Cervical radicular pain is defined as pain arising in the upper limb with a sharp, shooting and lancinating character caused by ectopic activation of the nerve roots or other neuropathic mechanisms3). Radicular pain is a symptom that is caused by ectopic impulse formation, while radiculopathy includes neurologic signs such as sensory or motor changes9). These two disorders may occur simultaneously also9). Although many treatment modalities are described, the available evidence for efficacy is not sufficient to allow definitive conclusions on the optimal therapy to be made10).

Radiofrequency (RF) treatment, adjacent cervical dorsal root ganglia (DRG), was first described by van Kleef et al.8). They reported good results and some side effects, which are transient neuritis and a loss of muscle strength in the hand8). Due to these side effects and the possibility of deafferentation pain, pulsed radiofrequency (PRF) to the cervical DRG becomes in popularity.

The goal of this retrospective study is to evaluate the efficacy of the application of PRF treatment to adjacent cervical DRG in treatment of cervical radicular pain patients.

The mean age of the patients was 54±10 years. 12 (55%) patients were males and 10 (45%) were females. Cervical MRI or CT findings revealed that 13 (59%) patients had herniated cervical disc and 9 (41%) had the foraminal stenosis. PRF on C5 DRG performed in 4 (18%) patients. PRF on C6 DRG was done in 17 (72%) patients. 5 (22%) patients underwent PRF on C7. 4 (18%) patients were treated PRF on two lesions. The other patients underwent single PRF treatment. The averages of NRS scores was declined from 7±1.7 at pretreatment to 3.1±1.9 (change in NRS [%]=59.3%) at 2 weeks of posttreatment, 2.8±2.2 (59.3%) at 1 month, 2.5±2.2 (62.4%) at 3 months and 2.7±2.2 (59.5%) at 6 months. Among 22 patients, 15 (68%) patients were successes groups (improvement NRS≥50% at six months PRF treatment) and seven (32%) patients were failure groups. This is summarized in Table 1 and Fig. 1. There were no complications related with PRF treatment during the follow-up period. Cervical DRG impedance mean was 382.9 Ω, which ranged from 290 to 490. Between success and failure group, we do not find any successful outcome prognostic factor (Table 2). Change in NRS (%) at 6 months, foraminal stenosis (n=9) is 76.94±21.57% and herniated cervical disc (n=13) is 47.52±37.13%. Interestingly, PRF treatment on foraminal stenosis were better outcome than herniated cervical disc. However, there is no statistically significant (p-value=0.13).

Cervical radicular pain is characterized by pain radiating from the neck over the posterior shoulder into the arm according to a particular segmental pattern corresponding with involvement of the spinal nerve segments C5, C6, or C7. A positive Spurling test has been demonstrated to be a valuable tool in the clinical diagnosis of cervical radicular pain7).

The principle of epidural administration of corticosteroids relies on the anti-inflammatory response induced by inhibition of the phospholipase A29). Benyamin RM et al.1) reported systematic review of cervical interlaminar epidural injections. The global conclusion of this systematic review is that interlaminar cervical epidural corticosteroid injections provide a significant effect on cervical radicular pain. However, sometimes interlaminar cervical epidural steroid injection may have major complications which included epidural hematoma and accidental subdural injection with, as a result, hypoventilation and hypotension9).

RF treatment adjacent cervical DRG for cervicobrachial pain patients had been described by van Kleef et al8). In their study, each of 20 consecutive patients with a history of at least 1 year of intractable chronic cervicobrachial pain were randomly assigned to one of two treatment groups (Sham group vs. RF treatment group). They suggested that a 67℃ RF lesion adjacent to the cervical DRG can result in a significant alleviation of pain in chronic cervicobrachial pain patients after 2 months treatment. Slappendel et al.5) reported the efficacy of RF lesion treatment of the cervical DRG in cervicobrachialgia. They investigated in 61 patients by a randomized prospective double blinded study. They did not find any difference between a group of RF treatment at 40℃ compared with at 67℃. Both groups shows that the visual analogue scale scores being significantly reduced 1.5 months and 3 months after the procedure. Above two randomized controlled trials showed limited evidence that RF of the cervical dorsal root is more effective than placebo in chronic cervical radicular pain. However, transient neuritis and/or a burning sensation in the treated spinal nerve were noted and a slight loss of muscle strength in the hand or arm on the treated side was reported5,8).

For this reason a modification of the technique, resulting in less neural damage, would be more attractive for chronic pain management. PRF has been described as a nondestructive alternative to radiofrequency thermo-coagulation for the management of chronic pain2). Although the mechanism of action is not completely understood, one of the prevailing theories postulates that the electrical fields reversibly disrupt the transmission of impulses across small unmyelinated fibers4,6). The concept that PRF may produce inhibition of excitatory C-fiber responses using a phenomenon such as long-term depression2). Maintaining the temperature at the tip of the electrode at 42℃ that may allow the dissipation of heat, avoiding the complication of thermal injury, thereby decreasing post-procedure side effects4,6).

Van Zundert et al.10) reported that the effect of PRF treatment adjacent cervical DRG in chronic cervical radicular pain group showed a significantly better outcome than sham group at post-treatment 3 months.

Choi et al.3) reported that effect of PRF on refractory cervical radicular pain patients. In this report, 14 patients (66.7%) after cervical PRF stimulation reported pain relief of 50% or more at the 3-month and 12-month follow-up periods, respectively. 15 patients (71.4%) were satisfied with their outcome at 12 months post-treatment.

Our study showed that the degree of change in pain reduction rates at 3 months, 6 months after treatment were 62.4% and 59.5%, respectively. This study showed that the PRF treatment on adjacent cervical DRG appears to be relatively safe and effective treatment method. However, our study has some limitations. Absence of control group with similar characteristics and the small number of subjects. In the future, a controlled and randomized study design with a larger populations are needed.

PRF treatment of the adjacent cervical DRG in cervical radicular patients may provide pain relief of carefully selected patients with cervical radicular pain patients.