Objective: Infusion tests are important tools to assess cerebrospinal fluid (CSF)dynamics used in the preoperative selection of patients for shunt surgery, or to predict the scope of improvement from shunt revision. The aim of this study was to assess the repeatability of the key quantitative parameters describing CSF dynamics that are determined with infusion testing.
Materials and Methods: Eighteen patients in whom a constant infusion test was repeated within 102 days, without any intermediate surgical intervention, were studied. From each test baseline ICP, baseline pulse amplitude, outflow resistance, elastance coefficient and slope of the amplitude-pressure line were calculated and investigated with a regression and Bland-Altman analysis.
Results: Significant correlations (P < 0.01) were found for the outflow resistance (R = 0.96), the elastance coefficient (R = 0.778) and the slope of the amplitude-pressure line (R = 0.876). The estimated 95% confidence level for outflow resistance was 3 mmHg/ml min. Likewise, the elastance coefficient lay within a range of 0.16/ml and the slope of the amplitude-pressure line within 0.25. The most inconsistent parameter found were baseline ICP (R = 0.272) and baseline pulse amplitude (R = 0.171).
Conclusion: The results of this study imply that the parameters resulting from an infusion study have to be considered within a range rather than as an absolute value.
This study was supported by the National Institute of Health Research, Biomedical Research Centre (Neuroscience Theme) and NIHR Senior Investigator Awards (JDP). We thank Dr. Hugh K.Richards for checking our statistical methodology and results. GVV is supported by an A. G. Leventis Foundation Scholarship.
- Cerebrospinal fluid
- Infusion test
- Intracranial pressure