Paper 1

Question 1

Describe the embryological development of the cauda equina. You may use well labelled diagrams as
your answer. Explain how the further development postnatally impacts on the level of a lumbar
puncture.

Answer 1

Clinical application: level of LP = L4\5 in neonate and L3/4 in adult due to change in level of conus
medullaris.

Question 2

Describe the key features of the following neural tube defects: a) Spina bifida occulta b) Meningocele c) Anecephaly

Answer 2

a) Spina bifida occulta
(2 x ½ = 1 mark)
a. Vertebral defect (1/2 mark)
b. Normal cord and membranes(1/2mark)
b) Meningocele
(2 x 1= 2 marks)
a. Bony defect with protruding meningeal sac (1 mark)
b. Covered by intact skin (1 mark)
c) Anecephaly
(3 x 1 = 3 marks)
a. Cranial vault missing (1 mark)
b. Base of skull malformed (1 mark)
c. Disorganised brain tissue and vessels – cerebrovasulosa (1 mark)

Question 3

Mr Big’s 36 year old daughter is pregnant. She is well and her pregnancy is uncomplicated thus far. Her
doctor however recommends that she should have prenatal screening performed.
3. Outline two (2) indications for prenatal screening in this case.

Answer 3

Memo:
1. Advanced maternal age (> 35 years) (1)
2. Family history of neural tube defect (1)
3. Other possibilities (give only a half mark each):
* Other risk factors in pregnancy (1/2)
* Abnormalities detected during pregnancy (1/2)
* Family history of chromosome abnormalities, single gene disorders, congenital anomalies
(1/2)
* Previous child with any of the inherited / congenital anomalies (1/2)
* Any pregnant woman should have the right to choose to have prenatal screening done,
without any specific indications (1/2)

Question 4

Will Mr Big’s daughter and her husband or his nephew, Simon, and his wife be at a higher risk of
their next baby having spina bifida? Explain your answer.

Answer 4

Nephew as more family members and closer relationship so greater genetic risk

Question 5

His nephew was told that the cause of the baby’s problems were the result of the medication his wife
was started on when her pregnancy was confirmed on ultrasound at two months. Outline what you
would tell him.

Answer 5

No- neural tube closed by then

Question 6

List two (2) medications that increase the risk of neural tube defects.

Answer 6

Sodium valproate , carbamazepine, methotrexate… and others

Question 7

Mr Big’s nephew has read that they have an increased risk for a baby with anencephaly too. Is this
statement true? Give a reason for your answer

Answer 7

Yes – increase risk for any NTD with one affected child and + fhx

Question 8

List two (2) screening tests for anencephaly.

Answer 8

US / maternal serum AFP

Question 9

State whether it is legal to terminate a pregnancy for anencephaly at 33 weeks. Provide a reason.

Answer 9

Yes – post 20 weeks “severe” or life threatening

Question 10

State three (3) antenatal findings that will influence prognosis in spina bifida.

Answer 10

Level of the lesion
Associated abnormalities
Severity of ventriculomegaly

Question 11

Outline two (2) interventions that reduce the risk of spina bifida.

Answer 11

Periconception folic acid
Teratogen avoidance

Question 12

Draw a well labelled diagram of the anatomy of arachnoid villi including the surrounding structures.

Answer 12

arachnoid granulations, arachnoid mater, subarchnoid space, subdural space, arachnoid villi, arachnoid trabecular, meningeal dura, endosteal dura

Question 13

List the three (3) true barrier systems that contribute to the physiological blood-brain barrier,
and name the cell type that mediates the barrier function in each system.

Answer 13

(Cerebral capillaries – endothelium; choroid plexus – choroid epithelium; arachnoid mater/meninges –
arachnoid barrier, trabecular and pial cells)

Question 14

Describe the structural specializations of cerebral capillaries and explain how these contribute
to their function related to the blood-brain barrier

Answer 14

(Endothelium with tight junctions, lack of fenestrations and few pinocytotic vesicles; thick basement
membrane – block non-selective exchange of substances; pericytes; astrocyte foot processes – contribute to
development and maintenance of the BBB

Question 15

State the full name of the most likely causative bacteria in this case. Give a reason for your answer.

