Nervous System Development

Question 1

Failure of the neural crest cells to differentiate properly. Symptoms diverse and appear to be unrelated initially. e.g. white patch of hair, pale blue eyes of different hues (melanocyte issue).

Answer 1

Waardenburg Syndrome

Question 2

Due to failure of neural crest cells to migrate into the colon – most common in rectum and sigmoid colon. The parasympathetic ganglia do not form, so normal peristalsis does not occur. Fecal retention with ballooning of the colon and abdomen

Answer 2

Hirschsprung disease or congenital megacolon.

Question 3

Failure of a significant portion of the neural tube to close resulting in exposure of the malformed neural tissue along the back of the head and body.

Answer 3

Craniorachischisis

Question 4

Failure of rostral neuropore to close.

Answer 4

Anencephaly (no brain) or meroanencephaly (remnants of brain, especially brain stem).

Question 5

Failure of caudal neuropore to close.

Answer 5

Spina bifida. From least to most severe: spina bifida occulta, meningocele, myelomeningocele.

Question 6

Failure of neural tube to close in region of occipital bone. The brain and meninges protrude through a defect in the occipital bone. Can also occur in the frontal area but more common in the occipital.

Answer 6

Anterior neural tube defect or occipital encephalocele.

Question 7

Tubular cavitation of the spinal cord – generally cervical/upper thoracic. Pathogenesis unknown; probably diverse. Neural deficits begin with loss of pain & temperature sensation over shoulders and upper arms.

Answer 7

Syringomyelia (Non-NTD)

Question 8

The forebrain does not divide into 2 hemispheres.

Answer 8

Holoprosencephaly (Non NTD)

Question 9

Dilation of the ventricles due to excess amount of CSF. Due to CSF overproduction, obstruction of flow or failure of CSF reabsorption.

Answer 9

Hydrocephalus (Non NTD)

Question 10

Partial or complete absence of cerebellar vermis.

Answer 10

Dandy-Walker Malformation (Non NTD)

Question 11

Herniation of cerebellar tonsils.
Type 1: may be asymptomatic or may not be evident until 30’s or 40’s
Type 2: herniation below foramen magnum; often accompanied by myelomeningocele
Type 3: occipital encephalocele, syringomelia
Type 4: lack of cerebellar development

Answer 11

Arnold-Chiari malformation (Non-NTD)

Question 12

Failure of skull to form

Answer 12

Acrania

Question 13

Autosomal dominant genetic disorder characterized by craniosynostosis and other congenital abnormalities e.g. syndactyly of hands and feet; mental retardation

Answer 13

Apert syndrome

Question 14

Small head due to a brain that fails to grow

Answer 14

Microcephaly

Question 15

Skull defect through which the meninges and/or brain herniate.

Answer 15

Cranioschisis

Question 16

Premature closer of one or more sutures that produces a misshapen skull.

Answer 16

Craniosynostosis e.g. brachycephaly, oxycephaly, plagiocephaly, scaphocephaly.