Chapter 60 Fetal Neural Axis Flashcards
CNS arises from the ectodermal neural plate around _____
18 days gestation
Cephalic neural plate develops into the
forebrain
the caudal end forms the
spinal cord
the forebrain develops into the
Prosencephalon
the mesencephalon develops into the
midbrain
the rhombencephalon develops into the
hindbrain
by the end of the 3rd week, the cephalic end of the neural tube bends into a ____ shape
c-shape
in the ____ week, the neural tube bends again
5th
The prosenceohalon divides into the
Telencephalon and diencephalon
Telencephalon becomes the
Cerebral hemispheres
Diencephalon becomes the
Thalamus
Rhombencephalon divides into the
Metencephalon and mylencephalon
Metencephalon becomes
Cerebellum and pons
Mylencephalon becomes
Medulla
Neural function begins at
6 weeks gestation
Between _____ the fetus can grip objects and is capable of weak respiratory movements
4-5 months
Fetus displays sucking reflux at ____
6 months
Most common neural tube defect
Anencephaly
Absence of brain and skull
Anencephaly aka aprosencephaly/atencephaly
Risk of anencephaly can be reduced by 50-70% with use of ______ supplements beginning 1 month before pregnancy
Folic acid
Caused by failure of the neural tube at the cranial end. Resulting in absent cranial vault, complete/partial absence of forebrain
Anencephaly
Prenatal diagnosis of anencephaly is often made with sonography, following a lab value of ___
Elevated AFP
Causes for anencephaly:
Diabetes, Meckel-Gruber syndrome
Sonographic findings of anencephaly:
Bulging fetal orbits—frog face appearance
Absence of skull
Acrania
Acrania is also known as
Exencephaly
Absence of cranial bones with the cerebral hemispheres still there(although abnormal)
Acrania
Acrania usually progresses to anencephaly because:
Brain slowly degenerates from exposure to amniotic fluid
How to distinguish acrania from anencephaly:
Presence of significant brain tissue and lack of frog-face appearance indicated acrania
Neural tube defect in which meninges alone or meninges and brain herniate through a defect in the skull
Cephalocele
Herniation of meninges AND brain through defect
Encephalocele
Herniation of only meninges through defect
Cranial meningocele
Cephalocele more commonly involves the _____ bone
Occipital
Sonographic features of cephalocele:
Extracranial mass
Ventriculomegaly
Autosomal recessive disorder characterized by encephalocele, polydactyl, polycystic kidney disease
Meckel-Gruber syndrome
Cephalocele may be confused with
Cystic hygroma
Chromosomal anomalies and syndromes associated with cephaloceles
Trisomy 13
Meckel-Gruber syndrome
Wide range of defects that result from failure of neural tube to close
Spina bifida
Spina bifida most commonly occurs along the ____ and ____ region
Lumbar and sacral
The term spina bifida means
There is an cleft/opening in the spine
Spina bifida occulta is extremely difficult to detect if
Defect is covered by skin
AFP is normal
Spinal opening covered in skin, commonly with a tuft of hair
Spina Bifida Occulta
Sounds bifida term used when defect only involves the protrusion of meninges
Meningocele
Sounds bifida term used when both meninges & neural elements protrude through defect(more common)
Meningomyelocele
Sounds bifida term used when defect is very large and severe
Rashcischisis
Raschischisis is associated with increased
AFP