The Helsinki Unruptured Intracranial Aneurysm Quality of Care study: a prospective observational study

The aim of this study was to evaluate the safety of unruptured intracranial aneurysm (UIA) treatment by assessing postprocedural ischemic lesions using MRI diffusion-weighted imaging (DWI) and correlating these findings with clinical outcomes.

This investigator-initiated, single-center study prospectively enrolled consecutive patients undergoing UIA treatment at Helsinki University Hospital between December 2022 and August 2024. Postprocedural brain MRI was performed within 3 days, and clinical outcomes (modified Rankin Scale [mRS] score, neurological symptoms, and return to work) were assessed at 3 months. The authors compared the incidence of DWI lesions between treatment modalities and assessed the association between DWI lesions and outcome metrics.

A total of 169 consecutive UIA patients were included, of whom 120 (71%) were treated endovascularly and 49 (29%) surgically. At 3 months, 98% of patients had an mRS score of 0 or 1, 6% had a worsening of their mRS score, and 4% had new neurological symptoms. The incidence of a new DWI lesion was 63%, with no difference between the groups (endovascular 63% vs surgical 63%, p = 0.993). Endovascular patients more often had ≥ 6 DWI lesions (14% vs 0%, p = 0.012), while surgical patients more frequently had lesions ≥ 10 mm (20% vs 8%, p = 0.016). The majority (85%, 91/107) of DWI lesions were asymptomatic, but the presence of a lesion was associated with an increased risk of new neurological symptoms (15% vs 2%, p = 0.006 [59% of symptoms being transient]). There was no association between the presence of any DWI lesion and mRS score (mRS score 0 or 1: 96% with lesions vs 100% without, p = 0.298) or mRS score worsening (7% with lesions vs 5% without, p = 0.747). However, lesions ≥ 10 mm were associated with poorer mRS outcomes (mRS score 0 or 1 16/19 [84%] vs 149/150 [99%], p = 0.005) and an increased risk of mRS score worsening (4/19 [21%] vs 1/150 [1%], p = 0.016). Overall, 97% of patients who were working before treatment returned to work within 3 months.

New DWI lesions are frequent after UIA treatment, despite excellent clinical and mRS outcomes. The mRS score alone might not fully capture the neurological impact of treatment-related ischemia. DWI assessment can provide valuable additional information when evaluating the quality of modern neurovascular care. Clinical trial registration no.: NCT06147102 (ClinicalTrials.gov).