Ultrasound-Guided Infraorbital Nerve Pulsed Radiofrequency Treatment for Intractable Postherpetic Neuralgia - A Case Report -
A 60-year-old man visited our pain clinic with the chief complaint of left facial pain. The patient had been diagnosed with facial herpes zoster in the left V2 area 6 months previously. The left facial pain had continued for 6 months despite medical treatment. During this period, 150 mg pregabalin, 10 mg amitriptyline, 37.5 mg tramadol/375 mg acetaminophen combination tablet (Paramacet tab; Donga, Seoul, Korea) were administrated per os three times daily but had little effect. He had paroxysmal, sharp and shooting pain on his left cheek and lateral nose. The pain was aggravated by touching the left facial area, and palpation over the left infraorbital foramen reproduced the pain. Pain severity was 9-10/10 on the visual analogue scale (VAS).\nHence, we started pain intervention for trigeminal PHN in the left V2 area. We initially blocked the left infraorbital nerve under USG with a 10-12 MHz linear transducer (Vivid E, General Electronics, Fairfield, CT, USA) using a mixture of 2 ml 2% mepivacaine and 20 mg triamcinolone. This procedure decreased the pain immediately. When he returned to our pain clinic 1 month after the infraorbital nerve block, the patient stated that the VAS score had decreased from 9 to 4 for about 2 weeks following the infraorbital nerve block but then his symptoms returned to a previous state. Therefore, we tried the same additional USG left infraorbital nerve treatment, but the outcome was the same.\nThe USG infraorbital nerve blocks were effective but the effects were maintained for only 2 weeks, so we decided to perform PRFT. After explaining the procedure, efficacy, and possible side effects of PRFT, the patient was placed in a supine position. The skin was aseptically draped with betadine. The ultrasound was prepared with a sterile transparent sheath and aseptic ultrasound gel. The transducer was applied longitudinally to the lateral side of the nose and then rotated slightly clockwise to obtain an ideal longitudinal (long-axis) view of the infraorbital canal to find the left infraorbital foramen. We scanned his face from medial to lateral in the sagittal plane along the left lower orbital margin (). We easily identified the infraorbital foramen with a hyperechoic protuberance ().\nRadiofrequency needle (10 cm) insulated with a 5-mm active tip (22 G, SMK-C10; Radionics Inc, Burlington, MA, USA) was advanced slightly via the infraorbital foramen under USG (). Confirmation of the needle position inside the infraorbital foramen was achieved under fluoroscopy. Following negative aspiration, 0.5 ml of radio-contrast agent was injected to confirm no vascular uptake through the infraorbital artery (). Sensory stimulation using a 50 Hz, 0.3-0.5 V electrical current showed paresthesia over the left cheek and lateral nose. After confirming the needle position, we performed PRFT three times at 42℃ for 120 seconds. The patient did not show any problems throughout treatment.\nOne month after pulsed RF treatment, his pain severity was 1-2/10 on the VAS, and his pain relief scale was 80-90%. Because this pain relief was maintained continuously throughout the 2, 4, 6, and 12 month follow-ups after PRFT, no additional treatment including medication was provided.