Clinical manifestations

Presentation and course

Cervicogenic headache is typically defined as a unilateral headache that is "side-locked" at the onset but can spread to involve the contralateral side when severe (03). Reduced cervical range of motion is a common finding, often producing ipsilateral moderate to severe neck and arm pain exacerbated by active or passive movement of the cervical spine. These symptoms are usually chronic, with episodes varying in intensity and duration, although patients may report a constant baseline pain. Early in the course, purely episodic attacks are more common, but as the condition progresses, the pain becomes more constant, with frequent fluctuations in severity and character. The duration and severity of cervicogenic headache can help differentiate it from primary headache disorders like migraines or cluster headaches. Cervicogenic headache pain typically lasts longer, potentially hours to weeks, and is less intense than that of migraines and cluster headaches. Additionally, common symptoms associated with primary headaches, such as nausea, photophobia, dizziness, or vision changes, although possible in cervicogenic headache, are much more prevalent in primary headache disorders (12; 03).

Prognosis and complications

If left untreated, cervicogenic headache can result in chronic, debilitating pain. Studies have shown that factors such as advanced age, changes in pain characteristics with cervical movement, and job satisfaction are correlated with favorable outcomes when appropriate treatment is pursued (07).

Biological basis

Etiology and pathogenesis

The pathogenesis of cervicogenic headache is elucidated by the convergence of nociceptive input between upper cervical nerves and trigeminal nerves within the trigeminocervical complex. The trigeminocervical complex is a continuous longitudinal gray matter structure extending proximally within the upper three cervical spinal cord segments and the medulla of the brainstem. Understanding the spatial relationships within this complex, including the convergence of trigeminal afferents on cervical afferents and the interaction of cervical afferents from different levels, explains the pain referral patterns seen with cervicogenic headache. Specifically, pain originating from anatomical structures in the higher cervical regions innervated by the upper three cervical spinal nerves can manifest in areas, such as the posterior occiput, due to cervical-cervical convergence, as well as the frontal or parietal regions of the head due to trigeminal-cervical convergence (05; 06).

Hence, an understanding of the innervations of anatomical structures, such as joints, ligaments, muscles, dura, and vasculature supplied by the C1–3 spinal nerves, is crucial when attempting to discern the etiology of cervicogenic headache (05). The dorsal ramus of C1 innervates the muscles of the suboccipital triangle while the ventral ramus innervates the atlanto-occipital joint and, in addition to the cervical plexus, supplies the prevertebral musculature, including the longus capitus and rectus capitis lateralis and anterior (16). Through the recurrent meningeal branch of C1, there is also contribution to the medial atlantoaxial joint, posterior longitudinal ligament, vertebral artery, and dura mater (05).

The medial branch of the dorsal ramus of the C2 spinal nerve supplies innervation to the atlantoaxial joint, the transverse atlantoaxial and alar ligaments, as well as the splenius capitus and semispinalis capitus. The ventral ramus of C2 supplies the sternocleidomastoid muscle, rectus captius, and trapezius muscle. Furthermore, the dura of the posterior cranial fossa as well as the vertebral and internal carotid arteries also receive innervation from the recurrent meningeal branch of C2 (05). The greater occipital nerve originates from the medial aspect of the dorsal ramus of C2 and supplies sensory innervation to the scalp from the posterior skull to the vertex, and the lesser occipital nerve originates from the ventral ramus of C2 and C3 within the cervical plexus, supplying the scalp, temporal fossa, and the neck surrounding the auricle.

The dorsal ramus of the C3 spinal nerve supplies innervation to the C2–3 facet joint as well as the C2–3 intervertebral disc. Musculature, including semispinalis capitus, splenius capitus, longissimus, and multifidus, supplies innervation from the dorsal ramus of C3 as well (05). As with C1 and C2 spinal nerves, the C3 recurrent meningeal branch also innervates atlantoaxial ligaments and dura mater. The third occipital nerve emerges from the dorsal ramus of C3 and supplies sensory innervation to the occipital scalp and upper neck (04).

Epidemiology

The prevalence of all combined headache disorders is approximately 48.9% in the general population, with about 98% classified as primary headache disorders, including migraines, tension headaches, and cluster headaches (01). The prevalence of cervicogenic headache ranges from 0.4% to 4% among individuals with headache disorders, with the condition most commonly occurring in the third to fourth decade of life. Symptoms typically begin in one's 30s, although an official diagnosis of cervicogenic headache is often not made until the 40s. There is no significant gender bias, as the reported female-to-male ratio is 0.97 (02).

Differential diagnosis

Confusing conditions

The differential diagnosis for cervicogenic headache can be broad, with frequent overlapping symptoms of other conditions. Disorders that may present similarly to cervicogenic headache include primary headache disorders, such as migraine, tension headaches, and cluster headaches. Additionally, diagnosis that is like occipital neuralgia, post-herpetic neuralgia, trigeminal neuralgia, and persistent idiopathic facial pain (atypical facial pain) may mimic the presentation of cervicogenic headache. Cervicogenic headache is characterized by a lesion or processes intrinsic to the cervical spine and its surrounding structures that may manifest as headache and neck pain, although they can present with pain around varying parts of the head due to convergence. This should not be confused with other secondary headache disorders, such as occipital neuralgia, which is characterized by pain over the scalp in areas innervated by the greater, lesser, and least occipital nerves (04). Post-herpetic neuralgia can be distinguished from cervicogenic headache by its localization to the anatomical site of a previous herpes zoster infection. Trigeminal neuralgia may affect similar areas of the face and head as cervicogenic headache, but its attacks are brief, lasting only seconds to minutes, unlike the hours to weeks duration typical of cervicogenic headache. Atypical facial pain, on the other hand, does not follow anatomical boundaries and persists as a continuous dull pain (18).

