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Neuro Exam I > Neural Developments & Malformations I > Flashcards

Neural Developments & Malformations I Flashcards

1
Q

the neural plate forms from what tissue?

what causes the neural plate to form?

A
  • ectoderm
  • the underlying notochord & paraxial mesoderm
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2
Q

outline the sequence of events in neural tube formation.

when does neural tube formation begin and end?

where does neural tube formation occur?

A

day 20-22

in the cervical region.

steps:

  1. neural plate forms from ectoderm, d/t notochord & paraxial mesoderm
  2. neural folds - lateral elevations of the neural folds - develop
  3. neural tube forms from fusion of neural folds
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3
Q

what occurs after the neural tube has formed?

A

the neural tube extends cranially & caudally, and is in communication with the amniotic cavity

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4
Q

what are the neural tube neuropores?

when do they close?

why is this important?

A
  • are the site of communications between the neural tube and amniotic cavity.
  • they close after formation of neural tube vascularization is complete
    • cranial neuropore: closes day 25
    • caudal neuropore: closes day 27
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5
Q

what does the lumen and walls of the neural tube develop into?

A
  • walls: the brain & spinal cord
  • lumen: its innermost cavity, the neural canal, forms
    • the ventricles of the brain
    • the central canal of spinal cord
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6
Q

what is spina bidifa?

what is its cause?

how does it present?

A
  • definition: lack of vertebral arches
  • cause: a failure of the closure of the neural tube
  • presentation: three main presentations that lack in severity
    • spina bifida occulta
    • meningocele
    • meningomyelocele
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7
Q

in normal anatomy, how far should the meninges extend?

A

up until the proximal-most part of the spinal nerve, near the intervertebral foramen

in other words: not past the peduncles

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8
Q

spina bifida - prentation of

  • spinal cord
  • meninges
  • other
A
  • spinal cord - normal (or filum terminate connected to subQ)
  • meninges - normal - i.e., don’t pass pedicles)
  • other: hair skin patch overlies defect
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9
Q

meningocele - prentation of

  • spinal cord
  • meninges
  • other
A
  • spinal cord: normal - no extrusion of neural tissue
  • meninges: extrude dorsally
  • other: mild disuprtion of bladder / bosel control
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10
Q

meningomyelocele - presentation of

  • spinal cord
  • meninges
  • other
A
  • spinal cord: extruding neural tissue
  • meninges: extrude dorsally + meningeal sac contains malformed cord
  • other: LE dysfunction, loss of bowel & bladder control
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11
Q

during what part of the vertebral column are meningocele & meningomyelocele most common?

A

lumbosacral

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12
Q

what are the neural tube defects of the brain?

A
  • craniochischisis
  • encephlocele
  • anencephaly
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13
Q

craniorachischis

  • cause
  • presentation
  • prognosis
A
  • cause: neural tube fails to close at the cranial spinal cord - hindbrain junction
  • presentation: abormal spinal cord located outside of body, m/c occipital region
  • prognosis: rarely compatible with life
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14
Q

encephalocele

  • cause
  • presentation
  • prognosis
A
  • prognosis: defect in skull (m/c occipital): allows brain to protrude through
  • presentation: brain protrudes through occipital skull
  • prognosis: smaller cases may be resolved surgically, many incompatible with life
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15
Q

anencephaly

  • cause
  • presentation
  • prognosis
A
  • cause: malformation at anterior end of neural tube -> disruption of forebrain development
  • presentation: absence of brain/calvaria
  • prognosis:stillborn -> die within a few hours
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16
Q

which part of the neural tube develops into the spinal cord?

A

the part caudal to the fourth pair of somites

17
Q

the wall of the neural tube develops into what three general zones?

A
  • from deep -> superficial (in -> out)
    • ventricular
    • intermediate
    • marginal
18
Q

what is the ventricular zone lined with?

