A 7-year-old boy (24 kg) undergoes extensive bilateral lower-extremity orthopedic surgery. Epidural catheter placement under general anesthesia proves technically difficult, requiring several needle passes before a catheter is threaded. Twenty-four hours later he develops a bifrontal, throbbing headache with vomiting that is immediately relieved when supine and recurs on sitting or standing. Conservative therapy—including IV fluids, oral caffeine citrate, acetaminophen, ketorolac, and continuation of the local anesthetic infusion through the catheter—fails to provide durable relief. The parents are hesitant about further neuraxial procedures and ask whether any less-invasive options exist before proceeding to an epidural blood patch.

Which of the following interventions has documented success in children for aborting PDPH: