Epidural Block Treatment on Postherpetic Neuralgia and Comorbid Spine Metastasis of Malignant Tumor: Two Cases of Report

Jin-Yan Dai, An-Lan Hong, Yan Wang∗

Hospital for Skin Diseases (Institute of Dermatology), Chinese Academy of Medical Sciences and Peking Union Medical College,Nanjing, Jiangsu 210042, China.

Abstract

Introduction: Postherpetic neuralgia (PHN) is a painful condition that occurs after herpes zoster skin lesions have subsided and that lasts for more than 1 month. PHN is usually difficult to treat.

We herein present two cases of PHN comorbid with spinal metastasis of a malignant tumor. Both patients responded well to an epidural block.

Case presentation: Patient 1 was a 54-year-old woman who had PHN for 35 days. Patient 2 was a 74-year-old woman who had PHN for 65 days. Both patients were treated with an epidural block and found to have spinal metastasis from a malignant tumor.

Discussion: The routinely used dermatological medications for the treatment of herpes zoster and PHN have slow and unsatisfactory analgesic effects. Epidural block treatment provides a new approach for patients who cannot tolerate or do not respond to these commonly used drugs. Physicians should pay special attention to patients who have a history of a malignant tumor or are suspected to have spinal disease. Computed tomography or magnetic resonance imaging of the spine is recommended for such patients, and epidural block treatment should be performed after a spinal tumor or other lesions have been excluded.

Conclusion: Epidural block treatment provides a new approach for patients of herpes zoster or PHN, but the treatment should be performed after a spinal tumor or other spinal lesions have been excluded.

Keywords: epidural block treatment, postherpetic neuralgia, spinal tumor

Introduction

The American Academy of Neurology defines postherpetic neuralgia (PHN) as a painful condition that occurs after the herpes zoster (HZ) skin lesions have subsided and that lasts for more than 1 month.1The estimated prevalence rates of HZ and PHN in China are 7.7% and 2.3%,respectively, and approximately 2.8%of patients with HZ subsequently develop PHN.2

PHN is generally difficult to treat. We herein describe two patients with PHN who had comorbid spinal metastasis of a malignant tumor and could not tolerate or did not respond to most of the available drugs for PHN.Combination therapy is often necessary when the beneficial effect of monotherapy is insufficient. Anticonvulsants,antidepressants, opioids, and lidocaine patches have level A evidence supporting their use in patients with PHN.Intrathecal steroid injections, nerve blocks, and topical capsaicin have level B evidence in treating PHN. If treatment is still ineffective, spinal cord stimulation or intrathecal alcohol injection can be used as a last resort.3We performed an epidural block for both patients and achieved a good response.

Case report

Patient 1 was a 54-year-old woman weighing 62kg who had PHN for 35 days at the right T7/8level. She experienced intense cutting pain at the diseased site with a visual analog scale (VAS) score of 9 to 10. The patient took oral gabapentin at 300mg three times daily; however, she developed severe side effects, including vomiting, that were alleviated on discontinuation of gabapentin. The patient strongly requested treatment with an epidural block. She had undergone surgical excision of mediastinal tumors 1 year previously, and a computed tomography (CT) scan showed no abnormalities 3 months previously. After pretreatment tests and examinations, we performed routine disinfection followed by T7/8epidural puncture under close monitoring. The puncture was successful, and the epidural catheter was patent. A 3-cm catheter was inserted. After ensuring that the catheter was inside the epidural space, a 3-mL bolus of 1% lidocaine was injected as a trial dose. After 10 minutes, no adverse reaction had been observed. While the anesthesia is still effective, a 6-mL bolus of 0.125% of ropivacaine along with 40mg of methylprednisolone and 2mg of vitamin B12 was administered. The patient’s vital signs were continuously monitored for 1 hour, and her pain was completely alleviated. She had no other discomfort, and the epidural pump was sent home along with the patient (drugs in the pump: 150mg ropivacaine, 20mg vitamin B12, 3mg dexamethasone, and physiological saline to a volume of 100 mL); the background infusion volume was 2 mL. The patient generally did not feel pain during the pump usage period. Three hours after completing infusion of the drug solution, the patient felt recurrence of the pain but at a level that was still tolerable; her VAS score was 3 to 4. The patient developed a fear of pain due to her previous experience with pain, and she requested to change the pump again (the analgesic formulation remained unchanged except that dexamethasone was not present), and the pump was used for 48hours. The dressing was changed at the puncture site, a sterile dressing was applied, and the patient was discharged. The patient reported no pain after having used all of the drug solution. One week later,however, her pain on the right side gradually worsened. A follow-up consultation for pain showed no abnormalities of the skin on her back; however, percussion pain was present (++). No treatment was carried out, and the patient was instructed to undergo a thoracic vertebral magnetic resonance imaging (MRI) scan. This showed spinal metastasis at the T8 and T12 vertebral bodies. At the time of this writing, the patient was still undergoing treatment outside the hospital.

