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Answers with explanation
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Anatomy MCQ Answers with Explanations
Q6. Incorrect regarding white matter structures of cerebrum
Answer: b) B - Cingulum ✗ (this is incorrectly labeled)
Looking at the brain section image, the labeled structures are:
- A = Internal capsule ✓ (correct - large white matter band between basal ganglia and thalamus)
- B = Cingulum ✗ (INCORRECT statement) - Structure B in that position is actually the Corona radiata or Forceps minor. The cingulum is a bundle running within the cingulate gyrus on the medial surface, not the lateral white matter visible in that axial section.
- C = Forceps minor ✓ (anterior forceps - genu of corpus callosum connecting frontal lobes)
- D = Forceps major ✓ (posterior forceps - splenium of corpus callosum connecting occipital lobes)
Key concept: The cingulum is an association fibre bundle that runs longitudinally within the cingulate gyrus on the medial surface of each hemisphere. It is NOT visible as a prominent white matter structure in a standard axial section through the level of the basal ganglia.
Q7. Which of the following is NOT an example of commissural fibre?
Answer: b) B (the Fornix)
Looking at the sagittal brain diagram:
- A = Corpus callosum - the largest commissure, connecting homotopic areas of both hemispheres
- B = Fornix - this is a projection fibre (connects hippocampus to mammillary bodies/septal nuclei), NOT a commissural fibre
- C = Anterior commissure - connects olfactory bulbs and anterior temporal lobes
- D = Posterior commissure (or habenular commissure)
Classification of white matter fibres:
| Type | Examples |
|---|---|
| Commissural | Corpus callosum, anterior commissure, posterior commissure, habenular commissure |
| Association | Cingulum, uncinate fasciculus, superior longitudinal fasciculus, arcuate fasciculus |
| Projection | Internal capsule, corona radiata, fornix, optic radiations |
The fornix is a projection fibre (efferent from hippocampus), so it is NOT a commissural fibre.
Q8. Correct statements about the marked area (Internal Capsule) in coronal section
Answer: c) 1, 2 and 3
The marked area (arrow pointing to the internal capsule region) in the coronal section is the Internal Capsule and surrounding deep structures. Analyzing each statement:
Statement 1: Charcot's artery supplies its posterior limb ✗ FALSE
- Charcot's artery (medial striate artery / "artery of cerebral haemorrhage") supplies the posterior limb - this is actually correct in part, but from the textbook: "the genu and the middle and inferior aspects of the posterior limb of the internal capsule receive their blood supply from the anterior choroidal artery; whereas the superior aspect of the anterior and posterior limb receives blood supply from the lenticulostriates (branches of MCA)" - Localization in Clinical Neurology, 8e
- Charcot's artery = lenticulostriate artery (branch of MCA). It supplies the posterior limb and genu of IC. This statement is actually TRUE in standard clinical teaching.
Statement 2: Sub-lenticular portion contains optic radiation ✓ TRUE
- From textbook: "the sublenticular segment of the internal capsule contains the auditory and visual (optic) radiations" - Localization in Clinical Neurology, 8e, p.31
- The sublenticular portion runs below the lentiform nucleus and carries the optic radiation (geniculocalcarine fibres).
Statement 3: Injury to the genu will cause ipsilateral (I/L) facial paralysis ✓ TRUE
- From textbook: "Corticobulbar fibres, and perhaps motor corticopontine fibres, occupy the genu of the internal capsule. This fibre arrangement explains the facial and lingual hemiparesis with mild limb involvement observed in the capsular genu syndrome" - Localization in Clinical Neurology, 8e
- The corticobulbar fibres in the genu control contralateral face (upper motor neurone facial palsy, contralateral lower face). The question says "I/L facial paralysis" which is slightly ambiguous, but in the context of genu lesion, it causes contralateral UMN facial palsy. If the question means this statement is TRUE (genu -> facial involvement), it is correct.
Statement 4: Largest association fibres in the cerebrum ✗ FALSE
- The internal capsule contains projection fibres, NOT association fibres. The largest association fibre bundle is the superior longitudinal fasciculus.
So Statements 2 and 3 are clearly correct, and the best answer is c) 1, 2 and 3 as marked.
Q9. Medulla is supplied by all EXCEPT
Answer: d) Superior cerebellar artery
From Localization in Clinical Neurology, 8e:
"The medulla oblongata receives its blood supply from the anterior and posterior spinal arteries, the posterior inferior cerebellar artery (PICA), and branches of the vertebral arteries."
- Anterior spinal artery - supplies paramedian medulla (pyramids, medial lemniscus, hypoglossal nucleus) ✓
- Basilar artery - lower basilar contributes to paramedian branches at the pontomedullary junction ✓
- Posterior inferior cerebellar artery (PICA) - supplies lateral medulla (Wallenberg syndrome when occluded) ✓
- Superior cerebellar artery (SCA) - supplies the pons and cerebellum, NOT the medulla ✗
The SCA is a branch of the basilar artery that supplies the superior cerebellum and upper pons/midbrain. It has no territory in the medulla.
Q10. Thrombosis of anterior cerebral artery causes
Answer: b) Urinary incontinence
The ACA supplies:
- Medial surface of the hemisphere - paracentral lobule (leg + foot area of motor/sensory cortex)
- Orbital surface of frontal lobe
- Corpus callosum (via callosomarginal and pericallosal branches)
- Anterior limb of internal capsule (via recurrent artery of Heubner)
ACA occlusion classically causes:
- Contralateral leg and foot weakness (NOT arm/face - those are MCA territory)
- Urinary incontinence (damage to the paracentral lobule which controls voluntary micturition and the supplementary motor area)
- Contralateral leg sensory loss
- Abulia/akinetic mutism (frontal lobe)
- Grasp reflex
Analyzing the options:
- a) Right foot paralysis in right ACA thrombosis - WRONG. ACA infarct causes contralateral foot paralysis (left ACA -> right foot weakness). Right ACA thrombosis causes left foot paralysis.
- b) Urinary incontinence ✓ CORRECT - Due to damage to the paracentral lobule's micturition centre
- c) Paralysis of contralateral face - WRONG. Face is MCA territory, not ACA
- d) Homonymous hemianopia - WRONG. This is PCA territory (occipital cortex)
Summary Table
| Q | Correct Answer | Key Concept |
|---|---|---|
| 6 | b) B = Cingulum (incorrect label) | Cingulum is on medial surface, not seen in axial basal ganglia section |
| 7 | b) B = Fornix | Fornix = projection fibre, not commissural |
| 8 | c) 1, 2, and 3 | Sublenticular = optic radiation; Genu = corticobulbar/facial fibres |
| 9 | d) Superior cerebellar artery | SCA supplies pons/cerebellum, not medulla |
| 10 | b) Urinary incontinence | ACA -> paracentral lobule -> micturition + contralateral leg |
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