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The Nervous System: Pathology > Embryology and Congenital Malformations > Flashcards

Embryology and Congenital Malformations Flashcards

1
Q

From what layer of cells does the neural tube develop from

A

The ectoderm

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2
Q

When does neural tube formation begin

A

Beginning of the third week (during gastrulation)

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3
Q

What occurs in neuralisation

A

The ectoderm thickens forming the neural plate at the cranial end of the embryo (ad grows down to caudal end)

The lateral edges then become elevated and move together to from neural folds

The neural folds migrate in the middle of the embryo and fuse together forming the neural tube

The neural tube extends in both cranial and caudal direction

The cells cells on the crest of the neural tube detach

The neural tube closes

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4
Q

What does the cranial end of the embryo go on to develop

A

The future brain

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5
Q

What does the cauda end of the embryo develop into

A

Future spinal cord

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6
Q

What does detached cells to the neural tube from and develop into

A

Form neural crest leading to the formation of the peripheral nervous system

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7
Q

What is is essential for normal development and function

A

Neural tube closure - completes the process

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8
Q

When does neural tube closure begin and end for cranial and caudal

A

Begins day 18

Cranial closes - 25 days (18-20 somite stage)

Caudal closes -27 days

Completely closed by the 4th week

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9
Q

How many closure sits are present in humans

A

5

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10
Q

Failure of neural tube to close properly results in neural tube defects

A 
Anencephaly
Encephalocoele
Spina bifida
Craniorachischisis
Iniencephaly
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11
Q

What is the presentation of anencephaly

A

The skull is absent and so is cerebral hemisphere of the brain

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12
Q

When does anencephaly occur

A

23-26 days after conception

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13
Q

What is the cause of Craniorachischisis

A

Failure of neural tube closure along entire neuroaxis

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14
Q

What is the presentation of encephalocoele

A

Hernatio of cerebral tissue through a defect in the skull

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15
Q

What causes encephalocoele

A

Failure in closure of rostral neural tube

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16
Q

What is the affect of encephalocoele

A

Variable degree of neurological deficits

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17
Q

What is the affect of anecephaly

A

Incompatible with life

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18
Q

What is the two shapes of encephalocoele

A

Occiittal encephalocele (most frequent)

Fronto-nasal encephalocele

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19
Q

What is the presentation of Iniencephaly

A

Occipital and spine defect with extreme retroflexion of the head

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20
Q

What is the cause of spina biffida

A

Defective closure of the caudal neural tube

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21
Q

What does spina bifida affect

A

Tissue overlying spinal cord

Potential may affect neural tissue

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22
Q

What is the two forms of spin bifida

A

Spina bifida occulta - minor/closed

Spina bifida cystica - severe/open

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23
Q

What is the cause of spina bifida occulta

A

Failure of the embryonic halves of the vertebral arch to grow normally and fuse

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24
Q

What is the presentation of spina bifida occulta

A

Dimple with a small tuft of hair typically occurring and L5 /L6 vertebrae

No clinical symptoms

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25
Q

What is the cause of spina bifida cystic

A

Protrusion of spinal cord and/or meninges through the defect in the vertebral arches

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26
Q

What is the three forms of spina bifida cystic

A

Spina bifida with meningocele

Spina bifida with meningomyelocele

Myeloschisis

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27
Q

What occurs in Spina bifida with meningocele

A

protrusion of meniges and cerebrospinal fluid through a defect in spine

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28
Q

What occurs in spina bifida with meningomyelocele

A

Open spinal cord with meningeal cyst with nerve roots/spinal cord included in the sac

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29
Q

What are the neurological defecits of spina bifida with meningomyelocele

A

Loss of sensation and muscle paralysis

Are affected determined by level of lesion

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30
Q

What is spina bifida with meningomyelocele associated with

A

Hydrocephalus

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31
Q

What occurs in myeloschisis

A

Spinal cord in affected is open de to failure of neural tubes to fold

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32
Q

What is the most severe spina biffida

A

Myeloschisis

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33
Q

What is taken in prenatal care to prevent neural tube deficits

A

Folic acod

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34
Q

What are the three prenatal diagnosis for neural tube defects

A

Maternal blood screening (16-20 weeks)

Amniocentesis

Ultrasound

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35
Q

What is the market found in amniocentesis and maternal blood screen for neural tube deficits

