Endoscopic third ventriculostomy (ETV) is an established treatment for obstructive hydrocephalus in both children and adults and is increasingly used as an alternative to cerebrospinal fluid shunting. Contemporary series and systematic reviews suggest an overall complication rate of approximately 5–15%, with permanent morbidity around 2–3% and procedure-related mortality below 1% . Although these rates compare favorably with shunt surgery, the spectrum of possible complications includes rare but catastrophic events such as basilar artery rupture and late sudden deterioration due to stoma closure .

This chapter provides a contemporary, evidence-based overview of ETV complications across pre-operative, intra-operative, early post-operative, and late phases. We emphasize the interaction between patient selection, ventricular and vascular anatomy, intra-operative technique, and long-term follow-up in determining risk. Key topics include hemodynamic instability and bradycardia during floor perforation, hemorrhagic and vascular injury within the interpeduncular cistern, neuroendocrine and electrolyte disturbances, infection, neurocognitive sequelae from fornical or hypothalamic injury, and the mechanisms and clinical patterns of ETV failure. Particular focus is given to third ventricle floor and basilar artery morphometry, the concept of a vascular “safe zone,” and emerging strategies to prevent catastrophic complications. Rather than viewing complications as idiosyncratic events, we frame them as largely predictable and often preventable outcomes of anatomical, technical, and organizational factors. Protocolized peri-operative care, meticulous anatomical planning, and structured long-term surveillance underpin a modern, systems-based approach to safe ETV.