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PBL Y2 S3 > Case 1 - NTDs > Flashcards

Case 1 - NTDs Flashcards

1
Q

What are the 3 germ layers and what do they become?

A

Endoderm - linings of digestive system, forms organs, i.e. liver and pancreas
Mesoderm - muscle, bone, connective tissue (forms CV and respiratory systems)
Ectoderm - hair, skin and the nervous system

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2
Q

What germ layer forms the notochord?

A

Mesoderm

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3
Q

What is the process of neuralation?

A

1: Notochord releases growth factors, leading to ectodermal proliferation
2: Inhibition of BMP and thickening of the ectoderm produces a neural plate (around day 17)
3: Invagination of the neural plate, i.e. centre descends and the sides roll up
4: Neural groove and neural folds (with neural crest cells) are formed - around day 18
5: Neural tube is formed around day 21, but the neuropores still remain open
6: Folate (vit B9) is required for the neuropores (anterior and posterior) to close:
- Day 25 = anterior neuropore closes
- Day 27 = posterior neuropore closes

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4
Q

What NTD’s occur if the neuropores dont close?

A

If anterior neuropore fails to close = ancephaly
If posterior neuropore fails to close = spina bifida

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5
Q

What are the 3 primary vesicles formed from the cranial end of the neural tube?

A

Prosencephalon
Mesencephalon
Rhombencephalon

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6
Q

What does the prosencephalon form?

A

secondary vesicles = telencephalon and diencephalon
Telencephalon –> cerebrum
Diencephalon –> thalamus and hypothalamus

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7
Q

What does the mesencephalon form?

A

Midbrain

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8
Q

What does the rhombencephalon form?

A

Secondary vesicles = metencephalon and myelencephalon
Metencephalon –> pons and cerebellum
Myelencephalon –> medulla oblongata

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9
Q

Which plates become the dorsal and ventral grey horn? What neurons do they contain?

A

Alar plate - becomes the dorsal grey horn, contains sensory neurons
Basal plate - becomes the ventral grey horn, contains motor neurons

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10
Q

What morphogens control patterning?

A

BMP and SHH on a dorsoventral axis:
- BMP = decreases dorsoventrally
- SHH = decreases ventrodorsally

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11
Q

What morphogens control segmentation?

A

Retinoic acid - secreted onto anterior end by somites
FGF - secreted onto posterior end

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12
Q

What is hydrocephalus and what can it be caused by?

A

Abnormal accumulation of CSF in intracranial cavity. Can be caused by:
- Excess CSF production (rare)
- Decreased reabsorption via arachnoid granulations
- Obstruction of flow in ventricles or subarachnoid space

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13
Q

What is the most common cause of hydrocephalus?

A

Obstructed CSF flow in the 4th ventricle into the subarachnoid space

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14
Q

How many SB cases are associated with hydrocephalus?

A

Around 50%, but complicates 90% of myelomeningocele cases

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15
Q

What is a sign of hydrocephalus in babies?

A

Bulging anterior fontanelle (enlarged head)

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16
Q

What are the symptoms of hydrocephalus?

A

Similar to increased intracranial pressure - headaches, nausea, vomiting, cognitive impairment, impaired vision, decreased level of consciousness

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17
Q

How can hydrocephalus be treated?

A

Allow CSF to bypass obstruction and drain from the ventricles:
- Ventriculostomy (external ventricular drain): drains fluid from lateral ventricles into a bag outside the head
- Ventriculoperitoneal shunt: more permanent, shunt tubing from lateral ventricle out of the skull, drains into peritoneal cavity of abdomen. Has valves for one-way flow

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18
Q

What is normal pressure hydrocephalus and what is the typical triad of presentation?

A

Chronically dilated ventricles, seen in the elderly
Triad: gait difficulties, urinary incontinence, mental decline

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19
Q

How can SB be caused?

A

Genetics, folate deficiency or taking folate antagonists (i.e. Valproate, aminopterin), obesity, poorly controlled diabetes

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20
Q

What is the recommended dose of folate for prevention of SB?

A

400mg folate every day, for 3 months before pregnancy and 3 months during

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21
Q

What is spina bifida occulta?

A

Mildest and most common form of SB - where 1 or more of the vertebrae are malformed. A layer of skin covers the opening (‘closed NTD’), can be seen by a hair tuft, caused when CSF leaks from the spinal cord which stimulates hair follicles.

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22
Q

What are the symptoms of SB occulta and where is the lesion usually located?

A

It is asymptomatic, but gait disturbance and disturbed bladder control are possible
Lesion - usually L5 and S1

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23
Q

What is folate required for?

A

DNA methylation

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24
Q

What is meningocele (SB Opperta)?

