Neck pain and cervical muscle tightness are common and prominent symptoms of primary headache disorders such as tension-type headache (TTH) and migraine.¹ Conversely, head pain referred from bony structures or soft tissues of the neck is a condition that is commonly called cervicogenic headache.² Cervicogenic headache can be a perplexing pain disorder that is often refractory to common headache treatments when it is not recognized. The successful treatment of cervicogenic headache usually requires a multifaceted approach using pharmacologic, nonpharmacologic, anesthetic, and occasionally surgical interventions.

Cervicogenic headache can be generally defined as a recurring or persistent pain that is referred to the head from bony structures or soft tissues of the neck. Although the condition’s pathophysiology and source of pain have been debated,^3–5 pain is believed to be referred to the head or face from one or more muscular, neurogenic, osseous, articular, and vascular structures in the neck through a functional convergence of cervical spinal and trigeminal sensory pathways in the upper cervical spinal cord.⁶ It is often a sequela of head or neck injury but may also occur in the absence of recognized injury. The clinical features of cervicogenic headache may mimic those commonly associated with primary headache disorders such as TTH, migraine, or hemicrania continua, and as a result, distinguishing the etiology of chronic head pain from among these headache types by medical history alone can be difficult.

The Cervicogenic Headache International Study Group developed diagnostic criteria that have provided a detailed, clinically useful description of the condition⁷ (Table 31-1).

The prevalence of cervicogenic headache in the general population is estimated to be 0.4% to 4.0% but may be as high as 20% in populations of patients with chronic headache.^8–11 Although there have been no large epidemiologic studies, available information suggest the mean age of patients with cervicogenic headache is 40 to 45 years and the condition is up to four times more prevalent in women. Interestingly, the mean age and gender prevalence of cervicogenic headache are similar to those associated with migraine.

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 cervical spinal and trigeminal sensory pathways is thought to allow the transfer of painful sensations between anatomic structures of the neck and trigeminal sensory receptive fields of the face and head.⁶

The first three cervical spinal nerves and their rami are the primary peripheral nerve structures thought to be most involved in the referral of pain sensations from the neck to the head:

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  The suboccipital nerve (dorsal ramus of C1) innervates the atlanto-occipital joint; injury or pathology affecting this bony joint is a potential source for head pain that is referred to the occipital region of the head.

  
  
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  The C2 spinal nerve and its dorsal root ganglion have a close proximity to the lateral capsule of the atlanto-axial (C1–C2) zygapophyseal joint and innervate the atlantoaxial and C2 to C3 zygapophyseal joints; injury or pathology affecting these joints can be potential sources of referred head pain. Pain from C2 neuralgia is typically described as a deep or dull pain that usually radiates from the occipital to the parietal, temporal, frontal, and periorbital regions of the head. A paroxysmal sharp or shocklike pain is often superimposed over the constant pain. Ipsilateral eye lacrimation and conjunctival injection can commonly be 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.^12–14

  
  
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  The third occipital nerve (dorsal ramus C3) has a close anatomical proximity to and innervates the C2 to C3 zygapophyseal joint. This joint and the third occipital nerve appear most vulnerable to trauma from acceleration–deceleration (“whiplash”) injuries of the neck.¹⁵ Pain from the C2 to C3 zygapophyseal joint is referred to the occipital region but is also referred to the frontotemporal and periorbital regions of the head; the condition is commonly known as third occipital headache. One study found a 27% prevalence of third occipital headache in patients with chronic neck pain after whiplash injury.¹⁶ The majority of cervicogenic headaches occurring after whiplash are believed to resolve within 1 year of the injury.¹⁷

In general, involvement of the C2 to C3 zygapophyseal joint is believed to be the most frequent source of cervicogenic headache, accounting for up to 70% of cases.^16,18–22 The atlantoaxial joint is likely the second most common pain source, although its true prevalence in cases of cervicogenic headache is not known.^19,22 Uncommon sources of cervicogenic headache include the C3 to C4 zygapophyseal joint, upper cervical intervertebral discs, and lower cervical zygapophyseal joints.^18,23–25

A comprehensive and carefully conducted history; review of systems; and physical examination, including a complete neurologic assessment, often identify symptoms and signs that can be considered characteristic of an etiologic structural or systemic disorder for cervicogenic headache.²⁶ Several historical elements and physical findings obtained from a directed medical history and physical examination can be helpful in the clinical identification of cervicogenic headache (Table 31-2).

