Painful pupil-involving third nerve palsy in an older woman
A 66-year-old woman presents with a five-day history of right-sided headache followed by drooping of the right upper lid; the next morning she noticed double vision that is both horizontal and vertical. She has hypertension treated with amlodipine and no history of diabetes. She has lost 4 kg unintentionally over three months and reports jaw discomfort when chewing. Visual acuity is 6/6 in each eye with normal colour plates. There is complete right ptosis, the right eye is deviated down and out, and elevation, depression, adduction and abduction are all markedly reduced. The right pupil is 6 mm and unreactive to light; the left is 3 mm and briskly reactive. Corneal sensation is normal. Fundoscopy is normal. Erythrocyte sedimentation rate is 58 mm/hour and C-reactive protein is 18 mg/L.
1. What is your leading diagnosis and what must be excluded first? Justify your priorities.
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This is an acute painful, pupil-involving third nerve palsy, and the priority is to exclude a compressive lesion, specifically a posterior communicating artery aneurysm at the internal carotid–posterior communicating junction. The reasons are:
- The pupil is involved (6 mm, unreactive) with a dilated, fixed pupil and complete ptosis and ophthalmoplegia. Pupillary parasympathetic fibres run on the outside of the nerve and are affected early by compression.
- The onset is painful and sudden, which fits expansion or minor leak of an aneurysm.
- Diabetes and hypertension can cause ischaemic third nerve palsy, but ischaemic palsies are typically pupil-sparing, and this patient has no history of diabetes.
Other diagnoses to consider and exclude include pituitary apoplexy (would usually cause visual field loss and a different pattern), cavernous sinus pathology (additional fourth and sixth nerve involvement, and sensory loss in V1–V2 - corneal sensation is normal here), orbital apex disease, ophthalmoplegic migraine, and giant cell arteritis.
The first investigation is urgent CT angiography (or MR angiography) of the circle of Willis. If that is negative, I would proceed to MRI with contrast and possibly catheter angiography, since a small aneurysm can be missed on non-invasive imaging. I would not perform a lumbar puncture before imaging because of the risk of herniation if there is raised intracranial pressure from a bleed.
Giant cell arteritis is a genuine parallel consideration in a 66-year-old with headache, jaw claudication, weight loss and an ESR of 58. It is an unusual cause of third nerve palsy and usually produces a pupil-sparing ischaemic palsy, but the systemic features should not be ignored.
2. How does giant cell arteritis influence your management, and what would you do if imaging is negative?
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The systemic features are too suggestive to dismiss: age over 50, new headache, jaw claudication, 4 kg unintentional weight loss, ESR 58 and raised CRP. Jaw claudication is the most specific symptom of giant cell arteritis, and the risk of irreversible visual loss from arteritic anterior ischaemic optic neuropathy is real, so this needs action in parallel with the aneurysm work-up rather than after it.
Practical sequencing:
- Send urgent CT angiography for the third nerve palsy - this takes minutes and does not delay anything else.
- Send ESR, CRP, full blood count and liver function, and arrange temporal artery biopsy and urgent rheumatology review.
- Start high-dose corticosteroid (typically intravenous methylprednisolone followed by oral prednisolone) once imaging has been obtained or is under way, because steroids do not obscure an aneurysm and the risk of waiting is bilateral blindness. I would give steroids before biopsy, since biopsy remains informative for up to about two weeks after starting treatment.
- Arrange same-day ophthalmology assessment of the optic discs and visual fields, with instruction to return immediately if vision changes.
If CT and MR angiography are negative and the palsy persists, I would repeat imaging after a few weeks, consider catheter angiography, and only then accept a microvascular or GCA-related cause. A pupil-involving third nerve palsy that does not improve, or that develops aberrant regeneration, still warrants re-imaging rather than reassurance. I would explain to the patient that two separate problems may be present and that both are being pursued.