Abstract text (incl. figure legends and references)

Background: Spontaneous intracranial hypotension (SIH) is diagnosed based on at least one of abnormal findings in brain MRI, spinal imaging, and lumbar puncture. However, the sensitivity of brain MRI, spinal myelography, and lumbar puncture is low. We questioned if patients with suspected SIH would respond to epidural blood patch (EBP) although they do not have imaging abnormalities.

Methods: We prospectively registered patients with suspected SIH admitted to Samsung Medical Center from 2017 January and 2021 July. For patients whose brain MRI and CT or MR myelography were normal and received EBP for the first time in our hospital, we analyzed their treatment outcome at discharge and 3 months after EBP which was defined as the remission of orthostatic headache and 50% response in maximal headache intensity.

Results: A total of 22 treatment-naïve patients with orthostatic headache and negative brain and spinal imaging who received EBP were identified and included in this study. Spinal imaging was performed with CT myelography in 6 (27%) and MR myelography in 16 (73%). Out of 9 (41%) patients who underwent lumbar puncture, none had an opening pressure lower than normal range (median 13.8 cmH2O, interquartile 9.8 – 16.6). After EBP (mean 1.4 times, range 1–3), orthostatic headache was remitted in 77% and 95% of patients, and 50% response was achieved in 77% and 91% of patients, respectively at discharge and 3 months after treatment.

Conclusion: Our study shows that EBP yielded a high rate of treatment response in imaging-negative patients with suspected SIH. We suggest that the empirical EBP should be considered for the treatment of new onset orthostatic headache although brain and spinal imaging are negative. The necessity of lumbar puncture is questionable in such patients considering the high response rate of EBP and low detection rate of "low pressure".