Radiofrequency ablation of C2–3 medial branches/third occipital nerve to treat cervicogenic headache

Introduction

Cervicogenic headache (CGH) is a secondary headache disorder originating from dysfunction in the cervical spine. The prevalence of CGH in the general population is estimated to be around 4.1%, with a higher incidence in individuals with chronic headaches as well as neck pain (1,2). The etiologies of CGH are diverse and typically involve structural abnormalities or dysfunctions in the upper cervical spine, commonly the C2–3 facet joints, such as osteoarthritis, cervical disc pathology, trauma, inflammatory conditions, and muscular and ligamentous strain leading to radicular pain that causes headache (3-6).

CGH diagnosis is made based on clinical history, physical exam findings, and imaging evidence. While there is often a mechanical etiology associated with the development of CGH, it is not required for diagnosis (1). The American College of Radiology (ACR) recommends imaging studies such as magnetic resonance imaging (MRI) or computed tomography (CT) to identify structural abnormalities in the cervical spine that may contribute to CGH (7). Common characteristics of CGH include unilateral pain without side-shift and pain that starts in the neck and radiates to the fronto-temporal and orbital regions. CGH is usually precipitated or aggravated by neck movements or sustained awkward head positions. The cervical flexion-rotation test (CFRT) is a useful clinical tool for differentiating CGH from other headache types. Moderate certainty evidence supports its diagnostic accuracy, with sensitivity and specificity around 83% (6).

First-line treatment options for CGH are multidisciplinary and involve conservative strategies such as physical and manual therapy, nonsteroidal anti-inflammatory drugs (NSAIDs) and muscle relaxants, and transcutaneous electrical nerve stimulation (5,8-10). However, CGH is often refractory to conservative management, and these analgesic choices usually lack efficacy in managing the pain associated with CGH (10,11). In the scenario of CGH refractory to first-line treatments, interventional procedures may be considered and include nerve blocks (10), intra-articular steroid injections (12), and radiofrequency ablation (RFA) (10).

Using nerve blocks targeting C2–3 has shown efficacy in reducing headaches; however, the results are limited to approximately three months of pain relief. Similarly, while intra-articular steroid injections have been used increasingly to manage CGH, benefits are also seen for around 3 months (13). Furthermore, the American Academy of Pain Medicine (AAPM) and the American Society of Regional Anesthesia and Pain Medicine (ASRAPM) guidelines suggest that intra-articular steroid injections can be effective for CGH. Still, the evidence remains limited and should be interpreted cautiously (8). The limited time duration of pain relief in both nerve blocks and intra-articular steroid injection is problematic, as CGH is a chronic condition in which patients require longer-term results.

As a minimally invasive procedure, we propose cooled RFA of the C2–3 innervating nerves as an alternative therapy for chronic refractory CGH. Cooled approaches can provide greater precision and accuracy than thermal or pulsed ablation techniques. This paper details the technique of the RFA procedure, relevant anatomy to consider, and the discussion. We present this article in accordance with the SUPER reporting checklist (available at https://apm.amegroups.com/article/view/10.21037/apm-25-114/rc).

Preoperative preparations and requirements

Procedural

Consistent with the established practice guidelines, patients were required to undergo a diagnostic nerve block trial before proceeding. Patients who reported sufficient improvement in their pain, as indicated by a greater than 50% decrease in pain, were eligible to proceed with the cooled RFA procedure (6).

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for publication of this article and the accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Anatomy

RFA treatment of CGH occurs at the C2–3 joint, where the primary innervating nerves are located. Innervation of the C2–3 facet joints is unique compared to other cervical facet joints. While each of the C3–7 joints is innervated primarily by the medial branches of the dorsal rami above and below its joint (for example, the C4–5 joint is innervated by the medial branches of the C4 and C5 dorsal rami), the C2–3 joint receives innervation primarily from one nerve, the third occipital nerve (TON) (14).

