6.02 Spina bifida, hydrocephalus, epilepsy Flashcards
What is the first important day in CNS development?
Day 18
Ectoderm thickens to form neural plate. It starts to invaginate to form the neural groove
What is the process of neural tube development called?
Neurulation
What are the 3 layers of the embryo?
Ectoderm, mesoderm, endoderm
When does the cranial neuropore close?
Day 24
Neuropore
The cranial and caudal openings before they fuse
Primary neurulation
Folding down to S2
Secondary neurulation
From S2 to coccyx. Neural tissue extends from the closed neural tube as a solid cord. The neural tube cavity grows into the structure.
Neural tube defects are caused by …
defective closure of the neural tube at the neuropores
Anencephaly
Failure of closure of the cranial neuropore. Skull fails to develop over the brain tissue. Exposed tissue degenerates and child born with most brain missing at birth
Once the neural tube closes, what happens to the cells?
Cell division, proliferation and migration. This happens in the cells closest to the lumen and they migrate “inside out”
When does cell division occur?
Weeks 7-16.
What happens during migration in the cortex?
The radial glia (scaffolding cells) form first and migrate out. Each new cell formed migrates past the existing cells via the radial glia. (“Inside out” formation)
Notochord
Made of mesoderm. Secretes SHH and initiates the formation of the neural plate
Types of spina bifida
Spina bifida occulta, spina bifida cystica meningocele, spina bifida cystica myelomeningocele
When is most brain neuronal proliferation complete?
By 16 weeks
When does cerebellar neuronal proliferation occur?
First postnatal year
What are the 3 original subdivisions of the head region?
Prosencephalon, mesencephalon, rhombencephalon
What are the 5 subdivisions of the head region?
Telencephalon, diencephalon, mesencephalon, metencephalon, myelencephalon
The metencephalon becomes the …
pons and cerebellum
The myelencephalon becomes the …
medulla
Encephalocele
When brain tissue herniates through the cranium, similar to a meningocele
What % of spina bifida cystica is myelomeningocele?
90%
Which is caused by earlier defects, myelomeningocele or meningocele?
Myelomeningocele
What are the consequences of myelomeningocele?
LMN paralysis - bowel and bladder problems. Gait disturbance/LMN paralysis re lower limbs, depending on level of injury.
Chiari type II malformation and possible hydrocephalus on closure
Latex allergies (from being handled with latex from birth)
Learning difficulties (reasons unknown)
What can cause spina bifida?
Anticonvulsants, particularly valproate, carbamazepine.
Prepregnancy obesity
Does giving excess folic acid protect against risks if a person is taking anticonvulsants during pregnancy?
No. Folic acid does not protect against spina bifida risks if a person is taking anticonvulsants
What could a grand mal seizure to do a foetus?
Cause hypoxia (and foetus will die)
Chiari Type II malformation
Where the cerebellum and medulla become wedged in the foramen magnum, blocking off the openings for the CSF to get out
What type of hydrocephalus can Chiari II malformation cause?
Non-communicating/obstructive hydrocephalus
Types of hydrocephalus
High pressure hydrocephalus
Normal pressure hydrocephalus
Low pressure hydrocephalus
CSF contains
Similar osmolarity to plasma
Higher Mg and Cl
Lower glucose and Ca
