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Neuroscience BB Exam 1 > Section 6 - Embryology > Flashcards

Section 6 - Embryology Flashcards

1
Q

Anencephaly (brain not formed) results from:

A

Anterior neuropore defect

Meninges and skull may also be absent; defects can extend from lamina terminalis to foramen magnum - always fatal.

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2
Q

What is an encephalocele?

A

Herniation of intracranial contents through the cranium (cranium bifidum)

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3
Q

Define meningocele.

A

Cyst structure containing meninges

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4
Q

Define meningoencephalocele.

A

Cyst structure containing meninges plus brain.

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5
Q

Define meningohydroencephalocele.

A

Cyst structure contains meninges, brain, and part of ventricular system.

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6
Q

What are dysraphic effects?

A

Congenital malformations associated with defective neurulation. Can be prevented with folic acid prior to pregnancy.

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7
Q

What is Arnold-Chiari sydrome?

A

Cerebellar herniation into foramen magnum - there are two types.

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8
Q

Chiari I malformation:

A

Congenital herniation of the cerebellar vermis through foramen magnum –> pressure on medulla and cervical spinal cord

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9
Q

Chiari II malformation (Arnold-Chiari deformity):

A

Similar defect to Chiari I, but with additional myelomeningocele (herniation of meninges, CSF, spinal cord through unclosed posterior neuropore)

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10
Q

Chiari I is associated with:

A

Syringomyelia and syringobulbia

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11
Q

What is syringomyelia?

A

cavitation of the spinal cord

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12
Q

What is syringobulbia?

A

cavitation of the medulla

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13
Q

What is exencephaly?

A

Cephalic disorder wherein the brain is located outside of the skull

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14
Q

What is meroencephaly?

A

Rare form of anencephaly characterized by malformed cranial bones and median cranial defect through which protrudes a cerebrovasculosa

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15
Q

What is microcephaly?

A

Circumference of the head is more than three standard deviations smaller than average - caused by abnormal growth of brain

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16
Q

Neural tube defects (dysraphic effect) are associated with inadequate ______; treat with ______

A 
Folic acid (shoutout to Dr. Forney)
Closure of spinal defects and ventricular shunts
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17
Q

What is myeloschisis?

A

Defect in the closure of the posterior neuropore - involves failure of vertebral arch to form completely to cover spina cord (spina bifida)

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18
Q

Define spina bifida occulta.

A

Neuroectoderm exposed on the lower back from incomplete posterior neuropore fusion; results in a tuft of hair and the skin covering the defect.

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19
Q

Define spinal bifida aperta.

A

Incomplete neuropore fusion, and there is an inadequate closure over the vertebral defect (patent aperture)

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20
Q

Define spina bifida cystica.

A

Meningocele: herniation of the meninges and CSF through the unclosed posterior neuropore
Meningomyelocele: herniation of meninges, CSF, and spinal cord (usually cauda equina) through unclose posterior neuropore.

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21
Q

What are some complications of spinal bifida cystica, with meningomyelocele?

A

May be unable to move lower limbs, perceive pain sensation. Often also have hydrocephalus, Arnold-Chiari malformation.

22
Q

What is septooptic dysplasia (or de Morsier syndrome)?

A

Dysgenesis of diencephalon, hypoplasia of optic n. and hypothalamus-pituitary, and midline structural defects

23
Q

de Morsier syndrome (septic optic dysplasia) causes:

A

Congenital blindness, hypothyroidism, diabetes insipidus, hypoadrenocorticism

24
Q

What is myelodysplasia?

A

Malformation of part of the neural tube formed by secondary neurulation (typically covered by skin); site may have unusual pigmentation, hair, telangiectases (large superficial capillaries), or prominent dimple

25
Q

What is tethered cord syndrome?

A

Conus medullaris and filum terminale are abnormally fixed to defective vertebral column, leading to weakness, sensory loss, and asymmetric growth of legs and feel, and bowel/bladder control issues

26
Q

What is caudal regression syndrome?

A

Infants born to mothers with diabetes mellitus - affects development of embryonic structures of the caudal region (like spinal cord)

27
Q

The acronym TORCH is good for remembering causes of defects from infectious diseases during gestation. What does it stand for?

A 
Toxoplasmosis
Other agents (syphilis)
Rubella
Cytomegalovirus
Herpes simplex virus (also, HIV)
28
Q

What are some defects associated with infectious diseases during gestation?

A

Cataracts, retinitis/blindness, deafness, cerebral calcifications, cerebral atrophy, and microcephaly

29
Q

What is a spinal dermal sinus?

