Neurology - Embryology Flashcards
What is the function of the notochord?
Inducing overlying ectoderm to differentiate into neuroectoderm, and form the neural plate -> give rises to the neural tube and neural crest cells
What is the adult remnant of the notochord?
Nucleus pulposus of the intervertebral disc
What is the alar plate?
Dorsal: sensory
What is the basal plate?
Ventral: motor
When is the neural tube formed?
Day 18-21 (3 weeks)
What are the three primary vesicles of the developing brain?
Prosencephalon (Forebrain)
Mesencephalon (Midbrain)
Rhombencephalon (Hindbrain)
What are the five secondary vesicles of the developing brain?
Telecephalon Diencephalon Mesencephalon Metencephalon Myelencephalon
Adult derivative of: telecephalon
Cerebral hemispheres
Lateral ventricles
Adult derivative of: diencephalon
Thalamus
Third ventricle
Adult derivative of: mesencephalon
Midbrain (Medulla)
Aqueduct
Adult derivative of: metencephalon
Pons and Cerebellum
Upper part of the fourth ventricle
Adult derivative of: myelencephalon
Lower part of the fourth ventricle
When does neural tube defects occur?
4th week
What is neural tube defects associated with?
low folic acid
What lab values suggest neural tube defect?
Elevated AFP
Elevated acetylcholinesterase
What is a confirmatory test for neural tube defect?
Elevated acetylcholinesterase
Spina bifida occulta
failure of bony spinal canal to close
no structural herniation, usually lower vertebral level; dura is intact
associated with tuft of hair or skin dimple
Meningocele
Meninges (but not spinal cord) herniate through spinal canal defect
Meningomyelocele
Meninges and spinal cord herniate through spinal defect
Anencephaly
Malformation of anterior neural tube - no forebrain, open calvarium (frog-like appearance)
Lab values for anencephaly
High AFP, polyhydramnios (no swalloing center)
What is anencephaly associated with?
materal diabetes (Type I)
What can decrease risk of anencephaly?
maternal folate supplement can decrease risk
Holoprosencephaly
Failure of left and right hemispheres to separate; usually weeks 5-6
What is suggested to be mutated in holoprosencephaly?
sonic hedgehog signaling pathway
What are moderate and severe forms of holoprosencephaly associated with?
cleft lip/palate - moderate
cyclopia - severe
Cerebral aqueduct stenosis
Accumulation of CSF in ventricular space - most common cause of hydrocephalus in newborns
Presentation of cerebral aqueduct
enlarging head circumference due to dilation of ventricles (cranial suture lines not fused)
What is dandy-walker malformation?
Congenital failure of cerebellar vermis to develop
Massively dilated 4th ventricle with absent cerebellum often accompanied by hydrocephalus
What is dandy-walker associated with?
hydrocephalus and spina bidifa
What is arnold-chiari malformation (type II)?
congenital extension of cerebellar tonsils through foramen magnum
Obstruction of CSF flow can result in hydrocephalus
What is arnold-chiari malformation associated with?
thoraco-lumbar meningomyelocele and syringomyelia
What is syringomyelia?
cystic enlargement of central canal of spinal cord
What fibers are damaged first in syringomyelia?
Fibers of spinohalamic tract
Presentation of syringomyelia
cape-like, bilateral loss of pain and temperature sensation in upper extremities (fine touch is preserved)
Where is syringomyelia most common in the spinal cord?
C8-T1
Which branchial arch forms the tongue?
1st branchial arch forms anterior 2/3 (sensation V3, taste VII)
3/4 archs form posterior 1/3 (sensation/taste IX, extreme posterior X)
What is motor innervation of the tongue?
CNXII
What nerves are involved in taste?
Anterior 2/3: VII
Posterior 1/3: IX
What nerves are involved in sensation of the tongue?
Anterior 2/3: V3
Posterior 1/3: IX
Muscles of tongue are derived from what?
occipital myotomes
