Nervous System Development + Abnormalities

Question 1

Nervous system develops from….

Answer 1

Ectoderm

Question 2

What occurs with the notochord in the third week of development?

Answer 2

Notochord induces development of neural plate via high cell proliferation

Question 3

The neural tube will first form into 3 vesicles, then 5. Name these 3 vesicles and what they will become

Answer 3

Prosencephalon –> Telencephalon and Diencephalon

Mesencephalon –> Mesencephalon

Rhombencephalon –> Metencephalon and Myelencephalon

Question 4

What will the Telencephalon go on to develop?

Answer 4

Cerebral cortex, Basal ganglia, Hippocampus, Amygdala

Question 5

What will the Diencephalon go on to develop?

Answer 5

Thalamus, Hypothalamus, pituitary (neurohypophysis), pineal gland

Question 6

What will the Mesencephalon go on to develop?

Answer 6

Midbrain

Question 7

What will the Metencephalon go on to develop?

Answer 7

Pons and Cerebellum

Question 8

What will the Myelencephalon go on to develop?

Answer 8

Medulla

Question 9

When the sulcus limitans appears at the midpoints of the neural canal, the dorsal and ventral neurocytes are differentiated into what plates? What are their ultimate functions?

Answer 9

Alar Plate = Dorsal = Sensory Neurons

Basal Plate = Ventral = Motor Neurons

NOTE: The Alar neurons are lateral to the Basal neurons in the brainstem due to the ventricles taking up space

Question 10

What is the main clinical problem in Anencephaly?

Answer 10

Failure of closure of the neural tube at the cranial end, leads to absence of skull and brain

Incompatible with life

May arise from Exencephaly, which first results in skull not forming. The brain is then exposed and often becomes necrotic

Question 11

What clinical condition may be seen in the mother in Anencephaly?

Answer 11

Polyhydramnios

No CNS in the baby means the baby cannot swallow any amniotic fluid, resulting in polyhydramnios

Question 12

What is spina bifuda?

Answer 12

Failure of the posterior vertebral arch to close

Question 13

What are 3 main kinds of spina bifuda?

Answer 13

Occulta – leads to dimple or patch of hair overlying the vertebral defect

Cystica – may lead to meningocele or meningomyelocele

Rachischisis- almost always fatal

Question 14

What is the difference between meningocele and meningomyelocele?

Answer 14

Meningocele – Meninges alone coming out of the defect in the spinal cord

Meningomyelocele – Meninges and brain coming out of the defect in spinal cord

Question 15

What is Cerebral Aqueduct Stenosis?

Answer 15

Congenital stenosis of cerebral aqueduct that drains the 3rd and 4th ventricles

Question 16

What condition does Cerebral Aqueduct Stenosis often lead to in the child?

Answer 16

Hydrocephalus (accumulation of CSF in the lateral ventricles)

Question 17

What is a Dandy Walker Malformation?

Answer 17

Congenital failure of the cerebellar vermis to develop

See massively enlarged 4th ventricle due to failure of Foramen of Lushka and Magendie to form

Often accompanied by hydrocephalus

Question 18

What is an Arnold-Chiari Malformation?

Answer 18

Congenital extension of the cerebellar tonsils through the foramen magnum

Obstruction of CSF flow may lead to hydrocephalus

Question 19

What is Microcephaly?

Answer 19

Cranial vault is smaller than normal, often due to a lack of brain development

Impaired mental developmental associated with over 50% of cases