Congenital Disorders I-III

Question 1

1. Recognize the normal levels at which the conus medullaris is found with respect to the vertebral column at different stages of development and describe the concept of tethering of the spinal cord that can be associated with neural tube defects.

Answer 1

Conus medullaris locations:
newborn = L3 
At age 3 mos = not below L2
in adult = at L1-L2
tethering = prevention of conus ascension over time --> tension --> compromise in blood supply---> spinal cord dysfunction--> pain, UMN signs (spasticity, hyperreflexia), urinary incontinence

Question 2

2. Describe the following prototypical congenital malformations, including the period during embryogenesis and development when they occur: Neural tube defects, holoprosencephaly, disorders of neuronal proliferation, disorders of neuronal migration, and disorders of elaboration of neurons and glia.

Answer 2

neural tube defects (Rachischisis, Dysraphism) = failure of neuroectoderm to form a complete, closed tube during 1a neurulation

1. cranioraschisis totalis = complete failure, most severe
2. anencephaly = failure of rostral neuropore to close–> forebrain doesn’t separate from ectoderm; NO EPIDERMAL COVERING
3. encephalocele = defect in skull w/ protrusions of leptomennges +/- brain but HAS EPIDERMAL COVERING
4. myelomeningocele = failure of closure of post. neuropore; usu. in lumbar area; CSF leak
5. meningocele = skin covered, CSF-filled mass
6. lipomyocele/lipomyelomeningocele = premature separation of cutaneous ectoderm–> mesenchyme enters neural tube–> lipoma into dorsal cord and tethers cord inferiorly
7. dorsal dermal sinus tract = ectoderm-lined tracts allowing communication btw skin and CSF–> tethering of spinal cord
8. spina bifada occulta = L5-S1; no s/s, no tx needed

holoprosencephaly (telecephailic disorder)= single ventricle in early embryonic forebrain fails to properly differentiate into the 3 ventricles –> cerebral hemispheres don’t develop–> face and eyes deformed–>”holoprosencephaly”

1. alobar holo.= no division of cerebral cortex
2. semilobar holo. = partial cleavage (frontal cortex only); horseshoe appearance
3. lobar holo. = little fusion

Question 3

3. Discuss the principal causes and consequences of stroke in the perinatal period.

Answer 3

causes = vascular malformations, congenital heart malformations, genetic abnormalities, clotting problems, sickle cell anemia, hereditary polycythemias, neurocutaneous syndromes, primary vascular diseases (fibromuscular dysplasia, Moya Moya; rare)

consequences:
full term infants =ulegyria (mushroom-shaped gyri bc one side of the cortex continues to grow)–> cerebral palsy
preterm infants = subependymal hemorrhages (SEH) –> bleed into the germinal matrix –> morbidity/mortality–> cerebral palsy

Question 4

4. Describe the association between Chiari I malformation and syringomyelia, and the association between Chiari II malformation and myelomeningocele.

Answer 4

Chiari I = cerebellar tonsils pushed thru foramen magnum –> CSF blockage–> hydromelia (accumulation of CSF in central canal) OR syingomelia (CSF-filled cyst that breaks out of central canal). NO myelomeningoceles.

Chiari II = elongation of cerebellar vermis pushed thru the foramen magnum –> CSF blockage –> brainstem abnormalities–> abnormal dural venous sinus and bone abnormalities —> ALMOST ALWAYS have thoraco-lumbar myelomeningocele

Question 5

5. Recognize symptoms that result when a process such as syringomyelia or tethering affects the spinal cord.

Answer 5

symptoms = pain, paralysis, paresis, PNS or SNS dysfunction

Question 6

Megalencephaly

Answer 6

abnormally large brain
mutation in the PI3K-AKT pathway
autism

Question 7

Dx?
abnormally large brain
mutation in the PI3K-AKT pathway
autism

Answer 7

Megalencephaly

Question 8

Microcephaly

Answer 8

small head
congenital (microcephalin genes) or acquired
Rett syndrome

Question 9

Dx?
small head
congenital (microcephalin genes) or acquired
Rett syndrome

Answer 9

Microcephaly

Question 10

Agyria

Answer 10

no gyri
aka Lissencephaly
defective neuronal migration during the 12th to 24th weeks of gestation

Question 11

Dx:?
no gyri
aka Lissencephaly
defective neuronal migration during the 12th to 24th weeks of gestation

Answer 11

agyria

Question 12

Polymicrogyria

Answer 12

excessive gyri

disorder of neuronal migration resulting in structurally abnormal cerebral hemispheres

Question 13

Dx?
excessive gyri
disorder of neuronal migration resulting in structurally abnormal cerebral hemispheres

Answer 13

Polymicrogyria