Interventional Radiological Treatment of Intracranial (Brain) Aneurysms

Authors: Dr Peter Mitchell*
                            Dr Winston Chong *

What are the prerequisites for having interventional radiological treatment of intracranial aneurysms done?

Aneurysm diagnosis may be with CT, CTA, MRI, MRA, or DSA. DSA is required for endovascular treatment and may be a separate diagnostic procedure prior to aneurysm treatment or performed immediately prior to definitive treatment under the same general anaesthetic.

Consultation with a neurointerventional specialist is essential for referring clinicians to obtain a full understanding of the risk of treatment versus the risk of rupture if untreated. This risk-benefit equation will vary from patient to patient and aneurysm to aneurysm and so the discussion is important.

Renal function must be tested prior to contrast administration–U&E, including eGFR estimation. Contrast dosage can be quite high for this procedure particularly if the aneurysm is large or hard to access.

Clotting function must be assessed prior to the procedure if the patient is on anticoagulant therapy, or has clinical risk factors for abnormal clotting function. Warfarin or heparin therapy will need to be ceased (3 days or 24 hours respectively) before treatment. Premedication discussed and arranged e.g. aspirin 100 or 150mg per day for 7 days prior to treatment in elective cases, sometimes combined aspirin with clopidogrel 75mg per day if more complicated treatment is anticipated.

Medical assessment for fitness for general anaesthesia needs to be undertaken in all cases.

What are the absolute contraindications for interventional radiological treatment of intracranial aneurysms?

Contraindications may not apply to emergency treatment for a ruptured aneurysm where there is a high risk of death without urgent treatment:

  • pregnancy;
  • renal failure;
  • severe contrast allergy to currently used contrast agents.

What are the relative contraindications for interventional radiological treatment of intracranial aneurysms?

  • Renal impairment.
  • Mild contrast allergy.
  • Aneurysm factors – wide neck aneurysm, fusiform truncal aneurysms, arterial branches arising from the aneurysm.
  • Arterial access factors – severe proximal stenosis, tortuosity, arterial dissection, fibromuscular disease.
  • Risk factors for a general anaesthetic.

What are the adverse effects of interventional radiological treatment of intracranial aneurysms?

Angiography related risks include:

  • puncture site haematoma;
  • false aneurysm;
  • infection;
  • contrast allergy;
  • renal impairment; and
  • neurological deficit (transient or fixed) 0.4-1.0% (for range of complications from DSA).

Aneurysm associated risk:

  • perforation with subarachnoid haemorrhage during the procedure 1-5% (higher in aneurysms presenting with SAH);
  • parent vessel occlusion;
  • distal embolisation; and
  • failed treatment – 1-3% dependent on geometry of aneurysm.


  • Major permanent neurological deficit 2-4% for elective. General statements not accurately applied to SAH (corrected by grade of bleed, other complications of the bleed itself, etc.).
  • Mortality <1% elective aneurysm treatment; higher in SAH determined mainly by grade of presentation.

Are there alternative imaging tests, interventions or surgical procedures to interventional radiological treatment of intracranial aneurysms?

The treatment options for most unruptured intracranial aneurysms are continued observation, neurosurgical clipping, and endovascular coiling.

Neurosurgical clipping involves a craniotomy, dissection in the subarachnoid space, brain retraction, occasional temporary clipping arresting blood flow to the brain, and final placement of one or more metal clips across the base of the aneurysm. When successful, the aneurysm is completely excluded from the lumen of the parent artery, and there is no narrowing or occlusion of branch vessels – either perforating branches which can be hard to identify, or larger branches. As the skull is opened and brain manipulated, there is a risk of post operative seizures, which often require a period on anticonvulsant medications, and not being permitted to drive.

Coil treatment involves an angiogram, with the patient under general anaesthetic. A microcatheter is then navigated into the aneurysm from the femoral arterial access. Once in position, one or more coils are placed into the aneurysm body, continuing until the aneurysm is fully packed and no longer filling with contrast when it is injected, indicating effective cessation of blood flow into the aneurysm. There is no brain retraction, and if no subarachnoid haemorrhage, no increased risk of seizures. The coils are very soft platinum, to minimise the chance of aneurysm perforation and rupture, and to allow them to fill all of the often irregular shapes that aneurysms may take. However, because they are soft, they can become compacted over time, and follow up investigations are necessary to confirm complete persistent “cure” of the aneurysm. This may be with MRI or DSA.

