title: Unjoined primary and secondary neural tubes: junctional neural tube defect, a new form of spinal dysraphism caused by disturbance of junctional neurulation.
abstract: BACKGROUND
  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.
  
  
  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.
  
  
  CONCLUSIONS
  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: Paediatric Neurosurgery, Regional Centre of Paediatric Neurosurgery, Kaiser Foundation Hospitals of Northern California, Oakland, CA, USA.|Paediatric Neurosurgery, Altona Children's Hospital, Hamburg, Germany.
authors: Sebastian
authors: S
authors: Eibach
authors: Neuropathology, Regional Centre of Paediatric Neurosurgery, Kaiser Foundation Hospitals of Northern California, Oakland, CA, USA.|Adjunct Faculty of Neuropathology, Stanford University School of Medicine, Stanford, CA, USA.
authors: Greg
authors: G
authors: Moes
authors: Intraoperative Neurophysiology, Regional Centre of Paediatric Neurosurgery, Kaiser Foundation Hospitals of Northern California, Oakland, CA, USA.
authors: Yong Jin
authors: YJ
authors: Hou
authors: Paediatric Neurosurgery, Regional Centre of Paediatric Neurosurgery, Kaiser Foundation Hospitals of Northern California, Oakland, CA, USA.
authors: John
authors: J
authors: Zovickian
authors: Regional Centre of Paediatric Neurosurgery, Kaiser Foundation Hospitals of Northern California, Oakland, CA, USA. pangtv@aol.com.|Paediatric Neurosurgery, University of California, Davis, CA, USA. pangtv@aol.com.|Great Ormond Street Hospital for Children, NHS Trust, London, UK. pangtv@aol.com.|Department of Paediatric Neurosurgery, Kaiser Permanente Medical Centre, Third Floor, Suite 39, 3600 Broadway, Oakland, CA, 94611, USA. pangtv@aol.com.
authors: Dachling
authors: D
authors: Pang
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D004576:Electromyography; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D016343:Monitoring, Intraoperative; D054259:Neural Tube / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery; D009436:Neural Tube Defects / Q000145:classification* / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000601:surgery; D009460:Neurologic Examination; D054261:Neurulation / Q000502:physiology*; D012007:Rectum / Q000473:pathology / Q000503:physiopathology; D012445:Sacrococcygeal Region / Q000000981:diagnostic imaging / Q000473:pathology; D012867:Skin / Q000473:pathology; D013116:Spinal Cord / Q000000981:diagnostic imaging; D016135:Spinal Dysraphism / Q000145:classification / Q000175:diagnosis / Q000503:physiopathology
keywords: Isolated conus medullaris; Junctional neural tube defect; Junctional neurulation; Primary and secondary neurulation; Spinal dysraphism