Postprocedural monitoring of cerebral aneurysms: which method and what length of follow-up after intervention?

Cerebral aneurysms are reported to be present in between 0.5% and 6% of the general population, and although a large number of aneurysms do not rupture, when they do it is a serious clinical event. The incidence of aneurysmal subarachnoid hemorrhage (SAH) varies greatly and is highest in Finland and Japan, with about 20 per 100,000 inhabitants. The treatment of cerebral aneuryms has revolutionized since the introduction of electrolytically detachable platinum coils 15 years ago and nowadays in Europe about half of all aneurysms are treated endoarterially. Short-term and mid-term results of endovascular treatment appear good, but long-term results are not yet fully known. The International Subarachnoid Hemorrhage Trial (ISAT) demonstrated that the risk of death and dependence at 1 year post-treatment is significantly reduced with endovascular coil embolization compared to neurosurgical clipping. This survival benefit has been reported to continue for at least 7 years. There was also a significant reduction of seizures in the endovascular group and a tendency towards poorer cognitive outcome in the surgical group (3). Coil compaction and re-growth of the aneurysmal neck, i.e. rebleeding, are the main concerns when evaluating the need for angiographic follow-up, but new aneurysms may develop at a new location (de novo) as well. The occlusion rate of aneurysms after endovascular treatment is difficut to assess. Subjective definitions of ‘‘complete’’, ‘‘subtotal’’, or ‘‘incomplete’’ occlusion vary from one published report to the next, and this hampers comparison of follow-up studies at different institutions and comparison of surgical versus endovascular treatment. Neurosurgical clipping has been standard in the treatment of cerebral aneurysms, but neither clipping nor endovascular treatment of cerebral aneurysms is the perfect method. Even after surgery by an experienced neurosurgeon, neck remnants are found in almost 10% of patients (1). In addition, in a large cohort of patients (n5752) who regained independence after SAH and in whom all detected aneurysms had been occluded by means of clipping, the incidence of recurrence within the first 10 years is 22 times higher than expected in a population of comparable age and sex. Whether this increased risk justifies screening for recurrent aneurysms in patients with a history of SAH and clipped aneurysms is not yet known (4). There is no definitive consensus on follow-up, i.e. on how to follow-up patients with coiled cerebral aneurysms. Endless repetitive angiographic followup is inconvenient for the patient even with noninvasive MR angiography. In this issue of Acta Radiologica, Dr Kähärä from Tampere University Hospital, Finland, presents a comprehensive review of ‘‘Postprocedural monitoring of cerebral aneurysms’’ (2). The potential of skull plain radiography, CT angiography, MR angiography, and catheter angiography is discussed thoroughly. One suggested strategy is to perform concurrent digital subtraction angiography with initial follow-up MR angiography to which later MR angiographies can be compared. This option has been employed successfully at Tampere University for 12 years now. The review article by Dr Kähärä is highly recommended reading.