The authors describe the case of a 47-year-old woman with a wide (14 × 12-cm) ulcerated lumbosacral myelomeningocele. The patient had sought medical attention for a sudden copious CSF leak from the lumbosacral sac followed by clinical signs of CSF leakage. After admission, neuroradiological assessment (spinal MR and 3D CT imaging) revealed the uncommon finding of a complex malformation characterized by a complete spine duplication originating at the L2-3 level, both hemicords having a separate dural sac. The myelomeningocele sac originated medially at the L-2 level. Surgical repair of the lumbosacral myelomeningocele was performed. The placement of a ventriculoperitoneal shunt became necessary to treat secondary hydrocephalus. After reviewing accredited classifications on spinal cord malformations, the authors believe that, to date, complete duplication and separation of the spine and dural sac seems exceptional, and its report in adulthood appears exceedingly rare.