Long-term follow-up of patients with non-ischemic cerebral enhancing lesions following endovascular aneurysm treatment: magnetic resonance imaging findings, clinical course, and treatment.

Background: Non-ischemic cerebral enhancing (NICE) lesions are a rare complication following endovascular therapy (EVT) for cerebral aneurysms. Although first described in 2008, data on long-term outcome and treatment response remain limited.

Objectives: In this study, we investigated the long-term follow-up of patients with NICE lesions, including magnetic resonance imaging (MRI) findings, clinical course, and treatment.

Design: For this single-center ambispective observational study, we enrolled nine patients with NICE lesions after EVT for cerebral aneurysms.

Methods: We analyzed patients diagnosed with NICE lesions following EVT between 2008 and 2024 at the University Hospital of Augsburg. Data collection included patients' and procedural characteristics, clinical course, MRI findings, and response to immunotherapies.

Results: We present the long-term follow-up of five patients already published and four additional cases. Nine female patients (mean age at diagnosis 50.67 ± 11.82 (± standard deviation, SD) years) were identified and analyzed with a mean follow-up of 1659.44 ± 1426.87 (SD) days, ranging from 328 to 5223 days (cumulative follow-up of 40.92 patient-years). In total, 112 MRIs were available for evaluation. Eight patients developed symptoms at a mean of 11 ± 13.41 (SD) days post-EVT, one patient remained asymptomatic. New NICE lesions during follow-up were detected in six patients, five patients developed new or increasing symptoms. All patients received glucocorticosteroids with variable duration, six patients required additional immunotherapies. At final follow-up, all patients had a favorable outcome (modified Rankin Scale 0-1), though residual symptoms persisted in four of them.

Conclusion: Hitherto, this study presents the longest follow-up period of patients developing NICE lesions after EVT. NICE lesions may have a highly variable course regarding radiological and clinical characteristics, with potential for both clinical and radiological recurrence years after initial presentation. While immunosuppressive therapy appears effective, optimal treatment regimens and duration have yet to be determined. Our findings underline the importance of regular clinical and MRI controls for individual patient care in this rare condition.