Anat Path

Question 1

Indicate the chromosomal constitution of a (complete) mole and state what conclusion can be drawn regarding its origin (2)

Answer 1

46XX. All the “tumour” is of paternal origin (“androgenetic”). Total paternal origin (empty ovum plus 46- 2 sperm fertilise)

Question 2

Explain how the typical microscopic structure determines the macroscopic appearance of a complete mole (2)

Answer 2

The absence of vessels in the villi causes them to become very enlarged and hydropic (swollen) – accounting for the typical “bunch of grapes” macroscopic appearance
Microsc the villi show hydropic degeneration with marked troph prolif  macroscopically you will not see any normal villi

Question 3

Briefly discuss the possible links between a mole and a suspected brain metastasis (4)

Answer 3

• The potential for persistent trophoblastic disease (in particular, choriocarcinoma) to develop from a partial mole is small, is greater for the complete variety – but is low overall
• Choriocarcinoma typically disseminates very widely – haematogenously (first to the lungs and then from there via the systemic arterial circuit to multiple sites amongst which the brain is common) [These could, pedantically, be called “tertiaries” – unless Batson’s plexus is invoked]
• Haematogenous- mole extends through uterus and may enter blood stream

Question 4

Dr Brown is called to evaluate a newborn infant in the labour ward. On physical exam he notes that the infant has normal vital signs and appearance with the following exception. Dr Brown notes that the infant has a bulging cyst-like structure approximately 4 cm in diameter protruding from his back. He also observes that the baby has limited movement of the lower extremities and that both feet are plantar flexed and inverted at the ankle.

List two (2) possible names for the bulging cyst on the back of the infant (1)

Answer 4

Meningocoel, meningomyelocoele - NOT myelocoele

Question 5

Explain the limited movement of the lower extremities (1)

Answer 5

Malformation of the spinal cord causing lack of neural innervation to the limbs

Question 6

Name the abnormality of the feet (½)

Answer 6

Clubfeet

Question 7

Explain the position of the feet (1) & List five (5) other causes of your answer (2½)

Answer 7

Paralysis /absence of muscle activity/compression causes deformation (1)
Causes of anhydramnios e.g. bilateral renal agenesis/bilateral cystic renal dysplasia/urethral atresia; causes of fetal akinesia/absent movement e.g. cerebral pathology, other causes of spinal disease (neuronal loss); muscle weakness

Question 8

The aetiology of NTD is multifactorial. List three (3) independent factors which may play a role in its aetiology and give an example of each (3)

Answer 8

Genetic e.g. monogenic mutations, chromosomal trisomy 18; environmental including specific geographic areas, maternal diet - folic acid deficiency, iatrogenic - drugs taken by mother (valproate), metabolic - maternal diabetes

Question 9

List two (2) methods to detect NTDs antenatally (1)

Answer 9

Careful ultrasound examination/screening of maternal blood or amniotic fluid for raised AFP

Question 10

Explain the association of a spinal NTD and bilateral club feet (2)

Answer 10

• Lumbosacral NTD frequently results in paralysis /weakness/akinesia of lower limbs
• Frequently associated with hydrocephalus which is often in a breech position -Arnold Chiari malformation
• Could be a syndromic association

Question 11

Baby was born with a meningomyelocoele in the lumbosacral area of his spine. O/E: limbs showed no sensory or motor deficits of the upper limbs, but the lower limbs had reduced muscle reflexes, were bowed in position, and there were areas of sensory loss on the skin. Preparations are underway for surgery to the lesion on his back.

