Neuroanatomy questions often test localisation: given a pattern of weakness, sensory loss or cranial nerve signs, identify the affected structure. A reliable method is to map the findings before choosing a diagnosis: note which side is affected, whether signs are above or below a crossing point, and whether the pattern fits a tract, nucleus, nerve or vascular territory.
These ten single-best-answer questions cover common neuroanatomy concepts. Each item is followed by its answer and an explanation, including why a tempting alternative does not fit. As you work, pay attention to the clue that changes the localisation—not just the name of the syndrome.
A neuroanatomy board in MySummaries might group these concepts by tract, region and clinical pattern:
- Pyramidal decussation — most fibres cross in the caudal medulla
- A lateral corticospinal lesion below the decussation causes ipsilateral upper motor neuron signs below the lesion
- Nasal retinal fibres cross at the optic chiasm
- A central chiasmal lesion can cause bitemporal visual field loss
- Carries vibration, discriminative touch and conscious proprioception
- First-order fibres ascend ipsilaterally in the cord; second-order fibres cross in the medulla
Cerebellar hemisphere lesions typically cause ipsilateral limb incoordination; examine for dysmetria and intention tremor.
- Carries pain and temperature
- Fibres cross through the anterior white commissure within about 1–2 spinal levels
Practise localisation with worked questions
For each item, identify the structure implicated by the signs and the relevant crossing point. The options are deliberately close enough that a single finding—such as whether the deficit is ipsilateral or contralateral—can rule one out. Read the explanation immediately after answering; the aim is to connect the finding to the anatomy.
1. Corticospinal tract
This question tests how the pyramidal decussation determines the side of weakness.
A patient has a lesion of the right lateral corticospinal tract at the level of T10. Which motor finding is most likely?
A patient has a lesion of the right lateral corticospinal tract at T10. Which motor finding is most likely?
The corticospinal fibres have already crossed at the pyramidal decussation in the caudal medulla. A right lateral tract lesion in the spinal cord therefore causes right-sided upper motor neuron weakness below the lesion. Left-sided weakness would suggest a lesion above the decussation.
2. Dorsal column pathway
This item distinguishes spinal cord ascent from the later crossing in the medulla.
A left dorsal column lesion at T8 would most directly impair which modality below the lesion?
A left dorsal column lesion at T8 would most directly impair which modality below the lesion?
Dorsal column fibres ascend on the same side in the spinal cord and cross in the medulla. A left-sided lesion at T8 impairs vibration and proprioception on the left below the lesion. Pain and temperature cross in the spinal cord and travel in the anterolateral system, so they are not the best answer.
3. Hemicord lesion
Use the different crossing levels of the major tracts to interpret this pattern.
A right hemisection of the spinal cord at T10 is most likely to produce which combination below the lesion?
A right hemisection of the spinal cord at T10 is most likely to produce which combination below the lesion?
Below a right hemicord lesion, the uncrossed lateral corticospinal and dorsal column pathways produce right-sided motor and proprioceptive deficits. Spinothalamic fibres from the left cross near their entry level, so left-sided pain and temperature loss usually begins a little below the lesion. Option 3 reverses the long-tract laterality.
4. Optic chiasm
The visual field pattern points to the fibres crossing at the chiasm.
A pituitary-region mass compresses the centre of the optic chiasm. Which visual field defect is expected?
A pituitary-region mass compresses the centre of the optic chiasm. Which visual field defect is expected?
The nasal retinal fibres cross in the central optic chiasm and carry information from the temporal visual fields. Compression there therefore causes bitemporal hemianopia. A homonymous hemianopia points to a lesion behind the chiasm, while monocular blindness usually localises to one optic nerve.
5. Middle cerebral artery territory
This question combines cortical function with the distribution of a named artery.
A lesion affects the superior division of the left middle cerebral artery in a patient whose language is left-hemisphere dominant. Which deficit best fits?
A lesion affects the superior division of the left middle cerebral artery in a patient whose language is left-hemisphere dominant. Which deficit best fits?
