Holoprosencephaly and Cephalocentesis: an Overview

This is a very brief discussion of Holoprosencephaly, and a similarly brief discussion on cephalocentesis, and it’s role in OBGYN. Both holoprosencephaly and cephalocentesis could be considered disturbing, if your sensibilities are easily offended, don’t read this post.

 It’s hard to call Holoprosencephaly one defect. It’s a spectrum of congenital defects in midline structures of the brain and face. That means that it effects structures that form on the line you’d get if you split your body into left and right halves.

It can be caused by almost anything, sometimes it’s genetic, or chromosomal. It is often caused by Trisomy 13. It can be associated with environmental factors, material overdose on salicylates, maternal diabetes, infection with a specific virus (CMV) while in the womb.

What I found most suprising while reading about holoprosencephaly is how wide a spectrum we’re talking about. In it’s mildest form, holoprosencephaly can be just having one midline incisor, instead of 2, on either side of the midline. In it’s more severe forms, it is not compatible with life. Defects can include cyclopia (having one, midline eye), having no nose, having a tubelike structure called a proboscis instead of a  nose. More importantly, and devastatingly, it can have midline brain malformations, the most severe being called alobar holoprosencephaly – basically not having much brain over the brainstem. The brainstem is the part of the brain that controls many automatic functions – unconcious breathing is among those functions. Some of these patients develop hydrocephalus, and have increased skull size.

About 10 percent of patients will have severe brain malformations, without other defects. In this case the infant will have severe neurologic issues. Generally, they do not live long, even if they outwardly look normal.

With very severe holoprosencephaly, many children are stillborn. Those that are born often don’t live long. A day, a few days, a week would be long.

Cephalocentesis is a procedure used to drain fluid from the skull of a fetus with hydrocephalus. It is a very rarely done procedure. Chasen suggests that it should be offered to mothers when the expectation is that the child will be stillborn, or will not survive very long outside the womb, and a vaginal delivery could be attempted if the fetal skull was smaller. 

The procedure uses ultrasound guidance to put a needle in the uterus, much like amniocentesis. Instead of withdrawing amniotic fluid, the needle is further inserted, into the CSF space, to drain excess fluid. The idea is to make the skull small enough to allow a vaginal delivery. In doing so, the hope is to prevent the mother from having to undergo a C-section, which is significantly more dangerous to the mother. The procedure shouldn’t be used if the fetus could likely survive outside the womb long term – it’s considered a destructive procedure.

 I hope that this post answers a few of the medical questions related to my other post from tonight, Bittersweet. After reading either or both posts, please post any scientific questions in the comments of this post.

Chasen, S. (2001). The role of cephalocentesis in modern obstetrics American Journal of Obstetrics and Gynecology, 185(3), 734-736 DOI: 10.1067/mob.2001.117487

Olsen, C., Hughes, J., Youngblood, L., & Sharpe-Stimac, M. (1997). Epidemiology of holoprosencephaly and phenotypic characteristics of affected children: New York state, 1984–1989 American Journal of Medical Genetics, 73(2), 217-226 DOI: 10.1002/(SICI)1096-8628(19971212)73:23.0.CO;2-S

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