Neurology- Embryo

Question 1

What induces the overlying ectoderm to differentiate into neuroectoderm and to form the neural plate?

Answer 1

Notochord

Question 2

What does the neural plate give rise to?

Answer 2

the neural tube and neural crest cells

Question 3

What does the notochord become?

Answer 3

the nucleus pulposus of intervertebral discs in adults

Question 4

When does neural crest development occur?

Answer 4

days 18-21

Question 5

What are the three primary developmental vesicles of the brain?

Answer 5

• forebrain (prosencephalon)
• midbrain (mesencephalon)
• hindbrain (rhombencephalon)

Question 6

What are the secondary vesicle derivatives of the forebrain?

Answer 6

telencephalon and diencephalon

Question 7

What are the adult derivatives of the telencephalon?

Answer 7

cerebral hemispheres and lateral ventricles

Question 8

What are the adult derivatives of the diencephalon?

Answer 8

thalamus and 3rd ventricle

Question 9

What are the secondary vesicle derivatives of the midbrain?

Answer 9

the mesencephalon

Question 10

What are the adult derivatives of the mesencephalon?

Answer 10

midbrain and aqueduct

Question 11

What are the secondary vesicle derivatives of the hindbrain?

Answer 11

metencephalon and myelencephalon

Question 12

What are the adult derivatives of the metencephalon?

Answer 12

pons, cerebellum

upper part of 4th ventricle

Question 13

What are the adult derivatives of the myelencephalon?

Answer 13

medulla and lower part of the 4th ventricle

Question 14

What are the CNS/PNS derivatives of the neuroectoderm?

Answer 14

CNS neurons, ependymal cells (inner lining of ventricles, make CSF), oligodenroglia, astrocytes

Question 15

What are the CNS/PNS derivatives of the neural crest?

Answer 15

PNS neurons, Schwann cells

Question 16

What are the CNS/PNS derivatives of the mesoderm?

Answer 16

microglia

Question 17

What neural tube defect can cause a persistent conenction between the amniotic cavity and the spinal canal? What is the cause?

Answer 17

failure of neuropores to fuse in the 4th week

This is associated with low folic acid intake before conception and during pregnancy

Question 18

What lab findings are seen in neural tube defects?

Answer 18

elevated a-fetoprotein in amniotic fluid and maternal serum

elevated AchE in amniotic fuid to confirm (fetal AchE in the CSF transudates across the defect into amniotic fluid)

Question 19

What are some common neural tube defects?

Answer 19

• spina bifide occulta
• meningocele
• meningomyelocele

Question 20

What is spina bifida occulta?

Answer 20

failure of the bony spinal canal to close, but with no structural herniation (dura is intact). Usually seen at the lower vertebral levels

Question 21

Spina bifida occulta- AFP is normal

Answer 21

See FA pg 449

Question 22

What is the difference between meningocele and meningomyelocele?

Answer 22

meningocele - meninges (but no neural tissue) herniate through the bony defect

meningomyelocele- meninges and neural tissue herniate

Question 23

What are two common forebrain anomalies?

Answer 23

anencephaly

holoprosencephaly

Question 24

What is anencephaly?

Answer 24

malformation of the anterior meural tube resulting in no forebrain, and an open calvarium

Question 25

What is holoprosencephaly?

Answer 25

failure of the left and right hemospheres to seperate

Question 26

When does holoprosencephaly typically occur?

Answer 26

5-6 weeks

Question 27

What typically causes holoprosencephaly?

Answer 27

mutations in the sonic hedgehod signaling pathway

Question 28

Holoprosencephaly is commonly seen in what syndromes?

Answer 28

Patau syndrome and fetal alcohol syndrome (moderate form has a cleft lip/palate and the most severe form results in cyclopia)

Question 29

How does anencephaly present in labs?

Answer 29

elevated AFp and polyhydramnios (no swallowing center in the brain)

Question 30

Anencephaly is associated with ________

Answer 30

maternal type I diabetes

Question 31

What is a Chiari II malformation?

Answer 31

significant hernation of the cerebellar tonsils and vermis through the foramen magnum with aqueductal stensosi and hydrocephalus

Question 32

What is a Dandy-Walker malformation?

Answer 32

agenesis of cerebellar vermis with cystic enlargement of the 4th ventricles (which fills the enlarged posterior fossa)

associated with hydrocephalus and spina bifida

Question 33

What is syringomyelia?

Answer 33

the formation of a cystic cavity within the spinal cord that results in a cape-like, bilateral loss of pain and temperature sensation in the upper extremities (fine touch is preserved)

Question 34

Syringomyelia is most common at what vertebral levels?

Answer 34

C8-T1

Question 35

What is a Chiari I malformation?

Answer 35

cerebellar tonsillar ectopia greater than 3-5mm; congential, usually asymptomatic in childhood and manifesting with HA and cerebellar symptoms

Question 36

What forms the anterior 2/3rds of the tongue?

Answer 36

1st and 2nd branchial arches

Question 37

Sensation to the anterior 2/3rds of the tongue is via ____

Answer 37

CN V3

Question 38

Taste to the anterior 2/3rds of the tongue is via ____

Answer 38

CN VII

Question 39

What forms the posterior 1/3rd of the tongue?

Answer 39

the 3rd and 4th branchial arches

Question 40

Sensation and taste to the posterior 1/3rd of the tongue is via what?

Answer 40

CN IX (extreme back is CN X)

Question 41

Motor innervation of the tongue

Answer 41

via CN XII to hyoglossus (retracts and depresses the tongue), genioglossus (protrudes the tongue), and styloglossus (draws sides of tongue upward to create a trough for swallowing)

via CN X to palatoglossus (elevates posterior tongue during swallowing)