Case 18-20 Flashcards by Daniel Sturrock

Criteria for screening tests

Common disease, causes significant morbidity/mortality
Cheap test
Non-invasive test
Long latent/asymptomatic period
Treatable if detected early
Natural history adequately understood

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Screening vs diagnostic tests

Healthy patient vs suspicious patient
Cheap vs expensive
Not definitive vs definitive
High false positive rate vs low false positive rate
Low false negative vs low false negative

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Non invasive prenatal tests

Ultrasound (from 11 weeks)
Doppler studies
MRI
Maternal serum biochemistry

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Invasive prenatal tests

Amniocentesis: 15-18 wks. Complications - miscarriage, transient amniotic fluid leakage, intrauterine infection

Chorionic villus sampling: 8-13 wks. Complications - miscarriage, infection, bleeding, limb defects. Problems - placental mosaicism, maternal contamination

Cordocentesis

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Down syndrome 1st trimester testing

11-13 weeks
Beta hCG increased
PAPP-A decreased
Nuchal translucency

Follow up with counselling, amniocentesis and karyotyping

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hCG

Glycoprotein made by the syncytiotrophoblasts
Alpha subunit common to TSH, FSH, LH
Beta subunit unique to hCG
Stimulates corpus luteum in early pregnancy

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AFP

Dominant fetal plasma protein
Initially produced by the yolk sac and then by the liver
Levels peak at the end of the first trimester
Marker for HCC and germ cell tumours

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Oestriol

Primary oestrogen of pregnancy
10% is unconjugated
Increases with gestational age
Requires fetal adrenals, liver and placenta to be functional

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Dimeric inhibin A

Produced in the pituitary, ovaries and placenta
Negative feedback regulator of FSH
Placenta produces large amounts to completely suppress FSH
Not produced by men

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PAPP-A

Glycoprotein produced by the syncytiotrophoblast
Cleaves insulin like growth factor binding protein
Marker of acute coronary syndrome

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Down syndrome second trimester screening

15-23 weeks
Triple test:
AFP decreased
hCG increased
Unconjugated E3 decreased

Add dimeric inhibin A for quad test (increased)

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Edward syndrome clinical features

Cardiac defects
Renal anomalies
Severe mental retardation
CNS defects

50% die within 2 months , 5-10% live to 1 year

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Edward syndrome 1st trimester testing

Decreased PAPP-A
Decreased hCG
Increased NT

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Edward syndrome 2nd trimester screening

Decreased AFP, hCG, uE3

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Cell free DNA

Fetal RhD

Fetal sex determination

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NTD teratogens

Diabetes
Anticonvulsants
Alcohol
Hyperthermia

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Genetic counselling session

Information gathering: pedigree, pregnancy course, teratogens, psychosocial circumstances

Information giving: test results, implications, options

Planning: investigations, TOP, follow up and support, future

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Periconceptual folic acid

1 month before and 3 months after conception

400 micrograms for normal risk

4 mg for high risk

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Primary prevention of NTDs

Impoved health, nutrition and antenatal care
Family planning
Periconceptual folate
Detection/treatment of maternal infection and chronic disease
Avoidance of teratogens
Generic counselling and screening

NTD secondary prevention

Identification of high risk pregnancies
Ultrasound evaluation of fetal health
Genetic counselling
Voluntary antenatal testing where appropriate
Access to voluntary TOP

Tertiary prevention of NTDs

Early and accurate diagnosis
Intervention to avoid and minimise complications
Medical and surgical treatment
Rehabilitation
Psychosocial support

Embryology of the medulla, basal plate nuclei

Medial to lateral:
Somatic efferent (XII)
Special visceral efferent (XI, X, IX)
General visceral efferent

Embryology of the medulla, alar plate nuclei

Medial to lateral:
General visceral afferent (GIT, heart)
Special visceral afferent (taste buds, oropharynx)
Somatic afferent (V, VIII)