ISAT showed a lower chance of poor outcome (stroke, death, disability) when patients with ruptured intracranial aneurysms were randomised to treatment with endovascular coiling rather then clipping. This was despite a higher chance of recurrent or residual aneurysm in the patients treated with coiling, and the benefit was not lost over prolonged follow up.

Such robust evidence of benefit from randomised controlled trials does not exist for treatment of unruptured aneurysms. In general, endovascular intervention is likely to be more easily tolerated, with lower procedural risks than are associated with surgery, but at the cost of a greater chance of incomplete aneurysm obliteration and increased likelihood of the need for further endovascular treatments due to aneurysm recurrence. The individual patient needs to have specific consultations with surgeons and neurointerventionists to assess patient factors (age, clinical condition, rupture, other illnesses), aneurysm factors (site and risk of rupture, and aneurysm geometry) to determine the best treatment and weigh the risks versus the benefits if treatment is undertaken.

Further information about interventional radiological treatment of intracranial aneurysms:

Please refer to the references below for some further information on natural history, diagnosis, and treatment options for intracranial aneurysms.

  1. Mitchell, P.J. Neurointervention (chapter) in Kaye, A & Black, P.M (eds). Operative Neurosurgery; London: Churchill Livingston, 2000.
  2. Lanzer & Topol “Panvascular medicine – integrated clinical management.” Chapter : Vascular diseases of the central nervous system: percutaneous approach. Mitchell PJ, Higashida RT, van Halbach VV, Dowd CF. Springer-Verlag, Berlin Heidelberg 2002.
  3. Molyneux, A., R. Kerr, et al. (2002). “International Subarachnoid Aneurysm Trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised trial.[see comment].” Lancet 360(9342): 1267-74.
    BACKGROUND: Endovascular detachable coil treatment is being increasingly used as an alternative to craniotomy and clipping for some ruptured intracranial aneurysms, although the relative benefits of these two approaches have yet to be established. We undertook a randomised, multicentre trial to compare the safety and efficacy of endovascular coiling with standard neurosurgical clipping for such aneurysms judged to be suitable for both treatments. METHODS: We enrolled 2143 patients with ruptured intracranial aneurysms and randomly assigned them to neurosurgical clipping (n=1070) or endovascular treatment by detachable platinum coils (n=1073). Clinical outcomes were assessed at 2 months and at 1 year with interim ascertainment of rebleeds and death. The primary outcome was the proportion of patients with a modified Rankin scale score of 3-6 (dependency or death) at 1 year. Trial recruitment was stopped by the steering committee after a planned interim analysis. Analysis was per protocol. FINDINGS: 190 of 801 (23.7%) patients allocated endovascular treatment were dependent or dead at 1 year compared with 243 of 793 (30.6%) allocated neurosurgical treatment (p=0.0019). The relative and absolute risk reductions in dependency or death after allocation to an endovascular versus neurosurgical treatment were 22.6% (95% CI 8.9-34.2) and 6.9% (2.5-11.3), respectively. The risk of rebleeding from the ruptured aneurysm after 1 year was two per 1276 and zero per 1081 patient-years for patients allocated endovascular and neurosurgical treatment, respectively. INTERPRETATION: In patients with a ruptured intracranial aneurysm, for which endovascular coiling and neurosurgical clipping are therapeutic options, the outcome in terms of survival free of disability at 1 year is significantly better with endovascular coiling. The data available to date suggest that the long-term risks of further bleeding from the treated aneurysm are low with either therapy, although somewhat more frequent with endovascular coiling.
  4. Molyneux, A. J., R. S. Kerr, et al. (2005). “International subarachnoid aneurysm trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised comparison of effects on survival, dependency, seizures, rebleeding, subgroups, and aneurysm occlusion.” Lancet 366(9488): 809-17.
