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Assessment of non-invasive ICP during CSF infusion test: an approach with transcranial Doppler
D Cardim1, M Czosnyka2,3, J Donnelly2
1Brain Physics Laboratory, Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Box 167, Cambridge Biomedical Campus, Cambridge, CB2 0QQ, UK. dac69@cam.ac.uk.
Background:
This study aimed to compare four non-invasive intracranial pressure (nICP) methods in a prospective cohort of hydrocephalus patients whose cerebrospinal fluid dynamics was investigated using infusion tests involving controllable test-rise of ICP.
Method:
Cerebral blood flow velocity (FV), ICP and non-invasive arterial blood pressure (ABP) were recorded in 53 patients diagnosed for hydrocephalus. Non-invasive ICP methods were based on: (1) interaction between FV and ABP using black-box model (nICP_BB); (2) diastolic FV (nICP_FVd); (3) critical closing pressure (nICP_CrCP); (4) transcranial Doppler-derived pulsatility index (nICP_PI). Correlation between rise in ICP (∆ICP) and ∆nICP and averaged correlations for changes in time between ICP and nICP during infusion test were investigated.
Results:
From baseline to plateau, all nICP estimators increased significantly. Correlations between ∆ICP and ∆nICP were better represented by nICP_PI and nICP_BB: 0.45 and 0.30 (p < 0.05). nICP_FVd and nICP_CrCP presented non-significant correlations: -0.17 (p = 0.21), 0.21 (p = 0.13). For changes in ICP during individual infusion test nICP_PI, nICP_BB and nICP_FVd presented similar correlations with ICP: 0.39 ± 0.40, 0.39 ± 0.43 and 0.35 ± 0.41 respectively. However, nICP_CrCP presented a weaker correlation (R = 0.29 ± 0.24).
Conclusions:
Out of the four methods, nICP_PI was the one with best performance for predicting changes in ∆ICP during infusion test, followed by nICP_BB. Unreliable correlations were shown by nICP_FVd and nICP_CrCP. Changes of ICP observed during the test were expressed by nICP values with only moderate correlations.
