Lecture 8: Development Of The Brain Flashcards
(107 cards)
1
Q
Define pachygyria
A
Broad, thick gyri
2
Q
What is neurona heterotopia?
A
Cells in aberrant positions compared to a normal brain
3
Q
Over 12+ genetic loci have been implicated to cause holoprosencephaly and all have to do with inhibition of what biochemical process?
A
Cholesterol synthesis
4
Q
When does neurulation begin?
A
Day 22-23
5
Q
When do the rostral and caudal neuropores close?
A
Rostral at day 25
Caudal at day 27
6
Q
What do secondary versus primary neurulation give rise to?
A
Primary gives rise to brain and spinal cord and to lumbar region
Secondary gives rise to the sacral and coccyx parts of the neural tube
7
Q
What is the “region of secondary neurulation” in the developing neural tube?
A
Cluster of cells called the caudal eminence that fuses with the primary neurulation (neural tube) component giving rise to the secondary neurulation structures
8
Q
Explain the formation of the neural tube
A
- Notochord induces neural groove elongation
- Neural folds migrate toward midline and start to elongate bringing neural tube ends together
- Neural tube fuses
- Neural crest migrates down on both sides of neural tube
9
Q
What does neuroectoderm give rise to?
A
Neurons
Astrocytes
Oigodendrocytes
Ependymal cells -> choroid plexus
10
Q
What are microglial cells derived from?
A
Mesenchyme -> not neuroectoderm!
11
Q
List the primary brain vesicles
A
Prosencephalon = forebrain Mesencephalon = midbrain Rhombencephalon = hindbrain
12
Q
What secondary vesicles does the prosencephalon give rise to?
A
Telencephalon and diencephalon
13
Q
What secondary vesicles does the rhombencephalon give rise to?
A
Metencephalon and myelencephalon
14
Q
What portion of the neural tube becomes the brain?
A
Neural tube crania to fourth somites
15
Q
When do the forebrain and hindbrain divide into secondary vesicles?
A
5th week
16
Q
What structures does the metencephalon give rise to?
A
Pons and cerebellum
17
Q
What structures does the myelencephalon give rise to?
A
Medulla
18
Q
What structures does the telencephalon give rise to?
A
Cerebral cortex
19
Q
What structures does the diencephalon give rise to?
A
Anything with the word “thalamus” in it and the optic nerve
20
Q
What ventricle is found in the telencephalon?
A
Lateral ventricle
21
Q
What vesicle of the brain is the third ventricle located in?
A
Diencephalon
22
Q
What vesicle of the brain is the cerebral aqueduct located in?
A
Mesencephalon
23
Q
What vesicle of the brain is the 4th ventricle located in?
A
Upper 4th is in metencephalon and lower 4th is in myelencephalon
24
Q
What is the first flexure of the brain to form and what does it divide?
A
Cervical flexure -> divides the hindbrain from the spinal cord
25
What is the last flexure of the brain to form and what does it divide?
Pontine flexure -> divides the hindbrain into caudal myelencephalon and rostral metencephalon
26
What is the second flexure of the brain to form and what does it divide?
Cephalic flexure AKA mesencephalic flexure AKA midbrain flexure -> bend between midbrain and forebrain (diencephalon)
27
When do the basal ganglion and cortical structures develop?
Weeks 2-32
28
What structures does the basal ganglion include?
Caudate nucleus
Globus pallidus
Putamen
29
Subcortical white matter (including internal capsule), olfactory bulb and tract, basal ganglia, amygdala and the hippocampus are all located in what vesicle of the brain?
Telencephalon
30
The cerebral peduncles, superior and inferior colliculi, and CN III and CN IV are all found in what vesicle of the brain?
Mesencephalon
31
The medulla oblongata is found in the myelencephalon and encompasses what 2 structures?
Olive
| Pyramids
32
What does holoprosencephaly result from?
Incomplete separation of cerebral hemispheres (just rounded brain)
Most associated with facial abnormalities
Reduction of FNP
Hypotelorism
33
What are the causes of holoprosencephaly?
Genetic and environmental factors
Maternal diabetes
Tetragens (alcohol)
34
What are the clinical features of holoprosencephaly?