Answer 15

Neisseria meningitidis. Purpura in keeping with N. meningitidis infection.

Question 16

Briefly describe the pathogenesis of the organism identified in question 16.

Answer 16

Colonisation of the nasopharynx, with subsequent bloodstream invasion followed by central nervous system
invasion.

Question 17

Name the antibiotic that you would advise for treatment of the pathogen identified in question 16.

Answer 17

Ceftriaxone

Question 18

Outline three (3) risk factors that may have predisposed this patient to this disease.

Answer 18

Recent infection (especially respiratory or ear infection)
Recent exposure to someone with meningitis (college outbreaks)
Injection drug use
Recent head trauma
Otorrhea or rhinorrheaa
Recent travel, particularly to areas with endemic meningococcal disease such as sub-Saharan Africa, Mecca

Question 19

Name in full three (3) of the most common bacterial causes of meningitis in neonates.

Answer 19

Listeria monocytogenes, Streptococcus agalactiae, E. coli, Streptococcus pneumonia (Any 3).

Question 20

Outline three (3) ways in which Cryptococcus neoformans from a CSF sample is identified in the
microbiology laboratory.

Answer 20

Gram stain – Gram positive, oval/round, large
Cryptococcal antigen test
Culture of fungal media
India Ink test

Question 21

Outline the typical cell count and biochemistry characteristics of cerebrospinal fluid in bacterial
meningitis.

Answer 21

Raised pmns
Decreased glucose (relative to serum glucose)
Increased protein

Question 22

Name two (2) fungal causes of meningitis.

Answer 22

Cryptococcus
Candida
Histoplasma

Question 23

Define the following terms: meningitis, encephalitis, myelitis, meningooencempahlits, encephalomyelitis

Answer 23

a) Meningitis
Meningitis = inflammation of the meninges
b) Encephalitis
Encephalitis = inflammation of the brain parenchyma
c) Myelitis
Myelitis = inflammation of the spinal cord
d) Meningoencephalitis
Meningoencephalitis = inflammation of the meninges and brain parenchyma together
e) Encephalomyelitis
Encephalomyelitis = inflammation of the spinal cord and brain parenchyma together

Question 24

State the name (½ mark) of the group of viruses that are the most common cause of viral aseptic
meningitis, and briefly outline their epidemiology as it pertains to aseptic meningitis.

Answer 24

Enteroviruses. Most infections are asymptomatic, most symptomatic cases are mild and benign. Faecal-oral
and respiratory transmission. Outbreaks: especially among children. Seasonality: summer into autumn. <2
weeks of age: severe disease.

Question 25

State the most suitable laboratory test and sample for these viruses causing aseptic meningitis.

Answer 25

PCR on CSF

Question 26

List the three (3) forms of encephalitis associated with measles virus, and, for each, state the usual time period between measles rash and encephalitis onset.

Answer 26

1. Acute measles post-infectious encephalitis = days-weeks 2. Measles inclusion body encephalitis = months 3. Subacute sclerosing panencephalitis = years

Question 27

State the structural component of the rabies virus that is relevant to the wound management of someone who has been bitten by a potentially rabid dog (½ mark). State the reason for its relevance.

Answer 27

Answer: lipid envelope, easily destroyed by soap/alcohols.

Question 28

Using the table below, outline the three (3) categories of rabies exposure and state what post-exposure prophylaxis each requires.

Answer 28

Category 1 Touching/feeding animal, licking on intact skin No prophylaxis needed Category 2 Scratch without bleeding, nibble on intact skin, licking broken skin Vaccine Category 3 Licking mucosal membranes, bites/scratches that draw Blood Vaccine and antirabies antibody

Question 29

State the hallmark finding on CSF protein electrophoresis that suggests a diagnosis of multiple sclerosis.

