Combined scatter diagrams of sheath thickness and fibre calibre in human sural nerves: changes with age and neuropathy.

A computer-assisted method permits collection of large numbers of measurements of fibre profiles in electron micrographs of human sural nerve biopsies. The method is based on simultaneous demonstration of fibre calibre and of sheath thickness in terms of the g-ratio (quotient axon diameter/fibre diameter), and on the recalculation of all parameters for circular fibre profiles. The fibres of small and large diameters of human sural nerves were found to form separate populations with distinctly different trends for sheath thickness and also different patterns of maturation. Preliminary data in neuropathy show that this method gives a better distinction of the extent of damage to either of the two populations; it also permits assessment of the number of regenerating or remyelinating fibres.