02b: CNS defects

Question 1

Neuropores (rostral and caudal) are closed by (X) (day/week) of gestation.

Answer 1

X = 25th-27th day

Question 2

Spina Bifida oculta is caused by improper (X) and usually occurs at which vertebra level?

Answer 2

X = incomplete closure of vertebral arch

L5-S1

Question 3

Meningocele contains (X) and myelomeningocele contains (Y).

Answer 3

X = meninges and CSF
Y = meninges, CSF, neural tissue

Question 4

70-90% of patients with myelomeningocele have associated (X), esp if located in thoracolumbar region.

Answer 4

X = hydrocephalus

Question 5

There is up to 8% risk of (X) recurrence after birth of child with spina bifida.

Answer 5

X = myelodysplasia

Question 6

How are neural tube defects diagnosed in antenatal period?

Answer 6

1. Elevated alpha-fetoprotein in maternal serum

2. Ultrasound

Question 7

Encephalocele is:

Answer 7

herniation of brain and intracranial contents through skull defect

Question 8

Cranial meningocele is:

Answer 8

herniation of meninges and CSF through skull defect (no neural tissue)

Question 9

Failure of the brain to divide is called (X); it arises before (Y) day/week of gestation.

Answer 9

X = holoproscencephaly;
Y = 23 day

Question 10

List the forms of holoproscencephaly, from least to most severe.

Answer 10

1. Lobar
2. Semilobar
3. Alobar

Question 11

Lobar holoproscencephaly: (X) brain ventricles are fused and the ventricular system is comprised of:

Answer 11

X = deeper

Two ventricles (lateral ventricle division is not formed)

Question 12

Semilobar holoproscencephaly: (X) brain ventricles are fused and the ventricular system is comprised of:

Answer 12

X = anterior and deep

Two occipital horns only

Question 13

Facial features such as single eye, nare, or incisor can be seen with which CNS defect?

Answer 13

Holoprosencephaly

Question 14

Neurons normally migrate (inward/outward) starting from (X) to form the cortex layers. (Inner/outer) cortical layers form first.

Answer 14

Outward
X = periventricular zone

Inner (layer 1, most superficial, forms last)

Question 15

Migration of neurons during cortex formation occurs via which two mechanisms?

Answer 15

1. Somal translocation (cell body moves toward pial surface)

2. Radial glial cell guide/track

Question 16

CNS deformity resulting in smooth brain is called:

Answer 16

Lissencephaly

Question 17

Genetic syndrome particularly associated with lissencephaly involves (X) gene, responsible for regulating (Y).

Answer 17

X = LIS-1
Y = neuronal migration

Question 18

Lissencephaly Type (I/II) shows severely disorganized cortex with areas of gyri that are:

Answer 18

II;

1. Absent (agyria)
2. Thick (Pachygyria)
3. Excessive and small (Polymicrogyria)

Question 19

Lissencephaly Type (I/II) occurs earlier than the other Type.

Answer 19

I (10-14 weeks gestation with completely smooth brain)

Question 20

Double Cortex deformity is inherited via (X) pattern and presents with which which symptoms?

Answer 20

X = X-linked

Lissencephaly (males), seizures, developmental delays

Question 21

Schizencephaly is flawed development of (X) during (Y) developmental event. This occurs in trimester (1/2/3).

Answer 21

X = cortical mantle
Y = neural cell migration
1

Question 22

Schizencephaly: cleft is most commonly formed in (X). How does it differ from Porencephaly cleft?

Answer 22

X = sylvian fissure

Lined with grey matter (and abnormal gyri)

Question 23

Corpus callosum originates from (X) (before/after) the neural tube closes.

Answer 23

X = rostral neuropore (lamina terminalis)

After (forms on days 74-115)

Question 24

List some etiologies of CC agenesis.

Answer 24

Genetic, metabolic, toxic (fetal alcohol)

Question 25

Megancephaly or microencephaly are defined as brain weight/size that is (X) SDs above/below the mean.

Answer 25

X = 2

Question 26

Megalencephaly is (uni/bi)-lateral and associated with heterotopias, aka (X).

Answer 26

Can be either uni/bi-lateral;

X = neurons in areas where they don’t belong (migrational issue)

Question 27

Cerebellar malformations means there was issue with (X) portion of primitive neural tube.

Answer 27

X = metencephalon (previously the rhombencephalon), which forms pons and cerebellum

Question 28

Chiari malformation Type (I/II) refers to (X) structural abnormality and can be asymptomatic.

Answer 28

Type I

X = herniation of cerebellar tonsils

Question 29

Chiari malformation Type I associated with which symptoms and/or other abnormalities?

Answer 29

Syringomyelia, HA, dizziness, sensory loss, scoliosis

Question 30

Chiari malformation Type (I/II) refers to (X) structural abnormality and can cause thinning/elongation of (Y) brainstem structure.

Answer 30

II;
X = herniation of cerebellum (not just tonsils)
Y = medulla

Question 31

Which structures are atrophied in Chiari malformation Type II?

Answer 31

Pons and cervical SC

Question 32

Chiari malformation Type II associated with which symptoms and/or other abnormalities?

Answer 32

Hydrocephalus (CSF flow blocked) and myelomeningocele (in over 95% of cases)

Question 33

Which structures are affected in Dandy Walker malformation?

Answer 33

1. Enlarged 4th ventricle (extends into spinal canal) as well as other ventricles
2. Absent/dysplastic cerebellar vermis

Question 34

CN (X) palsy can be seen in Dandy Walker malformation.

Answer 34

X = VI