Neuro - Embryology

Question 1

What role does the notochord play in embryological development?

Answer 1

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

Question 2

To what does the neural plate give rise?

Answer 2

Neural plate gives rise to neural tube and neural crest cells

Question 3

What is the fate of the notochord in adults?

Answer 3

Notochord becomes nucleus pulposus of the intervertebral disc in adults

Question 4

During what time frame in embryogenesis does neural plate progress to neural tube and neural crest cells?

Answer 4

Day 18 - Day 21

Question 5

What is the orientation of the alar versus basal plate? What are their functions?

Answer 5

Alar plate (dorsal): sensory; Basal plate (ventral): motor; Think: Same orientation as spinal cord

Question 6

Draw a 3-stage progression of neurological development, labeling the following: (1) Neural plate (2) Notochord (3) Neural crest (4) Neural tube (5) Neural crest cells.

Answer 6

See p. 444 in First Aid 2014 or Pg. 408 in First Aid 2013 for image at top left

Question 7

How many primary versus secondary vesicles are there in the developing brain? What are their names? Give 2 names for each of the primary vesicles.

Answer 7

3 PRIMARY VESICLES: (1) Forebrain (prosencephalon) (2) Midbrain (mesencephalon) (3) Hindbrain (rhombencephalon); 5 SECONDARY VESICLES: (1) Telencephalon (2) Diencephalon (3) mesencephalon (4) Metencephalon (5) Myelencephalon

Question 8

To what secondary vesicles does the forebrain (prosencephalon) give rise? In turn, what adult brain structures develop from each of these secondary vesicles?

Answer 8

FOREBRAIN (PROSENCEPHALON) –> Telencephalon & Diencephalon; TELENCEPHALON –> Cerebral hemispheres (walls) & Lateral ventricles (cavities); DIENCEPHALON –> Thalamus (walls) & Third ventricle (cavities)

Question 9

To what secondary vesicle does the midbrain (mesencephalon) give rise? In turn, what adult brain structures develop from this secondary vesicle?

Answer 9

MIDBRAIN (MESENCEPHALON) –> Mesencephalon; MESENCEPHALON –> Midbrain (walls) & Aqueduct (cavities)

Question 10

To what secondary vesicles does the hindbrain (rhombencephalon) give rise? In turn, what adult brain structures develop from each of these secondary vesicles?

Answer 10

HINDBRAIN (RHOMBENCEPHALON) –> Metencephalon & Myelencephalon; METENCEPHALON –> Pons (walls), Cerebellum (walls), & Upper part of fourth ventricle (cavities); MYELENCEPHALON –> Medulla (walls) & Lower part of fourth ventricles (walls)

Question 11

Draw and label the regional specification of the developing brain from primary vesicles to secondary vesicles to adult derivates (categorized as walls versus cavities derivatives).

Answer 11

See p. 444 in First Aid 2014 or Pg. 408 in First Aid 2013 for visual

Question 12

Name 4 parts of the nervous system that are derived from neuroectoderm?

Answer 12

Neuroectoderm - (1) CNS neurons; (2) ependymal cells (inner lining of ventricles, make CSF); (3) oligodendroglia; (4) astrocytes

Question 13

Name 2 parts of the nervous system that are derived from the neural crest?

Answer 13

Neural crest - (1) PNS neurons; (2) Schwann cells

Question 14

Name one part of the nervous system that is derived from the mesoderm?

Answer 14

Mesoderm - Microglia; Think: “like Macrophages, originate from Mesoderm”

Question 15

What happens if neuropores fail to fuse? At what week in development does this usually occur?

Answer 15

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

Question 16

With what deficiency are neural tube defects associated, and in what context?

Answer 16

Associated with low folic acid intake before conception and during pregnancy.

Question 17

What lab value may be elevated in neural tube defects, and from where is this measured?

Answer 17

Elevated alpha-fetoprotein (AFP) in amniotic fluid and maternal serum.

Question 18

What is a helpful confirmatory test in neural tube defects, and why?

Answer 18

Increased acetylcholinesterase (AChE) in amniotic fluid is a helpful confirmatory test (fetal AChE in CSF transudates across defect into amniotic fluid).

Question 19

Name 3 kinds of neural tube defects.

Answer 19

(1) Spina bifida occulta (2) Meningocele (3) Meningomyelocele

Question 20

What happens (and does not happen) in spina bifida occulta?

Answer 20

Failure of bony spinal canal to close, but no structural herniation

Question 21

Where is spina bifida occulta usually seen? What impact does it have on the integrity of the dura?

Answer 21

Usually seen at lower vertebral levels. Dura is intact.

Question 22

What are 2 physical findings with which spina bifida occulta is associated?

Answer 22

Associated with tuft of hair or skin dimple at level of bony defect.

Question 23

What happens (and does not happen) in meningocele?

Answer 23

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

Question 24

What happens in meningomyelocele?

