Radiofrequency ablation for the cervical spine

Introduction

Background

Radiofrequency ablation (RFA) is a procedure that uses electrical currents to deliver heat through an electrode placed near a nerve, which the nociceptive pathway is thought to arise, to interrupt pain impulses (1). The thermal energy delivered creates a predictable area of tissue destruction, typically the nerves responsible for transmitting pain sensation. Other RFA techniques include pulsed RFA, water-cooled RFA, and cryoneurolysis. When the electrical current is delivered, thermal energy is also transmitted onto the patient, which can have the adverse effect of nerve and tissue injury. Pulsed radiofrequency (RF) delivers this electrical current in a pulsatile manner; this allows for some of the heat delivered with the electrical current to dissipate before another shock is delivered. Pulsed RF has been used for a wide variety of pathologies in chronic pain of the spine, including radiculopathy, facetogenic pain, and radiculopathy (2). Cervical RFA is a minimally invasive procedure used to manage chronic neck pain due to the cervical facet joints, cervicogenic headaches, occipital neuralgia (ON), and migraines.

The lifetime prevalence of chronic neck pain is estimated to be 48.5% (3). Cervical facet joints are considered the most common source of chronic neck pain reported in 26–70% of patients with chronic neck pain and an annual incidence of up to 60% in existing chronic neck pain conditions such as whiplash and osteoarthritis of the neck (4). This is followed by migraines affecting an estimated 15% of the global population with a reported annual incidence of up to 3% of the population (5,6). Cervicogenic headaches have an estimated prevalence of 0.5–4% of the population and an annual incidence of 1.0–4.0% of the population, and ON is reported to occur in only 3 out of every 100,000 patients (7,8).

Gaps in literature

RFA of the cervical spine is being increasingly utilized for chronic neck pain and headaches with a recent review of Medicare claims and encounters database reporting a 112% increase from 2009–2018 (9). Consensus guidelines demonstrate that RFA should only be done in patients who demonstrate a positive response to two diagnostic blocks (9,10). This literature reports the most common cervical facet joints associated with neck pain located at C2–3 (36%), followed by C5–6 (35%). The utilization of facet interventions, particularly the increasing use of RFA of the cervical spine, significantly exceeds the most frequently reported prevalence rates (9). There is a need to close the gap between insurance company guidelines and clinical practice guidelines. The objective of this paper is to improve the understanding of clinical needs for patients and appropriateness of cervical RFA in the clinical setting.

Diagnostic blocks are performed before RFA to confirm clinical pain pathology (9). Medial branch blocks are recommended over intraarticular blocks with ≤0.3 mL of local anesthetic only (11). Although medial branch blocks are clinically considered positive if the patient reports greater than or equal to 50% pain relief for the duration of the local anesthetic administered in the respective referral pattern for that particular medial branch nerve, before approving a second diagnostic block or RFA, many insurance carriers will require 80% or more sustained pain relief of each injection with documentation of improvement in function, including activities of daily living.

Although many insurance companies require two diagnostic blocks before proceeding to RFA, the most recent guidelines recommend against dual diagnostic blocks over a single diagnostic block (11). The exception is those with a low index of suspicion in which case dual diagnostic blocks are recommended. The use of dual medial branch blocks is employed to increase the rate of successful cervical RFA. The downside to performing two blocks is the increase in the number of false-negative blocks, denying some patients the benefit of an RFA. There are risks with medial branch block injections in the cervical spine which are increased with multiple injections. For example, inadvertent vascular injections could result in seizures or paralysis from vascular injury.

Types of RFA

The mechanism of action of RFA is the use of radio waves directed at specific nervous tissue to cause local destruction with the goal of disruption of the nociceptive pathway caused by that tissue (12,13). Three types of RFA are most commonly used in the area of interventional pain management.

Thermal

The first type of RFA that is commonly used in interventional pain practice is thermal RFA. Thermal RFA utilizes heat in addition to electrical current to cause localized destruction to nervous tissue and provide pain relief to patients with various etiologies of nerve-related pain (14). The combination of electrical and thermal activity is believed to be the source of pain relief using this method.

Pulsed

Pulsed RFA involves delivering the electrical currents used in RFA in an intermittent, pulsatile manner (15). The idea behind pulsed RFA is that the disruption of nociceptive pathways that results from RFA is primarily due to the electrical current rather than the continuous heat that thermal RFA (14,15). This saves the patient from the potential neurotoxicity that traditional thermal RFA has the potential to cause (15).

Water cooled

Water cooled RFA is the final methodology described in the literature for pain management (16). In this case, water is used to cool the electrical current as it travels through the electrode. Opposite to thermal RFA, the current is actively prevented from attaining high temperatures. As a result, the lesion formed is larger than in thermal RFA (15). This allows water cooled RFA to be used in select situations where the suspected etiology of pain is multiple, diffuse areas rather than one direct area of nervous tissue.

