Congenital Disorders I Flashcards
when does neural tube closure take place?
in general all neural tube dz related to?
during week 3 –> so see defects
failure of NT to close properly or failure of NT to separate from overlying ectoderm (can cause tethered spinal cord)
NT defect (0-4 wks) mechanism of cranioraschisiss totalis
- most severe defect
- complete failure of NT to close –> leaving plate where actual NT should be
lethal
NT defect (0-4 wks) mechanism of anencephaly
failure of rostral neuropore to close
forebrain neuroectoderm doesn’t separate from cutaneous ectoderm –> red area cerebrovasculosa protruding out of head
“bug eye” b/c diencephalon does develop
lethal
NT defect (0-4 wks) mechanism of encephalocele
defect in skull with protrusion of leptomeninges and/or brain
different from anencephaly because epidermal covering over protrusion
possibly survive
NT defect (0-4 wks) mechanism of myelomeningocele
failure of posterior neuropore to close
80% in lumbar area –> kids have urinary and gait problems
no epidermal covering + CSF leak
NT defect (0-4 wks) mechanism of meningocele
skin covered CSF filled mass continuous with CSF in spinal cord
usu rest of tissue of cord is normal
kids have urinary and gait problems
NT defect (0-4 wks) lipomyelocele/lipomyelomeningocele
Lipoma extends from subcutaneous tissue to dorsal aspect of cord, tethering cord infeirorly
cause = premature separation of cutaneous ectoderm during neurulation allowing mesenchyme to enter unclosed NT and diff into fat
NT defect (0-4 wks) dorsal dermal sinus tract
ectoderm lined tract that crosses dura and allow CSF and skin to communicate
can tether spinal cord and/or assoc with intradural dermoid cyst or epidermoid
NT defect (0-4 wks) spina bifida occulta
occurs at L5-S1
occurs when bony lamina of vertebral body fails to close over portion of meningeal sac
usu no sx but can have cutaneous abnormality
NT defect (0-4 wks)
disease assoc with spinal cord tethering (all caudal derived)
myelomeningocele
lipomyelocele/lipomyelomeningocele
dorsal dermal sinus tract
spina bifida occulta
NT defects can be prevented with
preconception folic acid supplementation
holoprosencephaly
occurs when
cleavage of prosencephalon during week 5
occurs when single ventricle in early forebrain fails to form two lateral ventricles and 1 3rd ventricle (complete or partial)–> failure of 2 cerebral hemispheres to divide properly
3 types of holoprosencpephaly
1) alobar
2) semilobar
3) lobar
disorders of telencephalic development (~4-8 wks)
define alobar holoprosencephaly
no evidence of division of cerebral cortex 1 forebrain, 1 ventricle fusion of thalami assoc with cleft lip/palate severe facial abnormality (most severe--> lethal)
disorders of telencephalic development (~4-8 wks)
define semilobar holoprosencephaly
partial cleavage of hemispheres with fusion of frontal lobes
horseshoe central ventricle
some fusion of thalami
no olfactory bulbs/corpus callosum
disorders of telencephalic development (~4-8 wks)
define lobar holoprsencephaly
hemispheres separated anteiorly and posteriorly with some fusion
- least severe
- normal life expectancy with severe mental/physical
disorders of telencephalic development (~4-8 wks)
in general facts
1) genetic or not?
2) what gene involved
3) assoc with what chromosome
1) strong genetic
2) shh
3) assoc with trisomy 13
disorders of telencephalic development (~4-8 wks)
Type of deformities common?
4) facial deform with
- cebocephaly- hypotelorism, 1 nostril
- cyclopia
- ethmocephaly-
- arhinia
- coloboma of iris and retina
- premaxillary agenesis (no nares or philtrum)
- midline facial clefts (cleft lip)
Disorders of cerebellar development (8-15 wks)
cerebellar aplasia
complete absence of cerebellum
Disorders of cerebellar development (8-15 wks)
dandy walker
most common
includes
a) partial or complete absence of vermis
b) cystic dilation of 4th ventricle
c) upward displacement of tentorium
assoc with cerebral/visceral but NOT NTDs or MATERNAL FOLATE
Disorders/of/Proliferation// Migration/(8.20/wks)/
MEGALENCEPHALY
too many neurons = too big brain
sx = delayed development
convulsions
corticospinal dysfunction
seizures
Disorders/of/Proliferation// Migration/(8.20/wks)/
microcephaly
a) primary microcephaly
too few neurons
multifacotral
2 copies of loss of fxn mutation in microcephalin gene
decr life expectancy
poor prognosis
Disorders/of/Proliferation// Migration/(8.20/wks)/
problems with onset of migration
Periventricular heterotopia
inheritance
mutation
X linked dominant
lethal in males
mutation in FLNA so neurons can’t leave VZ
female PH = epilepsy but no cog abnormalities
Disorders/of/Proliferation// Migration/(8.20/wks)/
problems in migration process
type 1 lissencephaly
gene
sx
neurons exit VZ but halt migration premature
brains smooth (agyria)
LIS 1 = gene (heterozygous, haploinsufficiency)
–> severe mental retard + epilepsy
