Primary tethered cord syndrome: a new hypothesis of its origin.

Primary tethered cord syndrome is defined as low placement of the spinal cord and thickened filum terminale with associated anomalies. This definition excludes anomalies concomitant with overt myelomeningocele and spinal cord tethering secondary to myelomeningocele repair. Embryologically, the primary tethered cord syndrome is an entirely different entity from overt myelomeningocele and associated Arnold-Chiari type II malformation, but its origins have not been satisfactorily explained. The authors postulate that primary tethered cord syndrome is a manifestation of local dysmorphogenesis of all three germ layers at the lumbosacral area, possibly triggered by a hemorrhagic, inflammatory, or some other local lesion occurring in embryogenesis.