A

Herniation of the meninges without involvement of spinal elements, i.e. nerves/ spinal cord, therefore is just a sac of CSF from the spine.
Has minor symptoms, but worse if nerves are damaged.

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25
Q

What is myelomeningocele (SB Opperta)?

A

Most severe form of SB - herniation of meninges and spinal cord, bulges out of the baby’s back. The exposed spinal cord is damaged by amniotic fluid (toxic) - the sac can also burst during child birth

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26
Q

What are the symptoms of and associated conditions to myelomeningocele?

A

Changes in brain structure, leg weakness, bladder and bowel dysfunction, possibly some paralysis
It is associated with hydrocephalus and chiari II malformation

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27
Q

How can myelomeningocele cause hydrocephalus?

A

NTD decreases intraspinal pressure, so CSF backs up into the ventricles. Accumulation of CSF around the brain causes increased pressure - the baby’s head enlarges and can also put pressure on the oculomotor nerve (causes ‘sunset eyes’)

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28
Q

What is the common lesion site for myelomeningocele? What is a higher lesion associated with?

A

Lumbosacral in 80% of cases
Higher lesion = bladder outlet obstruction, dilation of upper urinary tract, kidney infections

29
Q

When can SB be detected?

A

From 16-20 weeks

30
Q

How is SB detected / diagnosed?

A

Maternal serum alpha-fetoprotein (AFP) screen: blood test within 16-18 wks of pregnancy, if abnormally high then indicates SB or another NTD
If high AFP is detected:
- Ultrasound: either in 1st or 2nd trimester, look for banana sign
- Amniocentesis: sample of amniotic fluid for AFP, acetylcholinesterase and high protein

31
Q

What is the banana sign?

A

Where the cerebellum is more flatterened and curved due to caudal displacement - in SB the cerebellum wraps around the brainstem due to spinal cord tethering

32
Q

What is the lemon sign?

A

Whole image on an ultrasound looks like a lemon due to flattening of the frontal bones (pinch inwards). It is caused by the decreased intraspinal pressure leading to decreased intracranial pressure

33
Q

When is the lemon sign visible?

A

Up to 24 wk gestation

34
Q

How is SB occulta treated?

A

None required unless spinal cord is tethered - then need to detach SC from surrounding tissue

35
Q

How is meningocele treated?

A

Surgery to push meninges back into the body and close the hole in the vertebrae or skull - usually done in first few months of life.

36
Q

How is myelomeningocele treated?

A

Opening can be closed in utero (25th week) or shortly after birth (1-2 days later). Antibiotics may be given to reduce infection risk
» Better outcomes if in utero as reduced need to drain fluid from the brain

37
Q

What is the epidemiology of SB?

A

SB affects 1 in 2,500 newborns worldwide
SB occulta affects 8-15% of UK population (around 5-10 million people)

38
Q

What proportion of NTDs does SB account for?

A

40% (ancephaly also 40%)

39
Q

What is arnold-chiari malformation?

A

Congenital disorder where the base of the skull is distorted, leading to protrusion of the lower brainstem and cerebellum through the foramen magnum. There is downward displacement of the lower cerebellum, including the cerebellar tonsils.

40
Q

What is type 1 chiari malformation?

A

Herniation of cerebellar tonsils (no brainstem) - can be congenital or acquired

41
Q

What is type 2 chiari malformation?

A

Large herniation of cerebellar tonsils and brainstem, leads to paralysis below the defect. Associated with myelomeningocele

42
Q

What is type 3 chiari malformation?

A

Cerebellar tonsils are displaced into posterior encephalocele. Very rare and incompatible with life. Hydrocephalus and syringomyelia (fluid-filled cysts in the spinal cord) also occur due to CSF obstruction by cerebellum

43
Q

What is type 4 chiari malformation?

A

Form of cerebellar hypoplasia (incomplete and underdeveloped cerebellum)

44
Q

What symptoms can occur with arnold-chiari malformation?

A

Difficulty breathing, swallowing and arm weakness

45
Q

How can type 1 and 2 chiari malformation be treated?

A

Posterior fossa decompression surgery - creates more space for the cerebellum, relieves pressure on the spinal cord

46
Q

What is cephaloceles? What are the different types?

A

Herniation of the cranial contents through a skull defect:
- Cranial meningocele = herniation contains only meninges and CSF
- Encephalocele = herniation contains brain tissue
- Ventriculocele = herniation contains part of the ventricles

47
Q

What is holoprosencephaly?

A

A dirsorder when the prosencephalon (forebrain) fails to undergo segmentation and cleavage into the telencephalon and diencephalon, and thus fails to develop into 2 hemispheres.
This causes the forebrain, cranium and face to be abnormal

48
Q

How can holoprosencephaly be caused?

