congenital disorders Flashcards
(40 cards)
When does myelination occur in CNS
Mainly after birth, and by 6 years it is nearly complete.
How to prevent neural tube defects
folic acid supplementation periconceptually from 4 weeks before pregnancy through first trimester. 0.4mg/day (or 4mg/day for women with history of prior pregnancy with NTD)
How are neural tube defects detected
AFP elevation in amniotic fluid (peaks 12-14GW), elevated maternal serum or amniotic fluid acetylcholinesterase
Period during development when neural tube defects occur
day 14-26 (week 3) prenatally
Period during development when holoprosencephaly occurs
week 5-6 prenatally
Period during development when disorders of neuronal proliferation occur
weeks 8-16 prenatally
Period during development when disorders of neuronal migration occur
weeks 12- 16 prenatally
Period of development when disorders of elaboration of neurons and glia occurs
from week 20 prenatally - 5 years post natally
Cranioraschisis totalis
The most severe form of neural tube defect, a complete failure of primary neurulation. The word stem raschis means “main axis” or “shaft. Least common
Anencephaly
failure of the rostral neuropore to close, around day 23-25. The forebrain neuroectoderm fails to separate from the cutaneous ectoderm, and a red area cerebrovasculosa is seen where the calvarium would have developed.
Encephalocele
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
Myelomeningocele (spina bifida)
Results from failure of closure of the posterior neuropore, day 25-27. 80% in lumbar area (last area of neural tube to close). Consists of a neural placode without epidermal covering, with CSF leak. Can have lower extremity or urinary problems
Meningocele
a skin-covered, CSF-filled mass that is continuous with the CSF in the spinal canal
Lipomyelocele/lipomyelomeningocele
occurs when a lipoma extends from the
subcutaneous tissues to the dorsal aspect of the cord and tethering the cord inferiorly. This process reflects a premature separation of the cutaneous ectoderm during the process of neurulation that allows mesenchyme to enter the unclosed neural tube and differentiate into fat.occurs when a lipoma extends from the
subcutaneous tissues to the dorsal aspect of the cord and tethering the cord inferiorly. This process reflects a premature separation of the cutaneous ectoderm during the process of neurulation that allows mesenchyme to enter the unclosed neural tube and differentiate into fat.occurs when a lipoma extends from the
subcutaneous tissues to the dorsal aspect of the cord and tethering the cord inferiorly. This process reflects a premature separation of the cutaneous ectoderm during the process of neurulation that allows mesenchyme to enter the unclosed neural tube and differentiate into fat.
Dorsal dermal sinus tract
These are ectoderm-lined tracts that can transgress the dura and allow communication between the skin and the cerebrospinal fluid. The can also cause tethering of the spinal cord and can be associated with an intradural dermoid cyst or epidermoid.
Bony spina bifida occulta
At the L5-S1 level this is a common incidental finding on radiographs, both in children and adults, and it is usually not associated with symptoms or signs. Failure of bony laminar arch to completely envelop meningeal sac. Cutaneous abnormality often present, such as sacral dimple or hairy patch. If no signs are present, no further imaging workup is required
Sacrococcygeal teratoma
After primitive streak has regressed it forms pluripotent mass of cells called caudal eminence/end bud. These cells may give rise to a teratome
Where do most neural tube defects occur and what is the consequence of this
in lumbar region- In typical newborns, the conus medullaris is at L3 vertebral body , by 3 months its at L2 and by adulthood its at L1-L2. Lumbar NTD can tether the spinal cord, preventing its ascension over time and the tension on the cord may compromise blood supply and cause spinal cord dysfunction, pain and upper motor neuron signs (hyperreflexia and spasticity). Urinary incontinenc may occur.
Chiari type I malformation
Cerebellar tonsils are elongated and pushed down through the foramen magnum, blocking the normal flow of cerebrospinal fluid. CSF accumulates in central canal (hydromyelia), or a CSF-filled cyst breaks out of central canal and dissects into the cord (syringomyelia), or CSF accumulates in subarachnoid space (hydrocephalus). Myelopathy of spinal card can result. Likely mesodermal disorder, not NTD. usually discovered later in life and can affect urinary tract (spastic urinary bladders)
Chiari type II
complex malformation (elongated cerebellar vermis, breaking of midbrain tectal plate)- myelomeningocele, hydrocephalus, hindbrain, spine abnormalities, small posterior fossa with kinking of brainstem and herniation of cerebellum
Holoprosencephaly
when the single ventricle that exists in the early embryonic forebrain (ie., the prosencephalon) fails to form properly into the two lateral ventricles and one third ventricle. Partial failure of cerebral hemispheres to divide properly.
3 prosencephalic cleavages that occur during development
Horizontally to form paired optic vesicles, olfactory bulbs and tracts •Transversely to separate telencephalon from diencephalon (thalamus, hypothalamus) •Sagittally to form from the telencephalon the paired cerebral hemispheres, lateral ventricles
3 types of holoprosencephaly
Alobar: No division of cerebral cortex (single forebrain). Semilobar: Partial cleavage with cerebral hemispheres fused at frontal region only (horseshoe appearing central ventricle). Lobar: Cerebral hemispheres separated anteriorly and posterioly with some degree of fusion of structures.
Facial features in holoprosencephaly
Micocephaly, absent olfactory/optic nerves. Facial and ocular development is linked to the differentiation of the forebrain. May see cebocephaly (hypotelorism, single nostril), cyclopia (fused orbits with supra-orbital proboscis), ethmocephaly (hypotelorism, high midline proboscis), arhinia (no nose), coloboma of the iris and retina, microphthalmus, premaxillary agenesis (hypotelorism with absent nares and philtrum) and midline facial clefts.
