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

Brain Malformations Flashcards

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)?

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?

A

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

23
Q

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

A

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

24
Q

What causes Schizencephaly?

A

Most sporadic: exposures, infection, young mothers

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

25
Q

What are the symptoms associated with Lissencephaly?

A
  • Acquired microcephaly 1st year of life
  • Hypotonia → subsequent hypertonia
  • Paucity of movement
    *Feeding disturbance
  • Seizures
  • Bitemporal narrowing, small jaw
26
Q

What are examples of Lissencephaly-Pachygyria Type I?

A
  • Isolated lissencephaly
  • Miller-Dieker syndrome
27
Q

What are examples of Lissencephaly-Pachygyria Type II?

A
  • Walker-Warburg syndrome
  • Muscle-Eye-Brain disease
  • Fukayama Congenital muscular dystrophy
28
Q

What are the non-genetic factors that cause lissencephaly?

A

viral infections
placental insufficiency

29
Q

What genes are associated with lissencephaly?

A

LIS1, RELN, TUBA1A, NDE1, KATNB1, CDK5,
* ARX and *DCX genes

*X-linked

30
Q

What is the genetic cause of Miller-Dieker Syndrome?

A
  • Autosomal recessive
  • Chromosome 17p13.3 deletion (LIS1 gene + - contiguous gene syndrome)
31
Q

What is the phenotype of Miller-Dieker Syndrome?

A

Lissencephaly
Severe intellectual disability
Developmental delay
Seizures
Spasticity
Hypotonia
Feeding difficulties

Other: Cardiac malformations, genital anomalies (male), sacral dimple, deep palmar creases, clinodactyly

32
Q

What are the facial features in Miller-Dieker syndrome?

A

Bitemporal narrowing, small jaw, short nose, upturned nares, long and protuberant upper lip, flattened midface

33
Q

What is Band Heterotopia “double cortex”?

A

Condition in which nerve cells (neurons) do not move (migrate) to their proper locations in the fetal brain during early development.

34
Q

What are the genes associated with periventricular nodular heterotopia?

A

FLNA (x-linked)
FMR1 (x-linked)
RFGEF2
ERMARD
FAT4
DCHS1
LRP2

35
Q

What is Dandy-Walker?

A

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
Q

What are the brain findings in Dandy-Walker malformation?

A
  • 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
Q

What is the most common malformation of the cerebellum?

A

Dandy-Walker malformation

38
Q

What is the genetic cause of Dandy-Walker malformation?

A

ZIC1, ZIC4, FOXC1, FGF17, LAMC1, and NID1

39
Q

What is the recurrence risk of non-genetic Dandy-Walker malformation?

A

less than 5%

40
Q

What are some genetic syndromes with Dandy-Walker malformation?

A
  • 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
Q

What are other brain malformations associated with Dandy-Walker malformation?

A

dysgenesis or agenesis of the corpus callosum
occipital encephalocele
polymicrogyria
heterotopia
hydrocephalus (90% of patients)

42
Q

What are Cavernous malformations?

A

Clusters of abnormal, tiny blood vessels and larger, stretched-out, thin-walled blood vessels filled with blood and located in the brain

43
Q

What are the symptoms of Cavernous malformations?

A

Seizures
Weakness in arms or legs
Vision problems
Balance problems
Memory and attention problems
Headaches

44
Q

What genes are associated with Cavernous malformations?

A

KRIT1 (CCM1)
Malcavernin (CCM2)
PDCD10 (CCM3)

45
Q

What are the three primary findings in Joubert syndrome?

A

A distinctive cerebellar and brain stem malformation called the molar tooth sign (MTS)
Hypotonia
Developmental delays

46
Q

What percentage of patients with Joubert have genetic diagnosis?

A

62%-94%
biallelic pathogenic variants in one of the 33 autosomal recessive
one x-linked

47
Q

What are additional findings in Joubert syndrome?

A

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
Q

What is spina bifida occulta?

A

Often incidentally found
Small gap in the spine but there is no protruding sac
Possible hair tuft

49
Q

What is meningocele?

A

Protruding sac of fluid that does NOT contain the spinal cord
Little to no nerve damage

50
Q

Where does the encephalocele occur?

A

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
Q

What AFP level suggests an ONTD?

A

> 2.5 MoM

Survey of Human Genetic Disorders Second Half (10 decks)

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