Neuroembryology Flashcards
Describe growth of spinal cord/vertebral column of 5 month fetus
Vertebral column has grown longer than spinal cord.
Conus medullaris is at the level of the first scaral vertebra (SV1)
Describe growth of spinal cord and vertebral column of neonate
Conus medullaris is at the level of the third lumbar vertebra (LV3)
Describe growth of spinal cord/vertebral column
Conus medullaris is at the level of the LV1-2 interspace
Nerve roots coursing in lumbar cistern below level of conus medullaris are progressively lengthened due to this differential growth and will form the cauda equina
What is rachischisis?
Vertebral column defect with exposure of primitive spinal cord and/or nerves
What is spina bifida occulta?
Vertebral column defect with herniation of meninges or neural tissue
Usually presents as cystic, midline, hairy mass in lumbar region of vertebral column
Anomaly may be due to failure of roof plate of neural tube to induce development of overlying spinous processes
May be asymptomatic for years
What is meningocele?
Vertebral column defect with herniation of meninges
What is meningomyelocele?
Vertebral column defect with herniation of meninges, spinal cord, and/or nerves
What is hydrocephalus?
May be due to congenital stenosis of a portion of ventricular system or certain fetal infections (CMV, toxoplasmosis), and some autosomal recessive syndromes such as Hurler’s.
Commonly associated with meningomyelocele, Arnold Chiari,a nd Dandy-Walker malformations
What is Arnold-Chiari malformation?
Common cerebellar anomaly
Almost always present with meningomyelocele
A-C malformations involve an elongation of cerebellar vermis, which herniates through foramen magnum and overlies a dorsally flexed medullospinal segment.
Aqueductal stenosis, hydrocephalus, syringobulbia, syringomyelia, or polymicrogyria often accompany A-C malformation
What is anencephaly?
Probably arises when embryo is only 2.5-4.5 mm CR length
Many are spontaneously aborted early in pregnancy
Involve varying degrees of cranial or cervical rachischisis
Meroanencephaly = anencephaly with cranial rachischisis
Brainstem and vital functions are often intact, and patient may survive for a varying length of time after delivery
What is meningoencephalocele?
Cranial defect with herniation of meninges and brain tissue
Probably doesn’t occur in embryos older than 3-5 mm CR
Almost all infants with this have an A-C malformation
Many develop hydrocephalus
What is meningohydroencephalocele?
Cranial defect with herniation of meninges, brain, and ventricles
What is cranial rachischisis?
Congenital absence of forebrain usually with cranial defect of frontal and parietal bones
Fatal anomaly is due to failure of the neural tube to close
Describe growth of spinal cord/vertebral column of 3 month fetus
Spinal cord extends throughout entire length of vertebral column