Procedural technique

For successful treatment application the medial branches related to the painful condition need to be adequately coagulated, which requires the radiofrequency cannula to be in close enough proximity to the medial branches of interest (17). This is achieved by properly identifying the cervical levels responsible for the painful condition through history and physical exam, pre-injection imaging, followed by RFA of the medial branches identified under image guidance along with sensory and motor testing (18).

The cervical facet guidelines recommend a posterior or posterior oblique approach for the AO and AA joints and for the C8 level, and a lateral approach for the third occipital nerve (TON) and C3–7 facets (19). Anterior-posterior and lateral fluoroscopic views are necessary to verify needle placement. Contralateral oblique view may be used to confirm that the cannula tip is not in the neuroforamen. The contralateral oblique view is particularly helpful in lower cervical procedures in obese patients. The needle orientation should be parallel or near parallel, and at C2–3 the needle should be at the posterior two-thirds of the articular pillar (20).

Motor and sensory testing are needed for successful RFA and are used to avoid complications from lesioning the ventral ramus, spinal nerves, or other unintended structures (20). Sensory testing helps guide optimal cannula placement near the medial branches of interest. It is typically performed by delivering electrical energy at a frequency of 50 Hz with at ≤0.5 V, and the patient is asked if they experience paresthesias in the axial referral pattern. Sensory stimulation testing in the cervical regions is particularly important in the upper cervical levels (e.g., TON, C3 medial branch, and C4 medial branch) wherein motor stimulation does not always result in discernable distal muscle contraction as seen in lower cervical levels where the spinal nerves innervate the arm (19,20).

Repeat RFA may be considered in patients who have experienced greater than or equal to 30% pain relief for at least 3 months (18). RFA should not be repeated more than twice a year. The guidelines do not suggest repeating diagnostic medial branch blocks (MBBs) for repeat RFA if the patient has experienced successful RFA in the past and reports similar pain pattern presentation (19).

Implanted devices

There are special considerations when performing RFA in patients with implanted devices. In patients with implanted neurostimulators, the neurostimulator needs to be deactivated before the procedure. In patients with defibrillators and pacemakers, shared decision making with the electrophysiology team is needed. If possible, pacemakers should be placed in asynchronous mode and defibrillators should be deactivated. If a patient has implanted spinal hardware, the provider should use an approach that avoids contact with the hardware (18).

Sedation considerations

Sedation is avoided or minimized during RFA to achieve patient cooperation, assess pain threshold, avoid complications, perform motor and sensory testing, and avoid complications of sedation itself (17). Local anesthesia only is preferred to keep the patient awake and interactive during needle placement and during safety checks. If the patient does need sedation due to anxiety, then light sedation is the preferred method to keep the patient interactive during safety checks and to not be disinhibited. Deep sedation may preclude successful lesioning because the patient may be too sedated to help guide proper cannula positioning and interfere with sensory and motor testing (17,18).

RFA for headaches

Cervicogenic headache

One indication for pulsed RF in the context of headaches is cervicogenic headaches. Cervicogenic headaches arise from irritation to the spinal nerves C1–3 (19). This is most often secondary to an anatomic abnormality to the C2–3 zygapophyseal joint, but can also occur in the C3–4 joint. In particular, osteoarthritis of the facet joints can result in cervicogenic headache. Additionally, degenerative cervical disc can also result in this category of headache (20).

The pathogenesis of cervicogenic headache is thought to stem from inflammation within nerve fibers that occurs secondary to their irritation from the arthritis, disc disease, or other pathology (21). This leads to neurotransmission within C-fibers, which convey afferent nociceptive signals to the trigeminocervical nucleus (4). This often results in a unilateral headache that is exacerbated with neck movement and pressure placed on the neck (22).

RFA and pulsed RF deliver an electrical stimulus to the affected nerve roots with the goal of disrupting the described afferent nerve pathway. Traditionally, the C2 dorsal root ganglion has been targeted for this indication (23,24). A recent study has also demonstrated effectiveness in using nerve roots C3–5 for RF in the treatment of cervicogenic headaches (25). The idea of this approach is to capture the superficial medial branch of the dorsal ramus of C3 (TON), which innervates the semispinalis capitis muscles in the occipital area that have been shown to be involved in this type of headache. In addition, the C4 nerve root innervates the trapezius muscle, which contributes to the neck stiffness associated with this type of headache. The TON often is trapped by the trapezius muscle, so relaxing the muscle also theoretically reduces inflammation of the TON by alleviating its entrapment (25).