Microcephalic, small eyes, eyes closer together, midfacial hypoplasia and cleft lip with or without cleft palate
Intellectural disability or developmental delay -> more severe cases
Epilepsy, hydrocephaly, dystonia, movement disorder, Autonomic dysfunction, hypothalamic/pituitary dysfunction
35
Explain the development of the pituitary gland
1. First arch ectoderm in roof of mouth forms Rathke’s pouch
2. Rathke’s pouch migrates toward developing brain
3. Infundibulum from floor of diencephalon and Rathke’s pouch migrate and merge together
4. Rathke’s pouch forms anterior lobe and infundibulum forms posterior lobe
36
Where does Rathke’s pouch versus the infundibulum come from?
Rathke’s pouch = first arch ectoderm from the roof of the mouth
Infundibulum = floor of diencephalon
37
What gives rise to the anterior versus posterior lobes of the pituitary gland?
Anterior = Rathke’s pouch
Posterior = infundibulum (neuroectoderm)
38
What does the sulcus limitans separate?
Alar and basal plates
39
How are the alar and basal plates of the spinal cord induced?
BMPs rostrally induce the alar plate
Shh caudally induces basal plate
40
What does the alar plate give rise to in the spinal cord?
Dorsal gray columns, constitute afferent nuclei and groups of them form dorsal gray horns
41
What does the basal plate give rise to in the spinal cord?
Ventral and lateral gray columns -> form the efferent nucleus which forms ventral and lateral gray horns
42
Where does the spinal cord develop?
Caudal to the 4th pair of somites
43
Explain the formation of the spinal cord
Lateral walls of the neural tube thicken reducing the size of the neural canal until only a small central canal exists -> happens weeks 9-10
44
What are the 3 zones of the spinal cord?
1. Ventricular zone
2. Intermediate zone (mantle layer)
3. Marginal zone
45
What does the ventricular zone of the spinal cord contain?
Germ cells which give rise to ependymoblasts which give rise to ependymal cells and choroid plexus cells
46
What does the intermediate zone (mantle layer) of the spinal cord contain?
Neurons and glioblasts which give rise to astrocytes, radial glial cells and oligodendrocytes (zone 3)
Microglial cells found here too!
47
What does the marginal zone of the spinal cord contain?
Oligodendrocytes and microglial cells
48
How are efferent and afferent fibers distributed in the brainstem?
Efferents are more medial than afferents
Efferents lateral to medial = SVE, GVE, GSE
49
What is located on the dorsal versus ventral aspect of the lower medulla?
Dorsal aspect = gracile and cuneate nuclei -> both from alar plate
Ventral aspect = pyramids
50
What structures of the upper myelencephalon are from the basal plate?
Hypoglossal nucleus
Dorsal motor vagal nucleus
Nucleus ambiguus
51
What structures of the upper myelencephalon are from the alar plate?
Vestibular nuclei
Cochlear nuclei
Spinal trigeminal tract and nucleus
Solitary nucleus
52
What structures of the Metencephalon come from the alar plate?
Cochlear nuclei
Vestibular nuclei
Solitary nucleus
53
What structures of the Metencephalon come from the basal plate?
Abducens nucleus
Facial motor nucleus
Trigeminal motor nucleus
Superior salivatory nucleus
54
Where does the rhombic lip of the metencephalon come from and what does it give rise to?
Comes from alar plate and gives rise to cerebellum
Rhombic lip cells migrate and fuse in midline... when this happens the 4th ventricle is bounded by the cerebellum, pons and medulla
55
What structures of the mesencephalon come from the alar plate?
Superior and inferior colliculus
56
What structures of the mesencephalon come from the basal plate?
Edinger-Westphal nucleus
Occulomotor nucleus
Trochlear nucleus
Red nucleus
57
What categories of nerves come from the alar versus basal plates?
Basal = motor -> GSE, SVE, GVE
Alar = sensory -> GVA, SVA, GSA, SSA
58
What is the location of the damage causing spastic cerebral palsy?
Adjacent to the ventricles
59
What is the location of the damage causing athetoid cerebral palsy?
Basal ganglion
60
What is the location of the damage causing dyskinetic cerebral palsy?
Basal ganglion and ventrolateral thalamus
61
What is the location of the damage causing ataxic cerebral palsy?