Patient 2 was a 74-year-old woman weighing 68kg who had PHN for 65 days at the left T9/10level. The patient experienced intense cutting pain at the diseased site with a VAS score of 9 to 10. Her mental state was poor, and she had an extremely painful countenance. Because of her pain, she required support while walking. The patient had a weak constitution due to radiotherapy for lung cancer 1 year previously. The patient and her family strongly requested epidural block treatment. Routine blood examination and a three-item coagulation test were normal. Electrocardiography showed myocardial ischemia at the lateral wall. Routine disinfection followed by T10/11epidural puncture was carried out under close monitoring.The process of epidural block treatment with drug and dosage used were exactly same as those of the first patient. Oral gabapentin at 300mg three times daily and intramuscular neurotropin at 3 mL once daily were also prescribed. A follow-up consultation was carried out 48 hours later, and examination of the puncture site revealed that the catheter had become detached. The patient mentioned that her waist and abdominal pain at the original shingles sites was alleviated when the analgesic pump was used, but she felt that the pain at her left hip was more intense. The patient was instructed to increase the dose of oral gabapentin and to undergo a vertebral CT scan. A telephone follow-up was carried out 3 days later,and the dose of gabapentin was increased to 600mg three times daily. The pain was alleviated, but the patient experienced somnolence and dizziness. A CT scan verified that the patient had spinal metastasis, and she died 5months later.

Discussion

The incidence of HZ is higher in patients with than without malignant tumors, and PHN is one of the most common complications. PHN can be extremely difficult to manage.

The two herein-described patients with PHN underwent an epidural block and intrathecal steroid injection because of a poor treatment effect or intolerance of therapy supported by level A evidence. The pain was significantly alleviated and the results were satisfactory, indicating that an epidural block and intrathecal steroid injection may be effective methods in treating PHN. Kim et al.4suggested that somatic blocks, including repeated/continuous epidural blocks and paravertebral blocks, prevent PHN and reduce the likelihood of occurrence. Pasqualucci et al.5also reported that after epidural block treatment, the incidence of PHN-related pain was only 1.6% (4/255 patients). An epidural block is significantly more effective than intravenous acyclovir and prednisolone in preventing PHN. Dong et al.6administered a gabapentin epidural block and oral oxycodone-acetaminophen to patients with PHN, and the patients’ VAS score after treatment decreased with extension of the treatment time without obvious adverse reactions. They considered that this therapy is suitable for patients with severe pain and that its early use can quickly relieve pain. Park et al.7suggested that the response to a transforaminal epidural injection in the acute phase of HZ appears to be a strong predictive factor of progression to PHN.

The mechanism of an epidural block and intrathecal steroid injection in treating PHN is as follows. Lidocaine and ropivacaine block pain transmission along sensory nerves and improve the local circulation by blocking sympathetic nerves, thus increasing the oxygen and nutrient supply and accelerating the metabolism of algogenic substances. Additionally, dexamethasone eliminates inflammation and edema of the affected nerves,inhibits fibrosis, and promotes nerve restoration.

The two patients were found to have a comorbid metastatic spinal tumor after epidural block treatment,placing them at an extremely high treatment risk.

Although no serious complications or adverse outcomes occurred, the lesson learned in these cases is profound. Gao and Song8 described a patient with a spinal tumor who became paraplegic by epidural anesthesia. Therefore, before administering an epidural block in patients with HZ or PHN, physicians should take a detailed medical history and performa careful physical examination. For patients with a history of amalignant tumor or suspected spinal disease,CT or MRI of the spine is recommended to confirm the state of illness and avoid unexpected accidents and losses.

In conclusion, epidural block treatment provides a new approach for PHN patients who cannot tolerate or do not respond to these commonly used drugs. Additionally,patients who have a history of a malignant tumor or are suspected to have spinal disease should receive close attention by physicians, and epidural block treatment should be performed after a spinal tumor or other lesions have been excluded by CT or MRI.

Source of funding

This work was funded by the National Natural Science Fund of China (No. 81872216) and the PUMC Postgraduate Education and Teaching Reform Project in 2018 (No.10023201801701).