Effect of Tonsillar Herniation on Cyclic CSF Flow Studied with Computational Flow Analysis

Abstract

BACKGROUND AND PURPOSE:The Chiari I malformation, characterized by tonsils extending below the foramen magnum, has increased CSF velocities compared with those in healthy subjects. Measuring the effect of tonsillar herniation on CSF flow in humans is confounded by interindividual variation. The goal of this study was to determine the effect of herniated tonsils on flow velocity and pressure dynamics by using 3D computational models.

Patient-Specific 3D Simulation of Cyclic CSF Flow at the Craniocervical Region

“…4,[11][12][13][14] The greater spatial and temporal variations observed in Chiari I models have been reported in clinical 12 and CFD studies. [1][2][3] Jets observed in our study in the anterolateral locations in patients with Chiari I correspond to published observations. 3,4,12 Patients with Chiari I and, to a lesser extent, healthy subjects had synchronous bidirectional flow in agreement with previous reports.…”

“…1,2 The simulations use 3D mathematical models of subarachnoid space geometries. CSF flow velocities and pressures are then computed on discretized representations (meshes) of these models by solving Navier-Stokes equations.…”

Simulating CSF Flow Dynamics in the Normal and the Chiari I Subarachnoid Space during Rest and Exertion

“…Only such insignificant changes were observed as flow changed direction from caudal to cranial (not shown). The ratios of anteroposterior and left-right velocity components to the superior-inferior velocity component changed negligibly and were small, as reported previously by Linge et al, 1 and flow distributions of these components were not affected by an elevated heart rate.…”

“…Normal and Chiari 3D models (Fig 1), designed and validated previously, 1,4 were used for the simulations in this study. The normal model had dimensions and tapering typical of a normal adult human subarachnoid space.…”

“…For given boundary conditions, the shape of the subarachnoid space determines the distribution of flow velocities and pressures. Simulation studies 1 have effectively demonstrated differences in CSF flow between patients with Chiari and healthy volunteers due to specific anatomic features, such as tonsillar herniation. CSF flow in patients during exertion has not been well characterized because PCMR is not well-suited to studying individuals who are not at rest.…”