X-Linked Hydrocephalus - 1 - Introduction
Tuesday, October 14, 2008
Kenneth F. Trofatter, Jr., MD, PhD
At the time of her first visit at 12 weeks, there were no abnormalities seen in her baby, but we did suspect that the baby was male. We also knew that the condition may not manifest itself until midtrimester or even later, so follow-up was arranged. When she was seen at 19 weeks, no abnormalities were seen again and the baby was confirmed to be male. We also confirmed that a structure called the cavum septum pellucidum was present in the baby’s brain, a finding that often rules out agenesis of the corpus callosum that frequently accompanies L1CAM-associated, X-linked hydrocephalus syndromes. With these reassuring findings, we were all beginning to feel more optimistic about the pregnancy. To be on the prudent side, however, she was scheduled to return again.
At 25 weeks, the sonographer informed me that everything still looked fine, but she admitted the head had not been well-visualized because of its position in the pelvis. So I took my turn at looking. After a few minutes, I managed to elevate the fetal head, the head suddenly turned, and my sonographer took an audible deep breath as it was very apparent to both of us the baby had developed severe hydrocephalus in the 6 weeks between visits. Both lateral ventricles were symmetrically enlarged, as well as the third ventricle situated between the thalami, findings consistent with acqueductal stenosis typically associated with X-linked hydrocephalus. We all had tears in our eyes as we told our patient that her only son was affected by the condition…
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“X-linked hydrocephalus” is associated with diverse mutations in the L1CAM gene and the locations and the types of the mutations play a significant role on the expression and severity of the syndromes associated with them. Indeed, at least four phenotypes accompany mutations in the L1CAM gene:
X-linked hydrocephalus (HSAS)
MASA syndrome
Complicated spastic paraplegia type 1 (SPG1)
X-linked agenesis of the corpus callosum
The main clinical features of these have been given the acronym CRASH and this has the following components:
Corpus callosum hypoplasia
Retardation
Adducted thumbs
Spastic paraplegia
Hydrocephalus
Expression of these varies both between and within families, so even if a specific mutation is identified, there may be variable expression of the same.
In our next post, we will elaborate on HSAS/MASA syndromes and provide a little more information about the significance of L1CAM mutations in the pathogenesis of these conditions…
Labels: acqueductal stenosis, agenesis of the corpus callosusm, HSAS, L1CAM, MASA, X-linked hydrocephalus
4 Comments:
At Tue Oct 14, 10:35:00 PM 2008,
G.M. said…
Dear Doctor,
I dont know where to write to make sure you get my question.
I have been reading you for weeks, and give the out most value to your opinion. I hope I am lucky enough to get it.
I am 36, and in Canada. I will be 36 when I deliver in february. I am 21.5 weeks pregnant.
I had prenatal screening done, apparently the best on the market. It consists on first trimester nuchal translucency (nasal bone also) and blood test, plus second trimester blood tests including inhibin-a.
Apparently these tests have the best detection rate. (96%).
My nuchal translucency at 13.4 weeks was 1.7, nasal bone seen (2.4mm).
My overall results with all these tests for trisomy 21 were 1/694. (I like to round it out to 1/700, just to feel better!)
I had my 20 weeks routine ultrasound, where they measured the humerus, femur, head, abdomen, and looked at all organs.
I got:"congratulations for a perfectly healthy girl", and also that "this type of ultrasound detects 75% cases of trisomy21.
What I am wondering, from what I am reading from you is : does my 20 weeks ultrasound reduce my risk? And if so, since it is not a "genetic" ultrasound, by what percentage does it reduce my risk?
They DID measure the femur and humerus... And both were a few days ahead of the rest, which is good I think! The rest of her was right on time from the last ultrasound at 13.4 weeks, so she is growing perfectly.
Placenta perfect, liquid perfect, etc....
I am hoping this reduces my risk from 50%, but only if you tell me will I believe it.
My OB does not seem concerned at all. The estimated risk for my age (at the lab I tested at) was 1/238, so she says I did get good results.
Everything is pretty close to 1.00 mom :
HCG: 1,24 MOM
estriol: 1,00 MOM
inhibin-a: 1,31 MOM
I think that what brought my risk up was:
papp-A: 0.66 MOM
AFP: 0.64 MOM (with a reference range of: 0.5-2.5MOM)
Is my risk reduced by this ultrasound and if so, by what percent?
Thank you so, so much if you chose to answer me, you dont know how lucky I would feel!!!!!
G.M.
At Fri Oct 17, 11:41:00 AM 2008,
Kenneth F. Trofatter, Jr., MD, PhD said…
To GM: I left a response under the previous query but sometimes Healthline is a little slow getting comments to me. The simple answer is that a normal high-quality ultrasound by an experienced sonographer at 18-20 weeks reduces your a priori risks (based on the integrated screen) by at least 50% (if not 60-80%). So relax and enjoy the rest of your pregnancy! Dr T
At Sat Oct 18, 12:31:00 AM 2008,
G.M. said…
Dear, dear Doctor,
How lucky are we to have someone of your experience and knowledge answer us!!! I can not even believe it!
And to top it off, you are so gentle and pleasant! I can imagine you smiling when I read you!
Thank you so, so much! Your seal of approval and reading you say:"time to relax and enjoy" meant THE WORLD to me.
Thank you, thank you, thank you!
G.M.
At Tue Oct 21, 06:31:00 PM 2008,
Kenneth F. Trofatter, Jr., MD, PhD said…
To GM: Thank you for the kind remarks. They are very much appreciated. Dr T
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