Answer 29

Oligoclonal bands

Question 30

Briefly explain why CSF glucose does not increase beyond approximately 10mmol/L in cases of severe hyperglycaemia (uncontrolled diabetes).

Answer 30

Glucose transporters become saturated and cannot transport more glucose into CSF

Question 31

Indicate how normal CSF differs from plasma with respect to the following analytes. Use arrows [ ↑ - increased, → - unchanged, ↓ - decreased.

Answer 31

Protein ↓ Chloride ↑ Glucose ↓

Question 32

Outline the vaccine recommendations for meningitis. Your answer should include who is required to take the vaccine, who the vaccine is recommended for and who should consider taking it.

Answer 32

Required: Hajj pilgrims and travellers to Saudi Arabia (1) Recommended: 2 marks (½ mark for each of the following) - lab staff who work with N Meningitidis - travellers to meningitis belt - travellers to areas where disease there is an epidemic - persons with medical conditions at high risk of acquiring meningitis: asplenia, complement component deficiencies, Should be considered: 3 marks (½ mark for each of the following) - healthy children & infants - healthy adolescents/young adults entering university/college/Technicon - military recruits - miners - attendees of mass gatherings - HIV infection

Question 33

Outline the classification of vaccination based on their immunological responses.

Answer 33

Live inactivated and subunit vaccines - T cell dependent response - 1 mark Polysaccharide vaccines - T cell independent response – 1 mark Conjugate vaccines - T cell dependent response – 1 mark Inactivated, subunit and conjugate vaccines - evoke antibodies – 1 mark

Question 34

Identify the three (3) essential components that fill the intracranial space (3x½= 1½ marks). State the approximate percentage that each of these three contents contributes to the overall intracranial volume.

Answer 34

* Brain- 78% (2x0.5) * Blood- 12% (2x0.5) * CSF- 10% (2x0.5)

Question 35

Provide a brief description of OR the formula used to calculate the normal intracranial pressure.

Answer 35

CPP (Cerebral Perfusion Pressure) = MAP (Mean arterial pressure) – ICP (Intracranial pressure)

Question 36

Name the three (3) nuclei that are found in the medullary region (3 marks). Describe two (2) characteristics for each nucleus

Answer 36

Spinal nucleus of trigeminal: A large nucleus that extends the whole length of brainstem into the upper segments of the spinal cord. Efferents cross and then ascend as trigeminal lemniscus to relay in posteromedial ventral nucleus of thalamus (PMVNT). It receives primary efferent fibres conveying general sensation from the head which enter the brainstem in the trigeminal nerve. Nucleus Ambiguus: Upper, middle and lower parts are motor to CNs IX, X, and XI respectively. Sends motor fibres into glossopharyngeal and vagus nerves and cranial roots of the accessory nerve, from there, to the muscles of the pharynx and larynx. Nucleus Solitarius: Receives visceral afferent fibres entering the brainstem in the facial, glossopharyngeal and vagus nerves. Efferents cross them ascend to relay in posteromedial ventral nucleus of thalamus and hypothalamic nucleus

Question 37

Describe the circuitry for each of these pathways that show the role of the basal ganglia in the initiation and suppression of motor behaviour. You may use a well labelled diagram.