A

Defects of SHH gene

49
Q

What is ancephaly?

A

Partial or complete absence of telencephalon (cerebral hemispheres), meninges or bones at the rear of skull. The absent brain is replaced by malformed cystic tissue, which may be exposed or covered with skin.
> Babies are usually stillborn or die shortly after birth

50
Q

Describe consent legalities for minors

A

If over 16 years - assumed to be competent to consent unless clear reason otherwise, so can consent without parental responsibility
Under 16 years - assess competency, can consent if they are deemed to be Gillick competence
Anyone under 16 years - can be overruled by a doctor if they decline a treatment that prevents serious harm or death

51
Q

If a 15 year old deemed ‘competent’ wishes to have an abortion, could this decision be overruled by a parent?

A

No - a parents refusal to give consent for an abortion cannot override consent of a competent young person

52
Q

According to the Fraser guidelines, when can contraceptive advice be given?

A

if they have:
- Sufficient maturity and intelligence to understand the nature and implications of proposed treatment (i.e. have capacity)
- Cannot be persuaded to tell parents or allow doctor to do so
- Likely to continue sex with or without contraceptive treatment
- Physical and mental health is likely to decline without advice/ treatment
- it is in their best interest to have this treatment/ advice

53
Q

What is bipolar disorder?

A

Patient experiences recurrent periods of sustained depressed mood and hopelessness (major depressive episodes) and periods of abnormally elevated mood with increased energy (manic or hypomanic episodes)

54
Q

What is the difference between bipolar disorder I and II?

A

Bipolar I: elevated mood is severe and sustained (‘mania’)
Bipolar II: elevated mood is less severe (‘hypomania’)

55
Q

What are symptoms of mania?

A

Irritable mood, increased activity, decreased need for sleep, excessive involvement in pleasurable activities, increased self-esteem, distractibility

56
Q

What are some depressive symptoms?

A

Depressed mood, decreased interest in nearly all activities, appetite changes, insomnia, fatigue

57
Q

What is the epidemiology of bipolar disorder?

A

Lifetime prevalence: 2.4% across the world
Bipolar I - more common in men
Bipolar II - more common in women
But overall, equally common in men and women
Mean age of onset = 21
Strong evidence for genetic aetiology: 60-80% concordance in monozygotic twins compared to 15% dizygotic

58
Q

How is bipolar disorder treated?

A

Medications used for 3 phases:
1: Acute manic/ hypomanic episodes: antipyschotics (D2 receptor antagonists), lithium (mood stabiliser), valproate (antiepileptic), carbamazepine (antiepileptic)
2: Acute major depressive episodes:
Low dose quetiapine (2nd generation antipsychotic), lamotrigine (anti-epileptic), lithium
3: Maintenance:
Lithium, quetiapine (better for depression), valproate (good choice if predominantly mania)

59
Q

Why are anti-depressants not useful first-line for bipolar disorder?

A

Risk of causing manic episodes

60
Q

When is valproate used for bipolar disorder?

A

If lithium is ineffective or poorly tolerated

61
Q

What is the metabolically active form of valproate?

A

Valproic acid

62
Q

What is the mechanism of action of valproate?

A

1: valproic acid dissociates and binds to GABA transaminase, inhibiting it - this increases GABA levels
2: altering voltage-dependent Na+ channels, suppressing firing by inhibiting these channels

63
Q

How does valproate increase the risk of NTDs if taken during pregnancy?

A

It inhibits the DHFR enzyme, which coverts folic acid into active folate, which is used to synthesise purine/ pyrimidine. This has a crucial role in closing the posterior neuropore:
- Increases risk of SB by 12-16x
- Dose >800-1000mg have a poorer cognitive outcome

64
Q

What are the options for woman taking valproate but wanting to get pregnant?

A

WITHDRAW - can restart after baby is born, or if it must be used then follow the pregnancy prevention programme

65
Q

What are the social determinants of health?

A

Conditions in which people are born, grow, live, work and age, and the distribution of power, money and resources

66
Q

What are the wider determinants of health?

A

Term used in UK policies to describe living conditions that shape health outcomes, including housing, level of income, quality of built environment

67
Q

What is a breech presentation compared to normal?

A

Normal - head of baby lies proximal to cervix, easier delivery as head opens womb for rest of body
Breech- baby’s head lies distal to cervix with caudal end most proximal, this is harder as the bigger end has to go through first

68
Q

Why is breech presentation more common in babies with SB?

A

Legs only undergo spontaneous spasms, thus don’t develop strongly enough to kick the baby round into normal birthing position

PBL Y2 S3 (10 decks)

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