Usefulness of third ventricle volumetry in patients with normal pressure hydrocephalus.

Objective: To use third ventricle morphometric variables as a tool for the selection of patients with idiopathic normal pressure hydrocephalus (iNPH) who are candidates for ventriculoperitoneal shunts (VPS).

Material And Methods: Retrospective study enrolling patients with iNPH. Katzman infusion test was performed and a Rout > 12 mmHg/mL/min was considered a positive result. The transverse diameter and the volume of the third ventricle were measured in the preoperative MRI. Postoperative improvement was assessed with the NPH score. The results were analysed with SPSS software.

Results: 52 patients with a mean age of 76 years were analysed. There was no difference in the diameter of the third ventricle among patients with a positive result and those with a negative result in the infusion test (12.28 vs 11.68 mm; p = 0.14). Neither were difference detected in the ventricle volume of both groups (3.6 vs 3.5cc; p = 0.66). Those patients who improved after VPS had a smaller third ventricle compared to those who did not respond after surgery (11.85 mm vs. 12.96 mm; p = 0.009). Diameter and volume of third ventricle present a significant strong correlation (Pearson correlation coefficient = 0.72; p < 0.0001).

Conclusion: Morphometric variables of third ventricle may be useful in predicting a good response to VPS in patients with idiopathic normal pressure hydrocephalus.