Hierarchical models for epidermal nerve fiber data

Authors

Affiliation

Claes Andersson

Chalmers University of Technology and the University of Gothenburg

Tuomas Rajala

Chalmers University of Technology and the University of Gothenburg

Aila Särkkä

Chalmers University of Technology and the University of Gothenburg

Abstract

While epidermal nerve fiber (ENF) data have been used to study the effects of small fiber neuropathies through the density and the spatial patterns of the ENFs, little research has been focused on the effects on the individual nerve fibers. Studying the individual nerve fibers might give a better understanding of the effects of the neuropathy on the growth process of the individual ENFs. In this study, data from 32 healthy volunteers and 20 diabetic subjects, obtained from suction induced skin blister biopsies, are analyzed by comparing statistics for the nerve fibers as a whole and for the segments that a nerve fiber is composed of. Moreover, it is evaluated whether this type of data can be used to detect diabetic neuropathy, by using hierarchical models to perform unsupervised classification of the subjects. It is found that using the information about the individual nerve fibers in combination with the ENF counts yields a considerable improvement as compared to using the ENF counts only.

Figure 1: Three illustrations of the data. In the leftmost panel is a schematic illustration of a nerve tree. The order is to the right of each segment. In the middle panel we show a 2D projection of a sample, where the black dots are entry points, red dots branching points and grey dots end points. A part of the sample is illustrated in 3D in the rightmost panel. Here the black spheres are entry points and grey spheres end points.