Cerebellum
62
What congenital abnormality is syringomyelia highly associated with?
Type I Chiari malformation
63
What are the common signs of spastic cerebral palsy?
Toe walking and scissor gait
64
What are the common signs of athetoid cerebral palsy?
Slow writhing movements of the extremities and/or trunk
65
What are the signs of ataxic cerebral palsy?
Incoordination, weakness and shaking during voluntary movement
66
What body regions are affected in diplegia?
Lower limbs more affected than upper limbs
67
Arnold-chiari malformation is a deformity involving what region of the brain?
Hindbrain
68
What causes Chiari type 1 malformations?
Herniation of cerebellar tonsils thorugh foramen magnum
69
What are the symptoms of chiari type I malformations and when do pts typically present with this?
Present in late adolescence and early adulthood
Usually no symptoms but when there are they are head and neck pain, and lower cranial nerve issues -> problem with tongue, facial muscles, Arterial eye movements, decreased hearing, dizziness, coordinating movements
70
What is Arnold-Chiari type II caused by?
Herniation of medulla and cerebellum through foramen magnum -> compresses medial and lateral aperatures causes hydrocephalus
71
What are the symptoms of Arnold-Chiari type II and when do pts typically present with this?
Pts present in infancy or as children
Sx = Hydrocephalus and lower cranial nerve problems -> problem with tongue, facial muscles, lateral eye movements, decreased hearing, dizziness, paralysis of SCM, coordinating movements
72
What is Arnold-Chiari type II highly associated with?
Spina bifida myelomeningocele
**Dx can be made in utero
73
What is dandy walker malformation?
Large posterior fossa cyst continuous with 4th ventricle causing hypoplasia of cerebellum, partial or absence of vermis, atresia of foramen of Luschke and magendie
74
What is hydranencephaly and what is it due to?
Water in brain; exact cause unknown but though to be due to obstruction of blood flow to the areas supplied by the ICA
75
What are signs and symptoms of hydranencephaly?
Absences of cerebral hemispheres or represented by membranous sacs with dispersed tissue
Brainstem intact
Excessive head growth after birth
Little to no cognitive development
76
When during embryological development do gyri and sulci of the brain begin to develop?
At 5 months cortex is smooth and gyri and sulci begin forming at mo 6 and 7
77
How many lamina does the cerebrum versus the cerebellum contain?
Cerebrum has 6 and cerebellum has 3
78
What lamina of the cerebrum are the first to form and what do they contain?
1, 5 and 6
1 = mainly dendrites
5 = projects mostly to subcortical structures such as the brainstem, SC and basal ganglia
6 = projects primarily to the thalamus
79
What lamina of the cerebrum are the last to form and what do they contain?
2 and 3 (2 is the very last)
They both contain mainly neurons that project to other areas of the cortex
80
What does lamina 4 of the cerebrum contain?
Receives the majority of inputs from the thalamus
81
What is the outside-in sequence of cytodifferentiation of the cerebrum?
1. Neurons produced from ventricular zone form a superficial layer, the preplate
2. Axons from these neurons form intermediate zone
3. Neurons to be born migrate into the middle of the preplate and divide into 3 parts -> marginal zone (corresponds to lamina 1), cortical plate and sub plate
82
During cytodifferentiation of the cerebrum, early neurons of the cortical plate will form what lamina?
5 and 6
83
What is lissencephaly/agyria and what is it caused by?
Smooth brain; caused by incomplete or failure of neuronal migration during 12-24 weeks (3-4 mo)
84
What is lissencephaly/Agyria characterized by?
Microcephaly
Ventriculomegaly
Wide sylvian fissures and minimal operculum of insula
Complete or partial agenesis
- infants have apnea, poor feeding or abnormal muscle tone
- pts later develop seizures, mental retardation and mild spastic quadriplegia
85
What are the 2 mechanisms of microcephaly?
- Abnormal or lack of brain development during neurogenesis
| - injury or insult to previously normal Brian
86
What is the etiology of microcephaly?
- Genetic
- Prenatal and perinatal Brian injury due to viruses such as cytomegalovirus, rubella, toxoplasma Gondii, and Zika
- Craniosynostosis
- ionizing radiation
- postnatal brain injury
87
The cerebellar external germ layer gives rise to what layer of the cerebellum?
