Localisation: brainstem & cord flashcards
13 high-yield MRCP Part 1 cards from the Intellect Medicos Neurology course. Try to answer each question before you open it — then study them properly with spaced repetition, which brings each card back just before you would forget it.
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After a stab wound, a man has right leg weakness with an extensor plantar and loss of vibration sense in the right leg, plus loss of pain and temperature in the left leg. What is the lesion?
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Right hemisection of the spinal cord (Brown-Séquard syndrome).
Why? The corticospinal tract and dorsal columns cross in the medulla, so loss is on the same side. Spinothalamic fibres cross within 1-2 segments, so pain and temperature are lost on the opposite side.
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What is the classic sensory pattern in cervical syringomyelia?
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"Cape-like" loss of pain and temperature over the shoulders and arms, with preserved vibration and proprioception.
Why? The syrinx first damages spinothalamic fibres crossing in front of the central canal. Later, anterior horn cells are damaged, causing wasting of the hands.
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Name three causes of absent ankle reflexes with extensor plantar responses.
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Any three: subacute combined degeneration, motor neurone disease, Friedreich's ataxia, taboparesis (syphilis), conus medullaris lesion, syringomyelia.
Why? Each combines an UMN lesion (extensor plantar) with an LMN or sensory lesion of the reflex arc (absent ankle jerk).
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Sudden vertigo, hoarse voice and dysphagia, left facial loss of pain and temperature, left Horner's syndrome and left limb ataxia, with loss of pain and temperature on the right body. Which artery is occluded?
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Left posterior inferior cerebellar artery (lateral medullary / Wallenberg syndrome); often from vertebral artery disease or dissection.
Why? Hoarseness and dysphagia come from the nucleus ambiguus (CN IX/X). This is the hallmark that separates PICA from AICA.
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Ipsilateral third nerve palsy with contralateral hemiparesis: which syndrome and level?
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Weber's syndrome, ventral midbrain.
Why? A paramedian midbrain infarct hits the CN III fascicle and the cerebral peduncle (corticospinal tract) above its crossing point.
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A painful third nerve palsy WITH a dilated pupil: what cause must be excluded urgently?
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Posterior communicating artery aneurysm.
Why? Pupillomotor fibres run on the outside of the nerve, so compression affects the pupil early. Ischaemic (diabetic) third nerve palsy usually spares the pupil.
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What is the first-line investigation for suspected metastatic spinal cord compression?
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MRI of the whole spine, as soon as possible and always within 24 hours.
Why? Whole-spine imaging is needed because multilevel disease is common. MRI is the investigation of choice for cord compression.
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Which drug and dose are given immediately in suspected metastatic spinal cord compression with neurological deficit?
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Dexamethasone 16 mg orally (or the equivalent IV dose), as soon as possible.
Why? Steroids reduce cord oedema while definitive treatment (radiotherapy or surgery) is arranged. Continue 16 mg daily until then, then taper; NICE also says give a PPI and monitor blood glucose while on steroids.
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Sudden right hemiparesis and loss of vibration and joint position sense on the right. The tongue deviates to the left on protrusion. Which syndrome is this, and which artery is usually occluded?
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Left medial medullary (Dejerine) syndrome; anterior spinal artery.
Why? The lesion hits the left pyramid (contralateral weakness), medial lemniscus (contralateral dorsal-column loss) and CN XII (tongue deviates towards the lesion).
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After abdominal aortic aneurysm repair, a man has flaccid weakness of both legs, urinary retention and loss of pain and temperature below T10. Vibration and joint position sense are normal. What is the diagnosis?
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Anterior spinal artery syndrome.
Why? The anterior spinal artery supplies the front two-thirds of the cord. The dorsal columns get their blood from the posterior spinal arteries, so they are spared.
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Which recreational drug can precipitate subacute combined degeneration of the cord?
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Nitrous oxide.
Why? Nitrous oxide inactivates vitamin B12, causing dorsal column and corticospinal tract damage even with normal serum B12 levels.
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Upgaze palsy, light-near dissociation, eyelid retraction and convergence-retraction nystagmus: which syndrome, and what is the classic cause?
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Parinaud (dorsal midbrain) syndrome; a pineal gland tumour.
Why? The tumour compresses the vertical gaze centre in the dorsal midbrain. MRI brain is the investigation.
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A temporal lobe lesion causes a contralateral ______ homonymous quadrantanopia; a parietal lobe lesion causes an ______ one.
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superior; inferior
Why? Meyer's loop (lower optic radiation) runs through the temporal lobe and carries the upper visual field.