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Neurology > Lecture 25 Embryology and Congenital Malformation > Flashcards

Lecture 25 Embryology and Congenital Malformation Flashcards

1
Q

Where does the nervous system develop from

A

The embryonic ectoderm

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2
Q

What week does the CNS appear

A

3rd week

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3
Q

Define the neural plate

A

thickening of ectoderm anterior to the primitive node

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4
Q

Define the Neural folds

A

Edges of the neural plate thicken and move upwards to form the neural folds

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5
Q

Neural fold migrate towards each other to form what?

A

Neural tube

Remains open at anterior and posterior ends

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6
Q

When does the anterior (cranial/rostral) neuropore close

A

Dat 25

18-20 somite stage

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7
Q

When does the posterior (caudal) neuropore close

A

Day 27

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8
Q

Where is neural tube closure initiated

A

Several points along A-P axis

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9
Q

When does neural tube closure begin

A

Day 18

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10
Q

When is neural tube closure completed

A

Day 27 (end of 4th week)

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11
Q

How many closure sites are there in humans

A

Up to 5

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12
Q

Failure of neural tube to close properly leads to what neural tube defects

A

Anencephaly
Encephalocoele
Spina bifida

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13
Q

How common is Anencephaly

A

1:1500

4 x more common in women

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14
Q

What causes Anencephaly

A

Failure of anterior neuropore to close
Skull fails to form
Brain tissue degenerates
incompatible with life

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15
Q

Define Craniorachischisis

A

Failure of neural tube closure along entire neuraxis

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16
Q

How common is Encephalocoele

A

1:4000 births

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17
Q

What is Encephalocoele

A

Herniation of cerebral tissue though a defect in the skull

Failure in closure of rostral neural tube

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18
Q

Where is Encephalocoele most common and where else can it be found

A

Occipital region

Fronto-nasal region

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19
Q

What is the cause of Spina Bifida

A

Defective closure of the caudal neural tube. Affects tissues overlying the spinal cord. Non fusion of vertebral arches

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20
Q

What are the types of Spina bifida

A 
Spina bifida with meningomyelocele
Spina bifida with myeloschisis
Spina Bifida Occulta
Spina Bifida Cystica
Spina bifida with meningocele
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21
Q

Define Spina bifida with meningomyelocele

A

This is when the neural tube has failed to close and the neural tissue is exposed on the baby’s back

