Phd in CLINICAL EXPERIMENTAL NEUROSCIENCE AND PSYCHIATRY

Thesis title: SCOTOMA PERFUSIONALE NELL'ICTUS ISCHEMICO ACUTO: FREQUENZA, CAUSE E IMPLICAZIONI CLINICHE

Background: Acute ischemic stroke remains one of the leading causes of mortality and long-term disability worldwide. The introduction of mechanical thrombectomy has markedly improved clinical outcomes in selected patients. In this context, accurate patient selection is crucial, especially after the therapeutic window extension up to 24 hours, made possible by advanced neuroimaging techniques. Among the tools most widely used in clinical practice, the RAPID software provides automated, standardized quantification of the ischemic core and penumbra, supporting the selection of candidates for endovascular recanalization. However, such automated systems are not free from limitations, including potential overestimation (ghosting) and underestimation (perfusion scotoma) of the ischemic core. Methods: This retrospective single-center study analyzed 100 patients who underwent mechanical thrombectomy for anterior circulation large vessel occlusion between January 2021 and February 2024. Ischemic core volumes calculated automatically by RAPID were compared with MRI DWI and non-contrast CT (ASPECTS) to assess the frequency and determinants of volumetric discrepancies. Results: RAPID provided an accurate estimation of the ischemic core in 72% of cases, while 28% showed diagnostic inconsistencies: ghosting in 13% and perfusion scotoma in 15% of patients. The scotoma group showed a significantly higher proportion of unknown onset strokes (p = 0.011), a longer onset-to-imaging time (p = 0.013), and a larger MRI ischemic core volume (p = 0.002). No significant differences were found for age, sex, occlusion site, side, NIHSS, or mTICI score (p > 0.05). Conclusions: These findings suggest that perfusion scotoma is not merely a technical artifact but rather a pathophysiological phenomenon related to luxury perfusion, where necrotic tissue exhibits paradoxically increased blood flow due to loss of autoregulation. Although automated perfusion analysis represents a valuable diagnostic tool, expert neuroradiological review remains essential for accurate interpretation. In suspected underestimation of the ischemic core, combining perfusion parameters (rCBF <30%) with automated or manual ASPECTS evaluation enhances diagnostic accuracy. Future integration of artificial intelligence algorithms capable of identifying luxury perfusion patterns and dynamically adjusting perfusion thresholds according to patient-specific clinical and temporal parameters may further improve diagnostic precision and optimize patient selection for thrombectomy in extended time windows.