A
  • neuroepithelium: psuedostratified columnar neuroepithelium, made of
    • ependymal cells - ultimately line central canal
    • glioblasts
    • neuroblasts
19
Q

what cells does the neuroepithelium give rise to?

A

(lining of ventricular zone of neural tube)

  • ependymal cells: will line central canal
  • glioblasts: differentiate into astroblasts & oligodenroblasts
  • neuroblasts
20
Q

glioblasts

  • migrate how?
  • difffereniate into what cells?
A
  • migration: move superficially into intermediate + marginal zones
  • differentiate into:
    • astocytes: protoplastmic, fibrous
    • oligodendrocytes: myelinate axons in the CNS
21
Q

what are microglial cells?

A

macrophages of the CNS that migrate in from blood (are part of monocytic phagocyte system)

22
Q

what are radial glial cells?

why are they important?

A
  • they are the first cell to form in the diferentiation of glioblasts
  • serve as a scaffolding on which developing neurons can migrate in -> out of neural tube
23
Q

what directs & faciliates migration of developing neural cells? how?

what occurs to neurons as the migrate?

A
  • migration directed by: neurochemical transmitters (chemo-attractants, repellents), which drive the movement of the growth cone, the tip of the developing axon immature
  • migration facilitated by: radial glial cells, which serve as scaffolding
  • as neurons migrate, they differentiate
24
Q

what part of the neural tube wall is the destination for immature neurons?

what occurs once the neurons arrive?

A
  • the intermediate zone (middle zone)
  • once neurons arive, they:
    • produce dendrites & axons that extend into the marginal zone
    • form aggregations: early nuclei
25
Q

what are aggregations?

A

groups of immature neurons in the intermediate zone of the neural tube wall (their destination).

are early forms of nuclei

26
Q

what is the significance of the marginal zone?

A
  • becomes invaded with axons & dendrites from neurons in the intermediate zone, after which synaptogenesis occurs
  • gives rise to the white matter of the spinal cord
27
Q

what is the significance of each neural tube wall zone?

A
  • ventricular: site of massive neurolast mitosis
  • intermediate: destination for neurons
  • marginal: receives axons & dendrites from intermediate zone -> forms white matter of spinal cord
28
Q

do neurons go mitosis after the ventricular zone?

A

no

29
Q

synaptogenersis

  • results in?
  • is triggered by?
  • is guided by?
  • involves what processes?
  • has what significance?
A
  • results in: synapse formation
  • triggered by: invasion of axons & dendrites into marginal zone
  • guided by:
    • neurotrophins: permits neuronal growth & survival
    • astrocytes
  • involves: significant neuronal cell death (75% of neurons that just migrated)
  • significance: random pattern of cell death -> massive levels of plasticity:
    • ​”everyones brain is different”
30
Q

what is the cause of the cell death in synaptogenesis?

A

insufficient neurotrophins

neurotrophils promote neuronal growth & survival, & there is not enough for all neurons that migrated

31
Q

what is he sulcus limitans?

what does it form?

A
  • a longitudinal groove formed from the thickening lateral walls of the growing nueral tube/ divides the lateral tube into an:
    • basal plate - ventrally
    • alar plate - dorsally
32
Q

what do they alar plate and basal plate form?

A
  • alar plate = afferents (sensory)
    • dorsal horn
    • dorsal median sulcus
  • basal plate = efferents (motor)
    • ventral & lateral horn
    • ventral median fissure
33
Q

from what does the ventral median fissure form?

A

the basal plate of neural tube

34
Q

syringomyelia

  • pathogenesis
  • demographics
  • presentation
A
  • pathogenesis: associated with trauma, or charli I formation
  • demographics: adults
  • presentation:
    • a spinal cord cyst that is
      • fluid filled (but NOT CSF)
      • within gray matter
      • not contiguous with central canal \
      • m/c in cervical & upper thoracic segments
    • loss of pain’temp sensations in upper extremities

Neuro Exam I (15 decks)

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