Regional brain volumes and symptom severity in body dysmorphic disorder

Abstract

Body dysmorphic disorder (BDD) is a severe psychiatric condition in which individuals are preoccupied with perceived defects in their appearance. Little is known of the pathophysiology or neurobiology of BDD. Recent evidence from a functional MRI study examining visual processing of faces demonstrated abnormal activation patterns in regions including left-sided inferior frontal gyrus (IFG) and amygdala. To investigate morphometric abnormalities, we compared brain volumes from high-resolution T1 magnetic resonance images of 12 unmedicated subjects with BDD to images of 12 matched controls using voxel-based morphometry (VBM). In addition, we compared volumes in specific regions of interest including the IFG, amygdala, caudate, and total grey and white matter and examined correlations with symptom severity. VBM revealed no statistically significant volumetric differences, nor were there significant differences in any of the regions of interest. However, there were significant positive correlations between scores on the BDD version of the Yale–Brown Obsessive–Compulsive Disorder Scale (BDD-YBOCS) and volumes of the left IFG (r = 0.69) and the right amygdala (r = 0.54). These findings of correlations between BDD symptom severity and volumes of the left IFG and the right amygdala. These are in concordance with the involvement of these regions in pathological face processing, which may contribute to the primary symptomatology.

Introduction

Body dysmorphic disorder (BDD) is a severe psychiatric condition in which patients are preoccupied with perceived defects in their appearance. This causes them to believe they are disfigured and ugly, and causes significant suffering and functional impairment. Most patients with BDD have poor insight, and 36–38% are classified as delusional (Eisen et al., 2004, Phillips et al., 2006). BDD affects 1–2% of the population (Faravelli et al., 1997, Otto et al., 2001, Rief et al., 2006), and is associated with high rates of psychiatric hospitalization (48%) (Phillips and Diaz, 1997) and suicide attempts (22–27.5%) (Veale et al., 1996, Phillips and Diaz, 1997, Phillips et al., 2005).

Despite the prevalence and severity of this disorder, very little is known of the pathophysiology or neurobiology of BDD. Only one previous morphometric magnetic resonance imaging (MRI) study in BDD has been published. In this study eight females, some of whom were medicated, demonstrated greater total white matter compared with controls and a leftward shift in caudate asymmetry (Rauch et al., 2003a), which the authors interpreted as suggesting similar striatal pathophysiology to that in obsessive-compulsive disorder (OCD) (Saxena et al., 2001). A small functional imaging study of six BDD patients, using single photon emission computed tomography (SPECT), showed variable, discrepant findings including relative perfusion deficits in bilateral anterior-medial temporal and occipital regions and asymmetric perfusion in parietal lobes (Carey et al., 2004). This study, however, had no control or comparison group. We recently performed a functional magnetic resonance imaging (fMRI) study in BDD that examined visual processing of faces (Feusner et al., 2007). Individuals with BDD as compared with healthy controls demonstrated abnormal activation patterns that included greater left hemisphere activity in regions including the inferior frontal gyrus, as well as abnormal amygdala activation (R > L). No other neuroimaging studies of BDD have been published.

Given these previous findings and the paucity of data on the neurobiology of BDD, the objective of this study was to further investigate regional brain volumes in BDD as compared with healthy controls. Based on our fMRI findings (Feusner et al., 2007), we selected the inferior frontal gyrus (IFG) and the amygdala as regions of interest. Following up the previous morphometric MRI study's findings (Rauch et al., 2003a), we also examined total grey matter (GM), white matter (WM), and the caudate as a region of interest, and calculated laterality quotients. We also tested whether brain volumes in the regions of interest were correlated with symptom severity. In addition, we performed voxel-based morphometry for regional whole-brain analysis to detect any other brain volume differences. We hypothesized that in the BDD group there would be abnormal caudate asymmetry and greater total WM. Based on findings from our previous fMRI study in the same cohort of BDD patients, we also hypothesized that they would demonstrate greater volumes of the amygdalae and left IFG, given the previously found hyperactivity in these regions. In addition, we hypothesized that symptom severity would positively correlate with size of the left IFG and bilateral amygdalae. A better understanding of patterns of brain morphometry in BDD could assist in understanding the pathophysiology underlying the clinical symptoms, as well as how it relates to other disorders with similar features.