Answer 24

Meninges and spinal cord herniate through spinal canal defect

Question 25

What are the AFP levels with meningocele like?

Answer 25

Normal AFP.

Question 26

Draw a vertebrate and skin depicting findings in each of the following situations: (1) Normal (2) Spina bifida occulta (3) Meningocele (4) Meningomyelocele. Be sure to include and label the following in your drawing: spinal cord, dura, leptomeninges, transverse process, and subarachnoid space.

Answer 26

See p. 445 in First Aid 2014 or p. 409 in First Aid 2013 for visual

Question 27

What causes anencephaly, and what results?

Answer 27

Malformation of anterior neural tube resulting in no forebrain, open calvarium (“frog-like appearance”)

Question 28

What are 2 clinical findings associated with anencephaly?

Answer 28

Clinical findings: increased AFP; Polyhydramnios (no swallowing center in brain)

Question 29

With what maternal condition is anencephaly associated?

Answer 29

Associated with maternal diabetes (type I).

Question 30

What intervention decreases risk of anencephaly?

Answer 30

Maternal folate supplementation decreases risk

Question 31

What event fails to occur in holoprosencephaly? When does this usually occur?

Answer 31

Failure of left and right hemispheres to separate; usually occurs during weeks 5-6.

Question 32

Briefly describe the etiology of holoprosencephaly. To what mutations may it be related?

Answer 32

Complex multifactorial etiology that may be related to mutations in sonic hedgehog signaling pathway

Question 33

What is the physical finding in moderate holoprosencepahly? What is the physical finding in its most severe form?

Answer 33

Moderate form has cleft lip/palate, most severe form results in cyclopia.

Question 34

Name 2 posterior fossa malformations.

Answer 34

(1) Chiari II (Arnold-Chiari malformation) (2) Dandy-Walker

Question 35

What is another name for Chairi II? What is it?

Answer 35

Arnold-Chiari malformation; Significant herniation of cerebellar tonsils and vermis through foramen magnum with aqueductal stenosis and hydrocephalus

Question 36

How does Chiari II often present?

Answer 36

Often presents with lumbosacral myelomeningocele and paralysis below the defect

Question 37

What defines Dandy-Walker?

Answer 37

Agenesis of cerebellar vermis with cystic enlargement of 4th ventricle (fills the enlarged poserior fossa)

Question 38

With what 2 other neurologic conditions is Dandy-Walker associated?

Answer 38

Associated with hydrocephalus & spina bifida.

Question 39

What does “Syrinx” mean? What defines syringomyelia? What happens if the central canal is involved?

Answer 39

Syrinx = tube (as in syringe); Cystic cavity (syrinx) within the spinal cord (if central canal –> hydromyelia)

Question 40

Which fibers are typically damaged first in syringomyelia? What neurological deficit results from syringomyelia? What related ability is preserved?

Answer 40

Crossing anterior spinal commissural fibers are typically damaged first; Results in a “cape-like,” bilateral loss of pain and temperature sensation in upper extremities (fine touch sensation is preserved)

Question 41

At what vertebral levels is syringomyelia most common?

Answer 41

Most common at C8-T1

Question 42

With what other neurological condition is syringomyelia associated? Define this condition and give its presentation in an adult versus child. Draw a visual depicting both this condition and syringomyelia.

Answer 42

Associated with Chiari I malformation (>3-5 mm cerebella tonsillar ectopia; congenital, usually asymptomatic in childhood, manifests with headaches and cerebellar symptoms); See p. 446 in First Aid 2014 or p. 410 in First Aid 2013 for visual

Question 43

What forms the anterior 2/3 of the tongue? What nerves provide sensation and taste for the anterior 2/3 of the tongue?

Answer 43

1st and 2nd branchial arches form anterior 2/3 (thus sensation via CN V3, taste via CN VII)

Question 44

What forms the posterior 1/3 of the tongue? What nerves provide sensation and taste for the posterior 1/3 of the tongue?

Answer 44

3rd and 4th branchial arches form posterior 1/3 (thus sensation and taste mainly via CN IX, extreme posterior via CN X)

Question 45

What nerve provides motor innvervation for the tongue?

Answer 45

Motor innervation is via CN XII

Question 46

From which myotomes are the muscles of tongue derived?

Answer 46

Muscles of the tongue are derived from occipital myotomes.

Question 47

Which cranial nerves allow the tongue to taste?

Answer 47

Taste - CN VII, IX, X (solitary nucleus)

Question 48

Which cranial nerves allow the tongue to perceive pain?

Answer 48

Pain - CN V3, IX, X

Question 49

What cranial nerve handles motor function of the tongue?

Answer 49

Motor - CN XII

Question 50

Draw the tongue and its parts, labeling each part’s innervation and embryologic origin.

Answer 50

See p. 446 in First Aid 2014 or p. 410 in First Aid 2013 for visual