Background/Objectives: Adverse events (AE) associated with neurosurgical interventions can cause neurological deficits and impaired functional outcomes. The Therapy–Disability–Neurology (TDN) grade classifies AE severity based on treatment requirements, disability, and neurological deficits, but has not been validated in aneurysmal subarachnoid hemorrhage (aSAH). We aimed to validate the TDN grade in predicting functional outcomes and length of hospital stay (LOS) in aSAH patients, treated surgically and/or endovascularly. Methods: We conducted a single-center retrospective cohort study of a prospectively collected database of aSAH patients. Patients were recruited between 2009 and 2022. The TDN grade was retrospectively applied. Primary outcome variables were functional outcomes, assessed using the Glasgow Outcome Scale (GOS, selected for comparability with prior aSAH outcome literature), at discharge and last follow-up, and LOS. Results: We included 355 patients: mean age was 57.2 (12.9 SD) and 235 (66.1%) were female. The TDN grade showed a moderate positive correlation with length of hospital stay (rho = 0.4, p < 0.001). Negative correlations were observed with functional outcomes at discharge (GOS: rho = −0.56, p < 0.0001) and at last follow-up (GOS: rho = −0.58, p < 0.0001). The TDN grade demonstrated good discrimination for unfavorable outcome at last follow-up (AUC = 0.82) and good discrimination for employment status (AUC = 0.71). Patients with AEs stayed 7.63 days longer on average (p < 0.001). Conclusions: The TDN grade predicted hospital stay and functional outcomes in aSAH patients treated surgically and/or endovascularly, demonstrating good discrimination for unfavorable outcomes and employment status. These findings extend the grade’s applicability to both treatment- and disease-related complications and support its potential utility as a standardized tool for prognostication and resource planning. Results should be interpreted in light of the single-center retrospective design and selection bias.

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.