Asymptomatic spinal subdural epiarachnoid hygroma after lumbar laminectomy for lumbar spinal canal stenosis: illustrative case

BACKGROUND: Spinal subdural epiarachnoid hygroma (SSEH) after lumbar laminectomy is an extremely rare complication. OBSERVATIONS: An 84-year-old man presented to the hospital with lower back pain, radicular pain, and numbness in the lateral aspect of the left leg. Magnetic resonance imaging (MRI) revealed anterior lumbar spondylolisthesis at L3, severe disc herniation at L3–4, and severe lumbar spinal canal stenosis at L3–4 and L4–5. Lumbar laminectomy at L3–4 and L4–5 and discectomy at L3–4 were performed without complications such as cerebrospinal fluid (CSF) leakage and durotomy intraoperatively. Although lower back pain and numbness at the lateral aspect of the left leg were resolved postoperatively, postoperative MRI showed spinal nerve deviation to the ventral side due to SSEH from T12 to S1. Conservative therapy was performed for asymptomatic SSEH, and MRI 1 week postoperatively indicated improved ventral spinal nerve deviation and reduced SSEH. LESSONS: SSEHs after posterior decompression without durotomy are extremely rare. Asymptomatic SSEHs may resolve with conservative treatment. However, surgery should be performed to decompress hygroma in patients with symptomatic SSEH.