2.1.1 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.
2.1.2 The traditional treatment for ruptured or unruptured aneurysms involves open surgery to clip the abnormal blood vessels inside the skull.
2.2.1 The coil technique involves approaching the aneurysm from inside the diseased blood vessel, thereby 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. Once in position, it causes clotting and stops blood from entering the aneurysm. Multiple coils may be inserted into the aneurysm through the same tube until the aneurysm is filled with coils.
2.2.2 The coil technique is mainly carried out on ruptured aneurysms but may also be used to treat unruptured aneurysms.
2.3.1 In a large observational study, it was reported that overall morbidity and mortality associated with endovascular repair was 9% (41/451) at 1 year after having the procedure, compared with 12% (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 who underwent endovascular repair were often older than those who had surgery.
2.3.2 For the patients undergoing endovascular repair by coil embolisation in the International Study of Unruptured Intracranial Aneurysms, obliteration was complete in 55% (207/379) of patients, incomplete in 24% (91/379), unsuccessful in 18% (67/379), and unknown in 3% (12/379) of patients. At 1 year after the procedure, 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 section.
2.3.3 The Specialist Advisors considered that the main uncertainty related to the long-term durability of the procedure.
2.4.1 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 patients) and cranial neuropathy (11%, 7/62 patients). For more details, refer to the Sources of evidence section.
2.4.2 In the large observational study, perioperative haemorrhage was noted in 2% (10/451) and cerebral infarction in 6% (26/451) of patients who underwent endovascular repair.
2.4.3 The 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.