Congenital Disorders I

Question 1

when do neural tube defects occur?

Answer 1

week 3

Question 2

describe holoprosencephaly

Answer 2

disorder of TELENCEPHALIC development. prosencephalon fails to form properly into lateral ventricles and 3rd ventricle. can be complete or partial and results in failure of two cerebral hemispheres to divide properly.

Question 3

when does holoprosencephaly occur?

Answer 3

5 week of fetal organ formation.

Question 4

what are the disorders of neuronal proliferation?

Answer 4

macrencephaly, micrencephaly

Question 5

when do disorders of neuronal proliferation occur?

Answer 5

weeks 8-16, during fetal organ development.

Question 6

What are the disorders of neuronal migration?

Answer 6

lissencephaly, polymicrogyria.

Question 7

when do disorders of neuronal migration occur?

Answer 7

weeks 12-16, during fetal organ development.

Question 8

describe disorders of elaboration of neurons and glia.

Answer 8

These include dendritogenesis, axonal growth, myelination, malnutrition, metabolic disorders, prematurity. Weren’t discussed in first handout.

Question 9

when do disorders of elaboration of neurons and glia occur?

Answer 9

20-30 weeks up to 5 years.

Question 10

describe the association between Chiari I malformation and syringomyelia

Answer 10

A small posterior fossa causes the lower part of the cerebellum to protrude from its normal location in the back of the head into the cervical portion of the spinal canal. A syrinx may then develop.

Question 11

describe the association between Chiari II malformation and myelomeningocele

Answer 11

Incomplete closure of neural folds leads to leakage of CSF into the amniotic fluid and creates a collapse of the primitive ventricular system. so ventricles fail to increase in size and volume due to downward and upward herniation of the small cerebellum. This also leads to inadequate development of the posterior fossa.

Question 12

Describe the normal levels at which the conus medullaris is found with respect to the vertebral column at different stages of development.

Answer 12

newborn: found at L3. 3 months of age: shouldn’t be below the lower margin of L2. adult: L1-L2.

Question 13

what symptoms result from syringomyelia?

Answer 13

results in a “cape-like” bilateral loss of pain and temperature sensation in upper extremities.

Question 14

what symptoms result from tethering?

Answer 14

compromised blood supply + spinal cord dysfunction. This results in pain + UMN signs such as hyperreflexia and spasticity + urinary continence.

Question 15

What are the principal causes of stroke in the perinatal period?

Answer 15

1) vascular malformations 2) congenital heart malformations; 3) genetic abnormalities; 4) neurocutaneous syndromes; 5) primary vascular disease

Question 16

What are the principal consequences of stroke in the perinatal period?

Answer 16

spastic motor defects, most frequent cause of cerebral palsy.

Question 17

dysraphism

Answer 17

congenital abnormalities in vertebrae/spinal cord/nerve roots.

Question 18

what is carnioraschisis totalis?

Answer 18

Neural tube defect. Most severe form of neural tube defect. A complete failure of primary neurulation.

Question 19

anencephaly

Answer 19

Neural tube defect. Failure of rostral neuropore to close. Forebrain neuroectoderm fails to separate from cutaneous ectoderm, and a red area cerebrovasculosa is seen where the calvarium would have developed.

Question 20

encephalocele

Answer 20

neural tube defect. defect in the skull with protrusion of leptomeninges +/- brain. distinguished from anencephaly because they have an epidermal covering over the cranial neural tube closure defects.

Question 21

myelomeningocele

Answer 21

results from failure of closure of the posterior neuropore. no epidermal covering and CSF leak. usually in lumbar area.

Question 22

meningocele

Answer 22

skin-covered, CSF filled mass that is continuous with the CSF in the spinal canal.

Question 23

lipomyelocele/lipomyelomeningocele

Answer 23

occurs when a lipoma extends from the subcutaneous tissues to the dorsal aspect of the cord and tethering the cord inferiorly. reflects premature separation of the cutaneous ectoderm during the process of neurulation that allows mesenchyme to enter the unclosed neural tube and differentiate into fat.

Question 24

dorsal dermal sinus tract

Answer 24

these are ectoderm-lined tracts that can transgress the dura and allow communication between the skin and CSF. They can also cause tethering of the spinal cord and can be associated with an intradural dermoid cyst/epidermoid.

Question 25

spinal cord tethering

Answer 25

group of spinal cord syndromes. all forms involve the pulling of the spinal cord at the base of the spinal canal. The spinal cord normally hangs loose in the canal, free to move up and down with growth and bending/stretching. A tethered cord, however, is held taut at the end or at some point in the spinal canal.