Viral spread to the CNS

Retrograde via axons. HSV, rabies

Anterograde nerve uptake. HSV, VZV, influenza via olfactory nerve

Trojan horse entry via leukocyte. HIV, CMV

Infection of the endothelium. WNV

Viral aseptic meningitis

``` Fever, meningism, headache Normal LOC Anorexia and vomiting Usually excellent prognosis Supportive treatment ```

Commonest causes of viral meningitis

Enteroviruses. Children. Seasonal. Institutional outbreaks. HSV (2). Adults following primary genital HSV Mumps.

Outcomes of poliovirus infection

Sub clinical infection Abortive infection. Mild flu-like illness. Possible aseptic meningitis Major illness. Aseptic meningitis, flaccid paralysis etc

Laboratory diagnosis of enteroviruses

PCR Culture

Herpes simplex encephalitis

Commonest cause of sporadic viral encephalitis 2/3 viral reactivation (HSV 1) 1/3 primary infection (neonates, HSV 2) Affinity for temporal lobes Medical emergency, start immediate acyclovir Diagnose with PCR

CMV encephalitis

``` HIV associated Slow, progressive Optic neuritis, retinitis Diagnosis with PCR, viral load Treat with ARVs and gancyclovir NB immune reconstitution reaction ```

Mumps

Aseptic meningitis: Onset varies 1 week before or 3 weeks after parotitis. Symptoms subside 3-10 days later. Deafness 1/20000. Encephalitis: Convulsions, abnormal movement and sensation, focal signs Outcome varies

Measles CNS syndromes

Acute measles post-infectious encephalitis: within 8 days of onest. Autoimmune reaction against myelin protein Measles inclusion body encephalitis: immune compromised patients. A few weeks to 6 months. Mostly unilateral. Death within a few months. SSPE: 6-8 years after initial infection. Progressive, fatal, can sometimes take 20-30 years

Rubella

Rash, arthritis. Meningitis rare, usually benign. Post infectious encephalitis. Within a week of rash onset. ADEM

South african arboviruses

West nile virus | Rift valley fever

Rabies pathogenesis

Entry via bite Local replication Entry into nerves via neuromuscular junction Spread via retrograde fast axonal transport 5-10 cm/day. Replicates in CNS, spreads to periphery Not found in the blood

Rabies PEP

Touching/feeding animal, lick of intact skin: no action Non-bleeding scratch, nibble or lick of broken skin: vaccine Lick of mucous membranes, bites or scratches that draw blood: vaccine + Rabigam

Predisposing factor to S. Pneumoniae meningitis

``` Extremes of age Immunosuppression Csf leak Alcoholism, malnutrition Septic focus Splenectomy ```

Contraindication to LP before CT brain

GCS <10 Papilloedema Ventriculoperitoneal shunt Unexplained seizure or new neurological focal deficit excluding isolated CN palsies Severe cardiorespiratory compromise Evidence of abnormal bleeding Sepsis over LP site

Core consciousness

Level of consciousness + contents of consciousness

Extended cosciousness

Involves the ability to reflect on and remember conscious experiences

Four basic emotions

Seeking/curiosity. Dopamine mediated. VTA Fear. Amygdala Rage. Amygdala Panic, anxiety, loss. Anterior cingulate gyrus

Congenital bleeding disorders

Haemophilia A. Factor VIII deficiency Haemophilia B. Factor IX deficiency Both are X-linked recessive disorders Congenital defects in platelet function. Von Willebrand's disease. Autosomal dominant. Usually not severe

Why may females present with haemophilia even though it is X-linked?

Both X copies mutated Skewed X inactivation pattern Turner syndrome + other abnormalities of the X chromosome

Congenital predisposition to thrombosis

More common: Factor V Leiden Prothrombin mutation Rare: Antithrombin III deficiency Protein C and Protein S deficiency

Causes of apparent mineralocorticoid excess

Glucocorticoid excess Liquorice Defect of 11-beta-HSD Liddle's syndrome