The dominant hemisphere's superior MCA division supplies lateral frontal regions, including language areas involved in speech production, and motor cortex representing the face and arm. A lesion can cause non-fluent aphasia and contralateral face-arm weakness. Leg-predominant weakness is more characteristic of medial frontal territory supplied by the anterior cerebral artery.
6. Abducens nucleus
Distinguish a nucleus lesion from a lesion of the nerve after it leaves the brainstem.
A lesion damages the left abducens nucleus in the pons. What eye movement deficit is expected?
A lesion damages the left abducens nucleus in the pons. What eye movement deficit is expected?
The abducens nucleus drives the ipsilateral lateral rectus and sends internuclear fibres to the opposite oculomotor nucleus, coordinating conjugate horizontal gaze. A left abducens nucleus lesion impairs gaze to the left with both eyes. A lesion of the left abducens nerve alone would chiefly prevent abduction of the left eye.
7. Lateral medulla
Use the crossed sensory findings and bulbar signs to localise the lesion.
A right lateral medullary lesion involves the spinal trigeminal tract and nucleus and the spinothalamic tract. Which sensory pattern follows?
A right lateral medullary lesion involves the spinal trigeminal tract and nucleus and the spinothalamic tract. Which sensory pattern follows?
The spinal trigeminal system carries pain and temperature from the ipsilateral face, while the spinothalamic tract carries already-crossed pain and temperature from the contralateral body. A right lateral medullary lesion therefore produces right facial and left body pain-temperature loss. The crossed pattern is a useful localisation clue.
8. Cavernous sinus
This item checks which cranial nerve runs within the cavernous sinus beside the internal carotid artery.
Which cranial nerve passes through the cavernous sinus alongside the internal carotid artery?
Which cranial nerve passes through the cavernous sinus alongside the internal carotid artery?
CN VI runs within the cavernous sinus beside the internal carotid artery. CN III, CN IV, and the first two divisions of CN V are also associated with the sinus, but CN II, VII and XII do not pass through it. The optic nerve is associated with the optic canal, not the cavernous sinus.
9. Cauda equina
Localise a lower motor neuron pattern with saddle sensory loss to nerve roots rather than the spinal cord.
Which finding most strongly supports cauda equina involvement rather than a single spinal cord tract lesion?
Which finding most strongly supports cauda equina involvement rather than a single spinal cord tract lesion?
The cauda equina consists of lumbosacral nerve roots, so involvement can produce asymmetric lower motor neuron deficits, saddle sensory loss and bladder dysfunction. A sensory level with brisk reflexes suggests spinal cord involvement. New saddle sensory loss or bladder dysfunction needs urgent clinical assessment.
10. Cerebellar localisation
The side of the limb findings helps distinguish a cerebellar hemisphere lesion from a cerebral lesion.
A focal lesion of the right cerebellar hemisphere is most likely to cause which finding?
A focal lesion of the right cerebellar hemisphere is most likely to cause which finding?
A cerebellar hemisphere lesion typically causes ipsilateral limb incoordination, including dysmetria. Cerebellar output pathways cross, and motor pathways cross again, so the net clinical effect is usually on the same side as the cerebellar lesion. Spastic weakness instead suggests corticospinal tract involvement.
Turn missed marks into targeted revision
After each question, check whether your error came from a forgotten fact or a faulty localisation step. For example, confusing the spinal crossing of pain-temperature fibres with the medullary crossing of dorsal column fibres is a pathway-mapping error; revise the route and crossing point, then apply them to a new lesion. If you chose a distractor because it matched one symptom but not the whole pattern, practise accounting for every finding.
A review screen can sort weak areas by performance so revision starts with the topics costing marks:
When the same fact is missed more than once, make the next review prompt precise enough to test the distinction.
You lost this mark twice: where do dorsal column fibres cross, and what sensory modalities are carried before they cross?
The key habit is to justify an answer anatomically: name the structure, state where its fibres cross, and connect that route to the side and type of deficit. That method transfers better than memorising isolated syndrome names.
How MySummaries helps
Build a neuroanatomy board from your own notes, then generate practice questions and revision cards from it. You can organise material by pathways or regions and use your results to direct the next review session. Start at portal.mysummaries.app.