Sullivan, Edith V., and Adolf Pfefferbaum, ‘Diffusion Tensor Imaging in Aging and Age-Related Neurodegenerative Disorders’, in Derek K. Jones, PhD (ed.), Diffusion MRI: Theory, Methods, and Applications (2010; online edn, Oxford Academic, 1 Sept. 2012), https://doi.org/10.1093/med/9780195369779.003.0038, accessed 21 Dec. 2022.
Postmortem investigations reveal degradation of white matter microstructure and include evidence for decline in numbers of myelinated fibers of the precentral gyrus and corpus callosum. Small connecting fibers of the anterior corpus callosum are especially vulnerable in aging, and their disruption may contribute to age-related declines in cognitive processes dependent on functioning of the prefrontal cortical circuitry. Degradation of myelin and microtubules and even axon deletion also accompanies normal aging. Fluctuating morphology, especially on the microstructural level, may also be attributable to axonal and myelin repair, which is speculated to occur throughout life. These changes in white matter microstructure may be detectable with diffusion tensor imaging (DTI) quantification. Quantitative characterization of the changes that occur during normal aging is prerequisite for gauging changes that occur with neuropathological conditions affecting white matter. This chapter reviews evidence for changes in normal aging as the context for establishing abnormalities marking neurological and psychiatric conditions, including mild cognitive impairment, Alzheimer’s disease, frontotemporal dementia, Parkinson’s disease, and alcoholism.
Keywords: white matter, axon, myelin, neuropathology, age, brain, neurological conditions, psychiatric conditions