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. 2022 Aug 1:10:900644.
doi: 10.3389/fbioe.2022.900644. eCollection 2022.

A New Definition for Intracranial Compliance to Evaluate Adult Hydrocephalus After Shunting

Affiliations

A New Definition for Intracranial Compliance to Evaluate Adult Hydrocephalus After Shunting

Seifollah Gholampour et al. Front Bioeng Biotechnol. .

Abstract

The clinical application of intracranial compliance (ICC), ∆V/∆P, as one of the most critical indexes for hydrocephalus evaluation was demonstrated previously. We suggest a new definition for the concept of ICC (long-term ICC) where there is a longer amount of elapsed time (up to 18 months after shunting) between the measurement of two values (V1 and V2 or P1 and P2). The head images of 15 adult patients with communicating hydrocephalus were provided with nine sets of imaging in nine stages: prior to shunting, and 1, 2, 3, 6, 9, 12, 15, and 18 months after shunting. In addition to measuring CSF volume (CSFV) in each stage, intracranial pressure (ICP) was also calculated using fluid-structure interaction simulation for the noninvasive calculation of ICC. Despite small increases in the brain volume (16.9%), there were considerable decreases in the ICP (70.4%) and CSFV (80.0%) of hydrocephalus patients after 18 months of shunting. The changes in CSFV, brain volume, and ICP values reached a stable condition 12, 15, and 6 months after shunting, respectively. The results showed that the brain tissue needs approximately two months to adapt itself to the fast and significant ICP reduction due to shunting. This may be related to the effect of the "viscous" component of brain tissue. The ICC trend between pre-shunting and the first month of shunting was descending for all patients with a "mean value" of 14.75 ± 0.6 ml/cm H2O. ICC changes in the other stages were oscillatory (nonuniform). Our noninvasive long-term ICC calculations showed a nonmonotonic trend in the CSFV-ICP graph, the lack of a linear relationship between ICC and ICP, and an oscillatory increase in ICC values during shunt treatment. The oscillatory changes in long-term ICC may reflect the clinical variations in hydrocephalus patients after shunting.

