DEV2011 Lecture Notes - Lecture 14: Neural Tube, Neoteny, Retroflex Consonant
25 May 2018
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Lecture 14 – Neural Tube Development: Defects and Disorders
Neural tube Closure Defects
• Principles of Neural Tube Closure
o Starts from middle of neural tube
o Propagates bi-directionally in A-P axis
o Following closure → tube is hollow in middle → forms canal where
cerebrospinal fluid runs (fluid contains nutrients and morphogens
factors that promote proliferation of progenesis)
▪ Sometimes it doesn’t close → consequences
o Severity of defects depends on the developmental stage it went wrong
• Defects
o Anterior portion of neural tube
▪ Craniorachischisis
• No closure of neural tube – completely open brain and
spinal cord
▪ Anencephaly
• Open brain and lack of skill vault
▪ Iniencephaly
• Occipital skill and spine defects with retroflexion of
head
o Posterior portion of neural tube
▪ Spina bifida (SB) occula
• Closed ansymptomatic NTD in which some of
vertebrate are not completely closed
• Open SB occurs when closure processes is stopped
before edges of neural plate meet
• Cerebrospinal fluid flows out of open tube
• No obvious bulging: spinabifida occulta
• Detection of protruding mass – ultrasound
o Tuft of hair at end of spinal cord is indication
• To prevent SB – metabolism of folic acid is very
important
o Genetic cause
▪ Child carries mutation in gene of enzyme
o Mutation can occur at any level of cascade
o Renders folic acid supplementation redundant
o Supplementation with intermediate metabolites
▪ Myelomeningocele
• Neural tube isn’t closed
• Protrusion of nerve outside skin
• Open of spinal cord
• Severity and Consequences of Neural Tube Closure Defects
o The earlier during development – more severe the consequences
o Absence of CSF will impact aspects of brain and spinal cord
development
▪ Leads to paralysis in case of abnormal development
Microcephaly and Lissencephaly
• Two of the most common brain malformations
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