ABNORMAL DEVELOPMENT OF THE CNS Flashcards
Abnormal Development of the CNS
Timing of injury/insult during embryogenesis (week 3-
8) most detrimental
* During gestational development (between the 17th
and 30th day after conception), the neural tube forms
in the embryo and then closes
* Defective closure of the neural tube results in neural
tube defect (NTD)
Neural Tube Defects (NTDs)
Severe birth defects of the spine, spinal cord, and the
brain
* Occurs in about 3,000 pregnancies each year in the
United States
Neural Tube Development
(A) progression of neural tube closure
* (B) cross sections indicate closed (red) and opened (green) areas of
neural tube
* (C) Region-specific NTD (Neural Tube Defect)
anencephaly
neural tube fails to close during the
first few weeks of embryonic development
* Cerebral hemisphere(s) and cerebellum are
congenitally missing, reduced, or attached to the base
of skull
* 1/1000 deliveries
* More common in females
* Absence of optic nerve but eyes appear normal
* Survival 3-48 hours after delivery
Spina Bifida
neural tube fails to
close completely and remains an open channel
* Bones of the spine (vertebrae) do not close over the
spinal cord
* most commonly affects the spine in the lower back
* Can range from mild to severe, depending on the type of
defect, size, location and complications
Hydrocephalus
Ventricles enlarge because
expressive production of CSF and/or obstruction of
CSF drainage pathways
* Enlarged head, prominent forehead
* Brain atrophy
* Mental deficiency
* Convulsion
Microcephaly
Brain, skull
(calvaria), face are small
* MR/intellectual disabilities
* Environmental disturbances, genetic,
radiation during CNS dv/mt possible causes
Holoprosencephaly
Incomplete
development of midline neural
structures
Lissencephaly
Sulci and
gyri do not develop and brain appears
smooth
(left image)
