Pain Trajectories and Factors Associated with Repeated Greater Occipital Nerve Block in Post-Dural Puncture Headache: A Retrospective Observational Cohort Study.

Background: Epidural blood patch (EBP) remains the standard procedural treatment for post-dural puncture headache (PDPH) persisting after conservative care; whereas, the evidence for greater occipital nerve block (GONB) is limited. This study describes pain trajectories during GONB-based management and factors associated with repeated GONB. Methods: Single-centre retrospective observational cohort of all consecutive patients treated for PDPH between January 2016 and January 2018. Eligible patients met the current ICHD-3 criteria after spinal anaesthesia, had a Numerical Rating Scale (NRS) score ≥ 4 and had persistent symptoms after ≥24 h of conservative management. Bilateral landmark-guided GONB (2.5 mL bupivacaine HCl 5 mg/mL per side) was repeated when the NRS remained ≥4 at a 24 h assessment, so group membership reflected the response to treatment. Results: Sixty-two patients were analysed (mean age 33.9 ± 15.1 years; 64.5% women). NRS decreased over seven days (Friedman χ2 = 262.6, p < 0.001; Kendall's W = 0.847); on day 7, 57 patients (91.9%; 95% CI 82.5-96.5%) had absent-to-mild pain. Thirty-eight patients (61.3%; 95% CI 48.8-72.4%) received one block. In an exploratory Firth penalised model, baseline NRS (OR 2.41, 95% CI 1.55-4.15) and orthopaedic surgery (OR 5.02, 95% CI 1.36-21.56) were associated with repeated GONB. No GONB-related complications and no EBP were documented. Conclusions: NRS scores decreased during a strategy comprising one or more GONB sessions with concomitant conservative care, but these uncontrolled observations cannot separate any effect of GONB from spontaneous recovery, regression to the mean or concomitant treatment. They are hypothesis-generating and require prospective randomised confirmation.