The Effect of Ultrasound-Guided Erector Spinae Plane Blocks in Patients With Postherpetic Neuralgia: The Mechanism Approach Using Cone-Beam CT.

BACKGROUND: The erector spinae plane block (ESPB) is a frequently applied analgesic method in perioperative and acute pain conditions. However, there is an unpredictable and inconsistent effect, especially in chronic pain conditions, such as postherpetic neuralgia (PHN). Furthermore, aspects of the spread of local anesthetic and its action were unclear mechanisms. METHODS: We included 22 patients with PHN, and the patients were randomly assigned to a transverse (TV) or parasagittal (PS) approach group. Both groups of patients underwent ultrasound-guided ESPB and were confirmed with cone-beam computed tomography. RESULTS: The results showed that both approaches of ESPB spread cranially by 2.89 ± 1.45 and 2.46 ± 0.97 (mean ± standard deviation, TV vs. PS) and caudally by 3.67 ± 2.24 and 3.85 ± 1.34 sides of the interfascial plane, as well as to the muscle itself. A higher rate of epidural spread (55.6%) was observed in the TV group. All patients experienced significant pain reduction within 1 hour after ESPB; however, this analgesic effect was not sustained at 2 or 4 weeks. CONCLUSION: ESPB analgesia likely involves spread to the dorsal rami, with occasional paravertebral and epidural extension. Although the TV approach showed more frequent epidural spread, it did not improve analgesic efficacy. Both approaches provided significant short-term pain relief but no sustained benefit beyond several weeks.