The diagnostic value of the pulsatility curve to predict shunt responsiveness in patients with idiopathic normal pressure hydrocephalus

Objective: The aim of this study was to investigate the diagnostic accuracy of the pulsatility curve to predict shunt response in patients with idiopathic normal pressure hydrocephalus (iNPH). Methods: Lumbar cerebrospinal fluid dynamics were derived from an automatic lumbar infusion test (LIT) protocol. All patients were treated with ventriculoperitoneal shunting and re-examined 6 months after shunting. Patient demographics and outcomes were gathered in a prospective, electronic database that spanned from January 2012 to January 2020. A validated iNPH scale was used to assess patients preoperatively and 6 months postoperatively. The relationship of the relative pulse pressure coefficient (RPPC), delta amplitude, successful lowering of amplitude, and the pressure-value at a hypothetical amplitude of zero (P₀), resistance to outflow (R_out), and outcome, were assessed using receiver operating characteristic (ROC) curves. Results: We included 38 patients. The RPPC, delta amplitude, successful lowering of amplitude, and P₀ parameters did not predict shunt response. Mean P₀ was 0.5 (IQR 0.4–0.9) in improved patients and 0.4 (IQR 0–1.2) in non-improved patients. The delta amplitude was 0.16 kPa (IQR 0.10–0.23) in improved patients and 0.18 kPa (IQR 0.11–0.24) in non-improved patients. Furthermore, we found a technical failure rate of pulsatility curve measurements of 32%. Conclusion: Pulsatility curve results were not suitable in predicting shunt response in our cohort. The diagnostic value of LIT in case of normal pressure hydrocephalus should be subject to more rigorous research.