Introduction/Purpose The treatment of intracranial aneurysms has significantly advanced with the introduction of flow diverters. This retrospective cohort study aimed to compare the efficacy and safety of flow diversion with coil embolization for very small brain aneurysms (≤ 3mm).

Materials and Methods The study utilized data from the aneurysm database at the Medical University of South Carolina from 2017 to 2023 and included patients very small intracranial aneurysms (≤ 3mm) who underwent endovascular treatment with either coil embolization or flow diversion. Both clinical and angiographic data were collected and analyzed retrospectively.

Results Of 1,199 patients underwent endovascular treatment for intracranial aneurysms, 198 patients with very small aneurysms were included in the study. Of these, 116 (58.6%) were treated with coiling and 82 (41.4%) were treated with flow diversion. The baseline characteristics of the two groups were similar. Of the included patients, 73 (37.5%) presented with ruptured aneurysms, with 53 (46.5%) in the coiling group and 79 (85.4%) in the flow diversion group. Aneurysm occlusion was evaluated using the Raymond-Roy grading system. In the coiling group, 46.5% achieved RR grade 1, 32.6% achieved RR grade 2, and 20.9% achieved RR grade 3. In the flow diversion group, immediate occlusion was achieved at a rate of 42.9% for RR grade 1, 9.5% for RR grade 2, and 47.6% for RR grade 3. The coiling group had statistically significant better initial occlusion rates compared to the flow diversion group (p-value = 0.02). Follow-up was performed for a mean of 86 months in the coiling group and showed RR grade 1 in 61.1% of patients, RR grade 2 in 38.9%, and RR grade 3 in 0.0%. Follow-up was performed for a mean of 25 months in the flow diversion group and showed RR grade 1 in 88.9% of patients, RR grade 2 in 0.0%, and RR grade 3 in 11.1%. Retreatment was required in 16.0% of the coiling group and 0.0% of the flow diversion group (p-value: 0.006). There was no statistically significant difference between the two groups in terms of procedure-related complications.

Conclusion In patients with very small aneurysms (≤ 3mm), coil embolization is associated with better immediate outcomes than flow diversion, while flow diversion achieves higher rates of permanent occlusion.

Disclosures M. Mahdi Sowlat: None. S. Samir Elawady: None. A. S. Sumal: None. S. Al Kasab: None. A. M Spiotta: None.