title: Diffusion tensor imaging assessment of microstructural brainstem integrity in Chiari malformation Type I.
abstract: OBJECTIVE The diagnosis of Chiari malformation Type I (CM-I) is primarily based on the degree of cerebellar tonsillar herniation even though it does not always correlate with symptoms. Neurological dysfunction in CM-I presumably results from brainstem compression. With the premise that conventional MRI does not reveal brain microstructural changes, this study examined both structural and microstructural neuroimaging metrics to distinguish patients with CM-I from age- and sex-matched healthy control subjects. METHODS Eight patients with CM-I and 16 controls were analyzed. Image postprocessing involved coregistration of anatomical T1-weighted with diffusion tensor images using 3D Slicer software. The structural parameters included volumes of the posterior fossa, fourth ventricle, and tentorial angle. Fractional anisotropy (FA) was calculated separately in the anterior and posterior compartments of the lower brainstem. RESULTS The mean age of patients in the CM-I cohort was 42.6 ± 10.4 years with mean tonsillar herniation of 12 mm (SD 0.7 mm). There were no significant differences in the posterior fossa volume (p = 0.06) or fourth ventricular volume between the 2 groups (p = 0.11). However, the FA in the anterior brainstem compartment was significantly higher in patients with CM-I preoperatively (p = 0.001). The FA values normalized after Chiari decompression except for persistently elevated FA in the posterior brainstem compartment in patients with CM-I and syrinx. CONCLUSIONS In this case-control study, microstructural alterations appear to be reliably associated with the diagnosis of CM-I, with a significantly elevated FA in the lower brainstem in patients with CM-I compared with controls. More importantly, the FA values normalized after decompressive surgery. These findings should be validated in future studies to determine the significance of diffusion tensor imaging-based assessment of brainstem microstructural integrity as an adjunct to the clinical assessment in patients with CM-I.
authors: 1Division of Neurosurgery, Department of Surgery.|2Center for Neuromodulation, Department of Neurosurgery, Ohio State University, Columbus, Ohio.
authors: Vibhor
authors: V
authors: Krishna
authors: 1Division of Neurosurgery, Department of Surgery.
authors: Francesco
authors: F
authors: Sammartino
authors: 1Division of Neurosurgery, Department of Surgery.
authors: Philip
authors: P
authors: Yee
authors: 1Division of Neurosurgery, Department of Surgery.|3Division of Brain Imaging, Behaviour Systems Neuroscience, Toronto Western Research Institute; and.|4Institute of Medical Science, and.|5Joint Department of Medical Imaging, University Health Network, Toronto, Ontario, Canada; and.|6Department of Medical Imaging, University of Toronto.
authors: David
authors: D
authors: Mikulis
authors: 3Division of Brain Imaging, Behaviour Systems Neuroscience, Toronto Western Research Institute; and.
authors: Matthew
authors: M
authors: Walker
authors: 1Division of Neurosurgery, Department of Surgery.
authors: Gavin
authors: G
authors: Elias
authors: 1Division of Neurosurgery, Department of Surgery.|3Division of Brain Imaging, Behaviour Systems Neuroscience, Toronto Western Research Institute; and.|4Institute of Medical Science, and.|5Joint Department of Medical Imaging, University Health Network, Toronto, Ontario, Canada; and.
authors: Mojgan
authors: M
authors: Hodaie
mesh_terms: D000328:Adult; D001139:Arnold-Chiari Malformation / Q000000981:diagnostic imaging* / Q000473:pathology*; D001933:Brain Stem / Q000000981:diagnostic imaging* / Q000473:pathology*; D016022:Case-Control Studies; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D008297:Male
keywords: AC = anterior commissure; CM-I = Chiari malformation Type I; Chiari malformation; DTI = diffusion tensor imaging; FA = fractional anisotropy; PC = posterior commissure; ROI = region of interest; anatomy; brainstem compression; diffusion tensor imaging; diffusion-weighted imaging; fractional anisotropy; imaging marker