The National Institute for Clinical Excellence is examining coil embolisation of unruptured intracranial aneurysms and will publish guidance on its safety and efficacy to the NHS in England, Wales and Scotland. The Institute's Interventional Procedures Advisory Committee has considered the available evidence and the views of Specialist Advisors, who are consultants with knowledge of the procedure. The Advisory Committee has made provisional recommendations about coil embolisation of unruptured intracranial aneurysms.

This document summarises the procedure and sets out the provisional recommendations made by the Advisory Committee. It has been prepared for public consultation. The Advisory Committee particularly welcomes:

• comments on the preliminary recommendation
• the identification of factual inaccuracies
• additional relevant evidence.

Note that this document is not the Institute's formal guidance on this procedure. The recommendations are provisional and may change after consultation.

The process that the Institute will follow after the consultation period ends is as follows:

• The Advisory Committee will meet again to consider the original evidence and its provisional recommendations in the light of the comments received during consultation.
• The Advisory Committee will then prepare draft guidance which will be the basis for the Institute's guidance on the use of the procedure in the NHS in England, Wales and Scotland.

For further details, see the Interim Guide to the Interventional Procedures Programme, which is available from the Institute's website (www.nice.org.uk/ip).

Closing date for comments: 27 July 2004

Target date for publication of guidance: November 2004

Note that this document is not the Institute's guidance on this procedure. The recommendations are provisional and may change after consultation.

Current evidence suggests that coil embolisation of unruptured intracranial aneurysms is usually efficacious in obliterating aneurysms and that its safety is similar to that of surgical treatment. However, the risks of treating intracranial aneurysms by this procedure or by open surgery exceed the annual risk of rupture. Treatment of unruptured intracranial aneurysms may therefore not be clinically indicated or may not be the option that patients would choose.

The risk of rupture of intracranial aneurysms is low and depends in part on the patient's age, and the size and position of the aneurysms. Clinicians wishing to undertake coil embolisation of unruptured intracranial aneurysms should ensure that individual patients understand the particular risks associated with the procedure compared to the risk of having no treatment. Use of the Institute's Information for the Public is recommended.

Clinicians should also ensure that normal arrangements are in place for audit and clinical governance.

The procedure should only be performed in specialist units with expertise in the endovascular treatment of intracranial aneurysms.

Intracranial aneurysms are small balloon-like dilated portions of blood vessels that may occasionally rupture, causing haemorrhage, stroke or death. Usually, the cause is unknown, but people with genetic causes of weak blood vessels are more likely to develop aneurysms.

The traditional treatment for ruptured or unruptured aneurysms involves open surgery to clip the abnormal blood vessels inside the skull.

The coil technique involves approaching the aneurysm from inside the diseased blood vessel, avoiding the need to open the skull. A thin tube containing the coil on a guidewire is inserted into a large artery, usually in the groin, and passed up into the skull under radiological guidance. The coil is placed inside the aneurysm and detached from the guidewire. Multiple coils may be placed into the aneurysm through the same tube until the aneurysm is filled with coils, which cause clotting and stop blood from entering the aneurysm.

The coil technique is mainly carried out on ruptured aneurysms but may also be used to treat unruptured aneurysms.

In a large observational study, it was reported that overall morbidity and mortality associated with endovascular repair was 9.5% (41/451) at one year, compared to 12.2% (233/1917) for surgery. Similar results were reported in smaller studies comparing the two techniques. However, these comparisons are difficult because patient characteristics differed between the two groups; for example, those undergoing endovascular repair were often older than those who had surgery.

For the patients undergoing endovascular repair by coil embolisation in the International Study of Unruptured Intracranial Aneurysms, obliteration was complete in 55% (207/451) of patients, incomplete in 24% (91/451), unsuccessful in 18% (67/451), and unknown in 3% (12/451) of patients. At one year, less than 1% of patients (4/451) had a moderate or severe disability, as measured by the Rankin score. In other studies on this procedure, the rate of permanent complications ranged from 5% (6/116) to 8% (3/38). For more details, refer to the sources of evidence (see Appendix).

Specialist Advisors considered that the main uncertainty related to the long-term durability of the procedure.

In a retrospective study of 62 patients, the procedure-related complication rate was 23% (14/62) after coil embolisation. Major complications resulting in reduced functional status were reported in five patients (8%) and minor complications causing prolonged hospitalisation were reported in nine patients (15%). Adverse events during initial and follow-up hospitalisation included intra- or postoperative rupture (6%, 4/62) and cranial neuropathy (11%, 7/62). For more details, refer to the sources of evidence (see Appendix). 2.4.2 In the large observational study, perioperative haemorrhage was noted in 2% (10/451) and cerebral infarction in 5% (26/471) of patients who underwent endovascular repair.

Specialist Advisors considered that this was a safe procedure. One Advisor noted that complications during the procedure include rupture of the aneurysm or thrombo-embolic occlusion of intracranial vessels, but these complications are uncommon. There is also a small risk of delayed haemorrhage from the aneurysm.

This guidance relates to unruptured aneurysms. The Institute has considered the use of coil embolisation for ruptured intracranial aneurysms in separate guidance (www.nice.org.ukipg106).

The following document, which summarises the evidence, was considered by the Interventional Procedures Advisory Committee when making its provisional recommendations.

• Interventional procedure overview of coil embolisation of unruptured intracranial aneurysms, January 2004

Available from: www.nice.org.uk/ip274overview