title: Deformation of the corona radiata and internal capsule in normal pressure hydrocephalus.
abstract: OBJECTIVE
  The pathophysiology of the clinical manifestations in normal pressure hydrocephalus (NPH) remains obscure. Ventricular dilatation could generate forces on the paracentral fibers of the corona radiata (CR), hence interfering with their function and producing the classical clinical triad. The analysis of the regional displacement and deformation of the white matter bundles, forming the corona radiata and internal capsule, may clarify the relationship between ventricular dilatation and clinical manifestations in NPH.
  
  
  METHODS
  An experimental finite element (FE) analysis was used to simulate ventricular dilatation in 3 dimensions (3D) and to calculate the strain and deformation on the surrounding parenchyma. Magnetic resonance diffusion tensor imaging-based white matter tractography was then applied to retrieve the displacement and deformation exerted along various fiber bundles of the corona radiata and internal capsule. Anterior and posterior limb displacements and elongations were compared using a paired samples t-test.
  
  
  RESULTS
  The internal capsule, hence the corona radiata, of each cerebral hemisphere was segmented into anterior and posterior limbs. Mean displacements and elongations were calculated for each limb. Mean displacement was significantly larger in the anterior limb whereas mean deformation was larger in the posterior limb (P<0.01).
  
  
  CONCLUSIONS
  The present simulation demonstrates that ventricular dilatation does not have a homogeneous effect on the periventricular fibre tracts, with a particular load on the corticospinal tract. The affection of this tract remains thereby a potential factor in the generation of the NPH gait disorders.
authors.affiliation: Department of neurosurgery, university hospitals of Geneva and university of Geneva, rue Gabrielle-Perret-Gentil 4, 1211 Geneva 14, Switzerland. Electronic address: alister.rogers@icloud.com.
authors.forename: A
authors.initials: A
authors.lastname: Rogers
authors.affiliation: Department of neurosurgery, university hospitals of Geneva and university of Geneva, rue Gabrielle-Perret-Gentil 4, 1211 Geneva 14, Switzerland.
authors.forename: D
authors.initials: D
authors.lastname: Bichsel
authors.affiliation: Department of neurosurgery, university hospitals of Geneva and university of Geneva, rue Gabrielle-Perret-Gentil 4, 1211 Geneva 14, Switzerland.
authors.forename: S
authors.initials: S
authors.lastname: Momjian
mesh_terms: D056324:Diffusion Tensor Imaging / Q000379:methods; D020233:Gait Disorders, Neurologic / Q000503:physiopathology*; D006801:Humans; D006850:Hydrocephalus, Normal Pressure / Q000473:pathology* / Q000503:physiopathology; D020772:Internal Capsule / Q000473:pathology*; D009415:Nerve Net / Q000473:pathology
keywords: 3D brain mesh model; Analyse par éléments finis; Corona radiata; Finite element analysis; Hydrocéphalie à pression normale; Modèle du cerveau en maillage 3D; Normal pressure hydrocephalus; Tractographie de la substance blanche; White matter tractography