Malformations and Developmental Diseases Flashcards
How is a malformation caused?
intrinsic malformation
How is a deformation caused?
external force acts upon
How is a disruption caused?
a destructive force acts upon
When is the neurulation phase?
3-4wks
When is the prosencephalic phase?
2-3 mos
When is the neuronal proliferation phase?
3-4 mo
When is the neural migration phase?
3-5 mo
When is the organization phase?
5-postnatal years
When does myelination occur?
birth-postnatal years
When does neural tube closure occur?
28 days
What is the definition of a neural tube defect?
disurbance of formation of neuroectodermal and/or overlynig mesodermal structures or reopening or secondary rupture of closed tube
How can neural tube defects be detected?
prenatal folate supplement
What are the 3 main types of neural tube defects?
spina bifida
anencephaly
encephalocele
Which type of spina bifida causes neural defects?
myelomeningocoele
What drug can cause neural tube defects in 1-2% of pregnancies?
valproic acid
What are potential complications of myelomeningocoele?
hydrocephalus (type II chiari defect 80%)
meningitis
pneumonia
What is a chiari crisis?
downward herniation of the medulla and cerebellar tonsils
What is typically missing in anencephaly?
cerebral and cerebellar hemispheres
calvarium, meninges and scalp
What is an encephalocele?
broad-based pedunculated masses of cerebral tissue & dura protruding through cranial defect, covered by skin
Where is the most common site for an encephalocele?
occupital region, frontal/nasal location also common
What is meckel-gruber syndrome?
AR condition
occipital encephalocoele, cleft lip or palate, microcencephaly, micropthalmia, abnormal genitalia, polycystic kidneys and polydactyly
What is polymicrogyria?
too many irregular small fused gyri
What casues polymicrogyria?
results from the disordered organization of the neurons in the cortex at the time of migration
What is agyria?
absence of gyri
What are pachygyria?
decreased numbers of broad coarse gyri, brain is small
When does agyria or pachygyria occur?
4th month gestation
What chromosomes are associated with agyria or pachygyria?
17 & X
What are sx of a/pachy-gyria?
failure to thrive microcephaly marked developmental delay severe seizure disorder hypoplasia of the optic nerve microphthalmia
What is miller dieker syndrome?
prominent forehead, bitemporal hollowing, nteverted nostrils, prominent upper lip, micrognathia
What is schizencephaly?
unilateral or bilateral clefts within the cerebral hemispheres due to an abnormality of morphogenesis
cleft may be fused or unfused, and is usually surrounded by abnormal brain, microgyria
What are sx of schizencephaly?
severe MR
intractable seizures
microcephaly
spastic quadriplegia when clefts are bilateral
What is arrhinencephaly?
disorders of cleavage of forebrain
ie/holoprosencephaly & olfactory aplasia
What are signs/sx of holoprosencephaly?
profound MR, seizures, rigidity, apnea, temperature imbalance, hydrocephalus, facial abnormalities
What causes agenesis of the corpus callosum?
an insult to the commissural plate during embryogenesis
What are signs/sx of agenesis of the corpus callosum?
usually asymptomatic , margination defects (heterotopia, microgyria, pachygyria)
may present with MR, microcephaly, hemiparesis, diplegia and seizures
What do you see on CT/MRI for agenesis of the corpus callosum?
widely separated frontal horns with an abnormally high position of the 3rd ventricle
What is aicardi syndrome?
severe MR, intractable seizures w/onset between birth and 4 mo age, chorioretinal lacunae
hemivertebrae and costovertebral anomalies are common
independent activity from both hemispheres as a result of the absence of the corpus callosum
What is a type 1 chiari malformation?
chronic tonsillar herniation
assoc w/hydrocephalus, sudden death, cranial nerve palsies, ataxia, long tract signs, syringomyelia
What is another name for a type 2 chiari malformation?
arnold chiari malformation
What is a type 2 chiari malformation?
herniated cerebellar tissue through foramen magnum with displacement of dorsal medulla causing a hump or Z-shape in brainstem/spinal cord
What are signs/sx of a type 2 chiari malformation?
lower cranial nerve defects
arm weakness, spasticity, hydrocephalus sx
What is a dandy walker malformation?
agenesis of vermis
cystic dilatation of the 4th ventricle
enlargement of posterior fossa
hydrocephalus is frequently present
What are signs/sx of dandy walker malformation?
motor retardation, spasticity and resp failure
What is a risk factor for dandy walker malformation?
isotretinoin use during pregnancy
What is a syringomyelia?
fluid filled cleft like cavity in spinal cord
assoc w/chiari type 1 malformation and post traumatic
What are signs/sx of syringomyelia?
loss of pain/temp, retention of position and vibration senses & motor function
onset of symptoms in 2nd and 3rd decades, progressive
What happens with perinatal hypoxia/ischemia of white matter? White and gray matter?
white matter necrosis (periventricular leukomalacia)
multicystic encephalopathy
What happens with perinatal hemorrhagic lesions?
subependymal germinal plate/matrix hemorrhage
What causes cerebral palsy?
perinatal insults
What is cerebral palsy?
non-progressive neurologic motor deficit
-spasticity, dystonia, ataxia/athetosis, paresis
What does periventricular leukomalacia look like?
sharply defined foci of necrosis in white matter
selectively vulnerable oligodendrocytes lost
histology: central zone of necrosis, surrounding mineralization of axons
What does multicystic encephalopathy look like?
sponge-like glial lined cysts post destruction of both gray and white matter in 3rd trimester
Where do most subependymal germinal matrix hemorrhages originate/
germinal zone overlying head of caudate and thalamus
frequently break through into ventricular system or underlying parenchyma
What usually precipitates subependymal germinal matrix hemorrhage?
extreme physical distress/prematurity
perinatal occurrence, hemodrynamic instability, mechanical ventilation, hyaline membrane disease
Where do grades 1-4 of subependymal hemorrhages invade?
1-confined to germinal matrix
2-germinal matrix & lateral ventricle, no ventricular dilation
3-germina matrix & lateral ventricle, with acute ventricular distention
4- grade 3 plus extension into adjacent brain parenchyma