Question 26

spina bifida occulta

Answer 26

benign finding usually found incidentally. usually at L5-S1.

Question 27

what is a chiari type I malformation?

Answer 27

cerebellar TONSILS are elongated and pushed down through the foramen magum, blocking the normal flow of CSF. This blocks flow of CSF out of central canal of spinal cord into subarachnoid space leading to an accumulation of CSF within the central canal called hydromyelia, or it can lead to syringomyelia, or hydrocephalus.

Question 28

syringomyelia

Answer 28

CSF-filled cyst that breaks out of the central canal and dissects into the substance of the spinal cord.

Question 29

myelopathy

Answer 29

dysfunction of the spinal cord

Question 30

what is the underlying problem of type I chiari malformations?

Answer 30

mesodermal disorder. underdevelopment of the occipital somites.

Question 31

which chiari type malformation is commonly associated with myelomeningocele?

Answer 31

Type II malformation

Question 32

What are the features of a Chiari Type II malformation?

Answer 32

1) elongation of cerebellar VERMIS, which are pushed down through foramen magnum and can block CSF flow 2) abnormalities of the brainstem (beaking of tectal plate and “z-kink” in medulla) 3) abnormalities of the dural venous sinus including a low-lying confluence of sinuses and osseous abnormalities of the skull.

Question 33

myeloschisis

Answer 33

dorsal defect due to incomplete closure of neural folds

Question 34

underlying cause of chairi II malformation?

Answer 34

failure of neural folds to completely close.

Question 35

Dandy-walker malformation

Answer 35

a) partial or complete absence of formation of the cerebellar vermis b) cystic dilatation of the fourth ventricle c) upward displacement of the tentorium. may show d) hydrocephalus. mostly sproadic, NOT related to a neural tube defect, and NOT related to maternal folate deficiency. Often associated with other cerebral and/or visceral anomalies.

Question 36

what is the definition of megalencephaly?

Answer 36

abnormally large brain. usually defined as greater than 2 SD from mean weight.

Question 37

Why does megalencephaly occur?

Answer 37

mutation in PI3K-AKT pathway is believed to be the primary cause of brain proliferation and ultimately the root cause.

Question 38

what is the definition of microcephaly?

Answer 38

usually defined as a head circumference more than 2 standard deviations below the mean for age and gender.

Question 39

when does microcephaly occur?

Answer 39

disorder of neuronal proliferation. 8-16 weeks.

Question 40

what is the definition of agyria/lissencephaly?

Answer 40

brain disorder caused by defective neuronal migration during the 12-24 weeks of gestation that results in a lack of development of brain folds (gyria) and grooves (sulci)

Question 41

what is the definition of polymicrogyria?

Answer 41

developmental malformation of brain in which excessive number of small convolutions (gyri) on the surface o the brain.

Question 42

when does polymicrogyria occur?

Answer 42

Disorder of neuronal migration. So between 12 and 16 weeks.

Question 43

porencephaly

Answer 43

large unilateral holes in brain

Question 44

schizencephaly

Answer 44

abnormal clefts lined with grey matters. can occur bilaterally or unilaterally.

Question 45

hydraencephaly

Answer 45

cerebral hemispheres are absent to varying degrees are replaced with CSF.

Question 46

leptomeninges

Answer 46

arachnoid and pia mater

Question 47

what does sacral dimpling indicate?

Answer 47

spina bifida occulta. but if floor of dimple isn’t covered with skin = NTD

Question 48

what does abnormally narrow intercanthal distance suggest?

Answer 48

narrow indicates problems of cleavage or formation of midline structure.

Question 49

What does absence of palate indicate?

Answer 49

cleft lift and palate.

Question 50

underlying abnormality in medulloblastoma

Answer 50

Shh mutation

Question 51

What is the main site for birth of neurons?

Answer 51

germinal matrix.

Question 52

what is heterotopia? underlying protein abnormality?

Answer 52

Displacement of a particular tissue type from its normal physiological position. double cortex for example. bands of cortex form in the cerebrum. globs of grey matter that shouldn’t be there. common with filamin defects. Usually due to failure of x-chromosome inactivation (double check).

Question 53

pachygyria

Answer 53

unusually thick gyrations. Leads to seizure disorders.

Question 54

down syndrome brain abnormalities?

Answer 54

microcephaly, foreshortened/rounded forebrain, overproduction of amyloid leading to early onset AD,

Question 55

periventricular leukomalacia

Answer 55

white-matter brain injury characterized by coagulative necrosis of white matter near the lateral ventricles. Causes cerebral palsy or epilepsy.