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Neuro > Neuroembryology > Flashcards

Neuroembryology Flashcards

1
Q

The process of neurulation (neural plate forms and folds from dorsal ectoderm) occurs at what week ?

A

Week 3
(Day 16)

Neuroectoderm (derived from dorsal ectoderm) is the first indication of future nervous system and appears around day 16 of intra-uterine life. Underlying mesodermal cells (notochord) induce rapid growth of neural plate cells to form the neural groove with neural folds on each side.

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2
Q

Neural tube closure and the formation of the 3 primary vesicles occurs at what point during the embryonic period ?

A

Day 21-28

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3
Q

Neural folds begin to fuse from the middle region (future cervical spinal area) and neural groove becomes neural tube at what point in time ?

A

By day 21

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4
Q

The process of closing the neural tube progresses rostrally and caudally and the tube completely closes by day :

A

28

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5
Q

The posterior and narrower end of developing neural tube becomes :

A

Spinal cord

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6
Q

While neural tube is being formed, cells not incorporated into the tube separate and migrate dorsally to become :

A

Neural crest cells

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7
Q

Neural crest cells will differentiate into separate groups of cells and structures which include :

A

Cranial nerve ganglia
Dorsal root ganglia
Autonomic ganglia cells
Mesencephalic nucleus of midbrain
Enteric neurons
Adrenal medullary cells
Chromaffin cells
Schwann cells
Melanocytes
Meninges (pia & arachnoid)

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8
Q

The nervous system develops from :

A

Ectoderm

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9
Q

What are the 3 divisions (vesicles) that develop from the anterior aspect of the developing neural tube at week 3 :

A

During brain development, the neural tube differentiates into 3 primary brain vesicles :
1. Prosencephalon (forebrain)
2. Mesencephalon (midbrain)
3. Rhombencephalon (hindbrain)

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10
Q

At week 5, the primary brain vesicles give rise to secondary brain vesicles :

A

Prosencephalon forms Diencephalon & Telecenphalon.
Rhombencephalon forms Myelencephalon & Metencephalon.

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11
Q

BMP (bone morphogenic protein) and SHH (Sonic Hedge Hog) are :

A

Genes involved in transcription of induction and supression factors in early neurogenesis of the CNS.
BMP : part of TGF-b superfamily protein
SHH : associated with motor aspect
Both have effects on dorsoventral aspect.

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12
Q

Cerebral hemispheres and basal ganglia are adult derivates of :

A

Telencephalon

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13
Q

Ventricle associated with Telencephalon :

A

Lateral ventricle

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14
Q

Third ventricle in adult is associated with what embryonic part ?

A

Diencephalon

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15
Q

What are the adult derivates of the Diencephalon ?

A

Thalamus
Pineal gland
Hypothalamus
Neurohypophysis
Retina

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16
Q

What are the adult derivates of the Mesencephalon ?

A

Midbrain
Cerebral aqueduct

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17
Q

The fourth ventricle is derived from what embryonic structures?

A

Metencephalon
& Myelencephalon

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18
Q

Pons and Cerebellum are derived from what embryonic structures ?

A

Metencephalon

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19
Q

Medulla is derived from what embryonic structure ?

A

Myelencephalon

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20
Q

First appearance of neural plate from dorsal ectroderm ?

A

Day 16

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21
Q

At what day does the neural fold begin to fuse in cervical region to form neural tube?

A

Day 21

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22
Q

What happens at day 26 of neurulation ?

A

Anterior neuropore closes

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23
Q

Closure of posterior neuropore occurs at ?

A

Day 28

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24
Q

Period of profound neural differentiation, proliferation and migration from germinal matrix ;period of intense synaptic formation in brain and spinal cord ?

A

4th to 28th wk.

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25
Q

When does neuroglia first appear in the ventricular zone ?

A

19th wk

Ependymocytes, astrocytes, oligodendrocytes.

More neurons & neuroglia are present in embryonic stages than survive in adulthood.
Microglia enters CNS from hemoatopoetic tissue.

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26
Q

All neuroectodermal cells not incoporated into neural tube remain as :

A

Neural crest cells

Located dorsolaterally to the tube

27
Q

What are the 2 aspects of the developing neural tube ?