A

High levels of Alpha fetoprotein in serum/amniotic sac

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36
Q

What is the origin of AFP

A

From foetal liver leking into amniotic sac then into maternal blood

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37
Q

When is ancephaly and spina bifida best detected with an ultrasound

A

Ancephaly - from 12 weeks

Spina bifida - from 16-20 weeks

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38
Q

What is the risk factors for neural tube deficits

A

Genetic predisposition

Nutritional

  • to little folate
  • to much vitamin A

Environmental

  • hyperthermia
  • sodium valproate
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39
Q

What do the brain vesicles formation co inside with

A

Closure of the anterior neuropore (roughly day 25 days)

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40
Q

What are the 3 primary brain vesicles formed by the end of the 4th week

A

Prosencephalon
(forebrain)

Mesencephalon
(midbrain)

Rhombencephalon
(hindbrain)

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41
Q

What is the secondary vesicles produced from the proscencephala

A

Telencephalon

Diencephalon

42
Q

What is the secondary vesicle produce from the rhombencephalon

A

Metencephalon

Myencephalon

43
Q

The primary vesicle mesencephalon doesn’t further divide, what part of the brain develops from it

A

Midbrain

44
Q

What part of the brain develops from the Telencephalon

A

Cerebral hemispheres
Hippocampus
Basal ganglia

45
Q

What part of the brain develops from the diencephalon

A

Thalamus
hypothalamus
Pituitary gland
Pineal

46
Q

What part of the brain develops from the metecenphalon

A

Cerebellum

Pons

47
Q

What part of the brain develops from the myelencephalon

A

Medulla

48
Q

What is the three flexures in brain vesicle development

A

Cephalic

Cervical

Pontine

49
Q

When and where is the cephalic flexure produced

A

End of the 3rd week between the mesencephalon (midbrain) and the rhombencephalon (hindbrain)

50
Q

When and were is the cervical flexure formed

A

End of 4th week

between hindbrain and spinal cord

51
Q

When and where is the pontine flexure formed

A

5th week

Between mesencephalon and myelecephalon (in the hindbrain)

52
Q

What forms the ventricular system

A

Lumen of the neural tube

53
Q

When does cerebral spinal fluid begin to from

A

5th week

54
Q

Where is cerebral spinal fluid produced

A

By the choroid plexus

55
Q

Where is the choroird plexus formed

A

Lines the lateral ventricle

Lines the third ventricle

4th ventricle

56
Q

Where does the cerebral spinal fluid drain

A

Into the subarachnoid space via the opening of the roof in the 4th ventricle

some also flows through the central canal of the spinal cord

57
Q

Where is CSF absorbed

A

Absorbed into the dural venous sinus system via the arachnoid villi

58
Q

What is the 4 ventricle produced

A

Lateral ventricle

3rd ventricle

Cerebral aqueduct

4th ventricle

59
Q

What connects the lateral and third ventricle

A

Intraventricular foramina of monro

60
Q

What is hydrocephalus

A

Accumulation of cerebral spinal fluid resulting in enlarged brain and cranium

61
Q

What is the frequent cause of hydrocephalus

A

Blocked aqueduct preventing CSF passing from lateral and 3rd ventricle to fourth so cant drain properly

62
Q

What is the aetiology of a blocked aquedcut

A

Genetic

Prenatal viral infection

Intracentricular haemorrhage

Spina bifida cystica

63
Q

When does production of neuronal cells ( neurones and gila) and their connections begin

A

During early embryogenesis and continue into post natal period

64
Q

What is the neural tube initially

A

A single layer of rapidly dividing neuroepithelial cells

65
Q

What is the epithelium of the neural tube

A

Pseudo-stratified epithelium

66
Q

Where does neuroepithelial cells divide

A

The ventricular zone that lines the ventricular system

67
Q

What kind of cells are principally neuroepithelial cells before they divide

A

Radial gilal cells

68
Q

The neuroepihelai cells produce most cells of the CNS, name the cells produces

A

Neurone

Astrocytes

Ogliodendrocye

69
Q

Once the radial gila/neuroepithelial cells are finished divided what do they become

A

Ependymal cells (type of gilal cells that line the ventricles)

