Case report
A 83-year-old female visited our outpatient clinic with chief complaint of 3 months old headache, due to persistent CSF leakage. She reported that her headache started after PEN, performed at another institution, for her back and leg pain. Her headache was position dependent. No signs of inflammation were observed in the coccygeal area and her neurological examination was normal. The past medical history was otherwise unremarkable, except for her hypertension and dyslipidemia, and she was not taking any anti-coagulation agents. Initial laboratory findings were within normal limits, including C-reactive protein. For further evaluation, magnetic resonance imaging (MRI) examination was done, which showed a localized subcutaneous fluid collection at her coccyx area. Thus, we diagnosed her with coccygeal hygroma, caused by persistent cerebrospinal fluid (CSF) leakage around the dural puncture site during her PEN.
Initially, she had conservative management, including bed rest, fluids intake, and oral medications. They also performed coccygeal fluid aspirations multiple times. However, her PDPH persisted. Thus, we attempted epidural blood patch at L4-L5 level under fluoroscopic guidance with loss of resistance technique. Two weeks later, she visited our clinic for a follow up, with improved headache and decreased size of hygroma.

Discussion
In this case, intracranial hypotension with headache and coccygeal hygroma were probably the results of CSF leakage due to iatrogenic dural tear. CSF leakage can occur along the lower pressure site, and gravity can cause the leakage to persist. Epidural blood patch is the treatment of choice for PDPH. Injected blood can seal off the puncture site of dura by clotting, which leads to increased CSF pressure, subsequently causing rapid relief of headache.
Thus, we tried epidural blood patch at L4 and L5 level. After the treatment, the patient showed a relief in headache with decreased size of hygroma.

Conclusion
The awareness of possible complications and conscious effort to prevent them are important when performing PEN. To prevent a dural puncture, checking the optimal depth of injection by injecting dye with careful attention is needed. Also excessive progression of catheter and adhesiolysis should be avoided. Epidural blood patch can be an optimal choice for the treatment of persistent CSF leakage after PEN.