In the double tubular type, the dural theca consists of two independent subtubes within each of which, there is half portion of the spinal cord and a bony, cartilaginous or fibrous septum in between.

• 双管型特征：硬脊膜为两独立的次管，其内有各自分裂的半脊髓，两硬膜管间隙有骨性、软骨性或纤维性间隔。