skip to main content

Pupil-Involving CN III Palsy – Urgent CTA — SCE Neurology MCQ

Instant feedback + full explanation. One question, done properly.

HardNeuro-ophthalmologyPupil-Involving CN III Palsy – Urgent CTASCE Neurology

A 50-year-old woman presents with sudden onset of a right third cranial nerve palsy — she has right ptosis, the right eye is deviated down and out, and the right pupil is dilated and fixed. She has a severe right retro-orbital headache. She is alert with no other neurological deficits. CT head is normal. What is the SINGLE most urgent investigation?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: C — CT angiography or catheter angiography to exclude posterior communicating artery aneurysm

The best answer is “CT angiography or catheter angiography to exclude posterior communicating artery aneurysm”. Primary headache diagnosis follows attack phenotype and absence of secondary red flags; acute and preventive treatment is selected by headache type, frequency, disability and contraindications. The alternatives “MRI brain, after specialist assessment, when the phenotype supports it”, “Lumbar puncture, when the phenotype supports it, within the relevant UK pathway”, “Blood glucose, within the relevant UK pathway, after excluding important mimics”, “Thyroid function, after excluding important mimics, after specialist assessment” are clinically adjacent possibilities, but they do not match the defining chronology, localisation, physiology, investigation result or UK management sequence in this stem.

Reference: NICE CG150 headache recommendations: https://www.nice.org.uk/guidance/cg150/chapter/Recommendations