Optic nerve and eye-movement nerves flashcards
14 high-yield MRCP Part 1 cards from the Intellect Medicos Ophthalmology 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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What is the first-line investigation in suspected optic neuritis?
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MRI of the brain and orbits (with gadolinium).
Why? It confirms optic nerve inflammation and shows demyelinating white-matter lesions, which predict the risk of multiple sclerosis. VEPs show delayed conduction.
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What is the acute drug treatment for optic neuritis, and what does it change?
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High-dose IV methylprednisolone — it speeds recovery but does not change the final visual outcome.
Why? Most patients recover vision anyway; steroids shorten the course.
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A painful third nerve palsy with a dilated pupil — what cause must be excluded first?
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Posterior communicating artery aneurysm — urgent CT or MR angiography.
Why? Pupil fibres run on the outside of the nerve, so compression hits them early. A pupil-sparing palsy suggests microvascular ischaemia (diabetes, hypertension).
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A sixth nerve palsy with no other focal signs is a well-known "false localising sign" of what?
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Raised intracranial pressure.
Why? The long intracranial course of the abducens nerve makes it vulnerable to stretching. It causes horizontal diplopia, worse looking to the affected side and at distance.
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Which way does a patient with a fourth nerve palsy tilt the head?
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Away from the affected side.
Why? This offsets the extorsion of the affected eye. Vertical diplopia is worst looking down (reading, going downstairs). Causes: congenital, head trauma (the commonest acquired cause; its long, thin intracranial course makes CN IV the eye-movement nerve most vulnerable to head injury) and microvascular disease.
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What is Uhthoff's phenomenon?
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Temporary worsening of vision (or other demyelinating symptoms) with heat or exercise, e.g. a hot bath.
Why? Raised body temperature further slows conduction in demyelinated fibres. It is typical after optic neuritis and in MS.
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What is the typical visual field defect in optic neuritis?
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A central scotoma.
Why? Other key signs: reduced colour vision (red desaturation), an RAPD and pain on eye movement.
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Which form of optic neuritis shows a macular star and is rarely linked with MS?
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Neuroretinitis.
Why? Disc swelling plus a star of exudates around the macula. The classic infective cause is Bartonella henselae (cat-scratch disease). Retrobulbar neuritis, with a normal disc, has the strongest MS link.
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Foster Kennedy syndrome: ______ with contralateral papilloedema and anosmia, classically caused by an olfactory groove meningioma or other frontal mass.
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ipsilateral optic atrophy
Why? The tumour compresses the optic nerve on its own side (atrophy) and raises intracranial pressure, swelling the other disc.
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Foster Kennedy syndrome: ipsilateral optic atrophy with contralateral papilloedema and anosmia, classically caused by an ______ or other frontal mass.
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olfactory groove meningioma
Why? The tumour compresses the optic nerve on its own side (atrophy) and raises intracranial pressure, swelling the other disc.
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Describe the eye in a complete third nerve palsy.
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"Down and out", with ptosis and a dilated, unreactive pupil.
Why? The lateral rectus (CN VI) and superior oblique (CN IV) act unopposed. Ptosis is from levator palpebrae weakness; the dilated pupil from loss of parasympathetic fibres.
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Which way does a patient with a sixth nerve palsy turn the head?
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Towards the affected side.
Why? This avoids using the weak lateral rectus and reduces horizontal diplopia. The affected eye is turned in (esotropia).
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Alongside weight loss, what is the first-line drug for idiopathic intracranial hypertension with papilloedema?
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Acetazolamide.
Why? Carbonic anhydrase inhibition reduces CSF production. If vision is threatened despite treatment, urgent surgery (CSF shunting or optic nerve sheath fenestration) is needed.
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Which antibody should be tested in severe or bilateral optic neuritis with longitudinally extensive transverse myelitis?
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Anti-aquaporin-4 (AQP4) IgG — for neuromyelitis optica spectrum disorder.
Why? Anti-MOG antibodies are the other one to check. Both conditions need different long-term treatment from MS.