Neuro Embryology & Development

Question 1

Why is folic acid important if you are planning for or think you are pregnant?

Answer 1

Because the nervous system starts to form at Week 3, usually before a pregnancy test turns up positive (to avoid folic acid deficiency and neural defects)

Question 2

The Nervous system begins formation usually around week _____

Answer 2

3 (as soon as the 3 germ layers have formed via gastrulation)

Question 3

Formation of the 3 germ layers (Ectoderm, Mesoderm and Endoderm)

Answer 3

Gastrulation

Question 4

Portion of the Mesoderm; will give rise to the “somites” or body segments: examples are skeletal muscle, bone, cartilage, CT and blood vessels

Answer 4

Paraxial mesoderm

Question 5

Portion of the Mesoderm; will give rise to the genitourinary systems

Answer 5

Intermediate mesoderm

Question 6

Portion of the Mesoderm; will give rise to the anterolateral body wall, smooth muscle and CTs of the viscera, heart and blood vessels

Answer 6

Lateral mesoderm

Question 7

Process of forming the neural tube and neural crest

Answer 7

Neurulation

Question 8

Difference between the neural “fold” and neural “crest” during

Answer 8

neurulation

Question 9

Neurulation begins around week ____ and ends at week _____ with closure of the Cranial and Caudal Neuropores

Answer 9

3; 4

*extra importance to folic acid supplementation

Question 10

The end of Neurulation is marked by the closure of what structures

Answer 10

Cranial and Caudal Neuropores

Question 11

The neural tube will provide the (CNS/PNS)

Answer 11

CNS

Question 12

The neural crest will provide the (CNS/PNS)

Answer 12

PNS (ganglia and melanocytes)

Question 13

The neural tube (wall/lumen) is composed of neuroepithelium and will become neurons and glia

Answer 13

Wall

Question 14

The neural tube (wall/lumen) will become the ventricles (brain) filled with CSF and the central canal (spinal cord)

Answer 14

Lumen

Question 15

What are the 3 layers of the Neural Tube

Answer 15

Ventricular (inner): ependyma (ventricle lining)
Intermediate: gray matter (cell bodies)
Marginal (outer): white matter (axons)

Question 16

The (Ventricular/Intermediate/Marginal) layer of the neural tube is the innermost layer and will form the ependyma (glia cell lining of the ventricles)

Answer 16

Ventricular

Question 17

The (Ventricular/Intermediate/Marginal) layer of the neural tube will form the gray matter (cell bodies) and will subdivide into the Alar and Basal plates (dorsal and ventral regions)

Answer 17

Intermediate

Question 18

The (Ventricular/Intermediate/Marginal) layer of the neural tube is the outermost layer and will form the white matter (axons)

Answer 18

Marginal

Question 19

In the spinal cord, the (white/gray) matter is deep

Answer 19

Gray

Question 20

In the brain, the (white/gray) matter is deep

Answer 20

White

Question 21

The neural tube induces vertebrae formation from what somite portion

Answer 21

Sclerotome

Question 22

The Intermediate layer of the spinal cord will subdivide into the _________ and ___________ plates that will give rise to the Dorsal and Ventral horns of the gray matter in the spinal cord

Answer 22

Alar (posterior) and Basal (anterior)

Question 23

Why do the caudal spinal nerves not exit at the same level as they do the spinal cord (have to travel down the column and then exit)

Answer 23

Originally, the spinal cord and vertebral column are same length, but then the vertebrae grow faster and thus stretch the caudal spinal nerves downward (forming the Cauda Equina)

Question 24

The cranial tip of the Neural tube eventually forms 2 constrictions, forming what three portions

Answer 24

Forebrain (prosencephalon)
Midbrain (mesencephalon)
Hindbrain (rhombencephalon)

Question 25

Fancy name for the Forebrain

Answer 25

Prosencephalon

Question 26

Fancy name for the Midbrain

Answer 26

Mesencephalon

Question 27

Fancy name for the Hindbrain

Answer 27

Rhombencephalon

Question 28

The Forebrain (prosencephalon) will further subdivide into what 2 regions

Answer 28

Telencephalon | Diencephalon

Question 29

The Hindbrain (rhombencephalon) will further subdivide into what 2 regions

Answer 29

Metencephalon | Myelencephalon

Question 30

What is the order of the 5 portions of the neural tube during development (the -cephalons)

