The Effects of Caudal Epidural Injection on Optic Nerve Sheath Diameter and Hemodynamic Parameters in Adults with Failed Back Surgery Syndrome: A Prospective Clinical Study.

BACKGROUND

Failed back surgery syndrome (FBSS) is a challenging chronic pain condition following spinal surgery, often resistant to conventional therapies. Caudal epidural injection is a mainstay for managing FBSS, yet its effects on intracranial pressure (ICP), particularly in adults with post-surgical anatomical changes, remain poorly understood. Optic nerve sheath diameter (ONSD) measured by ultrasound offers a non-invasive surrogate marker for detecting alterations in ICP.

METHODS

This prospective single-center clinical trial enrolled 46 adult FBSS patients scheduled for therapeutic caudal epidural injection at Imam Hussein Hospital, Tehran, Iran. Each participant received a standardized two-stage, 30 mL caudal epidural injection. The ONSD and hemodynamic parameters [systolic, diastolic and mean arterial blood pressure (SBP), (DBP), (MAP), heart rate (HR)] were assessed at baseline, immediately, and then at 10, 20, and 40 minutes post-injection. All measurements were performed by blinded, trained personnel using validated protocols.

RESULTS

Caudal epidural injection produced a significant, transient increase in mean ONSD (baseline: 4.8 ± 0.49 mm; immediate post-injection: 5.1 ± 0.50 mm; P < 0.001), which normalized within the observation period. No patient exhibited symptoms or clinical signs of raised ICP. While serial monitoring indicated statistically significant reductions in SBP, DBP, MAP, and HR at 40 minutes, all values remained within physiologically acceptable ranges. No major procedural complications or adverse neurological outcomes occurred.

CONCLUSIONS

Standard-volume caudal epidural injection in adults with FBSS causes a temporary, asymptomatic elevation in ONSD, reflecting a reversible change in ICP. The procedure was well tolerated, with minimal and clinically insignificant hemodynamic effects, supporting its safety and utility in this patient population.