Evaluation of the cranial base in amnion rupture sequence involving the anterior neural tube: implications regarding recurrence risk.
BACKGROUND
Amniotic bands can cause disruption of the cranial end of the developing fetus, leading in some cases to a neural tube closure defect. Although recurrence for unaffected parents of an affected child with a defect in which the neural tube closed normally but was subsequently disrupted by amniotic bands is negligible; for a primary defect in closure of the neural tube to which amnion has subsequently adhered, recurrence risk is 1.7%. In that primary defects of neural tube closure are characterized by typical abnormalities of the base of the skull, evaluation of the cranial base in such fetuses provides an approach for making a distinction between these 2 mechanisms. This distinction has implications regarding recurrence risk.


METHODS
The skull base of 2 fetuses with amnion rupture sequence involving the cranial end of the neural tube were compared to that of 1 fetus with anencephaly as well as that of a structurally normal fetus. The skulls were cleaned, fixed in 10% formalin, recleaned, and then exposed to 10% KOH solution. After washing and recleaning, the skulls were exposed to hydrogen peroxide for bleaching and photography.


RESULTS
Despite involvement of the anterior neural tube in both fetuses with amnion rupture sequence, in Case 3 the cranial base was normal while in Case 4 the cranial base was similar to that seen in anencephaly.


CONCLUSIONS
This technique provides a method for determining the developmental pathogenesis of anterior neural tube defects in cases of amnion rupture sequence. As such, it provides information that can be used to counsel parents of affected children with respect to recurrence risk.
Jones
Kenneth Lyons
KL
Department of Pediatrics, University of California San Diego, School of Medicine, La Jolla, California, USA. klyons@ucsd.edu
Robinson
Luther K
LK
Benirschke
Kurt
K
D000650:Amnion / Q000473:pathology*; D006801:Humans; D009436:Neural Tube Defects / Q000175:diagnosis* / Q000473:pathology*; D012008:Recurrence; D012307:Risk Factors; D019291:Skull Base / Q000473:pathology*