with chronic headache had experienced substantial pain relief after diskectomy at spinal levels as low as C5–6.
26,27
Diagnostic anesthetic blockade for the evaluation of cervicogenic headache can be directed to several anatomic structures such as the greater occipital nerve (dorsal ramus C2), lesser occipital nerve, atlanto-occipital joint, atlantoaxial joint, C2 or C3 spinal nerve, third occipital nerve (dorsal ramus C3), zygapophyseal joint(s) or intervertebral discs based on the clinical characteristics of the pain and findings of the physical examination.
28 Fluoroscopic or interventional MRI-guided blockade may be necessary to assure accurate and specific localization of the pain source.
29-31
Occipital neuralgia is a specific pain disorder characterized by pain that is isolated to sensory fields of the greater or lesser occipital nerves.
32 The classic description of occipital neuralgia includes the presence of constant deep or burning pain with superimposed paroxysms of shooting or shocklike pain. Paresthesia and numbness over the occipital scalp are usually present. It is often difficult to determine the true source of pain in this condition. In its classic description, the pain of occipital neuralgia is believed to arise from trauma to or entrapment of the occipital nerve within the neck or scalp, but the pain may also arise from the C2 spinal root, C1–2, or C2–3 zygapophyseal joints or pathologic change within the posterior cranial fossa.
Occipital nerve blockade, as it is typically done in the clinic setting, often results in a nonspecific regional blockade rather than a specific nerve blockade and might result in a misidentification of the occipital nerve as the source of pain. This “false localization” might lead to unnecessary interventions aimed at the occipital nerve, such as surgical transection or other neurolytic procedures.
5
A regional myofascial pain syndrome (MPS) affecting cervical, pericranial, or masticatory muscles can be associated with referred head pain. Sensory afferent nerve fibers from upper cervical regions have been observed to enter the spinal column by way of the spinal accessory nerve before entering the dorsal spinal cord.
33,34 The close association of sensorimotor fibers of the spinal accessory nerve with the spinal sensory nerves is believed to allow for a functional exchange of somatosensory, proprioceptive, and nociceptive information from the trapezius, sternocleidomastoid, and other cervical muscles to converge in the trigeminocervical nucleus and ultimately resulting in the referral of pain to trigeminal sensory fields of the head and face.
Muscular trigger points, a hallmark of MPS, are discreet hyperirritable regions of contracted muscle that have a lowered pain threshold and refer pain to distant sites in predictable and reproducible patterns.
35,36 Anesthetic injections into trigger point regions can assist in the diagnostic evaluation and therapeutic management of referred head or face pain from cervical muscular sources.
35
Pharmacologic treatment modalities for cervicogenic headache include many medications that are used for the preventive or palliative management of tension-type headache, migraine, and “neuropathic” pain syndromes. The listed medications have neither been approved by the US Food and Drug Administration (FDA) nor rigorously studied in controlled clinical trials for the treatment of cervicogenic headache and are only suggested as potential treatments based on the anecdotal experiences of clinicians who treat this condition or similar pain disorders. The side effects and laboratory monitoring guidelines provided are not intended to be comprehensive, and consultation of standard references or product package inserts are recommended before prescribing any of these medications.
Many patients with cervicogenic headache overuse or become dependent on analgesics. Medication when used as the only mode of treatment for cervicogenic headache does not generally provide substantial pain relief in most cases. Despite this observation, the judicious use of medications can provide enough pain relief to allow greater patient participation in a physical therapy and rehabilitation program. To improve compliance, medications are initially prescribed at a low dose and increased over 4 to 8 weeks as necessary and tolerated.
The cautious combining of medications from different drug classes or with complementary pharmacologic mechanisms may provide greater efficacy than using individual drugs alone (eg, an antiepileptic drug combined with a tricyclic antidepressant [TCA]). Frequent follow-up visits for medication dosage adjustments, monitoring of serum drug levels, and evidence of medication toxicity are recommended.
Antidepressants—The TCAs have long been used for management of various neuropathic, musculoskeletal, head, and face pain syndromes. Analgesic dosages are typically lower than those required for the treatment of patients with depression. The serotonin and norepinephrine reuptake inhibitors (SNRIs) such as venlafaxine hydrochloride and duloxetine hydrochloride have been anecdotally observed helpful in the prophylactic management of migraine. Similar observations have been reported for venlafaxine in the treatment of painful diabetic neuropathy, fibromyalgia, and regional myofascial pain syndromes, while duloxetine is indicated for the management of painful diabetic neuropathy.
The selective serotonin reuptake inhibitors (SSRIs) are generally ineffective for pain control.
Antiepileptic Drugs—The antiepileptic drugs (AEDs) are believed to be modulators or stabilizers of peripheral and central pain transmission and are commonly used for the management of neuropathic, head, and face pain syndromes. Divalproex sodium is indicated for the preventive management of migraine headache and may be effective for cluster headaches as well as other neurogenic pain syndromes. Serum drug levels can be used as a therapeutic dosing guide. Monthly monitoring of liver transaminase levels and of complete blood cell (CBC) counts for evidence of toxicity is recommended, especially during the first 3 to 4 months of treatment or whenever dosages are escalated.
Gabapentin is indicated for the management of postherpetic neuralgia and has been used for management of other neuropathic pain syndromes and migraine. No specific laboratory monitoring is usually necessary.
Topiramate is indicated for migraine prophylaxis and has been anecdotally reported effective in the management of painful diabetic neuropathy and cluster headache. Intermittent monitoring of serum electrolyte levels might be needed because of this medication's diuretic effect through carbonic anhydrase inhibition.
Carbamazepine is an effective medication in the treatment of patients with trigeminal neuralgia and central neuropathic pain. Serum drug levels can be used as a therapeutic dosing guide. Monthly monitoring of liver transaminase levels and of CBC counts is recommended, especially during the first 3 to 4 months of treatment or whenever dosages are increased.
Several of the other newer AEDs might be used when other treatments are ineffective.
Analgesics—Simple analgesics such as acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs) may be used as regularly scheduled medications for round-the-clock management of chronic pain or as needed for the management of acute pain.
The selective cyclooxyenase-2 (COX-2) antagonist celecoxib might have less gastrointestinal toxicity than nonselective NSAIDs, but renal toxicity after long-term use remains as a concern. Recent reports have linked the long-term use of selective COX-2 antagonists with an increased risk of cardiovascular and cerebrovascular events; therefore, the risk-benefit ratio of their use requires strong consideration. It is recommended that prescribers review the safety information and warnings found in the product package inserts.
Narcotic analgesics are not generally recommended for the long-term management of cervicogenic headache
39 but may be cautiously prescribed for temporary pain relief to expedite the advancement of manual modes of therapy or improve tolerance for anesthetic interventions.
Migraine-specific abortive medications such as ergot derivatives or triptans are not effective for the chronic head pain of cervicogenic headache but may relieve the pain of episodic migraine attacks that can occur in some patients with cervicogenic headache.
Other Medications—Muscle relaxants, especially those with central activity such as tizanidine hydrochloride and baclofen, may provide some analgesic efficacy. Botulinum toxin, type A injected into pericranial and cervical muscles is a promising treatment for patients with migraine and cervicogenic headache,
37,40,41 but further clinical and scientific study is needed.