Long-Segment Pediatric Thoracolumbar Spinal Extradural Arachnoid Cyst

Spinal extradural arachnoid cysts (SEACs) are rare lesions, particularly in pediatric patients. Long-segment pediatric SEACs pose a surgical dilemma: achieving adequate decompression while preserving spinal stability after multilevel exposure. A 12-year-old boy presented with 1 month of progressive bilateral lower-limb pain and weakness. Neurological examination revealed upper-limb power 5/5 and lower-limb power 4/5 (MRC grading). Knee and ankle reflexes were exaggerated, plantar responses were flexor bilaterally, and sensory examination was intact. Bowel and bladder function were preserved. Magnetic resonance imaging demonstrated a long-segment dorsal extradural cerebrospinal fluid-intensity lesion extending from T9 to L2, causing ventral displacement and compression of the thecal sac. The patient underwent posterior multilevel decompression (T9–L2), excision of an extradural arachnoid cyst, and laminoplasty for posterior element reconstruction. An iatrogenic dural rent occurred during dissection and was repaired with 4-0 Prolene sutures, reinforced with an onlay dural substitute (DuraGen) and fibrin sealant to achieve watertight closure. Postoperative neurological status remained stable (lower-limb power 4/5). At 1-month and 3-month follow-up, the patient remained neurologically stable without new deficits. Long-segment pediatric SEACs require careful surgical planning. Complete decompression and meticulous dural repair are critical. Posterior element reconstruction with laminoplasty was performed to reduce the risk of postoperative deformity following multilevel thoracolumbar decompression. Multilevel posterior decompression mandates long-term surveillance for spinal alignment and recurrence, and defect-localising imaging may help tailor exposure in selected cases.