Clinical Presentation

A 40-year-old woman with progressive leg weakness that has worsened in the last year.

(A) Axial computed tomography (CT) scan of the lumbar spine demonstrates a bony spur in the spinal canal (arrow). (B) Axial T2-weighted image (WI) of the lumbar spine shows two hemicords (arrows) inside the thecal sac. (C) Axial T2-weighted magnetic resonance imaging (MRI) of the lumbar spine demonstrates the septum (arrow) dividing the spinal cord. (D) Sagittal T2WI of the lumbar spine shows a tethered cord. The cystlike lesion (arrow) is where the cord splits (arrowhead).

Differential Diagnosis

• Diastematomyelia (split cord malformation): Diastematomyelia is a focal or complete split of the spinal cord. It is the consequence of a split notochord. It is associated with congenital scoliosis (80% of cases), tethered cord syndrome (75% of cases), and spinal bony anomalies (50% of cases). Intersegmental laminar fusion is pathognomonic.

• Meningocele manqué: Meningocele manqué is characterized by dysraphic dorsal tethered bands (atretic neural tissue) adherent to dura. The following may be seen: diastematomyelia, filum lipoma, dermoid cysts, and neuroenteric cysts. These are difficult to see on imaging studies.