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22
Q

Define Spina bifida with myeloschisis

A

The nerve tissue is here fully bare and a dermal or meningeal covering is absent

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23
Q

Define Spina Bifida Occulta

A

Most minor form

Failure of embryonic halves of vertebral arch to grow normal and fuse

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24
Q

What are the features of Spina Bifida Occulta

A

No clinical symptoms

Dimple with small tuft of hair

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25
What vertebral level does spina bifida occult occur
L5 and L6
26
What is Spina Bifida Cystica
Protrusion of spinal cord and/or meninges through the defect in the vertebral arches
27
How common is Spina Bifida Cystica
1:1000
28
What is Spina bifida with meningocele
Rarest form | Protrusion of meninges and CSF
29
What is Spina bifida with meningomyelocle associated with
Hydrocephalus | Neurological deficits- loss of sensation and muscle paralysis(loss of sensation and muscle paralysis)
30
What is the most severe form of spina bifida
Myeloschisis- • Spinal cord in affected area open due to failure of neural folds to fuse
31
When does the brain vesicles develop
Begins with closure of anterior neuropore (~day 25; 18 – 20 somite stage)
32
How is Spina bifida prevented
Folic acid supplements
33
How is Spina bifida diagnoses pre-natal
Maternal blood screening- AFP from foetal liver (16-20 weeks) Aminocentesis (AFP in amniotic fluid) US- anencephaly (12 weeks ) and spina bifida (16-20 weeks )
34
The forebrain develops from what vesicle
Prosencephalon
35
The Midbrain develops from what vesicle
Mesencephalon
36
The hindbrain develops from what vesicle
Rhombencephalon
37
What week does the 3 primary brain vesicles develop
4th week
38
What week does the 5 secondary brain vesicles develop
5th week
39
What is the Prosencephalon (Forebrain) made up in the 5th week
Telencephaln | Diencephalon
40
What is the Rhombencephalon (hindbrain) made up of in the 5th week
Metencephalon | Myelencephalon
41
When does the cephalic flexure develop and where is located
between midbrain (mesencephalon) and hindbrain (rhombencephalon)
42
When does the cervical flexure develop and where is it located
End of 4th week | Between hind brain and spinal cord
43
When does the Pontine flexure develop and where is it located
``` 5th week In hindbrain (Rhombencephalon) between mesencephalon and Myelencephalon ```
44
What develops from the telencephalon (forebrain)
Cerebral hemispheres Hippocampus Basal ganglia
45
What develops from the Diencephalon (forebrain)
Thalamus Hypothalamus Pituitary gland Pineal
46
What develops from the Mesencephalon (midbrain)
Superior and inferior colliculi
47
What develops from the Mesencephalon (hind brain)
Cerebellum, Pons
48
What develops from the Myelencephalon (hind brain)
Medulla
49
What forms the ventricular system
Lumen of neural tube
50
The lateral ventricle is formed where
Telencephalon
51
The 3rd ventricle is formed from
Diencephalon
52
The cerebral aqueduct (of sylvius) develops where
Mesencephalon
53
Where does the 4th ventricle is located
Mesencephalon | Myelencephalon
54
What connects the lateral and 3rd ventricle
Intraventricular foramina (of Monro)
55
When does CSF begin to be produced
5th week
56
Where is the CSF produced
Choroid plexus (3rd, 4th, lateral ventricles)
57
Where does the CSF drain into
Subarachnoid space via openings in roof of 4th ventricle and absorbed by arachnoid villi
58
Define Hydrocephalus
Accumulation of CSF due to frequently due to blocked aqueduct. prevents CSF from lateral and 3rd ventricles passing into the 4th ventricle and can't drain it properly
59
What are the clinical features of Hydrocephalus
Enlarged brain and cranium
60
What are the causes of Hydrocephalus
Genetic Prenatal viral infection Intraventricular haemorrhage Spina Bifida Cystica
61
What is the purpose of cellular differentiation in the neural tube
Need to make neuronal cells (neuron and glia) and connect cells together. begins early embryogenesis
62
Describe the lining of neural tube
* Initially a single layer of rapidly dividing neuroepithelial cells. * Pseudostratified epithelium. * Divide at ventricular surface.
63
What produces most cells of the CNS
Neuroepithelium
64
What doe Neuroepithelial cells develop into
Neuron Astrocytes (protoplasmi, fibrous) Oligodendrocyte
65
What produces Microglia
Mesenchymal cells that migrate into CNS
66
What forms the PNS neurone and glia
Neural crest
67
Name some Neural Crest derivatives
* Sensory neurons * Autonomic neurons (sympathetic and parasympathetic ganglia) * Schwann cells + satellite cells of ganglia * Aortic plexuses (nerves surrounding the aorta) * Endocrine cells (chromaffin cells of adrenal medulla; calcitonin producing cells of carotid body; parafollicular cells of thyroid). * Enteric nervous system * Pigment cells (melanocytes) – all pigment except RPE * Leptomeninges of anterior brain (prosencephalon and part of mesencephalon) * Non-neural head structures (including bone, cartilage and connective tissue). * Teeth (dental papilla; odontoblasts) * Iris muscle and pigment; ciliary muscles * Corneal stroma * Inner ear development * Regions of the heart + walls of large arteries * “4th germ layer”
68
Neural crest extend 2 processes
Peripheral process--> body | Central process--> dorsal horn of spinal cord
69
Motor component of spinal cord is derived from where
Neural tube
70
Describe the position of the spinal cord 3 months into development
Extends entire length of vertebral column
71
Vertebral column and dura mater grow more rapidly than what? what is the result
Spinal cord Spinal cord at high levels )newborn L2/L3) Adult -L1
72
Spinal nerves become elongated and form
Cuada equina
73
The Pia mater forms what structure
Terminal filum
74
What is the purpose of cortical folding
Saves space | brings together brain regions that would otherwise be far apart and optimises brain wiring and organisation
75
What is the the initial appearance of the cerebral hemisphere and what causes it to change
Initially smooth | Sulci and Gyri cause it to become a more complex pattern
76
At what week is the cerebral hemisphere smooth
14 weeks
77
At what week does the cortical folding begin
26 weeks
78
Define Lissencephaly
Rare brain disorder where the brain is smooth due to gyro and sulk failing to develop.
79
What causes Lissencephaly
Defective neuronal migration
80
What is the consequence of Lissencephaly
Severe mental impairment, failure to thrive, seizures and abnormal muscle tone. Die before 10 Y.O
81
Define Polymicrogyria
Excessive number of small gyri | mental retardation, seizes, motor deficits
82
What is Micorcephaly and what causes it
Reduced brain and skull size | Genetics, drugs, infection (zika)
83
What are the clinical signs of Microcephaly
Intellectual impairment, delayed motor functions/speech, hyperactivity, seizures, balance/co-ordination problems etc.
84
What is Aegenesis Corpus Callosum
complete or partial absence of the corpus callosum.
85
What are the clinical signs of Aegenesis Corpus Callosum
* Effects range from subtle – severe | * Cognitive and social difficulties  intellectual impairment, seizures, hypotonia
86
What is Porencephaly
CSF filled cysts and cavities,
87
What is the cause and consequence of Porencephaly
Usually from stroke or infection | Delayed growth and development, seizures, hypotonia, intellectual impairment
88
What is Schizencephaly
Large clefts or slits in the brain
89
What causes Schizencephaly
Genetic In utero stroke Infection Paralysis, seizures, intellectual impairment, development delay
90
What is Diastematomyelia
• Spinal cord split longitudinally into 2 parts
91
What is Diastematomyelia associated with
Vertebral abnormalities | Scoliosis, weakness of lower extremities, hairy patch over lower back, foot deformities, loss of sensation.
92
Name some causes of intellectual impairment
``` Genetic- Down's Syndrome Radiation Infectious agents(rubella, , toxoplasmosis, cytomegalovirus) Birth trauma Postnatal insults Maternal alcohol abuse ```

Neurology (44 decks)

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