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.

Overall:

• 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.

Useful websites about Interventional Radiological Treatment of Intracranial Aneurysms:

National Institute of Neurological Disorders and Stroke – USA
www.ninds.nih.gov/disorders/cerebral_aneurysm/detail_cerebral_aneurysm.htm
eMedicineHealth – Practical Guide to Health
www.emedicinehealth.com/aneurysm_brain/article_em.htm

References:

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.” Lancet 360(9342): 1267-74.
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.
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.
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.

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

Page last modified on 31/8/2017.