The aim of this study is to investigate the efficacy of adjuvant hypertonic saline to cervical epidural block in patients with cervical radicular pain screened for neuropathic pain using DN4 questionnaire. 
Neuropathic pain cannot be clearly diagnosed but is presumed according to clinical symptoms since there are no biochemical markers for this condition. It has been found that neuropathic pain is distinguished from other chronic pain that has a combination of several characteristics.(burning pain, electrical pain, abnormal sensations, allodynia, etc.) Based on this, a number of simple symptom-based questionnaires have been developed to help select and screen patients with neuropathic pain. Douleur neuropathique en 4 questions (DN4) is a questionnaire that is most commonly used for screening and diagnosing neuropathic pain. It consists of a total of 10 items, 7 items related to the quality of pain and 3 items based on patient interviews. The DN4 questionnaire is easy to score and has proven to have excellent sensitivity (74-85%) and specificity (76-90%) in distinguishing between neuropathic and non-neuropathic (nociceptive) pain in many feasibility studies. This questionnaire has spread rapidly worldwide and is currently being translated and used in more than 90 languages, and its validity has been confirmed in many other languages ​​including Korea.
Meanwhile, in patients with chronic neuropathic pain, interventional treatments such as epidural nerve block and neuroplasty including epidural adhesiolysis may be performed as conservative treatments for pain control. In these epidural procedures, adjuvant hypertonic saline is sometimes added. In several studies, injection of hypertonic saline in epidural procedures has reduced the degree of pain, prolonged the pain reduction period, increased satisfaction, and decreased the frequency of additional procedures. The mechanism of pain reduction caused by hypertonic saline is speculated to cause blockage of nerves that transmit nociceptive stimuli by high concentration of chloride ions, and to reduce nerve swelling by osmosis. Still, the mechanism of hypertonic saline is not clearly identified, and data are insufficient.
Also, in many previous studies on epidural hypertonic saline, the subject was not clearly limited to neuropathic pain. This is because the researcher conducted a study on patients who judged neuropathic pain based on the patient's clinical symptoms such as radiating pain in which lesions were confirmed in the cervical and lumbar spine. Patients with cervical or lumbar disease may have some characteristics of neuropathic pain, but because nociceptive pain and neuropathic pain may be mixed, in some cases, patients who cannot be diagnosed as neuropathic pain may be included. Therefore, it remains a limitation that previous studies did not target patients identified as neuropathic pain using diagnostic tools whose validity had proven. In other words, there is no study on the effect of epidural hypertonic saline in patients with neuropathic pain screened by a validated questionnaire, such as DN4.
Therefore, we will investigate the effectiveness of adjuvant hypertonic saline in cervical epidural block in patients with chronic cervical radicular pain screened for neuropathic pain using the DN4 questionnaire.

Treatment

After obtaining informed consent, the patient's condition is evaluated before the procedure, and the site cervical spine to be performed is marked. After applying general monitoring device such as a pulse oximeter and a blood pressure cuff to the patient, a pillow is placed under the patient's chest to minimize the curvature of the cervical spine in prone position. After skin preparation, the target level is identified in the true anteroposterior (AP) view under fluoroscopic guidance. After local infiltration with 1% lidocaine, the needle is inserted and carefully advanced to the epidural space of target or below the target level using loss of resistance technique while checking the position of needle tip in the contralateral oblique view of 50 degrees. After connecting a syringe filled with contrast agent to the needle and aspirating to confirm that blood or cerebrospinal fluid does not flow out, 0.5-2 mL of contrast agent is injected to confirm epidural space. When the proper needle position and contrast dispersion are confirmed, 4 mL of 1% lidocaine is injected. After 5 minutes, confirming no change in sensory and motor function of the ipsilateral and contralateral upper limbs, 4 mL of 5% hypertonic saline including 5 mg of dexamethasone was additionally injected in the HS group, and an additional 4 mL of 0.9% saline containing 5 mg of dexamethasone is injected in the saline group (NS group). At this time, if there is any severe paresthesia, pain, intravascular or intrathecal injection, no additional drugs are administered. The type of additional drug is prepared and covered by a third party unrelated to the procedure so that the operator and the subject could not recognize throughout the procedure. After the drug is injected, the needle is removed, the patient is placed in a supine position and transferred to the recovery room. In the recovery room, a nurse or anesthesiologist blinded to the study group evaluates postoperative sensory and motor function.

Arm Label

Target Number of Participant

Arm Type

Arm Description

In the hypertonic saline group (HS group), 4 mL of 5% hypertonic saline including 5 mg of dexamethasone is injected.

Arm Label

Target Number of Participant

Arm Type

Arm Description

In the normal saline group (NS group), 4 mL of 5% normal saline including 5 mg of dexamethasone is injected.

Gender

Age

Description

1) Patients with chronic cervical unilateral radiating pain over 3 months
2) Patients with symptom-related unilateral 1-2 level lesions of the cervical spine in radiologic examination (CT or MRI)
3) Patients screened for neuropathic pain by obtaining 4 points or more in DN4 questionnaire
4) Patients whose symptoms have not improved even after conservative treatment for more than 3 months
5) Patients with pain intensity of NRS 4 or higher
6) 20 ≤ age <80
7) Patients who voluntarily agreed in writing to participate in this clinical trial

1) Patients in acute phase with pain period less than 3 months
2) Patients whose pain intensity is less than 4 points or 10 points in NRS
3) When the axial pain is more severe than the radiating pain
4) Patients with progressive motor weakness or neurological findings
5) Those who are contraindicated in nerve block procedure, such as coagulopathy or infection
6) Patients with uncontrolled medical or psychiatric problems
7) Patients with side effects from local anesthetics, steroids, or contrast agents
8) Pregnant or lactating patients
9) Patients diagnosed with cancer and undergoing treatment
10) Patients with a history of surgery on the cervical spine
11) If the patient does not agree to participate in the study

NRS (Numerical rating scale, 0 = no pain, 10 = unbearable pain)

3 months after procedure

NRS (Numerical rating scale, 0 = no pain, 10 = unbearable pain)

1,6 months after procedure

NDI (0 – 50; 0 = no disability, 50 = complete disability)

1, 3 and 6 months after procedure

MQS (Medication quantification scale)

1, 3 and 6 months after procedure

PHQ-9 (patient health questionnaire-9)

1, 3 and 6 months after procedure

GPE (Global perceived effect, 1-7)

1, 3 and 6 months after procedure

Responder rate (0 – 100% of patients)

1, 3 and 6 months after procedure