Answer 30

``` Telencephalon Diencephalon Mesencephalon Metencephalon Myelencephalon ``` *T is on top, and it's in alphabetical order from there

Question 31

The Telencephalon gives rise to what brain structure(s)

Answer 31

Cerebrum | Lateral Ventricles

Question 32

The Diencephalon gives rise to what brain structure(s)

Answer 32

Diencephalon (shocker) (thalamus and hypothalamus) | 3rd Ventricle

Question 33

The Mesencephalon gives rise to what brain structure(s)

Answer 33

Midbrain | Aquaduct

Question 34

The Metencephalon gives rise to what brain structure(s)

Answer 34

Pons Cerebellum Upper part of 4th Ventricle

Question 35

The Myelencephalon gives rise to what brain structure(s)

Answer 35

Medulla (oblongata) (always think of the movie Water Boy) | Lower part of 4th Ventricle

Question 36

In the BRAINSTEM, the lumen (4th ventricle) widens and pushes the alar plate (medial/lateral) and subsequently the basal plate (medial/lateral)

Answer 36

Alar (sensory)--> lateral | Basal (motor)--> medial

Question 37

During cerebrum development, explain how the Intermediate layer changes and migrates

Answer 37

Some neurons cluster within the Marginal (outer) layer (forming nuclei) Some neurons migrate beyond to form a NEW outermost layer of gray matter (cortex) *migrating neurons are guided by astrocytes

Question 38

Migrating neurons of the Intermediate layer (forming the nuclei and outer gray matter) are guided to their destination by what glial cells

Answer 38

Astrocytes

Question 39

Why do many structures within the brain adopt a C shape (lateral ventricles, caudate nucleus, corpus callosum)

Answer 39

Growth of the brain does so to fit in the skull, bending to corm a C shape in the process

Question 40

Once the neural tube forms, it induces the surrounding _______ and _______ to develop for protection

Answer 40

bone and skin *abnormalities result in neural tube defects

Question 41

Main risk factor for Neural Tube Defects

Answer 41

Maternal folic acid (B9) deficiency

Question 42

Vitamin B9

Answer 42

Folic acid

Question 43

Diagnosis of Neural Tube Defects (before birth)

Answer 43

Inc. a-fetoprotein (maternal blood) | Ultrasound

Question 44

When a portion of the neural tube fails to develop or close properly, causing defects in the spinal cord and in the bones of the spine; can range from mild to severe, depending on the type of defect, size, location and complications

Answer 44

Spina Bifida

Question 45

Type of Spinal Neural Tube Defect; due to a unfused vertebral arch (bony defect); typically mild, can see a tuft of hair; no functional impairments

Answer 45

Spina Bifida Occulta ("hidden")

Question 46

Type of Spinal Neural Tube Defect; the meninges protrude through the opening causing a lump or sac on the back, BUT the cord still remains within the vertebrae; often no functional impairments

Answer 46

Meningocele (Spina Bifida Cystica)

Question 47

Type of Spinal Neural Tube Defect; MOST COMMON; both the meninges AND the spinal cord protrude through the back, BUT still enclosed in a sac; paralysis below the lesion, bowel/urinary dysfunction and possible hydrocephalus

Answer 47

Myelomeningocele (Spina Bifida Cystica) (myelo= spinal cord, cele = sac)

Question 48

Type of Spinal Neural Tube Defect; due to complete failure of closure of the caudal neuropore; nerves are open to external environment; no function below, often anencephaly

Answer 48

Rachischisis

Question 49

Most common site for Spinal Neural Tube Defects

Answer 49

Lumbosacral region

Question 50

Functional impacts of the various Spinal Neural Tube Defects

Answer 50

SB Occulta: none Meningocele: often none Myelomeningocele: paralysis below, bowel/urinary impacts, possible hydrocephalus Rachischsis: no function below, often anencephaly

Question 51

Special name for Cranial Neural Tube Defects

Answer 51

Cranium Bifidum

Question 52

Cranial Neural Tube Defects usually are (soft/bony) and are located where?

Answer 52

Bony; occipital bone

Question 53

Cranial Neural Tube Defect; inadequate development of the upper end of the neural tube; herniated sac consists of only meninges.

Answer 53

Cranial Meningocele (B)

Question 54

Cranial Neural Tube Defect; inadequate development of the upper end of the neural tube; herniated sac consists of both meninges AND brain contents

Answer 54

Meningoencephalocele (or Encephalocele) (C)

Question 55

Cranial Neural Tube Defect; absence of a major portion of the brain, skull, and scalp; results from a neural tube defect that occurs when the rostral end of the neural tube fails to close; usually born unconscious, deaf, blind, etc. and usually are either stillborn or die soon after birth

Answer 55

Anencephaly (Meroanencephaly)

Question 56

Neural Tube Defect; herniation of the meninges from the vertebral canal, but normal spinal cord; still closed from the environment; no neurologic deficits

Answer 56

Meningocele

Question 57

Neural Tube Defect; herniation of BOTH the meninges and the spinal cord from the vertebral canal; still closed from the environment; associated with neurologic deficits

