Morphometric brain MRI findings in hair-pulling and skin-picking disorders in youth

Pediatric hair-pulling disorder (HPD) and skin-picking disorder (SPD) are treatment-resistant conditions understudied with neuroimaging. We report cross-sectional morphometric MRI results from the adolescent-early adult subsample of the Body-Focused Precision Medicine Initiative (BPMI), a major HPD-SPD MRI database. Participants aged 11-21 years comprised 30 with HPD, 13 with SPD, 16 with both HPD and SPD, and 29 typically developing (TD). Whole-brain MRI was parcellated into cortical and subcortical regions with FreeSurfer. Volume and (for cortex) thickness and surface area of each region were analyzed for effects of HPD and SPD, controlling for psychotropic medication, age, total intracranial volume, and scanning site. Morphometry of four regions most reflected diagnosis and severity of HPD: 1) left inferior frontal cortex (larger and thicker for more severe HPD); 2) corpus callosum (larger for more severe HPD); 3) lingual gyrus (smaller right cortical surface area and white-matter volume); and 4) fusiform gyrus (smaller right cortical and white-matter volumes for more severe HPD). For SPD, there were three regions: 1) parahippocampal gyrus (larger left white matter volume and larger bilateral cortical volume and surface area for more severe SPD); 2) fusiform cortex (thicker left cortex for more severe skin-picking urgency); and 3) entorhinal cortex (thicker right cortex for more severe urgency). Variations in regional morphometry may result from or predispose to HPD and SPD. Left inferior frontal and callosal findings suggest lateralized dysfunction in HPD similar to language disorders; in SPD parahippocampal findings may indicate dysfunction in emotion regulation and/or contextual association.