Neuroembryology

Question 1

Neuroepithelium:
What kind of cells is the neural groove lined with? To where do they extend?
What types of cells do neuroepithelium give rise to (in chronological order)?
What kind of cells do those give rise to?

Answer 1

Thick pseudostratified epithelium - extend over entire thickness of wall
Primitive nerve cells (neuroblasts) - neurons
Gliablasts - glial cells in CNS (except microglia)

Question 2

What controls induction of dorsal-ventral patterns of differentiation?
Name two contributing proteins to the above process.

Answer 2

Bone morphogenic protein (BMP)– sensory, secreted by ectoderm underlying neural tube. located roof plate

Sonic Hedgehog protein (SHH)– motor, secreted by notochord. located in floor plate

Question 3

Secondary brain development:
What does the prosencephalon develop into?
What does the mesencephalon develop into?
What does the rhombencephalon develop into?

Answer 3

Prosencephalon - Telencephalon (hemispheres) and Diencephalon (thalami, hypothalamus)
Mesencephalon - Mesencephalon (aqueduct)
Rhombencephalon - Metencephalon (pons and cerebellum) and Myencephalon (medulla)

Question 4

What is anencephaly?
What is the result?
Are there any associations?

Answer 4

Failure of closure of cephalic part of neural tube
Lack of vault formation and brain tissue degeneration
Maternal diabetes type I

Question 5

Spina Bifida Occulta:
Cause
Prevalence
Presentation

Answer 5

Lack of fusion of vertebral arches
10% of otherwise normal people
Patch of hair in lumbrosacral region (defect covered by skin and usually does not involve underlying neural tissue)

Question 6

Spina Bifida Cystica:
Cause
Basic Presentations

Answer 6

More extensive lack of fusion of vertebral arches

Neural tissue or meninges protrude through defect and skin to form cyst-like sac, neurological defects, hydrocephaly

Question 7

What is hydrocephaly?

Answer 7

Cutting off of CSF flow due to tethered nature of spinal cord to spinal column

Question 8

What is a meningocele?

Answer 8

Only fluid-filled meninges protrude through spina bifida cystic defect

Question 9

What is a meningomyelocele?

Answer 9

Neural tissue protrudes through spina bifida cystica defect

Question 10

Myeloschisis or Rachischisis:
Cause
Presentation

Answer 10

Failure of neural tube closure occurring in spinal or brain regions of neural tube
Exposure of necrotic neural tube

Question 11

Diagnosis of Spina Bifida Cystica:
Serum tests
Other diagnostic tests
Corrective surgery

Answer 11

Examine alpha-fetoprotein levels in maternal serum and amniotic fluid
Ultrasound around week 12
Prenatally around week 28 - expose fetus through cesarean, repair defect, place fetus back inside

Question 12

Holoprosencephaly (HPE):
General description
Severe cases
Cause

Answer 12

Spectrum of abnormalities causing loss of midline structures
Lateral ventricles merge into ingle telencephalic vesicle (alobar HPE)
Mutations in SHH, cholesterol synthesis (SLOS), fetal alcohol syndrome