Neuro - Embryology Flashcards
Pg. 444-446 in First Aid 2014 Pg. 408-410 in First Aid 2013 Sections include: -Neural development -Regional specification of developing brain -CNS/PNS origins -Neural tube defects -Forebrain anomalies -Posterior fossa malformations -Syringomyelia -Tongue development
What role does the notochord play in embryological development?
Notochord induces overlying ectoderm to differentiate into neuroectoderm and form the neural plate
To what does the neural plate give rise?
Neural plate gives rise to neural tube and neural crest cells
What is the fate of the notochord in adults?
Notochord becomes nucleus pulposus of the intervertebral disc in adults
During what time frame in embryogenesis does neural plate progress to neural tube and neural crest cells?
Day 18 - Day 21
What is the orientation of the alar versus basal plate? What are their functions?
Alar plate (dorsal): sensory; Basal plate (ventral): motor; Think: Same orientation as spinal cord
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.
See p. 444 in First Aid 2014 or Pg. 408 in First Aid 2013 for image at top left
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.
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
To what secondary vesicles does the forebrain (prosencephalon) give rise? In turn, what adult brain structures develop from each of these secondary vesicles?
FOREBRAIN (PROSENCEPHALON) –> Telencephalon & Diencephalon; TELENCEPHALON –> Cerebral hemispheres (walls) & Lateral ventricles (cavities); DIENCEPHALON –> Thalamus (walls) & Third ventricle (cavities)
To what secondary vesicle does the midbrain (mesencephalon) give rise? In turn, what adult brain structures develop from this secondary vesicle?
MIDBRAIN (MESENCEPHALON) –> Mesencephalon; MESENCEPHALON –> Midbrain (walls) & Aqueduct (cavities)
To what secondary vesicles does the hindbrain (rhombencephalon) give rise? In turn, what adult brain structures develop from each of these secondary vesicles?
HINDBRAIN (RHOMBENCEPHALON) –> Metencephalon & Myelencephalon; METENCEPHALON –> Pons (walls), Cerebellum (walls), & Upper part of fourth ventricle (cavities); MYELENCEPHALON –> Medulla (walls) & Lower part of fourth ventricles (walls)
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).
See p. 444 in First Aid 2014 or Pg. 408 in First Aid 2013 for visual
Name 4 parts of the nervous system that are derived from neuroectoderm?
Neuroectoderm - (1) CNS neurons; (2) ependymal cells (inner lining of ventricles, make CSF); (3) oligodendroglia; (4) astrocytes
Name 2 parts of the nervous system that are derived from the neural crest?
Neural crest - (1) PNS neurons; (2) Schwann cells
Name one part of the nervous system that is derived from the mesoderm?
Mesoderm - Microglia; Think: “like Macrophages, originate from Mesoderm”
What happens if neuropores fail to fuse? At what week in development does this usually occur?
Neuropores fail to fuse (4th week) –> persistent connection between amniotic cavity and spinal canal
With what deficiency are neural tube defects associated, and in what context?
Associated with low folic acid intake before conception and during pregnancy.
What lab value may be elevated in neural tube defects, and from where is this measured?
Elevated alpha-fetoprotein (AFP) in amniotic fluid and maternal serum.
What is a helpful confirmatory test in neural tube defects, and why?
Increased acetylcholinesterase (AChE) in amniotic fluid is a helpful confirmatory test (fetal AChE in CSF transudates across defect into amniotic fluid).
Name 3 kinds of neural tube defects.
(1) Spina bifida occulta (2) Meningocele (3) Meningomyelocele
What happens (and does not happen) in spina bifida occulta?
Failure of bony spinal canal to close, but no structural herniation
Where is spina bifida occulta usually seen? What impact does it have on the integrity of the dura?
Usually seen at lower vertebral levels. Dura is intact.
What are 2 physical findings with which spina bifida occulta is associated?
Associated with tuft of hair or skin dimple at level of bony defect.
What happens (and does not happen) in meningocele?
Meninges (but not the spinal cord) herniate through spinal canal defect
What happens in meningomyelocele?
Meninges and spinal cord herniate through spinal canal defect
What are the AFP levels with meningocele like?
Normal AFP.
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.
See p. 445 in First Aid 2014 or p. 409 in First Aid 2013 for visual
What causes anencephaly, and what results?
Malformation of anterior neural tube resulting in no forebrain, open calvarium (“frog-like appearance”)
What are 2 clinical findings associated with anencephaly?
Clinical findings: increased AFP; Polyhydramnios (no swallowing center in brain)
With what maternal condition is anencephaly associated?
Associated with maternal diabetes (type I).
What intervention decreases risk of anencephaly?
Maternal folate supplementation decreases risk
What event fails to occur in holoprosencephaly? When does this usually occur?
Failure of left and right hemispheres to separate; usually occurs during weeks 5-6.
Briefly describe the etiology of holoprosencephaly. To what mutations may it be related?
Complex multifactorial etiology that may be related to mutations in sonic hedgehog signaling pathway
What is the physical finding in moderate holoprosencepahly? What is the physical finding in its most severe form?
Moderate form has cleft lip/palate, most severe form results in cyclopia.
Name 2 posterior fossa malformations.
(1) Chiari II (Arnold-Chiari malformation) (2) Dandy-Walker
What is another name for Chairi II? What is it?
Arnold-Chiari malformation; Significant herniation of cerebellar tonsils and vermis through foramen magnum with aqueductal stenosis and hydrocephalus
How does Chiari II often present?
Often presents with lumbosacral myelomeningocele and paralysis below the defect
What defines Dandy-Walker?
Agenesis of cerebellar vermis with cystic enlargement of 4th ventricle (fills the enlarged poserior fossa)
With what 2 other neurologic conditions is Dandy-Walker associated?
Associated with hydrocephalus & spina bifida.
What does “Syrinx” mean? What defines syringomyelia? What happens if the central canal is involved?
Syrinx = tube (as in syringe); Cystic cavity (syrinx) within the spinal cord (if central canal –> hydromyelia)
Which fibers are typically damaged first in syringomyelia? What neurological deficit results from syringomyelia? What related ability is preserved?
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)
At what vertebral levels is syringomyelia most common?
Most common at C8-T1
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.
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
What forms the anterior 2/3 of the tongue? What nerves provide sensation and taste for the anterior 2/3 of the tongue?
1st and 2nd branchial arches form anterior 2/3 (thus sensation via CN V3, taste via CN VII)
What forms the posterior 1/3 of the tongue? What nerves provide sensation and taste for the posterior 1/3 of the tongue?
3rd and 4th branchial arches form posterior 1/3 (thus sensation and taste mainly via CN IX, extreme posterior via CN X)
What nerve provides motor innvervation for the tongue?
Motor innervation is via CN XII
From which myotomes are the muscles of tongue derived?
Muscles of the tongue are derived from occipital myotomes.
Which cranial nerves allow the tongue to taste?
Taste - CN VII, IX, X (solitary nucleus)
Which cranial nerves allow the tongue to perceive pain?
Pain - CN V3, IX, X
What cranial nerve handles motor function of the tongue?
Motor - CN XII
Draw the tongue and its parts, labeling each part’s innervation and embryologic origin.
See p. 446 in First Aid 2014 or p. 410 in First Aid 2013 for visual