In practice, cervicogenic headaches have been successfully treated with RFA. One such study demonstrated the effectiveness of RFA relative to a sham treatment in the setting of a cervicogenic headache (26). In this study, patients who received the sham treatment did not have significant resolution of their headache symptoms over a three-month span, while those who did receive the treatment did. Another study a similar population of RFA patients and did not see significant pain relief in patients who underwent RFA for cervicogenic headache (27).

Occipital neuralgia

A second type of headache for which pulsed RF is commonly used is ON. ON affects the posterior region of the head; the headache can originate from three nerves: the greater occipital nerve (GON), the lesser occipital nerve (LON), and the TON (28). The headache can originate from one of these nerve roots or any combination of the three. The greater and LON originate from C2; the greater from the dorsal ramus and lesser from the ventral ramus. As discussed above, the TON originates from C3 (superficial medial branch of the dorsal ramus (28).

The GON is implicated in 90% of cases of due to its susceptibility to being compressed by structures such as the obliquus capitis inferior muscle, the semispinalis capitis muscle, and the occipital artery (29). Stress and trauma have been implicated in ON; it is possible that these factors contribute to nerve inflammation or hypertrophy of surrounding structures, thus contributing to compression. The pain in ON typically presents as “paroxysmal, lancinating, or stabbing pain lasting from seconds to minutes” (30).

Initial treatment includes conservative management such as nonsteroidal anti-inflammatory drugs (NSAIDs), selective serotonin reuptake inhibitors (SSRIs), steroids. Local anesthetic for confirmation of pain relief is also used as a diagnostic tool prior to RF (30). If the pain from the headache is alleviated by injection of local anesthetic to the suspected nerve distribution (most commonly GON), then pulsed RF can be performed.

Migraines

A migraine is a severe headache that is pathognomonic with a throbbing association on one side of the head and is often associated with light sensitivity (31). Of the categories of headaches described in this article, they are the most common, affecting approximately 14% of women and 7% of men.

Many treatment modalities exist for migraines. Conservative measures include dietary and lifestyle modifications, NSAIDs, triptans, and anti-psychotic medications (32). Additionally, acupuncture has been shown to aid in the treatment of this type of headache. The role of pulsed RF has been studied more recently and has been shown to be effective in a case report when the GON was targeted (33).

In addition, pulsed RF to a different target has been shown to be effective in the treatment of migraines: the superior cervical sympathetic ganglion (SCG) (34). The pathophysiology of migraines is thought to be in part due to inflammation of meningeal blood vessels. Afferent nociceptive signals from these vessels are carried via the SCG, and pulsed RF theoretically would disrupt this nociceptive pathway (35).

RFA for cervical facet joint pain

Chronic neck pain originating from the cervical facet joints can be due to osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, and cervical spinal instability (36,37). The most common implicated facet joints are C2–3 and C5–6 joints (33). Cervical RFA is a treatment modality for this pathology, and there have been several studies that have been done studying its effectiveness in the context of neck pain originating from the cervical facet joint (27,38). History and physical examination of cervical facet joint pain includes non-radicular neck pain that is consistent with referral maps, findings of paraspinal muscle tenderness, and pain with neck movement (39).

After confirming the etiology of the neck pain as originating from the cervical facet joint with MBB, cervical RFA is performed in the outpatient setting under fluoroscopic guidance (40).

A study was done performing cervical RFA against a “sham” treatment in whiplash patients. The patients and providers were blinded to which treatment was received. In the treatment group, seven out of twelve patients experienced complete relief of their pain over a 3-month period, while none of the patients who received the “sham” treatment experienced this relief.

A similar study was performed in whiplash patients that demonstrated similarly positive results (41). In this study, psychological distress was studied in addition to pain. Not only did cervical RFA relieve patients’ pain relative to those who received no treatment, but patients’ psychological ramifications of their injury were improved as well.

A study was done examining the long-term effect of cervical RFA on patients’ functional status. In this study, patients’ disability and pain scores were retrospectively analyzed relative to the patients’ pre-treatment scores. In this study, both scores significantly decreased relative to the patients; baseline pre-treatment scores (42).

Finally, a study was done comparing patients who had received pulsed RFA in addition to just RFA for facet joint osteoarthritis (43). Pulsed RFA is a variant of RFA that induces a similar physiologic modality of pain relief but prevents tissue destruction and procedure adjacent pain relative to standard RFA. In the group of patients who had received both treatments, those who had received both treatments had significantly more pain relief than those who just had RFA.

Discussion

Cervical RFA is an emerging treatment modality that has been shown to be effective in head and neck pain of a variety of etiologies. These include cervicogenic headache, ON, migraines, and cervical facet joint pain of a variety of origins.

