Advertisement

Myelination and Retarded Myelination

  • Jacob Valk
  • Marjo S. van der Knaap

Abstract

Flechsig (1920) was the originator of the view that the degree of myelination of the central nervous system might be correlated with functional capacity. In his theory he stated that myelination started in projection pathways before association pathways, in peripheral nerves before central pathways, and in sensory areas before motor ones. Although he did modify his theory slightly because of his critics, he maintained that fibers always myelinated in the same order: first the afferent (sensory), then the efferent (motor), then the association fibers. The histological study of fetal development has confirmed that myelination proceeds systemetically and, in nerve pathways with several neurons, in the order of conduction of the impulse. The first signs of myelination appear in the column of Burdach at the gestational age of 16 weeks, growing stronger from the 24th week. The column of Goll starts to myelinate at 23 weeks gestation. Cerebellar tracts start to myelinate at about 20 weeks gestation and the amount of myelin at birth is considerable. Pyramidal tracts start to myelinate at 36 weeks at the level of the pons, but at birth the amount of myelin is still scanty. In other tracts, for example, the rubrospinal tracts, the pattern of the pyramidal tract is followed. The olive and cerebellar connections begin to myelinate by 22 weeks gestation with rapid progression thereafter. In the pons some myelination is present at 36 weeks, but is still slight at birth. The corticopontine-cerebellar tracts are relatively late in myelination and show hardly any myelination at birth. In a full-term neonate of 40 weeks gestation, myelin stains reveal myelin in the medulla oblongata, in the central fibers of the cerebellum, in some fiber tracts in the pons and mesencephalon, in the posterior limb of the internal capsule, and some in the basal nuclei, spreading from there to the central parts of the centrum semiovale into the postcentral gyms. For further details see chapter 3.4.

Keywords

White Matter Gray Matter Internal Capsule Basal Nucleus Psychomotor Development 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Barkovich M, Kjos BO, Jackson DE, Norman D (1988) Normal maturation of the neonatal and infant brain: MR imaging at 1.5 T. Radiology 166: 173–180PubMedGoogle Scholar
  2. Boris P, Bundgaard F, Olsen A (1987) The CT ( Hounsfield unit) number of brain tissue in healthy infants. Childs Nerv Syst 3: 175–177Google Scholar
  3. Dietrich RB, Bradley WG, Zaragoza IV EJ, Otto RJ, et al. (1988) MR evaluation of early myelination patterns in normal and developmentally delayed infants. AJNR 9: 69–76Google Scholar
  4. Holland BA, Haas DK, Norman D, Brant-Zawadzki M, et al. (1986) MRI of normal brain maturation. AJNR 7: 201–208PubMedGoogle Scholar
  5. Holland BA (1987) Diseases of white matter. In: Brant-Zawadzki M, Norman D, eds. Magnetic resonance imaging of the central nervous system. New York: Raven Press: 259–277Google Scholar
  6. Johnson MA, Pennock JM, Bydder GM, Steiner RE, et al. (1983) Clinical NMR imaging of the brain in children: Normal and neurologic disease. AJNR 4: 1013–1026Google Scholar
  7. Levene MI, Whitelan A, Dubowitz V, Bydder CM, et al. (1982) Nuclear magnetic resonance imaging of the brain in children. Br Med J 285: 774–776CrossRefGoogle Scholar
  8. Lucas Keene MR, Hewer EE (1931) Some observations on myelination in the human nervous system. J Anat 6: 1–13Google Scholar
  9. McArdle CB, Richardson CJ, Nicholas DA, Mirfaljraee M, et al. (1987) Developmental features of the neonatal brain: MR imaging. Radiology 162: 223–229Google Scholar
  10. Mintz MC, Grossman RI, Isaacson G, Thickman DI, et al. (1987) MR imaging of fetal brain. J Comput Assist Tomogr 11: 120–123PubMedCrossRefGoogle Scholar
  11. Valk J (1987) Myelination. In: Valk J. MRI of the brain, head, neck and spine. Dordrecht/Boston/Lancaster: Martinus Nijhoff Publishers: 362–398CrossRefGoogle Scholar
  12. Yakovlev PI, Lecours AR (1967) The myelogenetic cycles of regional maturation of the brain. In: Minkowski A, ed. Regional development of the brain in early life. Oxford: Blackwel: 3–70Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1989

Authors and Affiliations

  • Jacob Valk
    • 1
  • Marjo S. van der Knaap
    • 2
  1. 1.Department of Diagnostic Radiology and NeuroradiologyFree University HospitalAmsterdamThe Netherlands
  2. 2.Department of Child NeurologyAcademic HospitalUtrechtThe Netherlands

Personalised recommendations