USMLE - NEURO EMBRYOLOGY

Three primary vesicles of the developing brain become what 5 secondary vesicles?

1. Forebrain -> Telencephalon + Diencephalon 2. Midbrain -> Mesencephalon 3. Hindbrain -> Metencephalon + Myelencephalon

Dandy-Walker posterior fossa malformations? Often presents w/ what other associated conditions?

Agenesis of Cerebellar Vermis w/ Cystic enlargement of 4th ventricle (fills the enlarged posterior fossa) Associated w/ Hydrocephalus + Spina bifida

Alar plate (dorsal/vental) (sensory/motor), what about basal plate?

Alar plate (dorsal) = sensory Basal plate (ventral) = motor * Same orientation as spinal cord

Notochord induces overlying __ to differentiate into neuroectoderm + form the ___.

Ectoderm and form the Neural Plate

Neural crest gives rise to?

PNS neurons Schwann cells

Adult Derivative of Metencephalon Walls + Cavities?

Pons Cerebellum Upper part of 4th ventricle

Adult Derivative of Diencephalon Walls + Cavities?

Thalamus + Third Ventricle

1st and 2nd branchial arches form ___ tongue. Sensation via CN ___ and taste via CN___.

anterior 2/3 sensation = CN V3 (trigeminal) taste = CN VII (facial)

Muscles of the tongue are derives from the ___ myotomes?

occipital

3rd and 4th brachial arches form ___ tongue. Sensation and taste which cranial nerve and extremely posterior what cranial nerve?

posterior 1/3 sensation + taste mainly = CN IX (glossopharyngeal) extreme posterior = CN X (vagus)

Syringomyelia is a cystic cavity (syrinx) in the___

spinal cord (central canal -> hydromyelia) Crossing anterior spinal commissural fibers damaged first = cape-like BL loss of pain and T

When the neuropores fail to fuse (4th week) what happens? What levels are elevated amniotic fluid? What is this associated w/ in the contraception and during pregnancy stage? What is a confirmatory test ?

Fails to fuse -> connection btw amnionic cavity + spinal canal Associated w/ Low FOLIC acid Elevated alpha-fetoprotein (AFP) in amniotic fluid maternal serum AChE in amnionic fluid (fetal AChE in CSF transudates across defect into amnionic fluid)

Spinal bifida occulta is failure of the ___ to close. Is there herniation? Associated with what on the skin at the level of the defect?

Failure bony spinal canal to close, NO herniation Dura intact usually lower vertebral levels Tuft of hair or skin dimple at level bony defect

Holoprosencephaly failure of what? When does this occur? Mutation in what? Moderate + Severe form differences?

Failure of L + R hemispheres to separate (5-6 weeks) Mutations sonic hedgehog signaling pathway, multifactorial etiology Moderate form = cleft lip/palate, most severe = cyclopia

Adult Derivative of Myelencephalon Walls + Cavities?

Medullar Lower part of 4th ventricle

Meningocele what herniates through the spinal defect?

Meninges (not spinal cord) herniate Normal AFP

Meningomyelocele what herniate through spinal canal defect?

Meninges + Spinal Cord herniate

Mesoderm gives rise to?

Microglia (like Macrophages, originate from Mesoderm) "M"

Adult Derivative of Mesencephalon Walls + Cavities?

Midbrain + Aqueduct

Neural Plate gives rise to what two things?

Neural tube + Neural Crest Cells

Notocord becomes the ___ of the interverterbral disc in adults?

Nucleus Pulposus

Syringomyelia is most common in which region of the spinal cord?

C8-T1

Pain to the tongue which cranial nerves?

CN V3, IX, X

Taste to the tongue which nerves?

CN VII, IX, X (solitary nucleus)

Motor innervation to the tongue is which CN?

CN XII (hypoglossal)

Neuroectoderm gives rise to?

CNS neurons Ependymal cells (inner living of ventricles, make CSF) Oligodendroglia Astrocytes

Adult Derivative of Telencephalon Walls + Cavities?

Cerebral Hemispheres + Lateral Ventricles

Syringomyelia associated w/ what malformation?

Chiari I malformation (>3-5 mm cerebellar tonsillar ectopia; congenital; asymptomatic in childhood, manifests w/ HA + cerebellar symptoms)

Chiari II (Arnold-Chiari malformation posterior fossa) herniation of what? Often presents w/ what other associated conditions?

Herniation cerebellar Tonsils + Vermis though Foramen Magnum w/ aqueductal stenosis + hydrocephalus Present w/ lumbosacral Myelomeningocele + Paralysis below the defect

Anecephaly = forebrain anomalies is malformation which part of the brain? Clinical findings? Associated w/ which maternal condition? What can DEC risk?

Malformation anterior neural tube = No forebrain, Open calvarium (frog-like appearance) INC AFP, polyhydramnios (no swallowing center in brain) Type I diabetes mother, DEC risk Folate supplementation