Evidence of altered epidermal nerve fiber morphology in adults with self-injurious behavior and neurodevelopmental disorders

Abstract

The purpose of this preliminary study was to examine the morphology and neuropeptide density of epidermal nerve fibers quantified through skin biopsy samples from three adults with neurodevelopmental disorders and chronic self-injurious behavior (SIB) secondary to mental retardation compared with non-SIB normal IQ controls. A cross-sectional design was used with 3mm punch skin biopsies collected from each participant from non-self-injurious body sites and compared with site-matched existing normal control skin samples. The study was conducted at an outpatient clinic. The primary dependent measure for the morphology analyses was the coefficient of variation (CV) to quantify the mean gap length between epidermal nerve fibers for each subject. Visual microscopic examination and quantitative analysis of the microscopy images suggested there were morphological abnormalities (increased CV) in the epidermal nerve fibers among the chronic SIB cases. Substance P (SP) fiber density was increased with 2-3 times as many fibers in SIB subjects as control subjects. Additional empirical work is needed to clarify the relation between sensory innervation of the skin and self-injury to improve assessment and treatment outcomes.

Figure 1

Confocal images of human skin. Nerves appear green, basement membrane surrounding capillaries and the dermal-epidermal (d/e) boundary appears red. The epidermis is blue. (a) Control skin sample with normal innervation pattern. Epidermal nerve fibers (ENFs) penetrate the d/e basement membrane in a uniform pattern; (b) Representative skin sample from a non-involved site of a self-injurious behavior (SIB) case from same plane of section as control demonstrating intact subepidermal stratum; (c) Representative skin sample from non-involved site of a SIB case demonstrating tufting and clustering; (d) SIB case substance P immunolabeling.