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.^27,28 Imaging is primarily used to search for secondary causes of pain that may require surgery or other invasive forms of treatment.²⁹ A laboratory evaluation may be needed to identify systemic diseases that can cause inflammation or pain in muscles, bones, joints, or blood vessels (e.g., rheumatoid arthritis, systemic lupus erythematosus, thyroid or parathyroid disorders, primary muscle disease, Lyme disease).

Distinguishing cervicogenic headache from primary headache disorders, such as TTH, migraine, or hemicrania continua, may occasionally be difficult by medical history and examination alone.³⁰ An accurate diagnosis has important implications for the selection of treatments that would have the greatest probability of being effective. When a headache diagnosis is indeterminable by medical history and physical, diagnostic anesthetic blockade can confirm the etiology of head pain that is referred from pain sources in the neck.³⁰ Anesthetic blockade for the evaluation of cervicogenic headache can be directed to several anatomical structures such as the atlanto-occipital joint, atlantoaxial joint, other cervical zygapophyseal joint(s), C2 or C3 spinal nerves, third occipital nerve (dorsal ramus C3), or intervertebral discs based on the location and characteristics of the pain, and findings of the physical examination.³¹ Fluoroscopic or interventional MRI–guided blockade can assure accurate and specific targeting of the suspected pain source.^32–34

MIGRAINE AND TENSION-TYPE HEADACHE

Neck pain and muscle tightness are common symptoms of a migraine attack.^1,35–37 In a study of 50 migraine patients, 64% reported neck pain or stiffness associated with their migraine attacks, with 31% experiencing neck symptoms during the prodrome, 93% during the headache phase, and 31% during the recovery phase.¹ In this study, seven patients reported that pain referred into the ipsilateral shoulder, and one patient reported that pain extended from the neck into the low back region. In another study of 144 migraine patients from a university-based headache clinic, 75% of patients reported neck pain associated with migraine attacks.³⁶ Of these patients, 69% described their pain as “tightness,” 17% reported “stiffness,” and 5% reported “throbbing.” The neck pain was unilateral in 57% of the respondents, 98% of whom reported that it occurred ipsilateral to the side of headache. The neck pain occurred during the prodrome in 61%, the acute headache phase in 92%, and the recovery phase in 41%. In addition, recurrent, unilateral neck pain without headache has been described as a variant of migraine.³⁸ Careful history gathering in cases of recurrent neck pain discovered that previously overlooked symptoms were either similar or identical to those associated with migraine.

Differences in neck posture, pronounced levels of muscle tenderness, and the presence of myofascial trigger points were observed in subjects with migraine, TTH, or a combination of both but not in a control group of subjects without headache.^1,39,40 A comparison of patients with chronic headache demonstrated no significant differences in myofascial symptoms or signs between headache diagnostic groups, dispelling the common belief that TTH is associated with a greater degree of musculoskeletal involvement (e.g., muscle tightness or spasm) than migraine.⁴⁰

OCCIPITAL NEURALGIA

Occipital neuralgia (ON) is a specific pain disorder characterized by pain that is isolated to the sensory fields of the greater or lesser occipital nerves.⁴¹ The classical description of ON 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 often present. It is often difficult to determine the true source of pain in patients with this condition. In its classical description, the pain of ON is believed to arise from trauma to or entrapment of the occipital nerve within the neck or scalp, but similar pain may also arise from the C2 spinal root, C1 to C2 or C2 to C3 zygapophyseal joints, or pathology within the posterior cranial fossa. Occipital nerve blockade, as it is typically performed in a clinic setting, often results in a nonspecific regional blockade rather than a specific nerve blockade, which could result in 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 Furthermore, there is no anatomic rationale for the use of occipital nerve blockade in the definitive diagnosis or treatment of cervicogenic headache.²²