Developmental disorders Flashcards
At what stage of development does neurulation occur?
The closure of the neural tube occurs at the 3rd and 4th week of gestation
prosencephalic diverticulation occurs at what stage of gestation?
the division inton the 5 vesicles occurs at the 5th week, forming primitive cerebral hemispheres, thalamus, cerebellum, medulla etc.
What is histogenesis?
The lining of the neural tube undergoes differentiation and progression into a ependymal layer and a germinal matrix zone. From here, young neurons travel along radial glia and migrate into the forming vesicles
What is the most common CNS malformation? What events result in its development?
dysraphias/neural tube defects are a malformation that occurs after defective neurulation during the 3rd and 4th weeks of gestation.
What is the most severe form of neural tube defect?
anencephaly:
absence of all/part brain with incomplete skull.
Incompatible with life
What neural tube defect is characterised by a midline skull defect that results in brain herniation?
encephalocele. Small ones are surgically fixed whereas large ones are incompatible with life.
What is a myelocele? What are the clinical consequences?
Myelocele/meningomyelocele- spinal column defect where protrusions of spinal cord/meninges occurs.
Higher risk of infection and bowel/bladder/lower extremity with some herniations.
How is meningocele different from a myelocele?
Only herniation of meninges, whereas myelocele has spinal cord herniations..
Spinia bifida occulta is classically viewed as?
hair tuft/skin covering over an incompletely fused vertebral arch.
What malformation results from defective prosencephalic diverticulation/ incomplete separation of cerebral hemispheres across midline?
holoprosencephaly, malformation begins around 5th week of gestation.
What is the presentation of pt with holoprosencephaly?
Midline facial structure abnormalities, cleft palate/lips, incomplete nose, and cyclopia (severe).
Often unilateral brain hemisphere or
mild case of 2 hemispheres w/o divison/1 ventricle/no corpus callosum
What CNS malformation results in a lack of olfactory nerve?
Arrhinencephaly, very mild holoprosencephaly and can be seen in nml individuals
What causes holoprosecephaly?
Toxins: maternal diabetes, toxoplasmosis, syphillis, rubella
Genetics: trisomy 13 and 18
mutations in SHH- sonic hedgehog
What are some common intrinsic causes of congenital hydrocephalus?
Ventricular system malformations:
aqueductal atresia/stenosis
arnold-chiari malformation
What are some extrinsic disruptions leading to hydrocephalus?
Aqueduct gliosis- organizing hemorrhage/infection
meningitis- subarachnoid space obliteration
dural sinus thrombosis
intraventricular hemorrhage