The C3 spinal nerve divides into ventral and dorsal rami immediately after exiting the C2–3 intervertebral foramen. The TON is the superficial medial branch of the dorsal rami of C3. Upon branching from the dorsal rami, the TON curves around the C2–3 facet joint and travels dorsally and superiorly (Figure 1). It pierces through the semispinalis capitis and splenius capitis muscles and finally reaches the posterior scalp and neck regions to innervate surrounding structures. Studies using adult cadavers have found the TON to become subcutaneous around 5 cm inferior and 3 cm lateral to the external occipital protuberance (17,18) (Figure 2). Because the TON is a post-foraminal branch of C3, it is highly accessible for RFA procedures once it becomes subcutaneous. It reduces the risk of injuring the essential structures surrounding the spinal cord (8,19).

Figure 1 Cross-sectional anatomy demonstrating the TON branching from the C3 medial branch and curving around the C2–3 facet joint (15,16) (image reproduced from NYSORA under their educational image use policy). MB, medial branch; NYSORA, New York School of Regional Anesthesia; TON, third occipital nerve.

Figure 2 The locations of emergencies of GON and the 3ON from the TP. The blue dots indicate the emergence of nerves. The numbers in the table are presented as mean ± standard deviation in millimeters (images reused from an open access article from Kim HS et al. under the terms of the Creative Commons Attribution 4.0 International License) (18). 3ON, third occipital nerve; EOP, external occipital protuberance; GON, greater occipital nerve; MP, mastoid process (lowermost point); OA, occipital artery; SCM, sternocleidomastoid muscle; SpC, splenius capitis; TP, trapezius muscle.

Interestingly, many studies have reported that the TON could demonstrate variability in its course, including its point of penetration of the two muscles, branching patterns, and emergence in the posterior scalp (20,21). Additionally, some studies have commented on a small C2 medial branch contribution to the C2–3 facet joint innervation (8).

This anatomical diversity can potentially impact the efficacy of RFA procedures that target the TON, mainly when the standard landmark-based approach is used to locate the nerve. Fluoroscopic imaging guidance is essential to safely and accurately insert a needle (22). Furthermore, given the variation in the C2–3 facet joint innervation, effective pain reduction through RFA may involve dual lesion targeting both the TON and the C2 medial branch, if applicable (23).

Step-by-step description

After obtaining informed consent, standard cardiopulmonary monitoring is performed and recorded. The patient was placed in a prone position and the skin overlying the cervical area is sterilely prepped and draped in the usual fashion. Before ablation, 1% lidocaine is administered subcutaneously over the C3 area as the local anesthesia, using a 25-gauge 2.5–3.5-inch needle. The patient typically remains awake throughout the entire procedure. With fluoroscopy guidance, a 17-gauge, 50 millimeter (mm), cooled, radiofrequency-insulated probe with a 2 mm active tip is advanced until it touches the area around the TON (Figure 3). The target was approached posteriorly by directing the needle to the lateral edge of C2 and C3 vertebrae. Then, in lateral view, the needles were advanced to the lower part of C2 just above the C2–3 facet joint as well as to the upper part of the C3 vertebra just below the C2–3 facet joint. Similar steps are completed if the procedure also targets the C2 medial branch, or TON. After injecting lidocaine into the C2 area, the C2 level is identified using fluoroscopy in the oblique view. A needle of the same size is inserted until it reaches the lateral edge of the C1–2 facet joint, where the TON is located, ensuring it does not enter the neuroforamina. Care was taken to make sure the needles are posterior to the cervical foramina and at the facet joint line. Placement of the probes is confirmed by verifying the absence of upper extremity motor simulation at 2 Hertz (Hz). Notably, these procedural steps are consistent with the established steps in traditional cervical medial branch ablation under fluoroscopy. Some procedural variation in tilt, obliquity, and depth may exist regarding final probe placement due to anatomic and surgeon variation.

Figure 3 Fluoroscopic visualization of the C2–3 joint, surrounding structures, and RFA probe placement during the procedure. RFA, radiofrequency ablation.

RFA is performed in lesion mode, continuous, at a temperature of 60 ℃ for 165 seconds at each nerve level. The thermal energy generated by the machine delivers 80 ℃ at the tip of the needle. Probe settings are adjusted to indicate the field of view and the generator mode. Needles are removed after the procedure, and the skin is cleaned and prepared. A sterile dressing is applied.

