Surgical treatment of a combined split cord malformation and spinal cord lipoma: illustrative case.

backgroundSplit cord malformations (SCMs) are uncommon congenital anomalies that are usually detected in children, but can present in adulthood with signs and symptoms of spinal cord tethering. SCMs rarely occur in association with a lipoma and a defect in the posterior elements. OBSERVATIONS: A 37-year-old man presented with 6 months of new-onset leg weakness, urinary urgency, and reduced sensation in his feet. He developed pain radiating from his low back into his legs, worsened by bending forward and walking. Prior to this presentation, he had not noticed any symptoms. MRI revealed a congenital fusion from L2 to L4 with a type I SCM and a lipoma extending through a dorsal bony defect and terminating at the duplicated spinal cord. A posterior L2-4 lumbar laminectomy was performed to excise the bony spur, resect the spinal cord lipoma, and section the fatty filum terminale. LESSONS: Removal of the bony or fibrous septum and intradural lipoma and sectioning of the fatty filum terminale are required for effective detethering. Careful lipoma debulking, which can be facilitated with a CO2 laser, must be performed while developing surgical planes and minimizing tension on the tethered cord. https://thejns.org/doi/10.3171/CASE25691.