A

Alar plate & Basal plate

28
Q

The Alar plate (dorsal aspect of the neural tube) induced by BMP forms :

A

Sensory neurons

29
Q

The basal plate (ventral/lateral aspects of the neural tube) induced by SHH form :

A

Motor and preganglionic autonomic neurons

Neurons in lateral horn and ventral horn

30
Q

What divides the Alar and Basal plates ?

A

Sulcus limitans

31
Q

What structure develops from the rhombic lip at the cranial end of roof of 4th ventricle during **wk 5-6 ** of IU life ?

(The rhombic lip differentiates from the alar plate of metencephalon)

A

Cerebellum

32
Q

Cerebral hemispheres undergo tremendous growth & differentiation during 3rd and 4th months to form :

A

Lobes, gyri, sulci and histologic layers of the cerebral cortex.

Growth of Telencephalic vesicles occurs from dorsal aspect of the forebrain at wk 5. Telencephalic vescicles eventually differentiate into the cerebral hemispheres.

33
Q

The thalamus (dorsal part), hypothalamus (ventral part), mammillary bodies, tuber cinereum and infundibulum are structures derived from :

A

Diencephalon

34
Q

What is the largest structure of the diencephalon ?

A

Thalamus

It has various nuclei of importance to sensory and motor functions

35
Q

What part of the basal ganglia are part of the Telencephalon ?

A

Caudate
Putamen
Globus pallidus

36
Q

What parts of the basal ganglia are found in the Diencephalon or Midbrain ?

A

Substantia nigra
Subthalamus

37
Q

Limbic system (emotions & memories) structures proliferate from :

Cingulate cortex, Hippocampus, Amygdala, mammillary bodies, olfactory nuclei, entorhinal and pirifiorm cortex

A

Immature neurons in the medial and ventral surface of the telencephalic vesicles.

38
Q

Myelination begins at what time in the cervical spinal cord, prenatally ?

A

4th month

wk 16 ; beginning of 2nd trimester

Spinal cord myelination continues for years, at least until age 2.5-3 y.o.

39
Q

Myelination in the brain begining at the basal ganglia starts at what month ?

A

6th month (end of second trimester)

40
Q

Post natally, corticospinal tract begins myelination when ?

A

6 months

41
Q

Myelination in the brain may continue up to how many years of life ?

A

Usually decades,
20-25 y.o.

42
Q

Myelination of the cerebral cortex starts in utero and is well advanced by age 2.5 in major ascending and descending tracts of the brain. What physical sign may be positive before this age due to incomplete myelination of corticospinal tracts ?

A

Babinski

A positive Babinski in children above 2.5 y.o. is a sign of UMN lesion.

43
Q

Failure of **anterior neuropore **(day 25-28) with gross associated problems with cranial bones and skin resulting from folic acid deficiency and characteristic rise in AFP levels :

A

Anencephaly

44
Q

Failure of posterior neuropore (day 21-28) with variable associated defects in vertebrae and skin ranging from cervical to lumbar regions?

A

Spina bifida

45
Q

Causes of Spina bifida include :

A

Folic acid deficiency
Antiseizure meds
Heredity

46
Q

What version of Spina bifida is benign and what is a classic sign ?

A

Occulta
Hairy patch or dimple at site

Later in life they may develop severe back pain

47
Q

Spina bifida cystica (aka Aperta) 3 subtypes :

A

Meningocele (protrusion of meninges)
Menigomyelocele (protrusion of meninges + nerves)
Myelocele (protrusion of nerve mass with no covering)

Also present with elevated AFP

48
Q

Which subtype of Spina bifidi cystica is the most severe ?

A

Myelocele
(protruision of nerves with no covering)

49
Q

Characterized by failure in process associated with closure of anterior neuropore. Meninges, brain, CSF protrude through the cranium with or without ventricles.

Caused by folic acid deficiency and/or teratogens.

Also presents with î AFP levels.

A

Encephalocele

Occurs commonly in the midline occipital region

Clinically associated with mental retardation and paresis.
Post surgical hydrocephalus common.

