Upper and lower neural tube defects: an alternate hypothesis

• Published in: Journal of medical genetics Vol. 30; no. 10; pp. 849 - 851
• Main Authors: Garabedian, B H, Fraser, F C
• Format: Journal Article
• Language: English
• Published: London BMJ Publishing Group Ltd 01.10.1993; BMJ; BMJ Publishing Group LTD
• Subjects: Anencephaly - embryology; Biological and medical sciences; Chi-Square Distribution; Encephalocele - embryology; family studies; Female; Gestational Age; Humans; Male; Malformations of the nervous system; man; Medical sciences; neural tube defects; Neural Tube Defects - classification; Neural Tube Defects - embryology; Neurology; pathogenesis; Sex Ratio; Spina Bifida Cystica - embryology; Anencephaly; Human; Disease of the spine; Nervous system diseases; Pathogenesis; Diseases of the osteoarticular system; Thorax; Congenital disease; Cerebral disorder; Encephalocele; Spina bifida; Neural tube; Malformation; Lumbosacral
• ISSN: 0022-2593; 1468-6244; 1468-6244
• DOI: 10.1136/jmg.30.10.849

It has been suggested that neural tube defects (NTDs) of the upper type (anencephaly, encephalocele, and thoracic spina bifida) may have a pathogenesis different from those of the lower type (lumbosacral spina bifida), since recurrent cases within a sibship were said always to be concordant with respect to NTD type. Also, spontaneous abortion, additional malformation, and recurrence rate were observed to be higher in the upper group, and there was an excess of females in upper NTD probands. To test this hypothesis, we measured the above variables in upper and lower NTDs in a sample from Quebec. We found less than full concordance (50%) of NTD type in 18 sib pairs. Recurrence rate was not significantly lower in the lower NTD group (5.6 v 5.8%). The other variables were in general agreement with previous studies, inconsistent findings possibly attributable to different NTD population incidences. These findings can be accounted for if upper and lower NTDs share a similar pathogenesis and the embryo is more susceptible during early than late neural tube formation.