Focus on Prenatal Diagnosis
at the JSF & RCD Conference 2004
Dr. Ian Glass from the University of Washington (UW) in Seattle
presented an overview of prenatal diagnosis and reproductive
options for couples who have had a child with Joubert syndrome
(JS). The purpose of prenatal diagnosis is to provide
information to couples so that they can make informed
reproductive decisions ranging from termination of an affected
fetus to preparation for the birth of an affected child. Couples
who have had a child with JS have a one in four (25%) chance of
having another affected child with each and every pregnancy.
Currently, there is no definitive test to diagnose JS before
birth; however, prenatal ultrasound and MRI hold the most
promise in the short term. Advances in the genetics of JS may
allow for DNA-based testing in the future. Of note, three genes
associated with JS have been identified. Dr. Glass summarized
the broad variety of reproductive options available for couples.
Based on current experience with at-risk pregnancies, they
proposed initial guidelines for monitoring at risk pregnancies.
Our group's experience with this approach has been published in
the medical literature (Doherty et al., 2005).
Genetic testing should be
strongly considered, especially if the first affected child has
already tested positive. It is important that the imaging
studies be reviewed by a physician experienced in the diagnosis
of posterior fossa malformations, and that couples receive
genetic counseling. Drs. Glass and Doherty would be happy to
help couples to obtain optimal information, and they are
interested in reviewing prenatal imaging studies from all
pregnancies of couples who have had an affected fetus or child.
The systematic comparison of prenatal imaging from affected and
unaffected pregnancies will improve understanding of the early
events in JS, and will improve the quality of prenatal diagnosis
in the future. Interested families should contact Drs. Glass and
Doherty through Dana
Knutzen, UW Joubert Syndrome Center genetic counselor.
|
Gestational
age |
Type of
Evaluation |
Details of
evaluation |
|
11-12 wk |
US |
Dates, nuchal
translucency measurement |
|
16 wk |
US |
Full anatomic
survey, close examination of the posterior fossa,
cisterna magna measurement, evaluation for
encephalocele, polydactyly, kidney abnormalities |
|
18 wk |
US |
Vermis
measurements (height, diameter), reexamination
of posterior fossa, cisterna magna measurement,
reevaluation for encephalocele, polydactyly,
kidney abnormalities |
|
20 wk |
US |
Vermis
measurements (height, diameter), reexamination
of posterior fossa, cisterna magna measurement,
reevaluation for encephalocele, polydactyly,
kidney abnormalities |
|
20-22 wk |
MRI |
Evaluation for
supratentorial abnormalities and confirmation of
posterior fossa findings from US |
The slides from the prenatal
diagnosis talk can be viewed at:
http://depts.washington.edu/joubert/prenatald.html
Dr. I Glass and
Dr. D Doherty
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