50
Q

Layer immediately deep to ependyma of ventricular system in early developing neural tube that consists of cells that give rise to neurons and glia cells of cerebral cortex and basal nuclei :

A

The germinal matrix

51
Q

The germinal matrix is responsible for generation and migration of neurons in the brain. Damage to it results in :

A

Poorly developed grey and white matter of the brain.

52
Q

What event, during 2nd trimester, can cause underdevelopment of cerberal cortex due to damage to germinal matrix ?

A

Hemorrhage of placenta

Thsi is revealed by MRI or CT

This is a common cause of 2nd or early 3rd trimester miscarriage.

53
Q

Risk factors associated with defective germinal matrix and subsequent halted migration of cortical cells :

A

Low birth weight babies (< 1500 g)
Premature babies (< 32 wks)
Pre-natal hypoxic events (placenta insufficiency, early placenta separation, maternal cardiopulmonary failure, maternal cocaine use)

54
Q

Germinal matrix blood supply supports Radial glial cells which provide the scaffold so that cortical cells can migrate to specific areas within the cerebral cortex. Failure of cortical cells to migrate to their final position caused by interruption of germinal matrix, especially during 2nd trimester results in :

A

Grey Matter Heterotopia

Ectopic areas of grey matter within the white matter tracts
55
Q

What is Lissencephaly ?

A

Failure of cortical cells to migrate to final position in germinal matrix, characterized by ‘‘smooth brain” lacking gyri.

Multiple genes implicated, as well as possible viral exposure

Usually associated with severe psychomotor disorders, intractable seizures, congenital facial abnormalities such as small jaw, high forehead, short nose and low set of ears.

56
Q

Arnold-Chiari Malformations herniation types :

A

Type 1 : cereballar tonsil
Type 2 : cerebellum
Type 3&4 : lower brain stem herniating through the foramen magnum

Dx : CT & MRI ; Present with signs of hydrocephalus and raised ICP.

Type I associated with Syringomelia
Type II associated with Spina bifida
Type III & IV associated with deformed 4th ventricle

57
Q

What syndrome is characterized by cerbellar agenesis (partial or complete) usually at Vermis or agenesis of Corpus Callosum resulting in dilated 4th ventricle and hydrocephalus.

Clinical presentation : macrocephaly, vomiting, delayed motor skills, truncal ataxia, and cranial nerve problems.

A

Dandy-Walker syndrome

Mnemonic : DWS for diated 4th venticle, water (hydrocephalus) and small vermis (cerebellar agenesis)

58
Q

What syndrome is associated with damage to fibers of spinothalamic and corticospinal tract that present with abnormal **enlargment **or cavitation of the central canal of the spinal cord ?

A

Syringomelia
Fluid fild cyst in spinal cord, usually at cervical level and associated with Arnold Chiari Type 1 syndrome.

Bilateral loss of pain and temperature in affected segmental dermatomes and if corticospinal tract involved, LMN lesion symptoms.

59
Q

Approx 75% of cases involve complications during pregnancy but not usually diagnosed until 6-9 months of age. Constellation of sx characteristics of white matter damage, as well as neuromuscular deficits :

A

Cereberal palsy

60
Q

Spastic type of Cerebral palsy (most common) is due to :

A

UMN lesions and GABAergic receptor dysfunction in spine.

Antispasmodic meds such as botulism toxin and Baclofen used for trx.

61
Q

Ataxic Cerebral palsy is characterized by :

Least common type

A

Cerebellar damage which causes difficulty with coordination and balance, decreased muscle tone and intention tremor.

62
Q

Subtype of Cerebral palsy characterized by damage to basal ganglia or substantia nigra ?

A

Athetoid/Dyskinetic/ADCP
1. Choreoathetoid ADCP (involuntary mvmts in face & extremities) - hypokinetic
2. Dystonic ADCP (strong, slow contractions, whole body or local) hyperkinetic

63
Q

Symptoms of kiernicterus include :

A

Athetoid dyskinetic cerebral pasly (choreoathetoid type)
Auditory and visual impairements

Choreoathetoid : involuntary mvmts in face & extremities (hypokinetic)

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