    BACKGROUND: Two types of treatment are being used for patients with ruptured intracranial aneurysms: endovascular detachable-coil treatment or craniotomy and clipping. We undertook a randomised, multicentre trial to compare these treatments in patients who were suitable for either treatment because the relative safety and efficacy of these approaches had not been established. Here we present clinical outcomes 1 year after treatment. METHODS: 2143 patients with ruptured intracranial aneurysms, who were admitted to 42 neurosurgical centres, mainly in the UK and Europe, took part in the trial. They were randomly assigned to neurosurgical clipping (n=1070) or endovascular coiling (n=1073). The primary outcome was death or dependence at 1 year (defined by a modified Rankin scale of 3-6). Secondary outcomes included rebleeding from the treated aneurysm and risk of seizures. Long-term follow up continues. Analysis was in accordance with the randomised treatment. FINDINGS: We report the 1-year outcomes for 1063 of 1073 patients allocated to endovascular treatment, and 1055 of 1070 patients allocated to neurosurgical treatment. 250 (23.5%) of 1063 patients allocated to endovascular treatment were dead or dependent at 1 year, compared with 326 (30.9%) of 1055 patients allocated to neurosurgery, an absolute risk reduction of 7.4% (95% CI 3.6-11.2, p=0.0001). The early survival advantage was maintained for up to 7 years and was significant (log rank p=0.03). The risk of epilepsy was substantially lower in patients allocated to endovascular treatment, but the risk of late rebleeding was higher. INTERPRETATION: In patients with ruptured intracranial aneurysms suitable for both treatments, endovascular coiling is more likely to result in independent survival at 1 year than neurosurgical clipping; the survival benefit continues for at least 7 years. The risk of late rebleeding is low, but is more common after endovascular coiling than after neurosurgical clipping.
  5. Wiebers, D. O. (2006). “Unruptured intracranial aneurysms: natural history and clinical management. Update on the international study of unruptured intracranial aneurysms.” Neuroimaging Clin N Am 16(3): 383-90, vii.
    In guiding treatment decisions for all patients with unruptured intracranial aneurysms, it is important to compare size-, site-, and group-specific natural history data with size-, site- and age-specific treatment morbidity and mortality data. Because patient age has a major effect on operative morbidity and mortality, but relatively little effect on natural history, surgical treatment of an UIA patient over age 50 and any treatment of UIA patients over age 70 should be considered with particular vigilance. Optimally, patients should be evaluated and treated at high-volume centers in a setting that emphasizes neurovascular teamwork and unbiased presentation and delivery of different therapeutic option, including the option of observation, which is often appropriate for patients with UIAs.
  6. Wiebers, D. O., J. P. Whisnant, et al. (2003). “Unruptured intracranial aneurysms: natural history, clinical outcome, and risks of surgical and endovascular treatment.[see comment].” Lancet 362(9378): 103-10.
    BACKGROUND: The management of unruptured intracranial aneurysms is controversial. Investigators from the International Study of Unruptured Intracranial Aneurysms aimed to assess the natural history of unruptured intracranial aneurysms and to measure the risk associated with their repair. METHODS: Centres in the USA, Canada, and Europe enrolled patients for prospective assessment of unruptured aneurysms. Investigators recorded the natural history in patients who did not have surgery, and assessed morbidity and mortality associated with repair of unruptured aneurysms by either open surgery or endovascular procedures. FINDINGS: 4060 patients were assessed-1692 did not have aneurysmal repair, 1917 had open surgery, and 451 had endovascular procedures. 5-year cumulative rupture rates for patients who did not have a history of subarachnoid haemorrhage with aneurysms located in internal carotid artery, anterior communicating or anterior cerebral artery, or middle cerebral artery were 0%, 2. 6%, 14 5%, and 40% for aneurysms less than 7 mm, 7-12 mm, 13-24 mm, and 25 mm or greater, respectively, compared with rates of 2 5%, 14 5%, 18 4%, and 50%, respectively, for the same size categories involving posterior circulation and posterior communicating artery aneurysms. These rates were often equalled or exceeded by the risks associated with surgical or endovascular repair of comparable lesions. Patients’ age was a strong predictor of surgical outcome, and the size and location of an aneurysm predict both surgical and endovascular outcomes. INTERPRETATION: Many factors are involved in management of patients with unruptured intracranial aneurysms. Site, size, and group specific risks of the natural history should be compared with site, size, and age-specific risks of repair for each patient.

Useful websites about Interventional Radiological Treatment of Intracranial Aneurysms

National Institute of Neurological Disorders and Stroke – USA
eMedicineHealth – Practical Guide to Health

*The author has no conflict of interest with this topic.

Page last modified on 26/7/2017.

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