Association Between Resistance to Cerebrospinal Fluid Flow Near the Foramen Magnum and Cough-Associated Headache in Adult Chiari Malformation Type I

Abstract

Cough-associated headaches (CAHs) are thought to be distinctive for Chiari malformation type I (CMI) patients and have been shown to be related to the motion of cerebrospinal fluid (CSF) near the foramen magnum (FM). We used computational fluid dynamics (CFD) to compute patient-specific resistance to CSF motion in the spinal canal for CMI patients to determine its accuracy in predicting CAH. Fifty-one symptomatic CMI patients with cerebellar tonsillar position (CTP) ≥ 5 mm were included in this study. The patients were divided into two groups based on their symptoms (CAH and non-CAH) by review of the neurosurgical records. CFD was utilized to simulate CSF motion, and the integrated longitudinal impedance (ILI) was calculated for all patients. A receiver operating characteristic (ROC) curve was evaluated for its accuracy in predicting CAH. The ILI for CMI patients with CAH (776 dyn/cm5, 288-1444 dyn/cm5; median, interquartile range) was significantly larger compared to non-CAH (285 dyn/cm5, 187-450 dyn/cm5; p = 0.001). The ILI was more accurate in predicting CAH in CMI patients than the CTP when the comparison was made using the area under the ROC curve (AUC) (0.77 and 0.70, for ILI and CTP, respectively). ILI ≥ 750 dyn/cm5 had a sensitivity of 50% and a specificity of 95% in predicting CAH. ILI is a parameter that is used to assess CSF blockage in the spinal canal and can predict patients with and without CAH with greater accuracy than CTP.

Keywords: Chiari malformation type I; cerebrospinal fluid; computational fluid dynamics; cough-associated headache; magnetic resonance imaging.

Fig. 1

Flow domain generation steps: (a) segmented CSF space, (b) CSF space after smoothing, and (c) CSF space with added extensions

Fig. 2

Example of a mesh generated for CSF space with enlarged views of the linearly increasing prismatic layers (lower left) and mesh structure near cerebellar tonsils (lower right)

Fig. 3

CFD simulation results for patient CAH-31: Pressure drop between the FM and a location that is 25 mm below the FM plane (top), volume flow rate (bottom), and LI result (center), with the corresponding ILI value (area under the curve from 1 to 8 Hz)

Fig. 4

ILI and CTP values for all CMI patients: ILI distribution (top) and corresponding CTP values (bottom). Black rectangular boxes in the plots on the left represent the median and interquartile range for ILI and CTP values.

Fig. 5

ILI versus CTP for patients in both groups

Fig. 6

ROC curves for all 44 CMI patients in this study

Fig. 7

ROC curve for two groups of patients: Patients with CTP ≤ 7 mm (ILI = solid line with circles, CTP = solid line with triangles) and patients with CTP > 7 mm (ILI = dashed line, CTP = dotted line)

Fig. 8

MR images for two CMI patients that show the sagittal and axial planes near the FM. The MR image demonstrates greater foraminal crowding in patient CAH-50, who has a CTP = 7 mm and an ILI = 27,000 dyn/cm⁵ (left) as compared to a patient non-CAH-7, who has a CTP = 24 mm and an ILI = 423 dyn/cm⁵ (right).