This review paper discussed the pathophysiology of diseases that benefit RFA, the physiological benefit to receiving RFA treatment, and a brief overview of studies that have been done assessing the effectiveness of this treatment.

RFA is a treatment modality that uses electrical current delivered through an electrode to ablate the nerve through which the nociceptive pathway is thought to arise. RFA directly counteracts the pathophysiology of the discussed disease processes, all of which involve some degree of nerve-induced pain. In the setting of cervicogenic headache, RFA is an emerging treatment that has been shown to directly improve these patients’ symptoms. Similarly, some patients with ON and migraine headaches have been shown to have symptom relief with cervical RFA (44).

Neck pain has been shown to stem from a wide variety of etiologies; cervical RFA has been studied most in patients with facet joint related pain of the cervical spine. In patients with this pathology, pain relief has been demonstrated by multiple studies that compared RFA to either no treatment or pre-treatment in the same patients.

While this review paper highlights the studies done regarding cervical RFA and its benefits in a wide variety of pathologies, it also demonstrates the fact that the number of studies on this treatment are limited. In particular, there is a low number of randomized controlled trials on cervical RFA, and those that have been done include a relatively low sample size. Future studies can improve upon this limitation.

Complications of RFA in the cervical spine

While it can be an effective treatment for chronic neck pain, there are potential complications and risks associated with the procedure including allergic reactions, temporary increased pain, infection, nerve damage, bleeding, neuritis, spinal cord injury, hoarseness, dysphagia, and failure to relieve pain. Not all patients may respond to cervical RFA treatment, and some patients may even experience an exacerbation of their painful symptoms.

Any invasive procedure poses some risk of infection anywhere along the needle track. Any interventional procedure around the spine has risk of an epidural abscess but the risk is low if proper considerations are followed (45). The risk of this complication is exceedingly rare but can be catastrophic when it does occur (46), because a patient could suffer from severe neurologic complications, such as loss of sensation and motor movement in the extremities (47). The treatment for epidural abscess is emergent evaluation and treatment with intravenous antibiotics and possibly surgical debridement (1).

Long-term neurologic injury has been reported in several case reports after cervical RFA (48). In one report, a patient felt pain immediately after the procedure in the neck and upper arm (32). In another case, a patient felt similar symptoms with the addition of left-hand weakness that persisted for several months after the injection. EMG should be used to confirm change in nerve function and possibly imaging if indicated. Treatment for increased pain and neuritis may include a Medrol dose pack and gabapentin, and possibly diagnostic local anesthetic blocks to the suspected nerve.

Inadvertent damage to the surrounding tissues is also a potential complication. For example, hoarseness or dysphagia is an extremely rare complication, but could occur due to the proximity of the nerves controlling the function of the vocal cords and swallowing. Vascular damage during the procedure may lead to bleeding from the vessels that may result in minor complications, such as bruises, or more serious complications, such as hematoma formation. Intravascular injection of medications could lead to strokes of the spinal cord leading to spinal cord injury and paralysis (49). Intravascular steroid, in particular particulate steroid, can cluster and block some of the small vessels leading to permanent weakness, paresthesias and pain (50).

The procedure itself introduces needles into the skin and can cause inflammation and post-procedural pain. This should be temporary and resolve within a day or two. If the ablation inadvertently targets the wrong nerve or affects adjacent nerves, it may cause temporary or permanent nerve damage, leading to increased pain, numbness, headaches, or weakness. Though extremely rare, spinal cord injury is a potential risk if the procedure is not performed accurately. This can result in permanent paralysis. Overall, the risks of severe neurologic sequelae after cervical RFA are rare. However, when they do occur, they can be serious to the point of being irreparable or requiring surgical intervention.

Conclusions

In summary, the risks and complications associated with cervical RFA must be balanced against its potential benefits, and a careful assessment of the patient’s medical history, underlying health conditions, and specific pain issues should be discussed with the patient in detail. The skill and experience of the practitioner plays a significant role in minimizing these risks. Detailed discussions with healthcare providers about the risks, benefits, and alternatives can help in making an informed decision about the procedure. Importantly, insurance companies should have clear guidelines that are uniform and fall in line with clinical practice and guidelines published by experts in the field. The focus of insurance company policy should be on patient care rather than financial reward.

Acknowledgments

Funding: 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.

Peer Review File: Available at https://apm.amegroups.com/article/view/10.21037/apm-23-520/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://apm.amegroups.com/article/view/10.21037/apm-23-520/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 2022 to May 2024. A.A.E. received consulting fees from Avanos and he is also a consultant for Medtronic and Curonix. The authors have no other conflicts of interest to disclose.

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.

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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