Diagnostic workup

Imaging of the cervical spine, such as x-ray, ultrasound, CT, or MRI, is not required to diagnose cervicogenic headache. This is because imaging findings are common and do not provide conclusive evidence of the cause. The ICHD-3 diagnostic criteria for cervicogenic headache are as follows:

According to the ICHD-3, tumors, fractures, infections, and rheumatoid arthritis of the upper cervical spine have not been formally validated as causes of headache but are accepted to fulfil criterion B in individual cases. Cervical spondylosis and osteochondritis may or may not be valid causes fulfilling criterion B, again depending on the individual case.

It is also important to understand that although an anesthetic block of the greater or lesser occipital nerves may be sensitive in identifying cervicogenic headache, it lacks specificity. This is because occipital neuralgia, as well as primary headache disorders, such as migraine, tension headache, and cluster headache, can also respond to these nerve blocks (04).

Management

When evaluating treatment options for cervicogenic headache, it is essential to consider the underlying etiology. As noted earlier, cervicogenic headache arises from pathology directly involving the cervical or occipital musculature, high cervical facet joints, intervertebral discs, and surrounding tissues. Thus, understanding the specific origin of the headache will guide appropriate treatment strategies.

Pharmacologic treatment is recommended as first-line intervention for cervicogenic headache. Muscle relaxers, nonsteroidal anti-inflammatories (NSAIDs), antiepileptics, and antidepressants are indicated (17).

Cervical and occipital musculature hypertonicity and myofascial pain as the source of cervicogenic headache can be managed with conservative treatments, such as heat or ice application, massage, traction therapy, or transcutaneous electrical nerve stimulation (TENS) (08). Additionally, trigger point injections, employing a needling technique with or without an injectate, may provide relief, particularly when targeting muscles, such as the trapezius, sternocleidomastoid, and splenius capitis. However, it is possible for patients to experience minimal response from trigger point injections if the facet joints are the actual pain generators as these may be difficult to distinguish on physical exam (15). Chemodenervation with botulinum toxin for focal cervical dystonia has shown over 80% satisfactory symptom relief, although it is not indicated for the treatment of cervicogenic headache as the mechanism of action is not fully understood (04). Instead, this intervention is more commonly used to treat migraine headache disorders (14).

Cervical facet pain is another potential cause of cervicogenic headache. Facet pain is quite common, with a reported prevalence of 70% by the age of 40 (13). Intra-articular facet injections may benefit patients whose pain can be reproduced with provocative neck maneuvers, although focal tenderness over the C2–3 facet joint is commonly the only presenting symptom (15). For more prolonged pain relief from high cervical facet joints, radiofrequency ablation is a viable consideration. A systematic review analyzed the treatment of cervicogenic headache with radiofrequency ablation (RFA) of cervical facet joints and found level II evidence supporting this treatment modality (13). Additionally, a single-center retrospective study evaluating RFA of the C2 dorsal root ganglion showed that the majority of subjects experienced over 50% pain relief, with sustained relief at 6 months (09).

If a patient experiences suboptimal relief following cervical RFA for the treatment of cervicogenic headache, the reason may lie in the potential variability of facet joint innervation. Cervical facet joints typically receive innervation from the medial branches of the adjacent levels, which are targeted during the RFA procedure. However, if a facet joint is innervated by nerves from a more distant level, the RFA may not adequately ablate all the nerves supplying the joint, leading to insufficient pain relief (13). There is also potential for unilateral cervical paraspinal muscular weakness.

Discogenic pain, especially stemming from degenerative disc disease at the C2–3 level, is another possible cause of cervicogenic headache. Although an identifiable anatomical pain generator is present, interventions for discogenic pain in the high cervical region are often avoided due to the risk of serious complications, such as vascular injury or discitis (15).

Regarding the use of cervical epidural steroid injections for treating cervicogenic headache, evidence suggests short-term benefits, particularly for radicular pain associated with cervicogenic headache, lasting approximately 4 weeks. Moreover, a retrospective study demonstrated that a continuous infusion of corticosteroid and anesthetic into the cervical epidural space over several weeks provided sustained relief at a 6-month interval and reduced the need for oral pain medication. Overall, cervical epidural steroid injections are relatively safe when performed by a skilled practitioner adhering to necessary safety protocols (15). In the aforementioned study, one patient with cervicogenic headache experienced transient post-injection flushing, and no patients who underwent continuous infusion reported any endocrine or gastrointestinal side effects. Notably, all patients who experienced pain relief from the continuous infusion had some degree of radiographic evidence of C2–6 disc pathology. This suggests that epidural steroids may be particularly effective for patients with cervicogenic headache who also have corresponding imaging findings.