  Degradation of the myelin sheath is a common pathology underlying
demyelinating neurological diseases from Multiple Sclerosis to
Leukodistrophies. Although large malformations of myelin ultrastructure in the
advanced stages of Wallerian degradation is known, its subtle structural
variations at early stages of demyelination remains poorly characterized. This
is partly due to the lack of suitable and non-invasive experimental probes
possessing sufficient resolution to detect the degradation. Here we report the
feasibility of the application of an innovative non-invasive local structure
experimental approach for imaging the changes of statistical structural
fluctuations in the first stage of myelin degeneration. Scanning micro X-ray
diffraction, using advances in synchrotron x-ray beam focusing, fast data
collection, paired with spatial statistical analysis, has been used to unveil
temporal changes in the myelin structure of dissected nerves following
extraction of the Xenopus laevis sciatic nerve. The early myelin degeneration
is a specific ordered compacted phase preceding the swollen myelin phase of
Wallerian degradation. Our demonstration of the feasibility of the statistical
analysis of SmXRD measurements using biological tissue paves the way for
further structural investigations of degradation and death of neurons and other
cells and tissues in diverse pathological states where nanoscale structural
changes may be uncovered.
