Chronic Back Pain Is Associated With Decreased Prefrontal and Anterior Insular Gray Matter: Results From a Population-Based Cohort Study

Chronic back pain (CBP) is associated with circumscribed atrophy in gray matter (GM) predominantly localized in areas of the so-called pain matrix and the prefrontal cortex (PFC). Previous studies applying voxel-based morphometry (VBM) for identifying structural brain alterations related to CBP have reported inconsistent results, were limited to small sample sizes, and often did not control for medication. We therefore used VBM for high-resolution magnetic resonance images to investigate the association of CBP and regional GM volume in 111 individuals with CBP and 432 pain-free controls derived from the representative Study of Health in Pomerania, controlling for effects of medication. CBP was associated with decreased regional GM in the ventrolateral PFC and dorsolateral PFC, both the ventral and dorsal medial PFC, and the anterior insula. Pain intensity showed a weak negative correlation with GM volume in the left dorsolateral PFC, ventrolateral PFC, and anterior cingulate cortex. The CBP sample showed alterations in regions commonly associated with pain processing and emotional demands. To our knowledge, this is the first VBM study reporting decreased regional GM volume in the medial PFC in a CBP sample. We were unable to confirm alterations in regions other than the dorsolateral PFC and the insula. Perspective: Previous studies reported inconsistent results for brain areas altered in chronic pain conditions, which may be in part attributable to small sample sizes, medication use, or emotional comorbidities. This study in a large and representative cohort helps to clarify these issues. (C) 2016 by the American Pain Society