Figure 1. Multidimensional Scaling Plot of Subgroup Assignments for Persistent Post-Traumatic Headache Phenotypes.

Two subgroups of individuals with persistent post-traumatic headache were identified using a Random Forest analysis and Partitioning Around the Medoids clustering of input features from 3 biologic domains: 1) resting state functional connectivity of the periaqueductal gray, 2) quality and size of cervical muscles, and 3) mechanical sensitivity and modulation of pain. Distinct clustering of participants assigned to High Pain Coping (gray squares, N=13) and Low Pain Coping (black circles, N=20) subgroups is visualized in two dimensions using multidimensional scaling to reflect non-linear combinations of features included in the analysis.