Congenital Malformations Flashcards
What is a neural tube defect, and what are some examples?
Failure of neural tube to close properly
Anencephaly
Encephalocoele
Spina bifida
What is anencephaly, and its features?
Failure of anterior neuropore to close
Skull fails to form
Brain tissue degenerates
Incompatible with life
Craniorachischisis - failure of neural tube closure along entire axis
What is an encephalocoele? Features
Herniation of cerebral tissue through skull defect
Failure in closure of rostral neural tube
Most frequent in occipital region?
Variable degree of neurological deficits
What is spina bifida and what are the different types?
Defective closure of caudal neural tube
Affects tissue overlying cord
In general = non-fusion of vertebral arches
Neural tissue may/may not be affected
Severity ranges from minor abnormalities to major clinical symptoms
Spina bifida occulta
Spina bifida cystica
Features of spina bifida occulta?
Minor form of spina bifida
Failure of embryonic halves of vertebral arch to grow normally and fuse
Occurs in L5 and 6 of 10% of otherwise healthy people
Usually no clinical symptoms
May result in dimple with small tuft of hair
Features and types of spina bifida cystica?
Protrusion of spinal cord and/or meninges through defect in vertebral arches
With meningocoele
= rarest form
- protrusion of meninges and CSF
With meningomyelocoele
- nerve roots and or/spinal cord included in sac
- neurological deficits (sensation loss, muscle paralysis) dependent on level
- often associated with hydrocephalus
Myeloschisis
- most severe form
- spinal cord in affected area open due to failure of neural folds to fuse
Risk factors for neural congenital malformations?
Genetic predisposition
Nutritional factors - too little folate, too much Vitamin A
Environmental - hyperthermia, drugs e.g. sodium valproate
Preventions for neural congenital malformations?
Folic acid supplements Prenatal diagnosis - maternal blood screening (high AFP) - amniocentesis (high AFP) - ultrasound - identifies anencephaly and spina bifida
What are features and causes of hydrocephalus?
Accumulation of CSF, frequently due to blocked aqueduct
- genetic
- prenatal viral infection or intraventricular haemorrhage
- spinal bifida cystica
Results in enlarged cranium/brain
What is lissencephaly?
Rare brain disdorder Defective neuronal migration Gyri/sulci fail to develop Severe mental impairment, failure to thrive, seizures, abnormal muscle tone Many die before 10yo
Also, polymicrogyria
- excessive number of small gyri, variable degree of neurological problems
Other examples of rare abnormalities?
Microcephaly Porencephalu Aegenesis corpus callosum Schizencephaly Diastematomyelia (split cord malformation)
Causes of intellectual impairment with no obvious gross defect?
Genetic Radiation Infectious agents Birth trauma Postnatal insults
Common cause = maternal alcohol abuse
- FAS 1:1000
- estimated 1:100 have some degree of impairment
