Associated aneurysms in supratentorial arteriovenous malformations: impact of aneurysm size on haemorrhage.

BACKGROUND

Associated aneurysms (AAs) are presumed to represent an additional risk factor for intracranial haemorrhage from cerebral arterio-venous malformations (AVMs). To date, efforts to capture their natural history, as well as to identify aneurysms with the potential capability of regression after AVM treatment remain incomprehensive. As the aneurysm size represents an important aspect for the treatment indication of incidental saccular aneurysms, this factor has rarely been encountered for the treatment of AAs so far. The present study aims to determine the angiographic and clinical characteristics of AAs with special focus on aneurysm size and their consequences for treatment.

METHODS

Patients with cerebral AVMs, treated in our department between 1990 and 2013, were analyzed retrospectively. Only patients with supratentorial AVMs and flow-related AAs of the feeding arteries were evaluated. Thus, patients harboring AVMs of the cerebellum and the brain stem and patients with intranidal, venous or remote aneurysms were excluded. Treatment strategies were assessed with special attention on bleeding source and on AA size.

RESULTS

In 59 of 409 patients (14%) with supratentorial AVMs, a total of 85 AAs of the feeding arteries were identified. 14 of 59 individuals (24%) presented with multiple AAs. Of 85 AA, 58 aneurysms (68%) were classified as proximal and 27 aneurysms (32%) as distal. The most common location of AAs was the middle cerebral artery (MCA, 39%), followed by the internal carotid artery (ICA, 27%) and the anterior cerebral artery (ACA, 21%). The mean AA size was 4.4 mm ± 3.4 mm. Intracranial haemorrhage was found in 21 of 59 patients (36%) with coexisting AAs. Among these, 10 individuals (17%) suffered from rupture of an AA, accounting for nearly half of all bleedings in this subgroup. Among those patients bearing a single AA, the size of ruptured aneurysms differed significantly from those unruptured (6.6 mm vs. 4.4 mm, p = 0.0046). Nineteen patients (32%) received treatment of 22 AAs, whereas sole AVM treatment was adopted in 26 patients (44%) and conservative management in 14 patients (24%). The main reasons to leave AAs untreated were the small AA size (<5 mm), poor clinical state or treatment denial by the patients.

CONCLUSIONS

The aneurysm size of AAs in AVM influences the risk of haemorrhage. Therefore, the treatment of larger (diameter ≥5 mm) AAs should be considered, even if a treatment indication of the associated AVM is not given.