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Neuro Pathology > Nervous System Embryology and Congential Malformations > Flashcards

Nervous System Embryology and Congential Malformations Flashcards

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1
Q

What embryological structure does the nervous system develop from?

A

The Embryonic Ectoderm

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2
Q

When does the CNS begin to develop?

A

Beginning of the 3rd week

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3
Q

How does the CNS develop?

A

Thickening of ectoderm anterior to the primitive node = neural plate
Edges thicken and move upwards to form the neural folds
Neural tube folds migrate towards each other and fuse at the midline forming the NEURAL TUBE
Neural tube intitally open at anterior and posterior ends
Anterior (cranial/rostral) neuropore closes 18-20 somatie stage (approx. 25 days)
Posterior (caudal) neuropore closes approx. day 27

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4
Q

How do brain vesicles develop?

A

Begins with closure of anterior neuropore (approx. day 25, 18-20 somite stage )

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5
Q

What happens in the neural development in the 5th week?

A 
Prosencephalon splits into 
- telencephalon 
- diencephalon 
Mesencephalon stays the same
Rhombencephalon splits into 
- metencephalon 
- myelencephalon
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6
Q

Flexures of the nervous system development

A 
Cephalic flexure
- end of 3rd week 
- between midbrain and hindbrain 
Cervical flexure 
- end of 4th week 
- between hindbrain and spinal cord
Pontine flexure
- 5th week 
- in hindbrain
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7
Q

Parts of the neural tube

A 
Telencephalon 
Diencephalon 
Mesencephalon (Midbrain) 
Rhombecephalon (hindbrain)
- Metencephalon 
- myelencephalon
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8
Q

What does the telencephalon form into?

A

Cerebral hemispheres
Hippocampus
Basal ganglia

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9
Q

What does he diencephalon form into?

A

Thalamus
Hypothalamus
Pituitary gland
Pineal

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10
Q

What does the mesencephalon form?

A

Superior and inferior colliculi

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11
Q

What does the metencephlon form?

A

Cerebellum

Pons

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12
Q

What does the myelencephalon form?

A

Medulla

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13
Q

What does the lumen of the neural tube form?

A

Ventricular system

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14
Q

What week does CSF begin to form?

A

During the 5th week

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15
Q

What is CSF produced predominately by?

A

Choroid plexus

- in 3rd and 4th and lateral ventricles

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16
Q

Where does CSF drain into?

A

Subarachnoid space via openings in roof of the 4th ventricle

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17
Q

Where is CSF absorbed into?

A

Venous system

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18
Q

Definition of hydrocephalus

A

Accumulation of CSF leading to enlarged brain and cranium

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19
Q

What is hydrocephalus frequently due to?

A

Blocked aqueduct

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20
Q

Pathology of hydrocephalus

A

CSF is prevented from lateral and 3rd ventricles passing into the 4th ventricle so cant drain properly

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21
Q

Causes of hydrocephalus

A

Genetic
Prenatal viral infection
Intraventricular haemorrhage
Spinal bifida cystica

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22
Q

What cellular differentiation needs to be done in the neural tube?

A

Neuronal cells need to be made (neurones and glia)

Connect cells together

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23
Q

What produces most of the cells of the CNS?

A

Neuroepitheliun

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24
Q

In what month does the entire length of the vertebral column extends?