Purkinje layer
88
What are the 3 laminar layers of the cerebellum?
Molecular layer = outermost
Purkinje layer = middle
Granular layer = innermost
89
Where does the spinal cord terminate in infants versus adults?
Newborn = L2 or L3
Adult = L1 or L2
90
What structures of the spinal cord come from neural crest?
Spinal ganglion cells (dorsal root ganglion)
Sensory neurons (first order neurons)
91
What 2 things form the PNS?
Neural crest and ectodermal placode
92
What cells of the PNS develop from neural crest?
Neurons of dorsal root ganglion
Sensory ganglia of cranial nerves
Schwann cells
Sympathetic ganglia
93
What cell types myelinated axons n the CNS versus PNS and when do they start?
CNS = oligodendrocytes -> starts at 6th mo - puberty and starts in lower brain stem (older tracts)
PNS = Schwann cells -> starts at 4th mo and starts with motor roots before sensory
94
Explain spina bifida oculta
Unfused neural arch, skin intact -> can have tuft of hair
Pts are normal with no problems
95
Explain spina bifida with meningocele
Meninges extrude -> cyst-like structure above unformed vertebral arch, skin intact
These pts may or may not have problems with motor and sensory
96
Explain spina bifida with meningomyelocele
Meninges and neural tube extends -> neural tube is up in pocket as well, neural arches missing, SC n improper location; pocket may or may not be covered with meninges or skin
Pts will have motor deficits -> trouble walking, sensory issues, and trouble with bowel and bladder
97
Explain spina bifida with myelocele (myeloschisis)
Open neural tissue -> tube didnt close at all and is now open to outside environment -> surgery needed immediately to prevent infection
These pts have motor and sensory issues below level of lesion
98
What s the underlying problem with all spina bifida types?
Caudal neuropore didnt close at the right time -> either it closed too slow or didnt close at all
99
What is anencephaly AKA meroanencephaly AKA meroencephaly?
No formation of brain, possibly have parts of brainstem
Pts die shortly after birth
100
What is encephalocele?
Large outgrowth of head containing CSF and possibly brain tissue
Pts have either severe or mild mental deficits but wont know until they hit developmental milestones
101
What is the underlying problem with anencephaly and encephalocele?
Rostral neuropore didnt close or closed poorly
**Can be prevented with folic acid and can be caused by drug use
102
```
The anterior and posterior neuropores normally close:
A. On the 14th day after fertilization
B. On the 21st day after fertilization
C. During the 3rd week of development
D. During the 4th week of development
E. During the 6th week of development
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D. During the 4th week of development
103
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Maternal toxoplasmosis may result in:
A. Spina bifida occulta
B. Holoprosencephaly
C. Microcephaly
D. Meningocele
E. Meroencephaly (anencephaly)
```
C. Microcephaly
104
The cervical flexure divides the:
A. Hindbrain into caudal myelencephalon and rostral metencephalon
B. Hindbrain from the SC
C. Midbrain from the forebrain
D. Forebrain into telencephalon and diencephalon
B. Hindbrain from the SC
105
```
Spina bifida occulta is most commonly found in which of the following regions?
A. Cervical
B. Upper thoracic
C. Mid thoracic
D. Lower thoracic
E. Lumbosacral
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E. Lumbosacral
106
A mother came to the clinic saying her baby’s head is getting larger. MRI shows an obstruction of the foramen Luschka and magendie and a large posterior fossa cyst. What other finding would be present on MRI?
A. Incomplete separation of the cerebral hemispheres
B. Damage to the basal ganglia
C. Syringomyelia of the cervical spinal cord
D. Hypoplasia of the vermis of the cerebellum
E. Herniation of the cerebellar tonsils thorugh foramen magnum
D. Hypoplasia of the vermis of the cerebellum
107
All of the following are true about hydrocephalus except:
A. Occurs in association with maternal infection of rubella (microcephaly)
B. It may result from obstruction of the cerebral aqueduct
C. It may result from absence of the foramen of Luschka and magendie (dandy-walker syndrome)
D. Occurs in association with spina bifida (Arnold-Chiari type II syndrome)
A. Occurs in association with maternal infection of rubella (microcephaly)