Answer 57

Myelomeningocele

Question 58

Neural Tube Defect; entire failure of the neural tube to close; open to the environment

Answer 58

Craniorachisisis Totalis

Question 59

Herniation of brain tissue through a skull defect

Answer 59

Encephalocele

Question 60

Bottom structures of the Cerebellum, located medially and caudally; above the foramen magnum; tend to herniate with increased ICP

Answer 60

Tonsils

Question 61

Midline portion of the Cerebellum

Answer 61

Vermis

Question 62

Herniation of part of a Cerebellar tonsil through the Foramen Magnum in the absence of an intracranial mass lesion or hydrocephalus (CSF can't escape, so builds up in head); strongly associated with Syringomyelia (inc. pressure pushes into spinal cord??)

Answer 62

Chiari Type I

Question 63

Chiari Type I is associated with...

Answer 63

Syringomyelia

Question 64

LESS common, but MORE severe herniation of BOTH the cerebellum and downward displacement of the brain stem through the foramen magnum; can also see "beak like" deformity of mesencephalon (above cerebellum); almost ALWAYS associated with lumbosacral myelomeningocele and hydrocephalus

Answer 64

Chairi Type II

Question 65

Difference between Chiari Type I and II

Answer 65

Type I: part of cerebellar tonsil herniates | Type II: herniation of BOTH cerebellum and brain stem

Question 66

Congenital Brain Malformation; combination of Vermal agenesis, dilated 4th ventricle, enlarged posterior fossa and hydrocephalus

Answer 66

Dandy Walker Syndrome

Question 67

Most common Forebrain anomaly; failure of the separation of the Forebrain (prosencephalon) into 2 hemispheres; associated with mutations in HPE gene; associated with midline facial defects from hypotelorism (eyes too close) to cyclopia

Answer 67

Holoprosencephaly

Question 68

Agenesis of the Corpus Callosum is associated with what syndromes

Answer 68

Dandy-Walker syndrome Chairi II Fetal-Alcohol syndrome

Question 69

Neuronal migration defect; absence of gyri and sulci

Answer 69

Agyria (Lissencephaly)

Question 70

Neuronal migration defect; reduced number of gyri and sulci

Answer 70

Pachygyria

Question 71

Abnormailty of cortical development; TOO MANY gyri that are small and have abnormal cortical lamination; can be caused by genetics, hypoxia or CMV; associated with maple syrup urine disease

Answer 71

Polymicrogyria

Question 72

Heterotopic neurons in cerebral white matter (normal tissue in abnormal location); scattered or clustered into nodules; associated with peroxisomal, mitochondrial or chromosomal disorders

Answer 72

Neuronal Heterotopias

Question 73

Malformation of the Spinal Cord; tubular cavitation of the spinal cord; frequently associated with Chiari type I; usually presents in 2nd and 3rd decade of life (wasting, weakness and loss of hand/forearm muscles)

Answer 73

Syringomyelia

Question 74

Class of metabolic disorders that primarily affect the White matter

Answer 74

Leukodystrophies (Krabbe's disease, Metachromatic, Adreno-, etc.)

Question 75

Examples of Leukodystrophies (3 total)

Answer 75

Krabbe's disease Metachromatic leukodystrophy Adrenoleukodystrophy

Question 76

Type of Leukodystrophy; AR inheritance; lysosomal storage disease due to deficiency of Galactocerebroside-B-Galactosidase; leads to accumulation of Galactocerebroside and destroys myelin (LOSS OF WHITE MATTER)

Answer 76

Krabbe's disease

Question 77

Krabbe's disease will result in a loss of (white/grey) matter

Answer 77

White *accumulation of Galactocerebrosidase destroys myelin

Question 78

Enzyme deficient in Krabbe's disease

Answer 78

Galactocerebroside-B-Galactosidase *excess galactocerebroside destroys myelin

Question 79

Metabolic disorder affecting GREY matter; AR inheritance; infantile Gangliosidosis; cherry red spot on retina; brain can be overly small or large (due to gyral atrophy)

Answer 79

Tay-Sachs disease

Question 80

Metabolic disorder affecting GREY matter; AR inheritance; usually due to Sphingomyelinase deficiency (Group 1); cherry red spot on maculla

Answer 80

Niemann-Pick disease

Question 81

Metabolic disorder affecting GREY matter; AR inheritance; deficiency of gluocerebrosidase; due to loss of myelin; "crumpled tissue paper" cells in spleen, lymph nodes, bone marrow and liver

Answer 81

Gaucher's disease

Question 82

Metabolic disorder affecting GREY matter; AR inheritance; affects storage of gangliosides in neurons; coarse facial features, hepatosplenomegaly and corneal clouding; associated with Dermatan Sulfate and deficiency in a-L-iduronidase

Answer 82

Hurler's Syndrome

Question 83

Metabolic disorder affecting GREY matter; X-Linked inheritance; affects storage of gangliosides in neurons; coarse facial features, hepatosplenomegaly and corneal clouding; associated with Dermatan Sulfate and deficiency in Iduronate sulfatase

Answer 83

Hunter's Syndrome

Question 84

Difference between inheritance and enzyme for Hurler's and Hunter's syndromes (Mucopolysaccharidoses)

Answer 84

Hurlers: a-L-iduronidase; AR inheritance Hunters: Iduronate sulfatase; X-Linked inheritance