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Survey of Human Genetic Disorders Second Half > Brain Malformations > Flashcards

Brain Malformations Flashcards

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1
Q

What does alobar mean?

A

No separation between the right and left half of the brain.

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2
Q

What is myelomeningocele?

A

The most serious type of spina bifida.
With this condition, a sac of fluid comes through an opening in the baby’s back
Part of the spinal cord and nerves are in this sac and are damaged.
Loss of feeling/movement in legs or feet
Incontinence

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3
Q

What is encephalocele?

A

Encephalocele is a sac-like protrusion or projection of the brain and the membranes that cover it through an opening in the skull.
Encephalocele happens when the neural tube does not close completely during pregnancy.

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4
Q

What is anencephaly?

A

“Mickey Mouse” sign
Missing large parts of the brain and skull
Low survival

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5
Q

What is the incidence of holoprocencephaly?

A

1 in 250 during early embryonic development, and approximately 1 in 16,000 live births.

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6
Q

What are the facial anomalies found in holoprocencephaly?

A
  • Cyclops eye
  • Rudimentary nasal structure (probiscis)
  • Hypotelorism
  • Single nostril nose
  • cleft lip and palate
  • None
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7
Q

What are the chromosomal abnormalities associated with holoprocencephaly?

A
  • Particularly characteristic of Trisomy 13
  • Also trisomy 13-15 mosaicism, ring 13, deletion 13
  • Trisomy or deletions of 18, 2, 3, 7, and 21
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8
Q

What percentage of holoprosencephaly is caused by chromosome abnormalities?

A

33%

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9
Q

What are the most common genes associated with holoprocencephaly?

A

SHH, SIX3, TGIF1, ZIC2

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10
Q

What syndromes are associated with holoprocencephaly?

A

Smith-Lemli-Opitz syndrome; Hartsfield syndrome, Kallman syndrome 2, Steinfeld syndrome

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11
Q

What is the recurrence risk for sporadic, nonchromosomal, nondysmorphic holoprosencephaly?

A

6%

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12
Q

What percentage of Isolated Partial and Complete Agenesis of the Corpus Callosum is caused by an abnormal karyotype?

A

4.8% (complete)
7.5% (partial)

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13
Q

What percentage of Isolated Agenesis of the Corpus Callosum is detected by SNP-array?

A

5.7%

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14
Q

What are the most common chromosomal anomalies associated with ACC?

A

Trisomy 18, trisomy 13, and mosaic 8

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15
Q

What is the phenotype for Aicardi syndrome?

A
  • Females (X-linked dominant)
  • Chorioretinal lacunes
  • Agenesis of corpus callosum
    -Complete 72%; partial 28%
  • Infantile spasms
  • Cortical heterotopias (50%)
  • Costovertebral defects (39%)
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16
Q

What percentage of Isolated Agenesis Corpus Collosum is the neurodevelopmental outcome normal?

A

76%

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17
Q

What is the phenotype of Septo-optic dysplasia?

A
  • Absence of the septum pellucidum
  • Optic nerve hypoplasia
  • Pituitary dysfunction

Decreased visual acuity
Endocrine dysfunction leading to growth delay, hyponatremia and/or hypoglycemia in newborn period
ID or DD

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18
Q

What is the genetic cause of Septo-optic dysplasia?

A

HESX1 (AR)

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19
Q

What is Schizencephaly?

A

Abnormal slits, or clefts, in the cerebral hemispheres of the brain.

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20
Q

What is Polymicrogyria?

A

In people with polymicrogyria, the brain develops too many folds, and the folds are unusually small

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21
Q

What is Periventricular nodular heterotopia (PVNH)?

Study These Flashcards
A

Brain malformation of cortical development.

PVNH is characterized by an abnormal clumping of grey matter (nerve cells) around the deep fluid chambers inside the brain called the ventricles.

22
Q

What percentage of Schizencephaly is unilateral? bilateral? Closed?

Study These Flashcards
A

65% (Unilateral)
35% (Bilateral)
50% closed

23
Q

What is the most severe form of Schizencephaly and what are the symptoms?

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A

Bilateral closed:
Cognitive 100%
Motor 86%
Seizures 100%

24
Q

What causes Schizencephaly?