Keywords: brain material; fluid–structure interaction; hydrocephalus; intracranial compliance; intracranial pressure; shunt; viscous component.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
The methodological workflow.
FIGURE 2
FIGURE 2
MRI, 3D geometrical model, meshed model, FSI simulation, grid independence study, and data validation. (A) and (B) show MRI of patient No. 2 pre-shunting and 12 months after shunting, respectively. (C) shows the head substructures in patient No. 2 18 months after shunting. The red and green areas show the fluid (ventricular system and subarachnoid space) and solid (brain tissue) domains, respectively. The borders and interfaces between red and green areas are FSI boundary conditions. (D) and (E) show the 3D geometrical model and meshed model of patient No. 2 prior to shunting, respectively. (F) shows the methodological workflow. (G) and (H) show two snapshots of ICP distribution at early systole and diastole phases, respectively, for patient No. 2 pre-shunting. (I) The grid independence study for the maximum ICP data. The difference between fine and very fine meshes in inpatient No. 2 prior to shunting was 0.28%. (J) The comparison of CSF velocity graphs in the aqueduct of Sylvius between CINE PC-MRI and FSI simulation data in a cardiac cycle for patient No. 1. (K) The comparison of the maximum CSF velocity in the aqueduct of Sylvius between CINE PC-MRI and FSI simulation data for all 15 patients. CSF: cerebrospinal fluid; FSI: fluid–structure interaction; CINE PC-MRI: cine phase-contrast magnetic resonance imaging; and ICP: intracranial pressure.
FIGURE 3
FIGURE 3
Changes of CSFV, brain volume, and ICP over 18 months after shunting. (A) The “mean value” of CSFV prior to shunting until 18 months after shunting. The decrease in “mean value” of CSFV from prior to shunting to 18 months after shunting was 80.0%. (B) CSFV changed in 15 patients prior to shunting until 18 months after shunting. Between the third and 12th months, patients had some increases in CSFV. After 12 months, CSFV reached a stable condition. (C) The “mean value” of the brain volume prior to shunting until 18 months after shunting. The increase in “mean value” of the brain volume from prior to shunting to 18 months after shunting was 16.9%. (D) The brain volume changes of 15 patients prior to shunting until 18 months after shunting. In all steps, there was an increase in the brain volume of all patients. After 15 months, the brain volume reached a stable condition. (E) The “mean value” of ICP prior to shunting until 18 months after shunting. The decrease in “mean value” of ICP from prior to shunting to 18 months after shunting was 70.4%. (F) ICP changes of 15 patients prior to shunting until 18 months after shunting. In the second month, 12 patients had an increase in ICP value. After 6 months, ICP reached a stable condition. The bold lines indicate the ascending trend, and blue areas show the stable areas of CSFV, brain volume, and ICP changes. Raw data for Figures 2A–C are included in Supplementary Tables S1, S2, and S3, respectively. CSFV: cerebrospinal fluid volume; and ICP: intracranial pressure.
FIGURE 4
FIGURE 4
Concurrent changes of CSFV, brain volume, and ICP. 3D graphs of CSFV–brain volume–ICP during shunt treatment for all 15 patients. The changes in CSFV, brain volume, and ICP from prior to shunting to 18 months after shunting were not uniform, and the surfaces of graphs are not smooth. Raw data for Figure 3 are included in Supplementary Tables S1, S2, and S3. CSFV: cerebrospinal fluid volume; and ICP: intracranial pressure.
FIGURE 5
FIGURE 5
CSFV–ICP graphs for all 15 patients. The general trend of the CSFV–ICP graphs in all 15 patients was not monotonic. The slopes of these graphs are representative of the long-term ICC changes during shunt treatment. There are 9 red circles in each panel with each circle representing a step. The steps include prior to shunting, and 1, 2, 3, 6, 9, 12, 15, and 18 months after shunting. In each panel, the first red circle on the left side represents prior to shunting, and the last red circle on the right side represents 18 months after shunting; hence, moving from the left to the right shows the progression of the treatment process. Raw data for Figure 4 are included in Supplementary Tables S1 and S3. CSFV: cerebrospinal fluid volume; ICP: intracranial pressure; and ICC: intracranial compliance.
FIGURE 6
FIGURE 6
Long-term ICC changes from prior to shunting to 12 months after shunting. The long-term ICC changes between prior to shunting and the first month after shunting are shown by the first red circle on the left side of each panel. The definitions of steps 0-1, steps 1-2, steps 2-3, steps 3-6, steps 6-9, and steps 9-12 in horizontal axes are the long-term ICC values between prior to shunting and 1 month after shunting, between 1 and 2 months after shunting, between 2 and 3 months after shunting, between 3 and 6 months after shunting, between 6 and 9 months after shunting, and between 9 and 12 months after shunting, respectively. It should be noted that after 6 months, the ICP changes (numerator of ICC equation) and CSFV changes (denominator of ICC equation) were 1.98 and 4.70%, respectively. Hence, despite an oscillatory increase in long-term ICC values over the course of 12 months, this increase until 6 months after shunting (0-1, 1-2, 2-3, and 3-6 steps) is more referable for our analysis. The dashed blue curves in each panel are the envelope curves of the long-term ICC graph. These envelope curves in all panels show a nonuniform and oscillatory increase in long-term ICC values during the treatment process (from the left to right). Raw data for Figure 5 are included in Supplementary Table S4. CSFV: cerebrospinal fluid volume; ICP: intracranial pressure; and ICC: intracranial compliance.
FIGURE 7
FIGURE 7
Relationship between long-term ICC and ICP. Pearson’s correlation results between long-term ICC and ICP in all 15 patients show that all ps are greater than 0.44, so the correlations are not statistically “significant.” This means there is no linear relationship between long-term ICC and ICP. Raw data for Figure 6 are included in Supplementary Tables S3 and S4. ICP: intracranial pressure; and ICC: intracranial compliance.

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