Early Decompressive Hemicraniectomy for High-Risk Large Ischemic Core Stroke Post-EVTAcute Ischemic Stroke (AIS), particularly Anterior Circulation Large Vessel Occlusion (LVO), is a major cause of global disability and death. While endovascular thrombectomy (EVT) is the standard first-line treatment for LVO, outcomes remain poor in patients with large ischemic cores (ASPECTS ≤5). Despite high recanalization rates (\>90%), only 14-30% achieve functional independence (mRS 0-2) at 90 days, with 33-50% dead or severely disabled (mRS 5-6). Outcomes worsen dramatically with larger core volumes (e.g., only 4.4% functional independence with cores ≥150mL in SELECT2).A critical complication is Malignant Cerebral Edema (MCE), affecting \ 50% of large-core patients post-EVT. MCE triggers a vicious cycle of rising intracranial pressure, reduced perfusion, and brain herniation. It drastically worsens prognosis: functional independence rates plummet (13.3% vs 51.2% without MCE), mortality significantly increases (OR=7.96, p=0.001), and functional outcomes deteriorate (OR=7.83, p=0.008). Strong predictors include low ASPECTS (\<7) and large infarct volume.Decompressive Hemicraniectomy (DHC) is a life-saving intervention for MCE. Landmark trials (DESTINY, DECIMAL, HAMLET) and their meta-analysis show DHC within 24 hours in patients aged 18-60 significantly increases 12-month survival (78% vs 29%, ARR 50%) and rates of ambulatory independence (mRS ≤3: 43% vs 21%, ARR 23%). DESTINY II confirmed benefit in patients \>60, improving functional outcomes (mRS 0-4: 38% vs 16%). Guidelines endorse DHC for large infarcts with deterioration.However, significant challenges persist: DHC is Underutilized: Despite evidence, clinical adoption remains low.Rescue DHC Fails to Improve Outcomes in Post-EVT MCE: Studies report poor functional outcomes (only 20% mRS 0-2) and high mortality (48.6%) with standard medical therapy (SMT) plus rescue DHC after MCE develops. Retrospective data confirms worse outcomes in these patients (mRS 0-2: 16.4% vs 50%; mortality: 46.5% vs 20%) compared to those without MCE. Crucially, rescue DHC itself fails to improve prognosis once MCE is established (mRS 5-6: 64% vs 57.7%; mortality: 48% vs 46.2%).High-Risk Identification: Patients defined as high-risk for MCE (ASPECTS 3-5 + NIHSS≥30 or ASPECTS≤2) have significantly worse 90-day outcomes (mRS 0-2: 23.2% vs 44.6%; mortality: 44% vs 22.7%).Timing is Critical: Rescue DHC is often performed too late, after irreversible neurological damage occurs. Early/Prophylactic DHC, performed before significant edema and herniation develop, offers a potential pathophysiological advantage. It may:Improve cerebral perfusion pressure earlier. Reduce mass effect and edema progression. Mitigate secondary injury (e.g., reduce oxygen-free radicals, excitatory amino acids).Potentially break the ischemic-edema-herniation cycle sooner.Rationale for the Study: While DHC is effective for established MCE in non-EVT contexts and rescue DHC post-EVT is ineffective, high-quality evidence for early prophylactic DHC in high-risk large-core patients after successful EVT is lacking. Current guidelines do not address this specific, high-risk population where MCE incidence is \ 50% and outcomes are dismal despite recanalization. Study Aim: This trial will evaluate the efficacy and safety of early prophylactic decompressive hemicraniectomy compared to standard medical treatment (which includes rescue DHC if MCE develops) in AIS-LVO patients at high risk of MCE (defined by ASPECTS and NIHSS criteria) following successful EVT. The goal is to determine if proactive intervention can improve functional outcomes and reduce mortality in this critically ill population where current strategies fail.