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Published on: August 11, 2016
Periventricular Nodular Heterotopia: Detection of Abnormal Microanatomic Fiber Structures with Whole-Brain Diffusion
Shawna Farquharson1, J-Donald Tournier1, Fernando Calamante1
1From the Imaging Division, Florey Institute of Neuroscience and Mental Health, Melbourne Brain Centre, 245 Burgundy St, Melbourne, Australia 3084 (S.F., J.D.T., F.C., S.M., I.E.S., G.D.J., A.C.); Department of Medical Imaging and Radiation Sciences, Monash University, Melbourne, Australia (S.F., M.E.S.); Department of Medicine, Austin Health, University of Melbourne, Melbourne, Australia (J.D.T., F.C., G.D.J., A.C.); Department of Biomedical Engineering (J.D.T.) and Centre for the Developing Brain (J.D.T.), King's College London, London, England; Departments of Radiology (S.M.) and Paediatrics (S.M., I.E.S.), Royal Children's Hospital, University of Melbourne, Melbourne, Australia; and Epilepsy Research Centre, Department of Medicine, Austin Health, University of Melbourne, Melbourne, Australia (R.B., S.F.B., I.E.S.).
Abstract:
Purpose To investigate whether it is possible in patients with periventricular nodular heterotopia (PVNH) to detect abnormal fiber projections that have only previously been reported in the histopathology literature. Materials and Methods Whole-brain diffusion-weighted (DW) imaging data from 14 patients with bilateral PVNH and 14 age- and sex-matched healthy control subjects were prospectively acquired by using 3.0-T magnetic resonance (MR) imaging between August 1, 2008, and December 5, 2012. All participants provided written informed consent. The DW imaging data were processed to generate whole-brain constrained spherical deconvolution (CSD)-based tractography data and super-resolution track-density imaging (TDI) maps. The tractography data were overlaid on coregistered three-dimensional T1-weighted images to visually assess regions of heterotopia. A panel of MR imaging researchers independently assessed each case and indicated numerically (no = 1, yes = 2) as to the presence of abnormal fiber tracks in nodular tissue. The Fleiss κ statistical measure was applied to assess the reader agreement. Results Abnormal fiber tracks emanating from one or more regions of heterotopia were reported by all four readers in all 14 patients with PVNH (Fleiss κ = 1). These abnormal structures were not visible on the tractography data from any of the control subjects and were not discernable on the conventional T1-weighted images of the patients with PVNH. Conclusion Whole-brain CSD-based fiber tractography and super-resolution TDI mapping reveals abnormal fiber projections in nodular tissue suggestive of abnormal organization of white matter (with abnormal fibers both within nodules and projecting to the surrounding white matter) in patients with bilateral PVNH. © RSNA, 2016.
Insights
Advanced MRI techniques visualized abnormal white matter organization in patients with periventricular nodular heterotopia (PVNH). This finding, previously seen only in histopathology, offers new insights into PVNH
Area of Science:
- Neuroimaging
- Neuropathology
- Radiology
Background:
- Periventricular nodular heterotopia (PVNH) is a developmental brain malformation.
- Abnormal white matter organization in PVNH has been suggested by histopathology.
- Non-invasive visualization of these abnormalities has been challenging.
Purpose of the Study:
- To investigate the in vivo detection of abnormal fiber projections in patients with PVNH using advanced MRI.
- To determine if diffusion-weighted imaging can reveal white matter abnormalities previously only seen in histopathology.
Main Methods:
- Whole-brain diffusion-weighted (DW) imaging was performed on 14 patients with PVNH and 14 controls using 3.0-T MRI.
- Constrained spherical deconvolution (CSD)-based tractography and super-resolution track-density imaging (TDI) maps were generated.
- Tractography data were analyzed for abnormal fiber tracks within heterotopic nodules.
Main Results:
- Abnormal fiber tracks were identified by all readers in all 14 PVNH patients.
- These abnormal fibers were not detected in control subjects.
- The abnormal structures were not visible on conventional T1-weighted images.
Conclusions:
- Whole-brain CSD-based tractography and super-resolution TDI mapping can reveal abnormal fiber projections in PVNH.
- These findings suggest abnormal white matter organization within and projecting from PVNH nodules.
- Advanced MRI techniques provide a non-invasive method to study white matter abnormalities in PVNH.
