Acute paraplegia following epidural analgesia: diagnostic pitfalls in distinguishing pneumorrhachis from surgical mass lesions. Illustrative case.

BACKGROUND: Although pneumorrhachis is usually considered a benign radiological finding, in the epidural setting it may act as a compressive lesion and mimic surgically urgent pathology. This report describes a case of acute paraplegia following thoracic epidural analgesia caused by epidural air and highlights diagnostic and systems-related pitfalls. OBSERVATIONS: A 68-year-old man with chronic pelvic osteomyelitis developed sudden thoracic pain and rapidly progressive bilateral lower extremity paresis during a programmed bolus administration through a thoracic epidural catheter. Emergency MRI demonstrated a dorsal epidural collection at T11-12 with marked conus medullaris compression that was interpreted as a spinal epidural abscess. Urgent surgical decompression was undertaken. Surgical exploration revealed epidural air without purulence or inflammatory tissue. The patient's neurological function recovered rapidly after decompression. Root cause analysis identified residual air within the infusion cassette combined with deactivated air-in-line detection as the most plausible mechanism for inadvertent epidural air delivery. LESSONS: Epidural pneumorrhachis should be considered in patients with acute neurological deterioration after epidural analgesia. When MRI findings are equivocal, CT can rapidly confirm the presence of air. Strict air-priming protocols and active air detection safeguards are essential to prevent neuraxial air complications. https://thejns.org/doi/10.3171/CASE26351.