Sebastian Eibach1,2, Greg Moes3,4, Yong Jin Hou5, John Zovickian1, Dachling Pang6,7,8,9. 1. Paediatric Neurosurgery, Regional Centre of Paediatric Neurosurgery, Kaiser Foundation Hospitals of Northern California, Oakland, CA, USA. 2. Paediatric Neurosurgery, Altona Children's Hospital, Hamburg, Germany. 3. Neuropathology, Regional Centre of Paediatric Neurosurgery, Kaiser Foundation Hospitals of Northern California, Oakland, CA, USA. 4. Adjunct Faculty of Neuropathology, Stanford University School of Medicine, Stanford, CA, USA. 5. Intraoperative Neurophysiology, Regional Centre of Paediatric Neurosurgery, Kaiser Foundation Hospitals of Northern California, Oakland, CA, USA. 6. Regional Centre of Paediatric Neurosurgery, Kaiser Foundation Hospitals of Northern California, Oakland, CA, USA. pangtv@aol.com. 7. Paediatric Neurosurgery, University of California, Davis, CA, USA. pangtv@aol.com. 8. Great Ormond Street Hospital for Children, NHS Trust, London, UK. pangtv@aol.com. 9. Department of Paediatric Neurosurgery, Kaiser Permanente Medical Centre, Third Floor, Suite 39, 3600 Broadway, Oakland, CA, 94611, USA. pangtv@aol.com.
Abstract
INTRODUCTION: Primary and secondary neurulation are the two known processes that form the central neuraxis of vertebrates. Human phenotypes of neural tube defects (NTDs) mostly fall into two corresponding categories consistent with the two types of developmental sequence: primary NTD features an open skin defect, an exposed, unclosed neural plate (hence an open neural tube defect, or ONTD), and an unformed or poorly formed secondary neural tube, and secondary NTD with no skin abnormality (hence a closed NTD) and a malformed conus caudal to a well-developed primary neural tube. METHODS AND RESULTS: We encountered three cases of a previously unrecorded form of spinal dysraphism in which the primary and secondary neural tubes are individually formed but are physically separated far apart and functionally disconnected from each other. One patient was operated on, in whom both the lumbosacral spinal cord from primary neurulation and the conus from secondary neurulation are each anatomically complete and endowed with functioning segmental motor roots tested by intraoperative triggered electromyography and direct spinal cord stimulation. The remarkable feature is that the two neural tubes are unjoined except by a functionally inert, probably non-neural band. CONCLUSION: The developmental error of this peculiar malformation probably occurs during the critical transition between the end of primary and the beginning of secondary neurulation, in a stage aptly called junctional neurulation. We describe the current knowledge concerning junctional neurulation and speculate on the embryogenesis of this new class of spinal dysraphism, which we call junctional neural tube defect.
INTRODUCTION: Primary and secondary neurulation are the two known processes that form the central neuraxis of vertebrates. Human phenotypes of neural tube defects (NTDs) mostly fall into two corresponding categories consistent with the two types of developmental sequence: primary NTD features an open skin defect, an exposed, unclosed neural plate (hence an open neural tube defect, or ONTD), and an unformed or poorly formed secondary neural tube, and secondary NTD with no skin abnormality (hence a closed NTD) and a malformed conus caudal to a well-developed primary neural tube. METHODS AND RESULTS: We encountered three cases of a previously unrecorded form of spinal dysraphism in which the primary and secondary neural tubes are individually formed but are physically separated far apart and functionally disconnected from each other. One patient was operated on, in whom both the lumbosacral spinal cord from primary neurulation and the conus from secondary neurulation are each anatomically complete and endowed with functioning segmental motor roots tested by intraoperative triggered electromyography and direct spinal cord stimulation. The remarkable feature is that the two neural tubes are unjoined except by a functionally inert, probably non-neural band. CONCLUSION: The developmental error of this peculiar malformation probably occurs during the critical transition between the end of primary and the beginning of secondary neurulation, in a stage aptly called junctional neurulation. We describe the current knowledge concerning junctional neurulation and speculate on the embryogenesis of this new class of spinal dysraphism, which we call junctional neural tube defect.
Authors: Cameron Schmidt; Vlad Voin; Joe Iwanaga; Fernando Alonso; Rod J Oskouian; Nitsa Topale; R Shane Tubbs; W Jerry Oakes Journal: Childs Nerv Syst Date: 2017-02-28 Impact factor: 1.475