title: Axon diameter and intra-axonal volume fraction of the corticospinal tract in idiopathic normal pressure hydrocephalus measured by q-space imaging.
abstract: OBJECTIVE
  Previous studies suggest that compression and stretching of the corticospinal tract (CST) potentially cause treatable gait disturbance in patients with idiopathic normal pressure hydrocephalus (iNPH). Measurement of axon diameter with diffusion MRI has recently been used to investigate microstructural alterations in neurological diseases. In this study, we investigated alterations in the axon diameter and intra-axonal fraction of the CST in iNPH by q-space imaging (QSI) analysis.
  
  
  METHODS
  Nineteen patients with iNPH and 10 age-matched controls were recruited. QSI data were obtained with a 3-T system by using a single-shot echo planar imaging sequence with the diffusion gradient applied parallel to the antero-posterior axis. By using a two-component low-q fit model, the root mean square displacements of intra-axonal space ( =  axon diameter) and intra-axonal volume fraction of the CST were calculated at the levels of the internal capsule and body of the lateral ventricle, respectively.
  
  
  RESULTS
  Wilcoxon's rank-sum test revealed a significant increase in CST intra-axonal volume fraction at the paraventricular level in patients (p<0.001), whereas no significant difference was observed in the axon diameter. At the level of the internal capsule, neither axon diameter nor intra-axonal volume fraction differed significantly between the two groups.
  
