ONSD Changes and Treatment Response After Epidural Blood Patch in Spontaneous Intracranial Hypotension

Plain-language summary

"This is a prospective observational study investigating changes in optic nerve sheath diameter (ONSD) and its association with clinical improvement following epidural blood patch (EBP) in patients with spontaneous intracranial hypotension (SIH). SIH is a secondary headache disorder caused by cerebrospinal fluid (CSF) leakage or low CSF pressure and is often underdiagnosed due to its diverse and nonspecific presentation. ONSD, measured via ocular ultrasonography, has emerged as a non-invasive surrogate marker for intracranial pressure (ICP), with its diameter decreasing in states of intracranial hypotension. Prior studies suggest that posture-related ONSD differences (e.g., between supine and upright positions) may be more sensitive in SIH than static values alone, and that ONSD may increase following dural repair, correlating with symptom improvement. However, no studies to date have systematically examined the time-series evolution of ONSD around EBP in SIH patients. In this study, adult patients diagnosed with SIH and scheduled for their first EBP at our hospital will be enrolled. ONSD will be measured using standardized ultrasound protocols at three timepoints: immediately before EBP (T0), immediately after EBP (T1), and at follow-up admission two weeks later (T2). Measurements will be taken in both supine and upright positions at each timepoint to calculate posture-related changes (ΔONSD = supine - upright). Concurrently, clinical symptom assessments will be conducted using standardized instruments: Numeric Rating Scale (NRS) for headache intensity, HIT-6 for headache impact, PHQ-9 and GAD-7 for emotional distress, and EQ-5D-5L for quality of life. These will be administered at T0 and T2. Primary outcomes include the change in ΔONSD over time. Secondary outcomes involve the correlation between ΔONSD and clinical improvement metrics (e.g., reduction in NRS or HIT-6 scores). Descriptive and inferential statistics will be performed, including repeated measures ANOVA or Friedman test for time-series data, and Pearson or Spearman correlation for association analysis. All ONSD measurements and EBP procedures will be performed by the same experienced anesthesiologist following a standardized institutional protocol. This study aims to evaluate whether ONSD can serve as a quantitative imaging biomarker reflecting treatment responsiveness in SIH.

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