Fetal Central Nervous System pt 1 Flashcards
______ begins with the formation of the neural plate, followed by an neural folds, and ultimate fusion and closure by six menstrual weeks
Neurulation
the neural tubes closes from the center temporarily leaving both ends open, they should be closed by ______ menstrual weeks, if not then it is a neural tube defect
six
how do you evaluate the fetal spine?
in transverse plane you must run the spine from the base of the skull to the coccyx
in sagittal plane asses the normal curvatures of the spine and the sacral caudal tapering
what 3 centers of ossification must you identify?
the round center (the vertebral body) and two centers of ossification posterior to the round (in which point posteriorly) they are posterior elements to the spine or the lamina
what structures must be documented of the fetal brian?
cavum septum pellucidum and lateral ventricles
this insures an in tact corpus callosum of the fetas and is evidenced by two parallel lines in the anterior aspect of the fetal cranium with a central lucency, these are at the midline
cavum septum pellucidum
these are filled with echogenic Choroid plexus
lateral ventricles
how do you measure the lateral ventricles?
at the atrium, or largest part of the ventricles, at the level of the thalami. Normal measurement is less than 10mm Do Not measure from the midline echogenic falx (this is a pitfall)
how is biparietal diameter (BPD) taken?
from outer side of the parietal bone in the near field to inner aspect of the parietal bone in the far field
how is the head circumference measured?
using ellipse button, taken at the level of the paired Thalami which look like a walnut
then angle inferiorly to see the cerebellum, cisterna magna, and nuchal fold in the posterior cranium
where is the cerebellum measured and what can it tell us?
at its widest point
it closely dates the pregnancy up until the third trimester
the ______ is a space at the midline posterior to the cerebellum and anterior to the echogenic fetal skull
cisterna magna
the measurement is taken from anterior to posterior
normal values are 2-12 mm
when and how is the nuchal fold (skin at the nape of the neck) measured?
it is measured in fetuses who are under 24 weeks gestation only!, the measurement is taken from the outer aspect of the echogenic skull to the edge of the skin
what is the normal value of the nuchal fold and what makes it thickened?
normal values are less than 6 mm, will be thickened in cases of chromosomal abnormalities like turners syndrome
these occur anywhere along the cranium or along the spine and will allow cerebrospinal fluid of the fetus to escape into the amniotic fluid, which results in elevation of amniotic fluid and in maternal serum levels of Alpha fetoprotein
neural tube defect
routine prenatal testing that reveals an elevated maternal serum ______ is an indication for targeted ultrasound to rule out a fetal neural tube defect
alpha-fetoprotein
______ can detect acetyl cholinesterase, which is elevated in the amniotic fluid when there is a neural tube defect
amniocentesis
______ is a congenital absence of the cerebral hemispheres and the cranial vault, occurs approximately one of every 1000 births
anencephaly
anencephaly occurs with failure of the neural tube to close by ______ days of gestation, it is characterized as an open defect which is covered by an angiomatous stroma rather than covered by ______ and ______ (the brainstem and the bony skull base is present)
24, skin and bone
what is anencephaly associated with?
polyhydramnios due to inefficient fetal swallowing and may also be associated with spina bifida
what is the US findings of anencephaly?
- absence of the fetal cranial vault (bones) and cerebral hemispheres
- the face and orbits are present and look very prominent (frog face)
- polyhydromnios will be present in 40-50% of cases
______ (also called exencephally) is a developmental abnormality in which the cranium is partially or completely absent but has development of abnormal brain tissue within, it is lethal and is also associated with elevated levels of maternal serum alpha-fatoprotein
Acrania
What are the sonographic findings of acrania?
No echogenic cranium with the presence of a large amount of brain tissue (seen at 12 weeks gestation, hard to see at 16 weeks d/t lack of an ossified cranium)
*an important note is that other bones of the fetus will be present
______ (also called cephalocele) is the herniation of the brain and meninges (covering of the brain and spinal cord) through a cranial defect, prognosis depends on how much brain is involved and other associations
Encephaloceles