Efficacy and factors predicting success of endoscopic third ventriculostomy in hydrocephalus

Objective: Hydrocephalus is a clinical condition that occurs as a result of the disruption of the physiological balance between cerebrospinal fluid (CSF) production and absorption, leading to increased CSF volume, ventricular enlargement, and elevated intracranial pressure. Surgical intervention constitutes the mainstay of treatment, and although shunt systems are widely used, they often fail to provide a permanent solution. Endoscopic third ventriculostomy (ETV) has become a more preferred alternative due to allowing physiologic CSF circulation, not requiring implantation of foreign material, having a lower infection risk, and being repeatable. This study aims to evaluate the effectiveness of ETV in the treatment of hydrocephalus and to investigate the factors influencing surgical success, including the ETV Success Score (ETVSS). Materials and Methods: Medical records of 144 patients who underwent ETV between November 2016 and December 2022 in a tertiary care center were retrospectively reviewed. A total of 113 patients diagnosed with hydrocephalus and treated solely with ETV (without choroid plexus coagulation) were included. Patients were evaluated in terms of age, sex, hydrocephalus type, etiology, primary or secondary ETV application, preoperative ETVSS, and radiological findings. Pre- and postoperative MRI measurements were used to calculate Evans index, FH/ID ratio, and bicaudate index; third ventricular floor bowing (ÜVTÇ) was also recorded. Patients who showed complete or partial clinical improvement after surgery and required no CSF intervention for at least six months were considered "successful ETV" cases. Statistical analyses included Chi-square, Fisher's exact, and Mann–Whitney U tests. Results: The mean age of the cohort was 26.16 years; 54% were children and 46% were adults. The overall ETV success rate was 75.22% (n=85). Although success rates varied clinically across age groups, these differences were not statistically significant (p > 0.05). Posterior fossa tumors were the most common etiology in both adult and pediatric groups. No significant difference in ETV success was observed between obstructive and non-obstructive hydrocephalus types (p = 1.000). Among obstructive hydrocephalus patients, success rates did not differ significantly between "pure mechanical" and "inflammatory" obstruction groups (p = 0.278). Primary ETV demonstrated a significantly higher success rate (78.43%) compared to secondary ETV (45.45%) (p = 0.026). Complete postoperative clinical improvement was strongly associated with success (98.31%, p < 0.001). Although higher ETVSS categories tended to show increased success, the difference was not statistically significant. The presence of third ventricular floor bowing did not significantly increase success (p = 0.828). Successful cases showed significant postoperative reductions in ventricular indices (Evans, FH/ID, bicaudate; all p < 0.001), whereas unsuccessful cases showed no meaningful change. Postoperative complications occurred in 23.89% of patients; CSF fistula was significantly associated with ETV failure (p = 0.00019). The need for reoperation was significantly higher in patients with complications (p = 0.0012). Conclusions: ETV is an effective treatment method with a high success rate in hydrocephalus management. Success is significantly higher when ETV is performed as a primary intervention. Postoperative radiological ventricular reduction is a strong indicator of surgical efficacy. CSF fistula is an important predictor of ETV failure. Although age, etiology, hydrocephalus type, ETVSS, and third ventricular floor bowing may influence outcomes clinically, these factors did not reach statistical significance in this study. Keywords: Hydrocephalus, Endoscopic third ventriculostomy, ETVSS, ventriculostomy success, CSF fistula.