External Ventricular Drainage for Hydrocephalus Following Cerebellar Infarction: A Scoping Review

<b>Background</b>: Cerebellar infarction complicated by obstructive hydrocephalus is a life-threatening condition. External ventricular drainage (EVD) has traditionally been regarded as hazardous due to concerns about precipitating upward transtentorial herniation, whereas suboccipital decompressive craniectomy (SDC) remains the definitive life-saving treatment. The optimal role and sequencing of these interventions remain controversial. <b>Methods</b>: A scoping review was conducted in accordance with PRISMA-ScR guidelines. PubMed/MEDLINE was systematically searched from inception to September 2025. Eligible studies included adult patients with cerebellar infarction and acute obstructive hydrocephalus managed with EVD, with or without SDC. Data on study design, patient characteristics, interventions, complications, and outcomes were extracted and narratively synthesized. <b>Results</b>: Forty studies were included, encompassing multicenter registries, retrospective cohorts, case series, and international guidelines. Evidence suggests that EVD alone can be effective in selected patients with preserved or moderately impaired consciousness, while outcomes in comatose patients are improved with SDC or combined approaches. Importantly, this scoping review integrates current evidence with a representative institutional case to provide a practical clinical context. Radiographic signs of upward transtentorial herniation before EVD were common, but clinically significant deterioration was infrequent. Prognostic factors for surgical decision-making included infarct volume (practical threshold 25-35 mL), location (vermian or bilateral infarcts), brainstem involvement, and level of consciousness. International guidelines increasingly recognize EVD as a valid treatment option, particularly as initial therapy for hydrocephalus. <b>Conclusions</b>: EVD should no longer be regarded as an absolute contraindication in cerebellar infarction with obstructive hydrocephalus. Controlled drainage can suffice in carefully selected patients, whereas SDC remains indispensable in cases with severe mass effect or brainstem compression. A pragmatic stepwise approach-beginning with cautious EVD and escalating to SDC when indicated-may optimize outcomes. Further multicenter studies are required to refine patient selection criteria and establish standardized management algorithms.