70
Q

What zone in the spine of you find differentiated neurones and axons

A

Mantle layer - differentiated neurones

Marginal layer - axons

71
Q

What is the exception of a neuronal cell not produced by the neuroepithelial cells and what is its origin

A

Microgilia - produced from mesenchymal cells that migrate into the CNS

72
Q

What does the neuronal crest cells go on to develop

A

PNS neuronal cells

Plus non neuronal cells:

  • Melanocytes
  • Bone and cartilage of the face and skull
  • Adrenal medulla
  • Meninges
73
Q

What does the sensory and motor component of the spinal cord embryonically derived from

A

Sensory - Neural crest cells

Motor - neural tube

74
Q

What two process extend from the neuronal crest cells development of the spinal cord

A

Peripheral - due to body

Central - due to dorsal horn of spinal cord

75
Q

What is the initial position of the spinal cord in the 3rd month

A

The spinal cord extends the entire length of the vertebral column and initially spinal nerve found at level of origin

76
Q

How does the position of the spinal cord change from 3rd month to birth

A

Spinal cord becomes elongate forming cud equine

Pia matter then extend forming terminal filum

77
Q

What does the autonomic nervous system sympathetic and parasympathetic ganglia embryonically derived from

A

Neuronal crest cells

78
Q

What does rapid development of the cerebral hemispheres lead to the formation of

A

Sulci (grooves) and gyri (elevations)

With the pattens becoming more complex as the brain enlarges

79
Q

What are to congenital abnormalities to do with sulci and gyro

A

Lissencephaly

Polymicrogyria

80
Q

What is the cause and presentation of lissencephaly

A

Caused by defective neuronal migration leading to the gyro and sulk failing to develop

81
Q

What is the symptoms and signs seen with lishencephaly

A

Severe mental impairment

Failure to thrive

seizures

abnormal muscle tone

82
Q

What is the cause of polymicrogyria

A

Excessive number of small gyro

83
Q

What is the symptoms and signs seen with pylormicrogyri

A

Neurological problems:
Mental retardation,
seizures,
Motor defecits

84
Q

Name 6 congenital abnormalities in the nervous system

A

Micricephaly

Agenesis of corpus callous

Porencephaly

Schizencephaly

Diastematomyelia

Intellectual impairment

85
Q

What is microcephaly

A

Abnormal smallness of the head, a congenital condition associated with incomplete brain development

86
Q

What is the causes of microcephaly

A

Genetic
drugs
Infection eg zika virus

87
Q

What is the symptoms of microcephaly

A

Intellectual impairment,

Delayed motor functions/speech, Hyperactivity,

Seizures,

Balance/co-ordination problems

88
Q

What is the subtle to severity of corpus callous

A

Cognitive and social difficulties to intellectual impairment, seizures and hypotonia

89
Q

What is the characteristic of porencephaly

A

cysts or cavities within the cerebral hemisphere

90
Q

What is the cause of porencephaly

A

Postnatal stroke

Infection

91
Q

What is the symptoms of porecephaly

A

delayed growth and development

seizures

hypotonia

intelectual impairment

92
Q

What is the characteristics of schizencephaly

A

Large clefts or slits in the cerebral hemisphere

93
Q

What is the cause of schizencephaly

A

Genetic
In utero stroke
Infection

94
Q

What is the symptoms of schiecenchphaly

A

Paralysis

seizures

intellectual impairment

developmental delay

95
Q

What is Diastematomyelia

A

Split cord malformation where the spinal cord splits longitudinally into two parts

96
Q

What is usually associated with Diastematomyelia

A

Vertebral abnormalities

97
Q

What “fixes” the vertebral abnormalities in Diastematomyelia

A

Bones or cartilaginous process fixes the cord in place

98
Q

What is the symptoms of Diastematomyelia

A

Scoliosis

Weakness of lower extremities

Hairy patch over lower back

Foot deformities

Loss of sensation

99
Q

There is often no obvious gross defects in intellectual impairment, what is the potentially causes

A

Genetics

Radiation

Infectious agnets (rubella, toxoplasmosis, cytomegalovirus)

Birth trauma

Post natal insults
(head injury, infections, lead exposure)

100
Q

What is the commonest cause of intellectual impairment

A

Maternal alcohol abuse

101
Q

What forms the vesicles

A

The expansion and the bending of the neural tube

The Nervous System: Pathology (25 decks)

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