Adverse Events After Microsurgical and Endovascular Treatment of Unruptured Intracranial Aneurysms Assessed with the Therapy-Disability-Neurology (TDN) Grade: A Single-Center Cohort Study

Background/Objectives: Unruptured intracranial aneurysms (UIAs) affect 2.3–6.6% of the population. Traditional complication classification systems focus solely on therapeutic interventions, underweighting the burden of neurological deficits in neurovascular patients. This study applied the multidimensional Therapy-Disability-Neurology (TDN) grade to a consecutive cohort of patients treated for UIA in order to characterize the distribution, severity and clinical correlates of adverse events (AEs); the comparison between treatment modalities was a secondary, exploratory objective. Methods: We retrospectively analyzed 296 patients treated for UIA between 2016 and 2025 (microsurgical treatment n = 135, 45.6%; endovascular treatment n = 161, 54.4%). The TDN grade, a three-domain assessment incorporating the therapeutic resources required to treat an AE, functional disability and neurological deficits, was assigned for all AEs occurring during the index hospitalization. AEs were defined as any deviation from the expected post-treatment course, including minor events not usually reported as complications. The primary endpoint was the TDN grade; secondary endpoints included individual AE categories, severe AEs (TDN ≥ 4), functional outcome and length of stay. Results: AEs occurred in 89 patients (30.1%); 37 patients (12.5%) were graded TDN 1 or 2 and 52 (17.6%) TDN 3 to 5, the range corresponding to morbidity as conventionally reported. Four patients (1.4%) died during the index hospitalization or within 30 days of treatment. Median TDN grades were 0 in both groups (microsurgical IQR 0–2; endovascular IQR 0–1; and p = 0.575). The spectrum of AE categories differed between treatment modalities. The TDN grade correlated with GOSE and KPS at discharge and with length of hospital stay (all p < 0.001); length of stay was explained better by the three subgrades together than by the therapy subgrade alone (R2 0.18 vs. 0.13). Treatment modality was not associated with the TDN grade in unadjusted analysis; exploratory adjusted associations with any AE depended on model specification, and no association was found for severe AEs. Conclusions: In this cohort treated for UIA, the TDN grade captured the clinical severity of AEs and may serve as a component of multidimensional outcome assessment in future prospective studies, provided its domains are defined a priori.