LAUSR

Periodic aggravation of pain after spinal cord stimulation (SCS) implantation is not uncommon in complex regional pain syndrome (CRPS) patients. Epidural catheterization is not recommended when SCS is implanted, due to concerns about interference with the existing SCS and risk of infection [1]. A lumbar plexus block is another option. However, complications from doing a continuous lumbar plexus block include permanent nerve damage or hematoma have been reported [2,3]. The erector spinae plane (ESP) block is a novel ultrasound-guided procedure that has been reported to be effective for postoperative pain control [4]. However, the use of an ESP block to treat lower extremity CRPS has not been reported. We report our experience of a continuous ESP block at the L4 level in a 57-year-old male patient with left lower extremity CRPS who had previously undergone SCS for 3 years prior. At the time of the admission, the patient complained of pain rated 7–8/10 on the numeric rating scale (NRS) in the left lower extremity. The function of implanted SCS was normal. Lumbar plexus blocks and peripheral nerve blocks had insufficient effects. A single ESP block with 0.5% lidocaine 20ml at the L4 level was performed and satisfactory pain reduction for 8 h was observed. We decided to perform a continuous ESP block. After receiving written informed consent from the patient, he was placed in the prone position and a 12–15MHz linear probe was placed longitudinally at the left transverse process (TP) of L4. A 18-gauge Tuohy needle was inserted in the cephalad to caudal direction toward the L4 TP using the in-plane technique. After bony contact was achieved, hydrodissection with 1–2ml of saline was used to confirm that the needle tip was located between the erector spinae muscle (ESM) and the TP (Fig. 1A, B). A 20-gauge epidural catheter was inserted through a Tuohy needle, and a total of 20ml of a mixture of 5ml of 2% lidocaine and 15ml of contrast medium was injected through the catheter, and the spread of the injectate was observed through fluoroscopic imaging (Fig. 1C–E). Then, 0.187% ropivacaine was continuously infused at the rate of 4ml per hour. The resulting sensory block was observed to range from L2 to the S1 dermatome using a cold test the day after the procedure. During catheterization, overall NRS decreased to 3/10, and requirement of intravenous tramadol was reduced from 200mg to 50–100mg per day, and the use of oral fast acting oxycodone was discontinued. Catheterization was maintained for 12 days without any complications and the patient was discharged after catheter removal while maintaining the pain intensity of NRS 3/10. Anatomically, the ESM is a structure that forms the paraspinal column, is surrounded by fascia, and extends to the lumbosacral level [5]. Therefore, just as injected local anesthetics (LA) spread to multiple thoracic and even lumbar levels during ESP blocks at lower thoracic levels, it is conceivable that LA may spread to lumbosacral levels during ESP block at lower lumbar levels. The patient reported that cold sensation was reduced by half after treatment. As LA can spread to the communicating rami including sympathetic nerve fibers as well as nerve roots during ESP block at the thoracic levels [4], such spread may be possible with ESP blocks occurring at the lumbar level. In conclusion, ESP block at the lower lumbar level for the control of lower extremity pain was easily and safely performed in a CRPS patient who underwent SCS, and the results were satisfactory. Future prospective studies are needed to demonstrate the efficacy of this method. The authors declare no conflict of interest.