Neurology Flashcards
What happens in neural development?
- notochord induces overlying ectoderm to differentiate into neuroectoderm and form the neural plate
- Neural plate gives rise to neural tube and neural crest cells
- Notochord becomes nucleus pulposus of the intervertebral disc in adults
- Alar plate (dorsal) - sensory
- Basal plate (ventral) - motor
What are the 3 primary vesicles at week 4 for the brain?
- forebrain = prosencephalon
- midbrain = mesencephalon
- hindbrain = rhombencephalon
What do the primary vesicles differentiate into at week 5 for the brain?
- Pro becomes telencephalon and diencephalon
- Mese stays mese
- Rhombo becomes metencephalon and myelencephalon
What does the telencephalon become?
Ceberal hemispheres, basal ganglia, hippocampus, and amygdala. Forms lateral ventricles
What does the diencephalon become?
thalamus, hypothalamus, optic nerve and tracts. Forms 3rd ventricle
What does the mesencephalon become?
midbrain and forms aqueduct
What does the metencephalon become?
pons and cerebellum and forms upper part of 4th ventricle
What does the myelencephalon become?
medulla and forms the lower part of the 4th ventricle
What are neural tube defects caused by?
-neuropores fail to fuse (4th wk) –> persistent connection b/w amniotic cavity and spinal canal. Associated w/ low folic acid intake before conception and during pregnancy.
What is usually seen in labs for neural tube defects?
elevated AFP in amniotic fluid and maternal serum. Elevated AChEsterase in amniontic fluid
What is spina bifida occulta?
failure of bony spinal canal to close but NO structural herniation. Usually seen at lower vertebral levels. Dura is intact. Assocated w/ tuft of hair or skin dimple.
What is meningocele?
Meninges ( but not the spinal cord) herniate through spinal canal defect
What is meningomyelocele?
Meninges and spinal cord herniate through spinal canal defect
What is anencephaly?
- malformation of anterior neural tube = no forebrain, open calvarium (frog-like appearance)
What are the clinical findings for anencephaly?
increased AFP, polyhydraminos (no swallowing center in brain). Associated w/ maternal diabetes. Maternal folate supplement decreases risk.
What is holoprosenecephaly?
- failure of left and right hemispheres to separate. usually occurs during 5-6 weeks.
- may be related to Sonic hedgehog gene
- Patau syndrome (trisomy 13)
- Fetal alcohol syndrome
What is clinical presentation of holoprosenecephaly?
moderate form has cleft lip/palate. Most severe forms result in cyclopia
What are examples of forebrain anomalies?
anencephaly and holoproenecephaly
What are examples of posterior fossa malformations?
- Chiarii II
2. Dandy- Walker
What is Chiarii II?
Significant cerebellar tonsillar and vermian herniation through foramen magnum w/ aqueductal stenosis and hydrocephalus. Often presents w/ thoraco-lumbar myelomeningocele and paralysis below the defect.
- syringomyelia can occur as well
What is Dandy-walker?
agenesis of cerebellar veins w/ cystic enlargement of 4th ventricle. Associated w/ hydrocephalus and spina bifida.
What is syringomyela?
- cystic enlargement of central canal of spinal cord.
- crossing fibers of spinothalamic tract are typically damaged first.
What is the clinical presentation of syringomyelia?
- bilateral loss of pain and temperature sensation in upper extremities (fine touch sensation is preserved)
- most common at C8-T1
What is involved w/ tongue development?
- 1st branchial arch forms anterior 2/3 (sensation via CN V3, tase via CN 7)
- 3rd/4th arches form posterior 2/3 (sensation and taste via CN 9, extreme posterior - CN 10)
Motor innervation via CN 12
Muscles of tongue are derived from occipital myotomes.