CNS pathology

Question 1

23524, 27839 – A bitemporal homonymous hemianopia may result from
1: unilateral infarction of visual cortex or radiation
2: craniopharyngioma
3: pineal tumour
4: pituitary tumour

Answer 1

FTFT

Question 2

21123 – Which of the following statements is true of a medium to large sized cerebral infarct 2 weeks old?
1: compound granular corpuscles are a prominent histological feature
2: numerous polymorphs infiltrate the brain adjacent to the infarct
3: gliosis is apparent at the periphery of the lesion
4: in the gross specimen the infarct is raised above the surface of the adjacent normal brain

Answer 2

TFTF
Robbins 5th ed. PAGES: 115; 1310. Pending review. Jan 2003

Question 3

16957 – Familial retinoblastoma
1: is always a congenital neoplasm
2: is activated by chromosomal translocation
3: inheritance pattern is autosomal recessive
4: develops only in a retinoblast which has the appropriate DNA defect in both of the paired chromosomes

Answer 3

FFFT
Familial retinoblastoma is inherited, but not necessarily congenital. The inheritance genetics is of a single defective gene, which is protected by the paired gene in each retinoblast cell. However, all of the retinoblasts are ‘primed’ by having one defective gene - mutation of the other gene in just one retinoblast, removes all of that suppressor gene activity from that cell. If that retinoblast is still in the ‘replication pool’, retinoblastoma ensues; if that cell has matured to join the ranks of permanent cells (differentiated), presumably cancer does not ensue.

Question 4

25991 – Medulloblastoma
1: characteristically occurs in the cerebrum of children
2: often shows rosette formation as a histological feature
3: is typically calcified
4: is often found in the vicinity of the 4th ventricle

Answer 4

FTFT
Robbins 5th ed. Chapter:29 PAGE:1347

Question 5

13445 – S: Microglia surrounding a cerebral infarct are DOPA positive because R: some cells in the brain contain melanin

Answer 5

S is false and R is true
Microglia are the phagocytes of the central nervous system, and accumulate in the vicinity of damaged tissues. They do not, however, manufacture melanin, and are therefore not DOPA positive (S false). Some cells in the brain (eg in the substantia nigra) are able to produce melanin (R true). These cells are not, however, microglia.

Question 6

27059 – Vertebrobasilar insufficiency may present with all of the following except
A. vertigo and nystagmus
B. dysphagia
C. diplopia
D. blurred vision
E. motor dysphasia

Answer 6

E
The vertebrobasilar system supplies the medulla, pons, cerebellum, and occipital cortex: regions of the central nervous system concerned with balance, coordination of eye movements, and vision. Additionally, cranial nerve nuclei driving the muscles of the mouth and pharynx may be affected, causing swallowing difficulty and dysarthria. Since the major motor pathways to the limbs must pass through this territory, transient ischaemia may result in drop attacks without loss of consciousness, due to weakness of the lower limbs. Motor dysphasia (not always easy to distinguish from dysarthria) is due to lesions affecting Broca’s motor speech area. The motor speech area is in the territory of the middle cerebral artery, and therefore is affected by carotid, but not vertebrobasilar, lesions. The exception is thus option E.

Question 7

20253 – S. The effects of beta-endorphin are very similar to many of the effects of morphine BECAUSE R. beta-endorphin is the endogenous ligand for mu receptors, for which morphine is considered the primary exogenous ligand

Answer 7

S is true, R is true and a valid explanation of S
A.C.P. 1996

Question 8

25519 – Viruses capable of producing diseases of the central nervous system include
1: herpes simplex virus
2: measles virus
3: polio virus
4: cytomegalovirus

Answer 8

TTTT
Robbins 5th ed. Pages: 1315-1326

Question 9

13125 – An intracranial aneurysm may be
1: caused by an infective embolus
2: due to a congenital weakness of the wall of the vessel
3: associated with polyarteritis nodosa
4: associated with atheroma

Answer 9

TTTT
Acute inflammation of the vessel wall may result from an infective embolus or from inflammatory diseases of the vessel wall such as polyarteritis nodosa (C true). Aneurysms may occur at any site as a result of infective emboli (A true). Berry aneurysms in the circle of Willis are due to a congenital weakness in the vessel wall (B true). Atheroma is common in the cerebral vessels, and consequently may give rise to intra-cranial aneurysms (D true).