Endoscopic third ventriculostomy for idiopathic normal pressure hydrocephalus: association of cerebrospinal fluid flow dynamics with outcome.

INTRODUCTION

Endoscopic third ventriculostomy (ETV) has been proposed for selected patients with idiopathic normal pressure hydrocephalus (iNPH), but predictors of sustained benefit are uncertain. Phase-contrast MRI (PC-MRI) may quantify cerebrospinal fluid (CSF) pulsatility and support patient selection.

RESEARCH QUESTION: Is sustained clinical improvement after primary ETV associated with preoperative aqueductal CSF flow parameters measured by PC-MRI?

MATERIAL AND

METHODS

In this prospective single-centre observational study, patients with iNPH underwent primary ETV after standardized diagnostic work-up. Preoperative assessment included the Kiefer scale and PC-MRI measurements at the cerebral aqueduct: peak velocity (PV), aqueductal stroke volume (ASV), and net ASV. Clinical follow-up was performed for 12 months. Sustained response was defined as an NPH recovery rate ≥3 at 3 and 12 months without secondary ventriculoperitoneal shunt implantation. Analyses were exploratory.

RESULTS

Thirty-one patients were included, of whom 10 (32.3%) achieved sustained clinical improvement. Responders demonstrated significantly higher preoperative ASV values compared to non-responders. Among the evaluated parameters, ASV was the only variable significantly associated with clinical response. Receiver operating characteristic (ROC) analysis demonstrated good discriminatory capacity for ASV (area under the curve [AUC] 0.83). An exploratory cut-off value of 280 μl yielded a sensitivity of 90%, specificity of 71%, positive predictive value of 60%, and negative predictive value of 94%.

DISCUSSION AND

CONCLUSION

Higher preoperative ASV was associated with sustained clinical improvement after primary ETV in this small iNPH cohort. PC-MRI-derived ASV may help identify candidates unlikely to benefit from ETV, but the proposed threshold requires external validation before clinical use.