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Med Gen Neuro > Brain Malformations > Flashcards

Brain Malformations Flashcards

1
Q

What is microcephaly an issue with?

A

cell division, specifically an error in neuroblast proliferation

extra neurons => megaencephaly

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2
Q

What is the pattern of development (at least neurologically)?

A

inside –> out
back –> front

helps to identify patients that may be genetic

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3
Q

What is the first step when considering genetic testing in a neurologic setting?

A

Is the developmental pattern representative of a genetic condition or an acquired one?

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4
Q

What is the pattern of inheritance for most brain malformations?

A

de novo

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5
Q

What is the inheritance pattern for most intellectual disabilities?

A

de novo

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6
Q

What head circumference percentile is considered microcephaly?

A

< 2 %

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7
Q

What is the inheritance pattern for most primary microcephaly cases?

A

autosomal recessive

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8
Q

What is the inheritance pattern for most postnatal microcephaly cases?

A

de novo
some are X-linked such as
* CDKL5
* MECR
* CASK
* MAC

this slide is based on photo in phone - need to check with notes

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9
Q

What is the pattern of inheritance for most cases of holoprosencephaly?

A

AD
autosomal dominant

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10
Q

What is the inheritance pattern for most cases of megaencephaly?

A

most are mosaic
some are X-linked?

post-zygotic change

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11
Q

What is a group o genetic diseases that is assocaited with megalencephaly?

A

lysosomal storage diseases
eg: Hunter, Hurler, etc.

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12
Q

What are two ongoing possible issues or causes for megalencephaly?

A

hydrocephalus (increased fluid)
extra neurons

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13
Q

Of the 3 germ layers, which one does blood originate from and which one does the brain develop from?

A

blood = mesoderm
brain development = ectoderm

endoderm is the third

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14
Q

When testing for a condition that is known to likely be mosaic, what is important to keep in mind in terms of the reliability of the genetic testing?

megalencephaly = mosaic

A
  1. depth of coverage
  2. mosaicism won’t be present in all reads
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15
Q

When assessing a patient in pediatric neurology, what is important to remember as opposed to memorizing single brain malformations which leas to differentials falling apart when more than one brain malformation is present?

A

patterns assocaited with genetic diagnoses

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16
Q

What are the basic classifications of CNS malformations?

A
  1. forebrain patterning
  2. cortical malformations
  3. midbrain/hindbrain malformations
17
Q

What malformations are of forebrain patterning?

A
  • anencephaly
  • holoprosencephaly
  • agenesis of the corpus callosum
  • midline facial dysmorphology: clefting, close eyes (hypotelorism), single front incisor

face predicts the brain

18
Q

What genetic disorders can mimic congenital CMV infection?

A
  • deletion 1p36
  • deletion 22q11
  • some other chromosomal deletions
19
Q

What is the most common inheritance pattern for congenital microcephaly and what is the most common assocaited gene?

A
  • autosomal recessive
  • ASPM - has no other malformaitons aside from simplication of the gyral pattern
20
Q

What is the best genetic testing option for a patient with congenital microcephaly?

A

microcephaly gene panel
(not CMA as usually would be)

21
Q

What is megalenchephaly?

A

large, heavy, often malfunctioning brain

22
Q

What is macrocephaly?

A

large head, >98 %ile

23
Q

How can you determine if a patient may have a megalencephaly syndrome without any imaging?

A

presence of skin or somatic growth findings that are consistent

24
Q

If you are suspicious of a megalencephaly syndrome what is the best genetic test to order?

A

overgrowth/megalencephaly gene panel
(another exception to the CMA-before-sequencing rule)

25
Q

What is the inheritance pattern for postcerebellar hypoplasia?

A

AR or XL

26
Q

What is the single best genetic test according to peds neuro doc?

A

CMA

27
Q

What genetic test should be ordered for postcerebellar hypoplasia?

A

sequencing panel of PCH genes
9another exception to CMA-before-sequencing rule)

all described genes are AR or XL

28
Q

For nearly all brain malformations what is the best genetic test?

A

CMA first to catch chromosomal microdeletions/microduplications

29
Q

What is the recommended test for holoprosencephaly?

A

karyotype to check for trisomy 13

30
Q

Regarding brain malformations, if CMA comes back normal, what is the next step in testing?

A

sequencing studies
targeted brain malformation gene panel or exome sequencing

eventually whole genome testing will come first

Med Gen Neuro (5 decks)

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