Duplicated filum terminale in the absence of split cord malformation: A potential cause of failed detethering procedures

Introduction: A duplicated filum terminale appears to be a rare finding in the absence of a split cord malformation. Herein, we discuss this finding and its potential dysembryology. Case reports: We report two cases of duplicated filum terminale without split cord malformation. The first case presented as an incidental finding with thickened filum terminale. At time of surgery, a thickened filum was resected and a smaller size filum was transected and both were confirmed with pathologic examination. The second case presented with a lumbar skin hemangioma. Screening MRI showed a duplicated filum terminale with fat signal in both structures. Pathology also confirmed the diagnosis of two fila terminalia. Conclusions: The neurosurgeon should consider the possibility of two fila terminalia during operation to transect a single filum for tethered spinal cord.