Split cervical spinal cord with Klippel-Feil syndrome: seven cases.

We report seven cases of rare high cervical split spinal cord associated with extensive vertebral fusions (Klippel-Feil anomaly). In light of previous embryological theories and recent research findings we attempt to explain the origin of split cord and vertebral fusions. Two distinctly separate mechanisms are suggested for the development of split cords observed in our cases: a midline lesion bisecting the neuroepithelium and the notochordal plate could be responsible for complete splitting of the cervical cord with anterior bony defect while a localized disturbance of cervical neural tube closure would account for cases with partial dorsal splitting of the cord with posterior vertebral defect. Vertebral fusion anomalies are likely to be associated with disturbance of Pax-1 gene expression in the developing vertebral column. We confirm with our cases the frequent association of failure of normal segmentation and split cord in the cervical region. Clinically, only three patients had neurological deficit which was mild and has remained stable, and they had no radiological evidence of tethering; the minimal disproportionate growth of the cord and spine and the rarity of a bony spur in the cervical region are the likely reasons. A conservative policy was therefore pursued in these cases with careful long-term follow-up.