Correlation of a new hydrodynamic index with other effective indexes in Chiari I malformation patients with different associations

Abstract

This study aimed to find a new CSF hydrodynamic index to assess Chiari type I malformation (CM-I) patients' conditions and examine the relationship of this new index with morphometric and volumetric changes in these patients and their clinical symptoms. To this end, 58 CM-I patients in four groups and 20 healthy subjects underwent PC-MRI. Ten morphometric and three volumetric parameters were calculated. The CSF hydrodynamic parameters were also analyzed through computational fluid dynamic (CFD) simulation. The maximum CSF pressure was identified as a new hydrodynamic parameter to assess the CM-I patients' conditions. This parameter was similar in patients with the same symptoms regardless of the group to which they belonged. The result showed a weak correlation between the maximum CSF pressure and the morphometric parameters in the patients. Among the volumetric parameters, PCF volume had the highest correlation with the maximum CSF pressure, which its value being higher in patients with CM-I/SM/scoliosis (R² = 65.6%, P = 0.0022) than in the other patients. PCF volume was the more relevant volumetric parameter to assess the patients' symptoms. The values of PCF volume were greater in patients that headache symptom was more obvious than other symptoms, as compared to the other patients.

Figure 1

Panels show the measurements of PCF made on T1-weighted MRI. (a) a: clivus; b: foramen magnum; c: supraocciput; d: Twining line. (b) Distance from the opisthion (op) to the inner surfaces of the basion (ba) is the anterior–posterior diameter of the foramen magnum; distance from the opisthion to the center of the internal occipital protuberance (iop) is the axial length of supraocciput; and distance from the basion to the top of the dorsum sellae (ds) is the axial length of clivus. (c) Shown the distance between asterions (as). (d) The perpendicular distance from the top of the jugular tubercle (jt) and the bottom of the occipital condyle (oc) along a line parallel with the orbitomeatal line is the axial height of condyle. (e) Distance between outer surfaces of occipital condyles (oc) is the width of condyles. (f) Distance between opisthion (op) and the basion (ba) is the maximum transverse diameter of the foramen magnum.

Figure 2

The mesh convergence study for the three grids: coarse, medium and fine meshes: (a) velocity profile along with line K (line K is shown in Fig. 3b), (b) maximum systolic velocity, (c) maximum systolic pressure. (d) The comparison of the PC-MRI velocity graph and the velocity graph calculated by the CFD simulation systolic. (e) The comparison of the maximum systolic velocity obtains from PC-MRI and CFD simulation for all samples.

Figure 3

(a) The type and size of meshes near the walls were defined differently from other locations for considering the effect of the boundary layer. (b), (c) compare the velocity and pressure distributions, respectively. (1), (2), (3), and (4) are the velocity distribution at the level of C5 for patients number 1 in CM-I 1, CM-I/SM, CM-I/hydrocephalus, and CM-I/TCS, respectively. (5), (6), (7), and (8) are the pressure distribution at the level of C6 for similar patients. The left side models of velocity and pressure distribution in panels (c) and (d) belong to the CM-I patient number 1. K is the direction of the assessment of velocity if Fig. 2a for the mesh convergence study.

Figure 4

(a), (b) the maximum CSF velocity and pressure in the term of spinal level for healthy subject number 1 and patients number 1, respectively. (c), (d) compare the CSF velocity and pressure graphs of healthy subject number 1 and patients number 1, respectively. (e), (f) show the relationship between prevalent symptoms of patients with maximum CSF pressure and velocity, respectively. For example, the intensity of the “headache” symptom was higher and more obvious than that of the other symptoms in the patients.

Figure 5

The PCC between the maximum CSF pressure of the patients with (a) PFB volumes, (b) CSF volumes, and (c) PCF volumes.

Figure 6

(a)–(c) show the relationship between prevalent symptoms of patients with PFB volumes, CSF volumes, and PCF volumes, respectively. For example, the intensity of the “headache” symptom was higher and more obvious than that of the other symptoms in the patients.