Neuro Embryology EC

Question 1

Describe the development of the neural tube

Answer 1

Notochord induces overlying ectoderm to differentiate into neuroectoderm and form the neural plate
Neural plate gives rise to the neural tube and neural crest cells
Notochord becomes nucleus pulposus of the intervertebral disc in adults

Question 2

What are the Alar and Basal plates?

Answer 2

Alar plate=Dorsal/Sensory

Basal plate=Ventral/Motor

Question 3

What are the three primary vesicles of the developing brain?

Answer 3

Prosencephalon (forebrain)
Mesencephalon (midbrain)
Rhombencephalon (hindbrain)

Question 4

To what structures does the prosencephalon give rise?

Answer 4

Telencephalon –> Cerebral hemispheres/Lateral ventricles

Diencephalon –> Thalamus/Third ventricle

Question 5

To what structures does the mesencephalon give rise?

Answer 5

Mesencephalon–> Midbrain/Cerebral aqueduct

Question 6

To what structures does the rhombencephalon give rise?

Answer 6

Metencephalon–> Pons and Cerebellum/upper 4th ventricle

Myelencephalon–> Medulla/lower 4th ventricle

Question 7

What is the mechanism of neural tube defects?

Answer 7

Neuropores fail to fuse (4th week) –> persistent connection between amniotic cavity and spinal canal.

Question 8

Failure of bony spinal canal to close but no structural herniation. Seen at lower vertebral levels. Dura intact and tuft of hair or skin dimple observed at level of bony defect.

Answer 8

Spina bifida occulta

Question 9

Meninges (but not spinal cord) herniate through spinal canal defect

Answer 9

Meningocele

Question 10

Meninges and spinal cord herniate through spinal canal defect

Answer 10

Meningomyelocele

Question 11

Malformation of anterior neural tube resulting in no forebrain, open calvarium (frog-like appearance). Clinical findings: Increased AFP, polyhydramnios,

Answer 11

Anencephaly

Associated with maternal diabetes
Maternal folate supplementation decreases risk

Question 12

Failure of left and right hemispheres to separate; usually occurs during weeks 5-6. Complex multifactorial etiology that may be related to Shh pathway. Moderate form has cleft lip/palate, most severe form results in cyclopia.

Answer 12

Holoprosencephaly

Question 13

Significant cerebellar tonsillar and vermian herniation through foramen magnum with aqueductal stenosis and hydrocephalus. Often presents with thoraco-lumbar myelomeningocele and paralysis below defect.

Answer 13

Chiari II malformation

Question 14

Agenesis of cerebellar vermis with cystic enlargement of 4th ventricle. Associated with hydrocephalus and spina bifida

Answer 14

Dandy-Walker malformation

Question 15

Cystic enlargement of central canal of spinal cord. Results in “cape-like” bilateral loss of P/T in upper extremities (fine touch preserved).

Answer 15

Syringomyelia

Associated with Chiari I

Question 16

Taste and sensation in anterior 2/3 of tongue

Answer 16

VII taste

V3 sensation

Question 17

Taste and sensation in posterior 1/3 of tongue

Answer 17

IX

Question 18

Taste and sensation of palate/extreme posterior tongue

Answer 18

X