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A

Most sporadic: exposures, infection, young mothers

Four genes identified (minority of cases): EMX2, SIX3, SHH, and COL4A1

25
What are the symptoms associated with Lissencephaly?
* Acquired microcephaly 1st year of life * Hypotonia → subsequent hypertonia * Paucity of movement *Feeding disturbance * Seizures * Bitemporal narrowing, small jaw
26
What are examples of Lissencephaly-Pachygyria Type I?
* Isolated lissencephaly * Miller-Dieker syndrome
27
What are examples of Lissencephaly-Pachygyria Type II?
* Walker-Warburg syndrome * Muscle-Eye-Brain disease * Fukayama Congenital muscular dystrophy
28
What are the non-genetic factors that cause lissencephaly?
viral infections placental insufficiency
29
What genes are associated with lissencephaly?
LIS1, RELN, TUBA1A, NDE1, KATNB1, CDK5, * ARX and *DCX genes *X-linked
30
What is the genetic cause of Miller-Dieker Syndrome?
* Autosomal recessive * Chromosome 17p13.3 deletion (LIS1 gene + - contiguous gene syndrome)
31
What is the phenotype of Miller-Dieker Syndrome?
Lissencephaly Severe intellectual disability Developmental delay Seizures Spasticity Hypotonia Feeding difficulties Other: Cardiac malformations, genital anomalies (male), sacral dimple, deep palmar creases, clinodactyly
32
What are the facial features in Miller-Dieker syndrome?
Bitemporal narrowing, small jaw, short nose, upturned nares, long and protuberant upper lip, flattened midface
33
What is Band Heterotopia “double cortex”?
Condition in which nerve cells (neurons) do not move (migrate) to their proper locations in the fetal brain during early development.
34
What are the genes associated with periventricular nodular heterotopia?
FLNA (x-linked) FMR1 (x-linked) RFGEF2 ERMARD FAT4 DCHS1 LRP2
35
What is Dandy-Walker?
Congenital brain malformation involving the cerebellum (an area of the back of the brain that coordinates movement) and the fluid-filled spaces around it
36
What are the brain findings in Dandy-Walker malformation?
* Inferior vermian agenesis * Uplifting of the vermis and tentorium cerebelli * Wide communication of the fourth ventricle posteriorly with a large CSF space. * Elevation of the straight sinus and torcula Herophili
37
What is the most common malformation of the cerebellum?
Dandy-Walker malformation
38
What is the genetic cause of Dandy-Walker malformation?
ZIC1, ZIC4, FOXC1, FGF17, LAMC1, and NID1
39
What is the recurrence risk of non-genetic Dandy-Walker malformation?
less than 5%
40
What are some genetic syndromes with Dandy-Walker malformation?
* PHACE syndrome -Posterior fossa brain malformations, Hemangionas, Arterial lesions, Cardiac abnormalities, and Eye abnormalities * Meckel-Gruber syndrome2 * Ritscher-Schinzel or cranio-cerebello-cardiac syndrome * Keratitis–ichthyosis–deafness syndrome (KIDS)
41
What are other brain malformations associated with Dandy-Walker malformation?
dysgenesis or agenesis of the corpus callosum occipital encephalocele polymicrogyria heterotopia hydrocephalus (90% of patients)
42
What are Cavernous malformations?
Clusters of abnormal, tiny blood vessels and larger, stretched-out, thin-walled blood vessels filled with blood and located in the brain
43
What are the symptoms of Cavernous malformations?
Seizures Weakness in arms or legs Vision problems Balance problems Memory and attention problems Headaches
44
What genes are associated with Cavernous malformations?
KRIT1 (CCM1) Malcavernin (CCM2) PDCD10 (CCM3)
45
What are the three primary findings in Joubert syndrome?
A distinctive cerebellar and brain stem malformation called the molar tooth sign (MTS) Hypotonia Developmental delays
46
What percentage of patients with Joubert have genetic diagnosis?
62%-94% biallelic pathogenic variants in one of the 33 autosomal recessive one x-linked
47
What are additional findings in Joubert syndrome?
episodic tachypnea or apnea atypical eye movements truncal ataxia develops over time acquisition of gross motor milestones is delayed. severe intellectual disability to normal retinal dystrophy renal disease ocular colobomas occipital encephalocele hepatic fibrosis polydactyly oral hamartomas endocrine abnormalities
48
What is spina bifida occulta?
Often incidentally found Small gap in the spine but there is no protruding sac Possible hair tuft
49
What is meningocele?
Protruding sac of fluid that does NOT contain the spinal cord Little to no nerve damage
50
Where does the encephalocele occur?
Anywhere on midline from nose to back of head Better prognosis if in the front of the head and less likely to contain brain matter
51
What AFP level suggests an ONTD?
>2.5 MoM

Survey of Human Genetic Disorders Second Half (10 decks)

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