A 17-month-old international adoptee presented to a neurosurgery clinic with a membrane-covered sac emanating from a lower thoracic spinal defect. The child had normal function of the right lower extremity and minimal movement of the left lower extremity with a left clubfoot. The asymmetry of findings suggested an underlying split- cord malformation, which was confirmed by spinal MRI (Fig. 1) and CT (Fig. 2). These scans showed a right hemicord (white arrow) separated by a bony spur (dashed arrow) from the left hemicord myelomeningocele (asterisk). Brain MRI showed typical Chiari II features.
The split-cord malformation (or diastematomyelia) represents a sagittal cleft of the spinal cord into two hemicords that can be enclosed in single or separate dural sheaths and separated by a fibrous or osteocartilaginous septum, respectively . Up to 85% have associated spinal anomalies, the most common being low-lying conus medullaris and thickened filum terminale . A myelomeningocele involving one of the hemicords (i.e. hemimyelomeningocele) is seen in up to 41% of cases .