A

Appears as a dimple of sinus close to midline with opening of 1-2 mm; potential pathway for infection (meningitis or abscess)

30
Q

What is heterotopia?

A

Disrupted migration of neurons from the ventricular surface of the cortex. Band heterotopia seen in severe cases - gray and white matter in banding pattern.

31
Q

List some characteristics of heterotopia.

A
  • Cell layers of cortex thickened
  • Large ventricles
  • Abnormal gyri and sulci patterns
  • Can associate with epilepsy and development disorders
32
Q

What is schizencephaly?

A

Condition with unilateral or bilateral clefts in cerebral hemispheres. Results from profound failure of cell migration or lack of blood during development.

33
Q

Closed lip schizencephaly:

A

Thin slit in hemisphere with communication between ventricle and surface of brain

34
Q

Open lip schizencephaly:

A

Large defect with substantial brain loss producing large open channels between ventricular cavity and subarachnoid space

35
Q

What are porencephalic cysts?

A

Cystic lesions from tissue destruction

36
Q

What is the Dandy-Walker Malformation?

A

Absence/atresia of foramina of Magendi/Luschka. Leads to hypoplasia of cerebellar vermis, cystic dilation of fourth ventricle, and often hydrocephalus; macrocephaly, ataxia, developmental delay

37
Q

What is Joubert syndrome?

A

Similar to Dandy-Walker, but without cystic dilation of fourth ventricle

Absence / underdevelopment of cerebellar vermis

38
Q

What is lissencephaly?

A

Failure of gyri to form within the cerebral cortex –> smooth surface. Often have retractable epilepsy.

39
Q

What is pachygyria?

A

Unusually large gyri formation.

40
Q

What is microgyria?

A

Unusually small gyri

41
Q

What is holoprosencephaly?

A

Prosencephalon fails to undergo cleavage; most common defect of forebrain and face - associated with abnormal Shh signaling

42
Q

What are some environmental causes of holoprosencephaly?

A

Maternal diabetes, alcohol, cyclopamine (retinoic acid)

43
Q

What are some defects association with holoprosencephaly?

A
  • Craniofacial abnormalities (cyclopia)
  • Motor deficits
  • Feeding and swallowing problems
  • Endocrine issues
  • Seizures
  • Developmental delay
  • Mental retardation
  • Hypotelorism (unusally close set eyes)
  • Rudimentary nasal structure (probiscus)
44
Q

Alobar holoprosencephaly:

A

No lobes develop; large single forebrain ventricle, thalamus poorly developed, and corpus callosum, longitudinal fissure, falx cerebri, olfactory structures missing

45
Q

Semilobar holoprosencephaly:

A

Some separation of forebrain into two lobes and partial development of falx cerebri, primitive lobes and gyri and rudimentary lateral and third ventricles can be present

46
Q

What is Hirschsprung’s disease?

A

Congenital megacolon; excess ECM molecules present in colon due to abnormal migration of neural crest-derived cells. Neurons forming enteric ganglia fail to migrate to lower bowel –> to motor signal to move bowels

47
Q

What is familial dysautonomia?

A

Aberrant development of neural crest derivatives.

  • Sensory symptoms: impaired pain/temp. perception
  • Autonomic symptoms: cardiovascular instability, GI dysfxn
48
Q

Mutant Shh gene lead to the “triple threat”:

A
  • Loss of notochordal induction –> holoprosencephaly
  • Medulloblastoma - tumor at cerebellopontine angle
  • Basal cell carcinoma
49
Q

What is Mobius syndrome?

A

Defect from developmental sequence of rhombomeres. Several developmental defects:

  • Aplasia of abducens and facial motor nuclei (6 and 7)
  • Weakness of muscles innervated by oculomotor and trochlear nerves (3 and 4)
  • Atrophy/weakness of tongue and mm. of mastication (12 and V3)
  • Skeletal defects of face/body
50
Q

What is amblyopia?

A

Input from one eye dysfunction during critical period at disadvantage b/c they compete for synaptic space –> “good” eye has exclusive access and “bad” eye is ignored –> functional blindness

51
Q

What is pontocerebellar hypoplasia?

A

Atrophy of pons/cerebellum –> hypotonia, poor feeding, growth retardation, profound mental retardation

52
Q

What factors can affect myelination?

A
  • Neurodegenerative diseases
  • Many amino acids/organic acid metabolism abnormalities (PKU)
  • Inadequate nutrition

Neuroscience BB Exam 1 (10 decks)

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