Postoperative considerations and tasks

RFA is typically a well-tolerated procedure, with patients being able to return home the same day. Patients were observed to frequently experience mild pain, soreness, and bruising around the treatment site (1,2,8). Due to the effects of anesthesia, patients are advised not to drive for 24 hours. Patients were also advised to rest for 1–2 days following the procedure, using self-discretion as to when to return to activities. Upon discharge, patients were given return precautions, most notably fever, chills, and severe pain that could indicate more serious adverse effects such as infection. At follow-up visits, updated pain scores should be collected and documented.

Tips and pearls

Patient selection

Patients with CGH should first be treated with first-line conservative therapies (8,9). When considering cooled RFA as a potential treatment, diagnostic nerve blocks are important to confirm the site causing pain and ensure the procedure will result in significant pain relief (6).

Anatomy

Given the importance of anatomy in cooled RFA, as well as the frequent anatomic variation of the TON, it is important that physicians have a thorough understanding of general and patient specific anatomy. Reviewing patient specific anatomy and closely monitoring intra-operative imaging and trajectory improves procedural accuracy.

Technique

Given that changes in probe direction, patient positioning, or RFA settings can meaningfully impact efficacy and patient outcomes, it is important to follow standardized procedural steps; in particular, approaching the target towards the lateral edge of C2 and C3 vertebrae, and then advancing towards the target branches.

Discussion

CGH is a debilitating secondary headache disorder that remains prevalent in the population. While many patients experience relief from primary treatments including over- the-counter analgesics and physical therapy, some patients continue to experience refractory pain. When these first-line treatments fail, more invasive treatments including nerve blocks and steroid injections targeting the C2–3 facet joint are indicated. While studies have shown that these options provide short-term relief, their effects are often not sustained and patients continue to experience pain (10,12,13). As an alternative, the use of RFA to treat CGH has been introduced and is gaining increasing attention as a minimally invasive procedure (24-26).

We propose cooled RFA, a more novel technique to further the effectiveness of nerve ablation. Cooled RFA utilizes a probe tip that is cooled to 60 ℃ via circulating water, allowing electrodes to produce more uniform and widespread lesions. Unlike the traditional thermal RFA, which rapidly delivers heat to a localized area, the cooled procedure applies heat to larger, deeper regions (27-29). While some research has been done to treat CGHs using thermal and pulsed RFA, there is minimal research on the utility and effectiveness of cooled RFA in treating CGH (3,30).

A key to achieving a positive and consistent outcome is a thorough understanding of the technical steps to completing the procedure, as described above. In addition, it is paramount to the procedure’s success to understand the TON and cervical spine anatomy, as well as accurate probe placement and visualization. It is important to note that individual variability during the TON could lead to reduced efficacy of the therapy and difficulty replicating the procedure even for the most experienced providers (20,21). Some patients may require multiple sessions before they see any improvement in pain.

Utilizing the cooled RFA and generating a larger lesion can increase the capacity to precisely cover the targeted nerves, facilitating the delivery of a successful ablation and subsequent pain relief. Incorporating a fluoroscopy to guide the probes and to confirm their accurate placement further ensures their reliability. The combination of real-time imaging and the cooled RFA thus maximizes the success rate of the RFA.

Conclusions

The novel cooled RFA technique described in this technical report has the potential to provide long-lasting pain reduction in patients suffering from refractory CGHs and to improve their quality of life substantially. The authors hope that this technical report will equip qualified providers to perform cooled RFA better and lead to increased data and research related to the effectiveness of this procedure in treating chronic pain.

Acknowledgments

None.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Annals of Palliative Medicine for the series “Advances in Radiofrequency Ablation”. The article has undergone external peer review.

Reporting Checklist: The authors have completed the SUPER reporting checklist. Available at https://apm.amegroups.com/article/view/10.21037/apm-25-114/rc

Peer Review File: Available at https://apm.amegroups.com/article/view/10.21037/apm-25-114/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://apm.amegroups.com/article/view/10.21037/apm-25-114/coif). The series “Advances in Radiofrequency Ablation” was commissioned by the editorial office without any funding or sponsorship. A.A.E. served as the unpaid Guest Editor of the series and serves as an unpaid editorial board member of Annals of Palliative Medicine from June 2024 to June 2026, and received consulting fees from Medtronic, Curonix, Avanos and Averitas. The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Declaration of Helsinki and its subsequent amendments. Written informed consent was obtained from the patient for publication of this article and the accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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