pathology of neural development Flashcards
What is spina bifida occulta?
failure of the bony spinal canal to close, but without structural herniation. usually seen at lower vertebral levels with intact dura. Associated with tuft of hair or skin dimple at the level of the bony defect
What is a meningocele? Efffect on in utero markers?
meninges, but not the spinal cord, herniates through the spinal canal defect. this baby will have normal AFP (remember, neural tube defects can be associated with elevated AFP in amniotic fluid and maternal serum)
What is a meningomyelocele?
meninges and spinal cord herniate through the spinal canal defect
What is anencephaly?
forebrain anomaly. malformation of the anterior neural tube resulting in no forebrain and an open calvarium (top of the head is open- “frog-like” appearance).
What are the clinical findings of anencephaly? Risk factors?
increased AFP, polyhydramnios (because they baby has no swallowing center and therefore can’t swallow the amniotic fluid). Associated with maternal diabetes, esp. type 1. maternal folate supplements decrease risk
What is holoprosencephaly? When does this defect occur?
failure of the left and right hemispheres to separate. usually occurs in weeks 5-6. It involves a complex multifactorial etiology that may be related to mutations in sonic hedgehog signaling pathways.
What are some clinical manifestations of holoprosencephaly?
moderate forms have cleft lip/palate
severe forms may have cyclopia
What is a Chiari type II malformation?
aka Arnold-Chiari malformation
significant herniation of cerebellar tonsils and vermis through the foramen magnum with aqueductal stenosis and hydrocephalus. Often presents with lumbosacral myelomeningocele and paralysis below the defect.
considered a posterior fossa problem.
What is Dandy-Walker syndrome?
agenesis of the cerebellar vermis with cystic enlargement of the 4th ventricle (it fills the enlarged posterior fossa). It is associated with hydrocephalus and spina bifida.
What is syringomyelia?
syringomyleia is a disorder in which there is a cystic cavity within the spinal cord (syrinx = tube, as in syringe).
this cavity usually damages crossing anterior spinal commissure fibers first. This casues a cape-like bilateral loss of pain and temperature sensation in the upper extremities.
What are the most common sites of syringomyelias? What things may be associated with syringomyelias?
C8-T1. associated with chiari I malformations. Chiari I malformation is a >3-5 mm cerebellar tonsillar ectopia that is usually asymptomatic in childhood but manifests with headaches and cerebellar symptoms later.
How does the tongue develop?
The anterior 2/3s comes from the 1st and 2nd branchial arches.
the 3rd and 4th branchial arches make the posterior 1/3rd of the tongue
muscles of the tongue are derives from occipital myotomes
Innervation of the tongue
Taste: CN VII, IX, and X (solitary nucleus)
Pain/touch: CN V3, IX, X
Motor: CN XII
Nerve histology: How are they stained? What happens if you injure an axon?
Stain cell bodies and dendrites with Nissl stain, which looks at the RER. Does not stain the axon, because there is no RER in the axon.
When axons are injured, they undergo Wallarian degeneration. This is degeneration distal to the injury and axonal retraction proximally. The cell body undergos chromatolysis (changes that reflect incr. protein synthesis- round cellular swelling, displacement of the nucleus to the periphery, and dispersion of Nissl substance throughout the cytoplasm). This process allows for potential regeneration of the axon if in the peripheral nervous system.
What are the functions of astrocytes? Marker? embryologic origin?
physical support, repair, K+ metabolism, removal of excess neurotransmitter, component of the BBB, glycogen fuel reserve buffer. They undergo reactive gilosis in response to neural injury.
GFAP is the marker
derived from neuroectoderm
What are microglia? What is its function, and what is its origin?
responsible for CNS phagocytes. of mesodermal origin. can’t be seen in nissl stains. have small irregular nuclei and relatively little cytoplasm. part of the mononuclear phagocyte system
What happens to HIV infected microglia?
they fuse to form multinucleated giant cells in the CNS
What is the effect of myelin on the neurons? (math-y stuff) What cells make it?
wraps and insulates axons. increases the space constant and increases conduction velocity.
made by oligodendrocytes in the CNS and Schwann cells in the PNS
What should I know about oligodendrocytes? What do they do, how many cells do they effect, appearance, embryonic origin
myelate CNS axons, can myelinate multiple axons.
predominant type of glial cell in white matter.
derived from neuroectoderm with a fried eff appearance.
In what diseases are the oligodendrocytes injured?
MS, progressive multifocal leukoencephalopathy, and leukodystrophies
What are Schwann cells? How many cells do they affect? Function? embryonic origin
myelinate PNS axon- each Schwann cell myelinates only one axon. Also promote axonal regeneration. derived from neural crest.
In what diseases are the Schwann cells injured?
destroyed in Guillain-Barre
acoustic neuroma is a type of schwannoma, usually located in internal acoustic meatus. If bilateral, it suggests an an association with NF2
