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Treatment of intracranial aneurysms — clip, coil and follow-up
A ruptured aneurysm is secured as early as possible — with endovascular coiling when the anatomy suits, with a clip when it does not — because the great danger in the first days is rebleeding; an unruptured aneurysm is treated only when its natural risk exceeds the risk of treatment.
Why it matters in the exam
The exam tests ISAT: in patients with a ruptured aneurysm suitable for both methods, coiling led to more independence at one year (dependency or death 23.7% versus 30.6% with clipping), at the price of slightly more rebleeding and retreatment. Clipping is preferred for a wide-necked middle cerebral artery aneurysm or one with a large haematoma to evacuate. Rebleeding is commonest in the first 24 hours, so repair is done within 24 hours whenever possible. Nimodipine 60 mg orally every 4 hours for 21 days improves outcome, although it does not prevent the arterial narrowing itself. Vasospasm and delayed ischaemia appear on days 3 to 14.
The aneurysm's location explains the symptom: an aneurysm of the posterior communicating artery presses on the third nerve and dilates the pupil; an ophthalmic artery aneurysm affects the visual field; the commonest ruptured aneurysm is on the anterior communicating artery. A fusiform PICA aneurysm is usually a dissection and is treated by vessel occlusion or bypass rather than a neck clip. For an unruptured aneurysm risk is estimated with the PHASES score (population, hypertension, age, size, earlier haemorrhage from another aneurysm, site); according to ISUIA an anterior aneurysm under 7 mm without previous haemorrhage carries a very low risk. Treatment is favoured with growth, an irregular shape with a daughter sac, symptoms, or a posterior communicating or posterior circulation location. Flow diverters suit wide-necked internal carotid aneurysms.
Key points
- Early repair — rebleeding is most dangerous in the first 24 hours.
- ISAT: coiling is preferred when both methods are suitable.
- Nimodipine 60 mg 4-hourly, for 21 days.
- Third nerve with pupil — posterior communicating artery.
- Unruptured aneurysm — PHASES and risk features.
Summary table
| Situation | Preference | Key figure | Note |
|---|---|---|---|
| Ruptured aneurysm suitable for both methods | Coil | ISAT: 23.7% versus 30.6% dependency or death | Angiographic follow-up for recurrence |
| Wide-necked MCA aneurysm or one with haematoma | Clip | Evacuate the haematoma in the same operation | Pterional approach |
| Small anterior unruptured aneurysm | Follow-up | ISUIA: under 7 mm — low risk | Stop smoking, control blood pressure |
| Wide-necked internal carotid aneurysm | Flow diverter | Dual antiplatelet therapy | Not in the acute phase of haemorrhage |
| Fusiform aneurysm or dissection | Vessel occlusion or bypass | No neck to clip | Test collateral flow |
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Sources
- AHA/ASA Guideline for the Management of Patients With Aneurysmal Subarachnoid Hemorrhage, 2023 — Aneurysm repair, nimodipine, delayed cerebral ischaemia
- AHA/ASA Guidelines for the Management of Patients With Unruptured Intracranial Aneurysms, 2015 — Risk factors and treatment decision
- International Subarachnoid Aneurysm Trial (ISAT), 2002 and long-term follow-up 2015 — Clipping versus coiling
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.
See also: Subarachnoid hemorrhage (SAH)