Answer 37

In both the direct and indirect pathways of the motor stream, transient activation of caudate/putamen projection neurons transiently inhibits projection neurons of the internal and external segments of the globus pallidus: ‘direct’ pathway (from basal ganglia to thalamus) (i) cerebral cortex → caudate/putamen (ii) caudate/putamen → internal segment of the globus pallidus (and substantia nigra, pars reticulata). Transient inhibition of projection neurons of the globus pallidus internal segment removes tonic inhibition of ventral anterior/ventral lateral complex. (iii) internal segment of globus pallidus (and substantia nigra, pars reticulata) → ventral anterior/ventral lateral complex of the thalamus (iv) ventral anterior/ventral lateral complex → motor cortical areas in frontal lobe, i.e., ventral anterior/ventral lateral complex neurons are transiently “released” to activate motor cortex ‘indirect’ pathway (from basal ganglia to thalamus) (i) cerebral cortex → caudate/putamen (ii) caudate/putamen → external segment of the globus pallidus (iii) external segment of globus pallidus → subthalamic nucleus. Transient inhibition of the external segment of the globus pallidus disinhibits the subthalamic nucleus (iv) subthalamic nucleus → internal segment of the globus pallidus- subthalamic nucleus is then “released” to transiently activate the internal segment of the globus pallidus (v) internal segment of globus pallidus → ventral anterior/ventral lateral complex of the thalamus- activation of internal segment of globus pallidus increases tonic inhibition of the ventral anterior/ventral lateral complex (vi) ventral anterior/ventral lateral complex → motor cortical areas in frontal lobe. Ventral anterior/ventral lateral complex neurons are inhibited from activating the motor cortex

Question 38

Briefly explain how both the direct and indirect pathways are modulated by dopamine in the striatum.

Answer 38

The effect of dopamine (from dopaminergic neurons in the substantia nigra) excites or drives the direct pathway, increasing cortical excitation. Dopamine excites the direct pathway through D1 receptors and inhibits the indirect pathway through D2 receptors.

Question 39

42. The table below represents the years of life lost (YLL) and disability adjusted life years (DALYs) for diabetes and lower respiratory tract infections in 1996 and 2000 Outline the possible reasons for the differences in YLL between 1996 and 2000 for these health conditions.

Answer 39

The actual number could have increased The BOD of another disease may have increased substantially Change in the data collection and Change in data analysis technique

Question 40

Interpret the DALY for diabetes in 2000.

Answer 40

Diabetes was responsible for 37 524 890 healthy years lost in 2000

Question 41

Based on the DALYs in the table above, which health condition had a greater burden of disease in the year 2000.

Answer 41

Diabetes

Question 42

Identify the disease categories that make up the quadruple burden of disease in South Africa

Answer 42

Communicable diseases, non-communicable diseases, HIV, Injury

Question 43

State the results of the chemical and cytological investigation of the CSF if the neurological changes were due to meningovascular syphilis. Give approximate levels by stipulating mild/moderate/marked. (4 marks) Explain how each is brought about. (4 marks)

Answer 43

Protein: mild to mod increase Sugar : normal Cells : number : mild to moderate increase type : lymphocytes and macrophages Chloride : Mild reduction Protein : increased capillary permeability [result of inflammation] Sugar : NO change : orgs cause damage by CUMULATIVE effect of minimal damage by scanty orgs over a sustained period of time. Cells : chronic inflammation thus lymphocytes and macrophages due to IL release Chloride : I accept sustained vomiting [but the chem path people have a more complex mechanism].

Question 44

Explain: a. one intrauterine and b. one postnatal potential neurological complication in the foetus/baby that could occur due to the Rhesus negativity of the mother and explain how they could be brought about.

Answer 44

Rh- mother, Rh +ve baby : foetal antigens may cross placenta →production of Rh ab’s in mother antibodies to RBC [anti Rh] produced in mother transplacental passage 2 marks hemolysis: i] intrauterine -→ problem of ANAEMIA in utero not JAUNDICE [placenta in situ providing this fx]]which if severe, → ischaemia : selective vulnerability of WM : myelin breakdown [leukoencephalopathy] 2 mark ii] postnatal a] immature liver enzymes to effect conjugation b] raised LIPID soluble bilirubin c] crosses blood brain barrier d] accumulation in cerebral nuclei : KERNICTERUS 2 marks

Question 45

List the clinical signs and symptoms in this case which indicate the presence of raised intracranial pressure and for each, explain how they are brought about

Answer 45

vomiting: direct pressure on vomiting centre (1½ marks) blurred optic discs : CSF cuff round the optic nerve exerts pressure on retinal vein → oedema (1½ marks) ptosis: III cranial nerve: implies compression in region of tentorium cerebelli [sympathetic component compression]: sympathetic fibres are peripheral and therefore are the first to be compressed.