Longitudinal changes in ventricular volume after treating aqueduct stenosis through endoscopic third ventriculostomy in adults.

Background: Assessment of ventricular size following endoscopic third ventriculostomy (ETV) often relies on linear measurements and indexes such as the Evans index (EI) and frontal and occipital horn ratio (FOHR). Long-term data on ventricular volume following ETV is scarce, which leads to uncertainties regarding optimal follow-up duration and whether ventricular size correlates with clinical outcomes. This study aims to analyze the longitudinal changes of ventricular volume following ETV for aqueduct stenosis (AS) in adults.

Methods: We retrospectively analyzed radiological images and clinical records of adult patients who underwent ETV for AS between the years 2010 and 2020. The primary endpoint was the change in lateral and third ventricular (LTV) volume at various follow-up periods in patients who did not require revision surgery (successful ETV group). Cluster analysis was performed to identify distinct volumetric patterns, and logistic regression was used to analyze the correlation between ventricular volume changes and clinical symptom improvement.

Results: A total of 238 radiological images with 197 (82.8%) MRI and 41 (17.2%) CT scans from 46 patients were analyzed. Thirty-nine (84.8%) patients did not require revision surgery (successful ETV group). In the successful ETV group, LTV volume decreased by 19.6% within 3 months, 31% after 3-6 months, and 47.5% after 6-12 months. Two main clusters were identified: one with a mean LTV volume decrease of 56% and the other of 18.9% after 1 year. The presence of a pineal or tectal lesion (OR 3.94, p = 0.074) tended to be predictive of the former cluster, and the presence of a membrane in the aqueduct (OR 5.1, p = 0.036) was predictive of the latter. Volumetric changes were significantly greater than those measured by EI and FOHR postoperatively (p < 0.001) and at the last follow-up (p = 0.002). There was no association between LTV volume reduction and clinical improvement during the follow-up period (OR 1.03, [95% CI 0.99-1.06]; p = 0.195).

Conclusion: Volumetric analysis provides a more accurate representation of ventricular size changes following ETV for AS. It demonstrates a continuous reduction in LTV volume during the first year after surgery, whereafter LTV volume appears to stabilize with a cumulative reduction of 38.7%, suggesting that lifelong imaging may be unnecessary in these patients. However, it does not predict the clinical outcome.