title: Normal ascent of the conus medullaris: a post-mortem foetal MRI study.
abstract: OBJECTIVE
  The position of the conus medullaris is considered abnormal if it ends below lumbar vertebrae three (L3) at birth. We used magnetic resonance imaging (MRI) to measure the position of the conus in post-mortem foetuses, to investigate the timing of normal ascent.
  
  
  METHODS
  The position of the conus in 84 post-mortem foetuses (mean gestation 26.3 weeks; range 14-41 weeks) was identified using 3D MRI datasets. A numerical scale was used for vertebral levels, from 1 (S2) to 15 (T12).
  
  
  RESULTS
  There was significant ascent of the conus medullaris with increasing gestation. At 20 weeks gestation, an estimated 84.2% (95% confidence interval (CI): 72.9, 93.2%) of foetuses have a conus position of L4/5 or higher, but only 22.8% (95% CI 11.7, 34.9%) at L3 or higher. By 26 weeks, an estimated 50.7% (95% CI 34.1, 67.5) will have reached L3, and 94.8% (95% CI 87.0, 98.5%) reach L3 by 40 weeks.
  
  
  CONCLUSIONS
  There is regular ascent of the conus throughout foetal life. Although growth for each individual foetus may be non-linear, most foetuses have a conus level within the normal adult range by 33 weeks gestation.
authors.affiliation: Great Ormond Street Hospital for Children, London, WC1N 3JH, UK. owen.arthurs@gosh.nhs.uk
authors.forename: O J
authors.initials: OJ
authors.lastname: Arthurs
authors.forename: S
authors.initials: S
authors.lastname: Thayyil
authors.forename: A
authors.initials: A
authors.lastname: Wade
authors.forename: W K
authors.initials: WK
authors.lastname: Chong
authors.forename: N J
authors.initials: NJ
authors.lastname: Sebire
authors.forename: A M
authors.initials: AM
authors.lastname: Taylor
mesh_terms: D001344:Autopsy; D047109:Fetal Development; D005333:Fetus / Q000033:anatomy & histology*; D005865:Gestational Age; D006801:Humans; D016015:Logistic Models; D008279:Magnetic Resonance Imaging; D011446:Prospective Studies; D012016:Reference Values; D013116:Spinal Cord / Q000196:embryology*