A

3rd,month

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25
What does the spinal nerves become elongated to form?
The cauda equina
26
What does the pia mater form?
Terminal filum (long fibrous thread)
27
What are sympathetic and parasympathetic ganglia formed by?
Neural crest cells
28
Where are parasympathetic ganglion found?
Near or within the organs they innervate
29
Where are sympathetic ganglia found?
Chains along side of spinal cord Preaortic ganglia Sympathetic organ plexuses (in e.g. heart, lungs, GI tract)
30
What are the surface or cerebral hemispheres initially like?
Smooth
31
What is a sulcus?
Groove
32
What is a gyri?
Elevation
33
What is lissencephaly?
Smooth brain
34
Pathology of lissencephaly
Defective neuronal migration | Gyri and sulci fail to develop
35
Results of lissencephaly
``` Severe mental impairment Failure to thrive Seizures Abnormal muscles tone Affected children die before 10 ```
36
What is polymyalgia?
Excessive number of small gyri
37
Results of polymyalgia
Variable degree of neurological problems - mental retardation - seizures - motor deficits
38
Causes of microcephaly
Genetic Drugs Infection (e.g. zika)
39
Results of microcepahly
``` Intellectual impairment Delayed motor functions/speech Hyperactivity Seizures Balance / co cordination problems ```
40
Causes of porencephaly
Postnatal stroke | Infection
41
What is porencephaly?
CSF filled cysts or cavities
42
What is schizencephaly?
Large clefts or slits
43
Causes of schizencephaly
Genetic In utero Infection
44
Results of schizencephaly
Paralysis Seizures Intellectual impairment Developmental delay
45
What is diastematomyelia?
Split cord manifestation where the spinal cord is split longitudinally into 2 parts
46
Presentation of diastematomyelia
``` Scoliosis Weakness of lower extremities Hairy patch over lower back Foot deformities Loss of sensation ```
47
Causes of intellectual impairment
``` Genetic (e.g. Downs) Radiation Infectious agents (e.g. rubella, CMV) Birth trauma Post natal insults Maternal alcohol abuse ```
48
Examples of post natal insults that would cause intellectual impairment
Head injury Infections e.g. meningitis Lead exposure
49
What is closure of the neural tube essential for?
Normal development and function
50
When does the neural tube close?
Begins day 18 | Completed by end of 4th week (approx. day 27)
51
What does failure to the neural tube to close result in? Give some examples of these
Neural tube defects - ancencephaly - Encephalocele - Spina bifida
52
Pathology of ancenecephaly
Failure of anterior neuropore to close
53
Presentation of ancenecephaly
Skull fails to form Brain tissue degenerates Incompatible with life
54
What is cranioarchischisis?
Failure of neural tube closure along the entire neuroaxis - resulting in degeneration and death
55
What is encephalocele?
Herniation of cerebral tissue through a defect in the skull
56
Pathology of encephaloecele
Failure in the closure of rostral neural tube
57
Types of encephaloecele
Fronto-nasal | Occipital
58
Most common site for encephalocele
Occipital region
59
Presentation of encephalocele
Variable degree of neurological deficits | Symptoms depend on location of the brain
60
Pathology of spina bifida
Defective closure of the causal neural tube Non fusion of vertebral arches Affects the tissues overlying the spinal cord
61
Types of spinda bifida
Spina bidifa occulta | Spina bifida Cystica
62
What is the most minor form of spina bifida?
Spina bifida occulta
63
Pathology of spina bifida occulta
Failure of embryonic halves of vertebral arch to grow normally and fuse Underlying tissue is completely fine
64
Where does spina bifida occulta occur?
L5 and L6 vertebrae
65
Presentation of spina bifida occulta
Usually no clinical symptoms | May result in dimple with small turft of hair
66
Pathology of spina bifida cystica
Protrusion of spinal cord and/or meninges through the defect in the vertebral arches
67
Pathology of spina bifida with meningocele
Protrusion of meninges and CSF forming a fluid filled sac outside the spine (Impact minimal as no neural damage)
68
What is the rarest form of spina bifida?
Spina bifida with menigocele
69
Pathology of spina bifida with meningomyelocele
Nerve roots and/or spinal cord included in the fluid filled CSF sac
70
Presentation of spida bifida with meningomyelocele
Neurological deficits Loss of sensation Muscle paralysis Area affected determined by level of lesion
71
What is spina bifida with meningomyelocele often associated with?
Hydrocephalus
72
What can be taken to prevent neural tube defects?
Folic acid supplements (400ug / day)
73
Prenatal diagnosis of neural tube defects is done by....
``` Maternal blood screening - AFP levels in serum Amniocentesis - AFP in amniotic fluid USS - anecephaly from 12 weeks - spina bifida from 16-20 weeks ```
74
Risk factors for neural tube defects
``` Genetic Nutritional - too little folate - too much vitamin A Environmental - hyperthermia - taking drugs e.g. sodium valproate ```
75
What week does the nervous system start to develop?
Week 3
76
Inheritance of tuberous sclerosis
Autosomal dominant
77
Presentation of tuberous sclerosis
Cutaneous features - depigmented "ash leaf" spots which fluorescence under UV light - roughened patches of skin over lumbar spine (Shagreen patches) - Adenoma sebaceum (angiofibroma); butterfly distribution over the nose - fibromata beneath nails (subungual fibroma) - Café au lait spots may be seen Neurological features - developmental delay - Epilepsy - intellectual impairment Retinal haemorrhages Rhabdomyomas of the heart Gliomatous changes that occur in brain lesions Polycystic kidneys, renal angiomyolipomata lymphangioleiomyomatosis: multiple lung cysts
78
What are axillary freckles indicative of?
NF type 1

Neuro Pathology (21 decks)

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