List two (2) unrelated investigations whereby a meningomyelocoele can be suspected in utero (2)

Answer 11

Ultrasound examination (1) and maternal serum and/or amniotic fluid alpha foetoprotein levels (1)

Question 12

How can the risk of this lesion be reduced? (1)

Answer 12

Planned pregnancy with folate (½) for 3 months prior to conception (½)

Question 13

This baby develops hydrocephalus. Explain the likely pathogenesis (4)

Answer 13

Hydrocephalus due to Arnold- Chiari malformation causing obstruction to CSF flow at the level of the foramen magnum due to downward displacement of the cerebellum]

Question 14

Explain how a spinal neural tube defect (NTD) can cause congenital hydrocephalus (2)

Answer 14

Obstruction of foramen magnum by displaced cerebellum from tethered cord

Question 15

State how many ventricles are dilated in this type of hydrocephalus (½)

Answer 15

4

Question 16

State the name of this malformation (½)

Answer 16

Arnold Chiari malformation

Question 17

List four (4) complications/effects of an untreated lumbar meningomyelocoele (2)

Answer 17

Paraplegia of legs/ urinary incontinence/ fecal incontinence/ ascending meningitis

Question 18

Briefly describe three (3) causes of hydrocephalus in the newborn (3)

Answer 18

Arnold Chiari malformation with NTD/ acquired haemorrhage occluding aqueduct/acquired inflammation postmeningitis occluding aqueduct of Sylvius/ mutant genes

Question 19

List four (4) features of hydrocephalus in the newborn (2)

Answer 19

Macrocephaly/ wide open sutures/ large fontanelles/ relatively small face

Question 20

Outline two (2) common outcomes in a neonate/ newborn with hydrocephalus if untreated (2)

Answer 20

Progressive intellectual impairment/spastic paraplegia/cerebellar ataxia

Question 21

46 y/o becomes pregnant with her 3rd child. On routine antenatal ultrasound the doctor suspects that the fetus may have a NTD. Patient is counselled on the implications of NTD’s for the child and the family and offered a termination of pregnancy which she refuses. At delivery by Caesarian section the infant is born with a large closed encepholocele.

State the most likely site of the defect (½)

Answer 21

Occipital region

Question 22

State the prognosis of this infant. Explain your answer (2)

Answer 22

Poor; there will be abnormal neuronal cortical migration in this region. There is likely to be cerebellar involvement with abnormality of gait & balance.

Question 23

Name the most common cause of congenital hydrocephalus (1)

Answer 23

Arnold Chiari malformation type II

Question 24

Indicate the primary mechanism for the hydrocephalus associated with your answer in the previous question (1)

Answer 24

Spinal neural tube defect/ meningomyelocoele

Question 25

Define “hydrocephalus ex vacuo” (1½)

Answer 25

Dilatation of ventricular system. Increase in CSF volume due to loss of brain parenchyma

Question 26

6 m/o infant who previously had a lumbo-sacral NTD repaired surgically & whose head begun to grow abnormally in circumference.

State the most likely diagnosis (1)

Answer 26

Obstructive hydrocephalus

Question 27

What is the most likely pathogenesis? (1)

Answer 27

Arnold-Chiari malformation

Question 28

If this is not treated what would happen to the brain? (2)

Answer 28

Progressive ventricular enlargement, accompanied by “thinning” and atrophy of the cortex

Question 29

Outline the treatment of choice for the diagnosis you made (2)

Answer 29

Insertion of a ventriculo-peritoneal or ventriculo-pericardial “shunt” to prevent further accumulation of CSF

Question 30

Some months after instituting the treatment you suggested above, the infant’s head begins to enlarge significantly again. What is the most likely explanation on this occasion? (2)

Answer 30

Blockage of the “shunt” by infection or thrombus

Question 31

Describe the likely pathogenesis of the dilated ventricles of the brain at birth (4)

Answer 31

Shallow posterior fossa, herniation of medulla through foramen magnum, obstruction at foramen magnum, dilatation of all ventricles Arnold Chiari malformation type II.

Question 32

State the possible sequelae if the myelomeningocoele is left open (2)

Answer 32

Local infection from skin or perianal region, ascending infection via CSF, meningitis, death.

Question 33

Outline the disabilities that you would expect in this child (2)

Answer 33

Lack of sphincter control, bladder and anal, & poor motor function of the legs.