  
  CONCLUSIONS
  Our results suggest that in patients with iNPH, the CST does not undergo irreversible axonal damage but is rather compressed and/or stretched owing to pressure from the enlarged ventricle. These analyses of axon diameter and intra-axonal fraction yield insights into microstructural alterations of the CST in iNPH.
authors.affiliation: Department of Radiology, Juntendo University Graduate School of Medicine, Tokyo, Japan; Department of Radiology, Graduate School of Medicine, the University of Tokyo, Tokyo, Japan.
authors.forename: Kouhei
authors.initials: K
authors.lastname: Kamiya
authors.affiliation: Department of Radiology, Juntendo University Graduate School of Medicine, Tokyo, Japan.
authors.forename: Masaaki
authors.initials: M
authors.lastname: Hori
authors.affiliation: Department of Neurosurgery, Juntendo University Graduate School of Medicine, Tokyo, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Miyajima
authors.affiliation: Department of Neurosurgery, Juntendo University Graduate School of Medicine, Tokyo, Japan.
authors.forename: Madoka
authors.initials: M
authors.lastname: Nakajima
authors.affiliation: Department of Radiology, Juntendo University Graduate School of Medicine, Tokyo, Japan; Philips Electronics Japan, Ltd., Tokyo, Japan.
authors.forename: Yuriko
authors.initials: Y
authors.lastname: Suzuki
authors.affiliation: Department of Radiology, Juntendo University Graduate School of Medicine, Tokyo, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Kamagata
authors.affiliation: Department of Radiology, Juntendo University Graduate School of Medicine, Tokyo, Japan.
authors.forename: Michimasa
authors.initials: M
authors.lastname: Suzuki
authors.affiliation: Department of Neurosurgery, Juntendo University Graduate School of Medicine, Tokyo, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Arai
authors.affiliation: Department of Radiology, Graduate School of Medicine, the University of Tokyo, Tokyo, Japan.
authors.forename: Kuni
authors.initials: K
authors.lastname: Ohtomo
authors.affiliation: Department of Radiology, Juntendo University Graduate School of Medicine, Tokyo, Japan.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Aoki
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001369:Axons / Q000473:pathology*; D016022:Case-Control Studies; D048429:Cell Size; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D006850:Hydrocephalus, Normal Pressure / Q000175:diagnosis* / Q000473:pathology*; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008297:Male; D011712:Pyramidal Tracts / Q000473:pathology*
references.citation: NMR Biomed. 2010 Aug;23(7):836-48
references.pmid: 20623793
references.citation: Magn Reson Med. 2013 Sep;70(3):711-21
references.pmid: 23023798
references.citation: Magn Reson Med Sci. 2012;11(4):221-33
references.pmid: 23269009
references.citation: AJNR Am J Neuroradiol. 1991 Jan-Feb;12(1):31-9
references.pmid: 1899515
references.citation: Magn Reson Med. 2000 Nov;44(5):713-22
references.pmid: 11064406
references.citation: Magn Reson Med. 2008 May;59(5):1079-89
references.pmid: 18429023
references.citation: Neurosurgery. 2010 May;66(5):917-24
references.pmid: 20404696
references.citation: AJNR Am J Neuroradiol. 2012 Jan;33(1):97-103
references.pmid: 22016412
references.citation: Brain Res. 1992 Dec 11;598(1-2):143-53
references.pmid: 1486477
references.citation: Acta Neuropathol. 1993;85(6):573-85
references.pmid: 8337936
references.citation: NMR Biomed. 2010 Aug;23(7):698-710
references.pmid: 20632416
references.citation: Radiology. 2005 Mar;234(3):649-53
references.pmid: 15665224
references.citation: J Comp Neurol. 1990 Jan 22;291(4):520-37
references.pmid: 2329189
references.citation: J Int Neuropsychol Soc. 2008 Nov;14(6):933-46
references.pmid: 18954474
references.citation: Magn Reson Med Sci. 2013;12(3):153-9
references.pmid: 23857149
references.citation: J Neurosurg. 2005 Jun;102(6):987-97
references.pmid: 16028756
references.citation: Neurology. 2005 Apr 26;64(8):1438-40
references.pmid: 15851738
references.citation: Neuroradiology. 2003 Aug;45(8):532-5
references.pmid: 12856090
references.citation: NMR Biomed. 2010 Aug;23(7):865-72
references.pmid: 20882528
references.citation: J Neurol Sci. 2007 Jun 15;257(1-2):105-13
references.pmid: 17360001
references.citation: N Engl J Med. 1965 Jul 15;273:117-26
references.pmid: 14303656
references.citation: Neuroradiology. 2014 Jan;56(1):5-13
references.pmid: 24158631
references.citation: Magn Reson Med. 2010 May;63(5):1323-35
references.pmid: 20432303
references.citation: Magn Reson Med. 2008 Jun;59(6):1347-54
references.pmid: 18506799
references.citation: Magn Reson Med. 2002 Jan;47(1):115-26
references.pmid: 11754450
references.citation: Neuroimage. 2013 Oct 15;80:234-45
references.pmid: 23711537
references.citation: AJNR Am J Neuroradiol. 2011 Oct;32(9):1681-7
references.pmid: 21816921
references.citation: Acta Neurochir Suppl. 2006;96:377-80
references.pmid: 16671489
references.citation: Neuroimage. 2010 Oct 1;52(4):1374-89
references.pmid: 20580932
references.citation: Mol Pathol. 2001 Dec;54(6):386-92
references.pmid: 11724913
references.citation: J Neurol Sci. 1977 Sep;33(3):437-52
references.pmid: 915528
references.citation: Proc R Soc Lond B Biol Sci. 1982 Dec 22;217(1206):29-35
references.pmid: 6131421
references.citation: Radiology. 2000 Nov;217(2):331-45
references.pmid: 11058626
references.citation: J Magn Reson. 2009 May;198(1):15-23
references.pmid: 19186086
references.citation: J Neuroimaging. 2011 Jan;21(1):69-72
references.pmid: 19555407
references.citation: Acta Neurochir (Wien). 2012 Jun;154(6):1097-104; discussion 1104
references.pmid: 22527572
references.citation: Neurol Med Chir (Tokyo). 2012;52(11):775-809
references.pmid: 23183074
references.citation: Acta Pathol Jpn. 1987 Jan;37(1):97-110
references.pmid: 3577765
references.citation: NMR Biomed. 2002 Nov-Dec;15(7-8):516-42
references.pmid: 12489099
references.citation: Neuroradiology. 2013 Aug;55(8):971-976
references.pmid: 23728069
references.citation: Surg Neurol. 1976 Mar;5(3):187-210
references.pmid: 1257894
references.citation: Neurosurgery. 2005 Sep;57(3 Suppl):S4-16; discussion ii-v
references.pmid: 16160425
references.citation: AJNR Am J Neuroradiol. 2006 Sep;27(8):1717-24
references.pmid: 16971621
references.citation: J Magn Reson Imaging. 2007 Sep;26(3):519-24
references.pmid: 17729353
references.citation: Stroke. 1996 Jan;27(1):24-9
references.pmid: 8553398
references.citation: Neuroradiology. 2008 Feb;50(2):117-22
references.pmid: 17992524
references.citation: Acta Neurochir (Wien). 2012 Sep;154(9):1699-706
references.pmid: 22610531
references.citation: NMR Biomed. 2013 Dec;26(12):1787-95
references.pmid: 24105913
references.citation: Neuroimage. 2013 Oct 15;80:273-82
references.pmid: 23727318
references.citation: AJNR Am J Neuroradiol. 2011 Sep;32(8):1496-503
references.pmid: 21700790
references.citation: Neuroimage. 2010 Jul 15;51(4):1360-6
references.pmid: 20350604
references.citation: J Magn Reson. 2008 Oct;194(2):230-6
references.pmid: 18667345
references.citation: Brain. 2004 May;127(Pt 5):1009-18
references.pmid: 15047586